AN ABSTRACT OF THE THESIS OF
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AN ABSTRACT OF THE THESIS OF Jerry J. Cordova for the degree of Master of Science in Fisheries Science presented on March 31, 1995. Title: Streamside Forests, Channel Constraint, Large Woody Debris Characteristics, and Pool Morphology in Low Order Streams, Blue Moun Redacted for privacy Abstract approved: Dr. James R. Sedell Currently evolving concepts of linkages between terrestrial and aquatic ecosystems provide a basis to evaluate the ecological role of large woody debris (LWD) with respect to specific channel and valley geomorphology. Geomorphic landforms can influence the lateral constraint of flowing streams and modify the role of LWD within the stream channel. Large woody debris was measured in 13 low order eastern Oregon streams (15 total study sites) in undisturbed grand fir (Abies grandis) forests to assess its natural abundance, character, and function in streams of varying channel constraint. Channel constraint was measured by a ratio of flood-prone area and bankfull width (i.e., Entrenchment Ratio "ER"). Four sites were highly constrained (ER<1.5), 6 sites were moderately constrained (ER=l.5-2.2), and 5 unconstrained (ER>2.2). The mean basal area of riparian trees was 38.7 m2/ha (SD=17.4), with little variation between 0-15 m and 15-30 m from the bankfull channel. Seral tree species (e.g., Ponderosa pine (Pinus ponderosa) provide a minor percentage of the total stand composition, but provide 40-52% of the total potential LWD recruitment volume to the stream channel. For all sites, mean stand density from 0-15 m and 15-30 m were 471 and 458 trees/ha, respectively. percent of the trees were Eight 5O cm diameter, and 31% of the trees were between 30-50 cm diameter. Riparian stand density of large diameter trees >50 cm DBH and basal area per hectare were positively correlated with the volume of LWD associated with the channel, although no relationship was found with LWD frequency. LWD volumes averaged 156.1 m3/ha within the bankfull channel and 237.0 m3/ha within and above the bankfull channel, respectively. Twenty-two pieces per 100 m were associated with the stream channel. An average of 2.1 pieces per 100 m were >50 cm diameter (at the large end). Large wood recruitment was similar for all streams and was dominated by windthrow (54%). Fluvial processes moved or repositioned 25% of the LWD with no significant difference in movement between levels of channel constraint. The dimensions of LWD pieces transported or repositioned averaged 26.2 cm in diameter and 5.8 m in length, significantly smaller and shorter than the average for all LWD pieces (34.9 cm in diameter and 10.8 m in length). The greatest proportion of the LWD was oriented perpendicular to the channel, however, orientation showed no significant relationship with gradient, channel constraint, or LWD dimensions. A total of 262 primary poois were measured in the 15 study sites, of which 63% (n=165) were formed by 11% of the total LWD pieces measured (n=1404). Pool frequency and spacing were best predicted by the frequency of LWD/100 m. Stratification of reaches by the entrenchment ratio, allowed for the comparison of relational differences between LWD and pool formation. For example, 40% of the pools were created by LWD within highly constrained stream reaches, although an average of 6% of the LWD functioned to form pools. In contrast, 80% of the pools were created by 13% of the LWD in unconstrained stream reaches. Large woody debris disproportionately favored the formation of plunge and dammed pool habitats. Plunge pools were formed by LWD 91% of the time, followed by dammed pools (76%) and scour pools (46%). The character of pools formed by LWD changed between levels of channel constraint. Within highly constrained channels, LWD formed 27% of the scour pools, while 68% of the scour poois within unconstrained channels were formed by LWD. Mean pool area of unconstrained channels were 58% and 65% larger than moderately constrained or highly constrained channels, respectively. Large woody debris within moderately constrained and unconstrained channels were twice as likely to form pools than LWD within highly constrained entrenchment and gradient, these variables were not related to pool volume. Pool area and volume were not related to LWD frequency or volume within the channel. The identification of the natural variability of LWD characteristics and function among each level of channel constraint defines the need to compare streams of like geomorphic character. In order to successfully manage or restore degraded stream ecosystems, the stream must be viewed in a watershed context to accommodate natural variability between streams and stream reaches. Streamside Forests, Channel Constraint, Large Woody Debris Characteristics, and Pool Morphology in Low Order Streams, Blue Mountains, Oregon. by Jerry J. Cordova A THESIS submitted to Oregon State University In partial fulfillment of the requirements for the degree Master of Science Completed March 31, 1995 Commencement June 1995 Master of Science thesis of JerrY J. Cordova presented on March 31, 1995 APPROVED: Redacted for privacy Major Protssor, representing Fisheries Redacted for privacy Chair of Department o'? Fisheries and Wildlife Redacted for privacy Dean of GrAduate SctIdol I understand that my thesis will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my thesis to any reader upon request. Redacted for privacy Jerfy L.)t'Cordova, Author Dedicated to my mother and father The people who taught me the value of an education. Jose E. and Matilde A. Cordova TABLE OF CONTENTS PAGE INTRODUCTION .1 SITE DESCRIPTION .......................................... 4 METHODS .................................................. 14 SITE SELECTION ......................................... 14 GEOMORPHIC MEASUREMENTS ................................ 15 VEGETATION MEASUREMENTS ................................ 19 LARGE WOODY DEBRIS MEASUREMENTS ........................ 19 DATA ANALYSIS .......................................... 24 RESULTS .................................................. 27 RIPARIAN FOREST ........................................ 27 LARGE WOODY DEBRIS ...................................... Dimensionsand Frequency ............................. Volume............................................... Recruitment.......................................... Association with Other Debris ........................ Horizontal Orientation ............................... Association with Large Tree Density .................. 32 32 32 41 43 44 44 POOLS.................................................. Association with Large Woody Debris .................. PoolSize ............................................ Frequency............................................ Spacing.............................................. PercentPool Area .................................... Slow-water Habitats: Scour, Plunge, and Dammed ...... Association of Slow-water Habitats with ChannelConstraint ................................... 49 49 57 57 60 60 61 65 DISCUSSION ............................................... 69 INFLUENCE OF RIPARIAN VEGETATION ON LARGE WOODY DEBRIS ..................................... 69 INFLUENCE OF CHANNEL CONSTRAINT ON LARGE WOODY DEBRIS ..................................... 78 TABLE OF CONTENTS (Continued) PAGE INFLUENCE OF LARGE WOODY DEBRIS AND CHANNEL CONSTRAINT ON POOL FORMATION ................... 81 MANAGEMENT IMPLICATIONS ................................ 84 BIBLIOGRAPHY ............................................. 96 APPENDICES .............................................. 106 APPENDIX A ............................................ 107 APPENDIX B ............................................ 139 LIST OF TABLES TABLE PAGE 1. Location of sites and occurrence of fish species within tributaries of the John Day and Maiheur River basins in eastern Oregon .......... 6 2. Channel morphological variables used to determine channel type as described by Rosgen (1994) ................................... 11 3. Channel hydrological characteristics of 15 studysites ........................................ 12 4. General channel morphological variables of 15 study sites ...................................... 13 5. Riparian stand characteristics for zone A (0-15 m) and zone B (15-30 m) ............................... 29 6. Large woody debris per 100 m and percent volume separated into piece size categories ............... 33 7. Large woody debris frequency, mean dimensions, mean volume (VOL) associated with the four hydrologic influence zones ("Zt' 1-4) ............... 37 8. Large woody debris volume per 100 in for each size category within each of the four hydrologic influencezones .................................... 39 9. Large woody debris association with other pieces, and delivery mechanism ...................... 42 10. Function of LWD within the channel ................. 55 11. Pool frequency, spacing, mean residual pool area, mean residual volume, and pool to riffle ratio (% of total wetted area) ........................... 58 12. The percentage of slow-water habitats formed and not formed by LWD .............................. 62 13. Differences in slow-water habitats (primary pools) between degrees of channel constraint ............... 67 14. Comparison of volumes and densities of large woody debris (LWD) in selected low order streams similar in size to this study (2-11 m bankfull channel widths) flowing through undisturbed forests ........ 71 LIST OF TABLES (Continued) TABLE PAGE 15. Comparison of valley floor width index and the entrenchment ratio .............................. 86 16. Comparison of LWD frequency by diameter categories between the minimum numeric standards developed by two eastern Oregon Forests for mix conifer stands (U.S.D.A. 1993, U.S.D.A. 1994), and findings from this study ........................... 93 LIST OF FIGURES FIGURE PAGE 1. Location of study sites .............................. 5 2. Degree of channel constraint and the associated entrenchment ratio (ER) ............................. 17 3. Riparian stand inventory within two belt widths from the bankfull channel (0-15 m and 15-30 in) ...... 20 4. Theoretical riparian area showing four hydraulic zones used for classification of LWD ................ 22 5. Method for characterizing horizontal orientation of LWD in relation to the channel ................... 23 6. Species composition (trees/ha) and volume/ha within zones A and B (0-15 m and 15-3 0 m from bankfull) .................. 30 7. Large woody debris diameter for all pieces measured (A), and length frequencies for allpieces measured (B) ............................. 35 8. Horizontal orientation for all measured large woody debris (n=719) ................................ 45 9. Relationship of LWD volume/lOO m (zone 1-2) and trees/ha >50 cm DBH from 0-30 in (A), and relationship of LWD volume/ 100 m (zones 1-4) and trees/ha >50 cm DBH from 15-30 m (B) ................. 46 10. Riparian stand composition, total LWD pieces measured, and LWD forming pool habitats bysize category .................................... 48 11. Relationship of pools formed by LWD and LWD/lOO in. . .50 12. Relationship of channel constraint on all primary pools (A), pools formed by LWD (B), and pools not formed by LWD (C) ............................... 51 13. Total pools formed and not formed by LWD ............ 52 14. Hierarchical structure and statistically significant correlations (P>0.05) of the primarypool analysis ............................... 53 LIST OF FIGURES (Continued) FIGURE PAGE 15. Function of LWD within pools for different levels of channel constraint ............................... 56 16. Number of slow-water habitats formed and not formed by LWD for all sites ................................ 64 17. Percent mean frequency of slow-water habitats not formed (A), and formed (B) by LWD ............... 66 LIST OF APPENDIX TABLES PAGE APPENDIX A 1. Length correction factors for each stream .......... 108 2. Select stream variables evaluated at each study site and appropriate transformation used to induce normality when applicable ................... 109 3. Raw data: Length, LWD, and riparian data of the 15 study sites ..................................... 110 4. Raw data: Large woody debris function and pool data of the 15 study sites ......................... 113 5. Trees per hectare for four species categories within zone A (0-15 in) and zone B (15-30 in) ....... 116 6. Basal area (m2/ha) of conifer categorized by four diameter classes within zone A (0-15 in) and zone B (15-30 m) .............................. 118 7. Trees per hectare for four DBH categories ......... 120 8. Mean stand volumes per hectare are shown for zones A (0-15 in) and zone B (15-30 in) ............. 121 9. Large woody debris per 100 m for all study sites.. .122 10. Large woody debris volume within the bankfull channel (zones 1-2), and within and above the bankfull channel (zones 1-3) ....................... 123 11. Relationships between LWD volume and select geomorphic variables between channel types ........ 124 12. Relationships between LWD association (i.e., individuals, group, or jam) andLWD abundance ................................. 125 13. Relationships of pools formed and not formed by LWD and gradient ................................ 126 14. Relationships of LWD and geomorphic variables on primary pool frequency (per 100 m) formed and not formed by LWD ...................... 127 15. Relationships of LWD and geomorphic variables on primary pooi spacing/b bankfull widths (10 BFW) formed and not formed by LWD ............. 128 LIST OF APPENDIX TABLES (Continued) APPENDIX A PAGE 16. Relationships of LWD and geomorphic variables on primary pool spacing/b wetted widths (10 WW) formed and not formed by LWD .............. 129 17. Relationships between LWD's role in pool formation and geomorphic variables ................. 130 18. Pools and the function of LWD associated with them .............................. 131 19. Relationships of LWD and geomorphic variables on primary pool area and volume ................... 133 20. Relationships of LWD and geomorphic variables on primary pooi frequency and spacing ............. 134 21. Relationships of LWD and geomorphic variables on primary slow-water habitat size: formed and not formed by LWD .................................. 135 22. Relationships of LWD and geomorphic variables on primary slow-water habitat frequency: formed and not formed by LWD ............................. 136 23. Relationships of LWD and geomorphic variables on primary slow-water habitat spacing per 10 bankfull widths: formed and not formed by LWD 24. Relationships of LWD and geomorphic variables on primary slow-water habitat spacing per 10 wetted widths: formed and not formed by LWD . . .137 . . .138 APPENDIX B 1. A Comparison of Geomorphic Features ................ 140 2. Relationships between geomorphic variables ......... 142 3. Geomorphic differences between degrees of channel constraint......................................... 143 Streamside Forests, Channel Constraint, Large Woody Debris Characteristics, and Pool Morphology in Low Order Streams, Blue Mountains, Oregon. Large wood provides an important component of fish habitat in small mountain streams in the Pacific Northwest (Sedell et al. 1982; Swanson and Lienkaemper 1982; Beschta et al. 1987; Bisson et al. 1987; Gregory et al. 1991). Salmonid fishes, in particular, have evolved in stream systems in which large woody debris (LWD) and fluvial processes develop and maintain channel morphology (Bisson et al. 1987; Ralph et al. 1994). Large woody debris helps retain organic and inorganic particulate matter that is important for channel stability, biological diversity and productivity (Bilby 1984; Nakamura and Swanson 1993). Large woody debris can significantly influence habitat for fish and other aquatic organisms by serving as energy dissipators, flow deflectors, and dams (Harr 1976; Beschta and Platts 1986; Carlson et al. 1990; Gregory et al. 1991). The spatial variability of LWD in small mountain streams results from differences in physical processes that shape valley floor landscapes, and the succession of terrestrial plant communities on these geomorphic surfaces (Swanson 1981; Cupp 1989; Ursitti 1991; Robison and Beschta 1990a; Gregory et al. 1991). There are interactions between landform/fluvial features of valley morphology and stream 2 channel relief, pattern, shape, and dimension (Grant 1988a). Channel morphology is consistently found to be related to channel slope and degree of lateral constraint (Grant et al. 1990) which can modify the stability of LWD or its role in pool formation (Kozel et al. 1989). Geomorphic dynamics of small mountain streams can change dramatically as they move through different geologic formations or encounter vegetative or landform perturbations (e.g., streamside roads). Longitudinal profiles, valley and channel cross- sections, and plan-view patterns can be deduced from adjacent geomorphic surfaces (e.g., terraces and bedrock outcrops) and the degree of lateral and vertical constraint (Rosgen 1988; Gregory et al. 1991). Recently, research on LWD has focused on the effect of either vegetative perturbation or stream size on LWD characteristics and function (Lienkaemper and Swanson 1987; Murphy and Koski 1989; Ursitti 1991). Studies have recognized the need to compare streams of like vegetative, fluvial, and geomorphic characteristics to appropriately describe the physical and biological role of LWD (Bull 1979; Rosgen 1985; Ursitti 1991; Richmond 1994). These studies recognize LWD and geomorphic processes as integral elements in determining the natural condition of streams in forested areas. Although it is evident that geomorphic surfaces play an important role in low order mountain streams, the characteristics and function of LWD within streams of different lateral containment are poorly understood. This study provides information regarding the character and function of LWD within different degrees of channel constraint. Identifying the causes of LWD variability will contribute towards a broader understanding of change in the natural stream environment as well as provide a basis for channel and fish habitat management and restoration. The purpose of this study is to describe the effects of channel constraint (i.e., lateral constraint) and adjacent riparian stand structure on LWD characteristics and function. The study includes small (low order) undisturbed old-growth grand fir forested streams in the Blue Mountains of eastern Oregon. The specific study objectives are: 1. Describe the composition and structure of riparian stands in old-growth grand fir forests. 2. Characterize and contrast quantity and character of LWD in 2nd and 3rd order old-growth streams flowing through constrained and unconstrained stream reaches. 3. Describe the characteristics and frequency of poois created or maintained by LWD within varying degrees of channel constraint. 4. Examine the concept of entrenchment as it relates to the character and function of LWD. 4 SITE DESCRIPTION The study area is located in eastern Oregon in the John Day and Malheur River basins in the southern portion of the Oregon Blue Mountain Range (Figure 1; Table 1). The study area lies within the Columbia Basin intermountain region of the United States. The area is underlain by basalt with small alpine glaciation. Most of the area consists of gentle to moderately steep slopes (up to 60%). Streams commonly exhibit a dendritic drainage pattern. Much of the area has been recently covered by a shallow layer of aerially deposited ash, most notably from the Mount Mazama eruption (approximately 7,000 years ago). Subsequent erosion has largely removed this material from south-facing slopes (Kovalchik 1987; Gordon per. comm.). Conifer stands dominate elevations between 1200 and 2300 In. These river basins exhibit features of both Pacific maritime and continental climatic patterns. Mean annual precipitation ranges 50 to 100 cm throughout the study area. Precipitation primarily occurs between October and April as rain or snow. snow melt. Stream levels peak in April and May during Precipitation can often vary greatly from year to year. The John Day River is one of the few remaining undainmed rivers in the United States. The John Day River maintains only wild stocks of steelhead trout (Oncorhynchus niykiss) Maiheur National Forest Figure 1. Location of study sites. Table 1. Location of sites and occurrence of fish species within tributaries of the John Day and Malheur River basins in eastern Oregon. Clear and L.Crane Creeks contained constrained and unconstrained reaches within the study sites. The list of salmonid fish species are based on historical stream inventories (Claire, unpublished Steelhead trout (SH) = Oncorhynchus mykiss, information). tshawvtscha, redband trout spring chinook salmon (CH) = (RB) = Q. mykiss spp., bull trout (BT) = Salvelinus confluentus, and brook trout (BR) = S. fontinalis. . Stream Name Basin Name/Location1 Stream Order2 Site Fish Species Present 1 Boulder M.F. John Day/lO-33-Ol 3 SH,RB 2 Indian John Day /14-33-15 3 RB,BT 3 Big (LC) M.F. John Day/09-33-14 2 SH,RB,BT 4 Reynolds John Day /13-35-21 2 SH,RB,BT,BR 5 S.F. Long M.F. John Day/ll-31-03 2 SH,RB 6 L. Malheur N.F. Nalheur /13-36-08 3 RB 7* Clear M.F. John Day/l2-35-03 2 SH,CH,RB 8* L. Crane N.F. Maiheur /16-35-16 2 RB,BT 9 Reynolds John Day /13-35-21 3 SH,RB,BT,BR 10 Snowshoe M.F. Maiheur /15-34-27 2 RB,BT,BR 11 Clear M.F. John Day! 12-35-03 2 SH,CH,RB 12 L. Crane N.F. Maiheur /12-35-09 2 RB,BT 13 Big (PC) M.F. Maiheur /15-34-27 2 RB,BT,BR 14 E.F. Canyon John Day /15-32-10 3 SH,CH,RB 15 E.F. Canyon John Day /15-32-12 3 SH,RB Township (south) - Range (east) 2 Section number Stream order based on perennial streams from quadrangle topographic maps (scale: 1:24,000). and spring chinook salmon (Q. tshawytscha). Native resident trout, such as, bull trout (Salvelinus confluentus), and westslope cutthroat (Q. lewisi) are found in both the John Day and Maiheur River drainages. The Maiheur River drainage, a tributary to the Snake River, is no longer anadromous due to a network of dams in the Snake River and small reservoirs within the basin. Quality spawning and rearing habitat within these basins have not only declined, but have become more isolated and fragmented due to past grazing, agriculture, and forestry activites (Buckman et al. 1992; Claire Pers. Comm.; Gritz Pers. Comm.). The remaining high quality habitats, which are generally found in areas of old-growth forested streams, are now even more critical for maintaining viable fish populations. Non-salmonid fish species include, but are not limited to, longnose dace (Rhinichthys cataractae), redside shiner (Richardsonius balteatus), and mottled sculpin (Cottus bairdi). Study sites are located on public lands administered by the U.S.D.A. Forest Service, Maiheur National Forest. Lower elevation ponderosa pine (Pinus ponderosa) riparian stands were harvested early in the century due to their high value and easy access. Many riparian areas have been harvested in conjunction with road construction and maintenance. Today, nearly all major stream drainages have roads adjacent to, or within, the riparian area limiting streamside forest development. Most streams with undisturbed riparian stands E3 occur at higher elevations with less commercially valuable tree species such as grand fir (Abies qrandis) and Engelmann spruce (Picea engellmannii). Riparian stand structure within the study area is highly dependent on the frequency and intensity of wildfire. Disturbance by wildfire plays an important role in shaping riparian and upland stands, where the combination of summer thunderstorms and low humidity allow for frequent low intensity fires (Hall 1973; Kauffman 1990). Fire can often allow seral species such as western larch (Larix occidentallis) and ponderosa pine to be a significant component of grand fir plant associations (Kauffman 1990). Riparian grand fir stands exhibiting a seral component are common throughout the study area. However, fire suppression has limited the re-establishment of seral species within many riparian and upland stands (Kauffman and Sapsis 1989). In the absence of fire, many grand fir stands within the study area have developed relatively dense, stagnant, multistoried grand fir stands as described by Hall (1973) and Agee (1990). Not only are such stands more susceptible to crown fires, but they are also often more susceptible to insect and disease infestation (Simpson et al. 1994). Study sites were located within grand fir climax plant associations. Seral species included; Engelmann spruce, lodgepole pine (Pinus contorta), western larch, and ponderosa pine. Mountain alder (Alnus incana) and red-osier dogwood (Cornus stolanifera) dominate the active stream channel-floodplain interface. In this study the term Itundisturbedt refers to the condition of the riparian vegetation (i.e., conifers and hardwoods). All study sites are within cattle grazing allotments. None of the sites exhibited evidence of bank or vegetative disturbance due to cattle. Six sites (3, 5, 7, 8, 11, and 12) exhibited timber management activities within their respective basins, however, timber management activities did not exceed 10% of the basin area or involve the riparian area for any study site. Several improved trails within sites 5, 6, 9, and 14 are also present. Abrupt ecotones are common within the study area. Geomorphic, fluvial geomorphic, and climatic gradients are often expressed vegetatively as you move away from the stream and floodplain (Simpson Pers. Comm.; Youngblood 1985). Hillslope stands are often structurally, compositionally, and functionally different from the adjacent riparian area. Riparian stand descriptions are rarely available from U.S.D.A. Forest Service stand exam inventories since riparian areas are not delineated from upland stand plots. Drainage basin area and stream order were obtained from United States Geological Survey (USGS) topographic maps (scale 1:24,000; contour interval 40-80 ft). Stream ordering included only perennial streams located on USGS 10 topographic maps. Study sites were also defined by channel entrenchment and reach classified by Rosgen (1994). The three major channel types used to stratify study sites were: Entrenchment Ratio Channel Constraint C >2.2 Unconstrained B >1.5-2.2 Moderately Constrained A <1.5 Highly Constrained Rosgen Channel Type Tables 2, 3 and 4, show the Rosgen (1994) channel type, general hydrological, and physical characteristics for each site. The classification developed by Rosgen (1994), is a hierarchical classification with a measure of lateral containment (i.e., entrenchment ratio), as the first broad level classification in differentiating stream reaches. The hierarchical classification continues with sinuosity, bankfull width to depth ratio, gradient, and channel substrate to attain a specific Rosgen stream classification (e.g., B3). The numerical element of the classification refers to the dominant substrate size. 11 Channel morphological variables used to determine Table 2. Flood-prone channel type as described by Rosgen (1994). area (FPA) width and bankfull width (BFW) are used to establish a ratio (i.e., channel Entrenchment Ratio "ER"). Sinuosity is measured as low (<1.2), medium (>1.2), and high (l.4). Bankfull width to depth ratio (W/D) and dominant channel material (BR=boulder, CO=cobble and GR=gravel) are given for each site. All measures are averages for individual sites. Site ER Sinuosity W/D Ratio Gradient (%) Channel Naterial Rosgen Type Highly Constrained 3 1.1 1.4 1.4 4 1.3 1 2 < < < < 1.2 1.2 1.2 1.2 8.4 6.3 8.9 6.6 5.5 5.2 7.1 5.6 BR BR BR Co A2 A2 A2 A3 Moderately Constrained 5 6 7 8 9 10 1.6 1.6 2.1 1.5 1.9 1.8 < < < < < < 1.4 1.4 1.4 1.4 1.4 1.4 13.6 12.6 8.4 11.4 23.3 10.0 2.0 1.4 1.5 2.0 2.5 2.2 BR CO CO CO CO GR B2 B3 B3 B3 B3 B4 > > > > > 1.4 1.4 1.4 1.4 1.4 9.0 15.0 8.7 15.6 10.3 0.5 0.7 1.2 1.2 2.0 GR GR GR C4 C4 C3 C3 C3 5.8 0.8 --- Unconstrained 11 12 13 14 15 3.7 2.6 3.4 3.6 3.2 Highly Constrained (sites 1-4) mean 1.3 -7.6 SD 0.2 -- 1.3 CO CO Moderately Constrained (sites 5-10) 1.9 mean 1.7 -13.2 SD 0.2 0.4 -- 3.3 1.1 0.6 -- 11.2 4.4 2.7 2.1 -- 5.3 Unconstrained (sites 11-15) mean 3.3 11.7 SD 0.4 All sites mean 2.1 SD 0.9 12 Table 3. General hydrological characteristics of 15 study sites. The maximum elevation range was derived from 200 foot contour intervals which included a minimum of 10% of the basin area. Valley floor width includes all terraces. Flood-prone and valley floor measurements are averages for individual sites. Stream flow measurements were taken between June and August. Basin Area Site (ha) Elevation Range (m) Flood-prone Area Width (m) Valley Floor width Discharge (xl02) (m) Highly Constrained 1 809 1520-2070 9.2 9.6 8.5 2 3833 1380-2310 8.7 8.7 12.5 3 1113 1760-2010 9.2 17.4 4.2 4 1904 1380-2070 5.3 7.2 12.7 Moderately Constrained 5 2185 1350-1710 18.1 21.9 1.1 6 3l08 1620-2260 12.1 31.0 12.7 7 4047 1350-1890 9.3 20.8 7.1 8 2732 1690-2070 9.4 29.8 8.8 9 2577 1370-2070 10.3 25.8 18.7 10 486 1720-2200 6.8 15.5 1.1 Unconstrained 11 4047 1350-1890 18.5 27.0 7.1 12 2732 1690-2070 18.2 29.0 8.8 13 1942 1730-2260 17.8 28.3 22.1 14 3116 1440-2200 22.8 83.4 5.7 15 809 1560-2200 22.1 28.3 4.2 13 Table 4. General channel morphological variables of 15 study sites. Study sites are within tributaries of the John Day and Maiheur River basins of eastern Oregon. Wetted Channel Bankfull Channel Site! Mean Channel Depth Type (m) Max Width (in) Mm Width (in) Mean Width (in) Mean Width (in) Depth Max Depth (in) (in) Avg. Highly Constrained 1 1.05 11.0 3.6 8.2 3.5 0.38 0.80 2 1.10 9.1 3.6 6.4 3.6 0.52 1.10 3 0.82 9.2 5.1 6.8 2.8 0.32 0.55 4 0.73 6.2 2.4 4.3 2.9 0.32 0.60 Moderately Constrained 5 0.81 17.7 6.4 11.0 3.8 0.33 0.75 6 0.65 10.6 6.1 7.6 4.6 0.28 0.60 7 0.50 4.8 4.2 4.5 4.1 0.35 0.50 8 0.55 11.3 3.9 6.4 4.6 0.29 0.60 9 0.45 7.5 3.5 5.3 3.0 0.28 0.65 10 0.45 5.7 1.9 3.8 2.1 0.22 0.35 Unconstrained 11 0.60 5.4 3.6 4.7 3.4 0.30 0.60 12 0.50 11.0 4.5 7.0 3.6 0.29 0.55 13 0.45 7.3 3.9 5.2 3.6 0.38 0.60 14 0.74 9.0 4.5 6.3 3.6 0.32 0.65 15 0.66 8.8 5.2 6.8 2.8 0.30 0.50 14 METHODS SITE SELECTION Sixty-six reaches (within 20 different streams) were identified following interviews with local land managers, aerial photo interpretation, and review of Naiheur National Forest stream surveys. Study sites were initially screened on the basis of three criteria: 1) riparian conifer vegetation unmodified by management activities, 2) stream reaches in 2nd and 3rd order basins, draining no more than 4050 ha, and 3) presence of an anadromous or resident fish population (Table 1). Fifteen study sites were selected from a stratified random sample of 40 constrained and 26 unconstrained stream reaches. After field measurements, constrained reaches were further stratified by the entrenchment ratio (see Rosgen 1994; Table 2). A secondary screening of the riparian conifer vegetation for each selected study site was completed to determine stand composition and potential LWD recruitment within 30 in of bankfull. Riparian stands which exhibited a minimum of 25 large trees per hectare (>50 cm diameter at breast height (DBH)) within 30 m of the bankfull channel, were designated as old-growth (Hopkins et al. 1992). Drainage areas upstream of the selected study sites varied from 5 to 41 km2 and elevations ranged from 1350 to 15 1760 in (Table 3). Study sites included approximately 380 m (range of 244-720 m, mean=381 in; 37.1-124.6 bankfull widths) of the stream channel and its surrounding vegetation. Nine sites supported steelhead populations and eight sites supported bull trout (Table 1). GEOMORPHIC MEASUREMENTS Field measurements were completed during the summer of 1990. At each study site, between 6-15 channel cross- section plots were taken approximately every 50 in of stream length within a riffle unit. All channel cross-sections avoided large roughness elements (i.e., LWD and large boulders) , when possible, to improve consistency between measurements. Bankfull width, bankfull depth, flood-prone width, and valley floor width were measured at each transect. Bankfull was defined as the stage that occurs several days in a year and is often related to the 1.5 year recurrence interval discharge (Rosgen 1988; Rosgen 1994). Bankfull was estimated by changes in vegetation composition and structure which was most often accompanied by an abrupt ledge on the stream bank. Occasionally within highly constrained reaches, water lines on bedrock were utilized to determine water elevation at bankfull discharge. features used to estimate bankfull included: Additional Water marks on streamside vegetation, streainside deposits of fine debris, and fluvially undisturbed fine debris (e.g., conifer needles) accumulations adjacent to the stream channel. Flood-prone area is defined as the width measured at an elevation which is determined at twice the maximum bankfull depth (Rosgen 1994). The entrenchment ratio is the ratio of the width of the flood-prone area to the bankfull surface width of the channel (Rosgen 1994). Within the shorter temporal framework of riparian vegetation succession and disturbance (e.g., fire; Minshall and Brock (1991)) of eastern Oregon forests, the entrenchment ratio is expected to be a more reliable measure of channel constraint as it relates to LWD character and function within different stream reaches. In addition, I expected that disturbance provided by bankfull discharge and more frequent floods would have had a more pronounced influence on stream channels (Swanson 1979) and LWD, regardless of channel constraint. Other measures of channel constraint, such as the valley floor width index (valley floor width/bankfull width), include rare flood elevations, and a longer temporal framework. Stream reaches were stratified into three categories by the entrenchment ratio (ER): 1) Highly Constrained (ER<l.5), 2) Moderately Constrained (ER=l.5-2.2), and 3) Unconstrained (ER>2.2) for further analysis (Rosgen 1994; Figure 2). The valley floor width includes the bankfull 17 Highly Constrained ER<1.5 flood- rune width ankfull width 2 flankfull depth UankiII depth Moderately Constrained Unconstrained R2.2 Degree of channel constraint and the associated Figure 2. Adopted froi Rosgen (1994). entrenchnient ratio (ER). channel, flood-prone area, and terraces. Channel slope was measured at distances no less than 15 m using an abney level. Pool and riffle habitat inventories were conducted following a hierarchical classification technique described by Hawkins et al. (1993). Fast water habitats under low flow periods were classified as riffles as described by Hawkins et al. (1993). Slow-water habitats were classified as scour pools, dammed pools, or plunge pools. Primary pools (pool surface area > wetted width2) and pocket pools (pool surface area > wetted width2/2, but smaller than a primary pool) were classified separately. Spacing between pools was calculated by dividing the total number of pools by 10 bankfull widths or 10 wetted channel widths. Substrate composition was visually estimated for the entire submerged area of a habitat type. Surface substrate composition was described as dominant and subdominant within each habitat unit (silt (<0.06 mm), sand (0.06-2 mm), gravel (2-64 mm), cobbles (64-256 mm), small boulders (256-512 mm), and large boulders (>512 mm)). by a pygmy current meter. Stream velocity was measured Discharge was calculated from the product of velocity and the cross-sectional area (Hewlett and Nutter 1982). All hydraulic measurements were taken during summer low-flow conditions (June - August). Length and width of channel habitat units were measured to the nearest 0.3 m. Maximum depth was measured to the 19 nearest 0.01 in. Residual pool depth was calculated by subtracting the pooi tail maximum depth from the maximum pool depth to account for different discharges between sites. Residual pool volume was calculated by multiplying the residual pool depth by the total pool surface area. VEGETATION MEASUREMENTS An inventory of each tree species larger than 10 cm DBH and snags larger than 30 cm DBH within 0 to 15 in and 15 to 30 m from each side of bankfull were completed for the entire study site length (except for study site 13 which was burned during the study by wildfire; Figure 3). Trees were categorized into four diameter (DBH) classes: 10-15 cm, 30 cm, 30-50, and 50 cm. 15- The frequency of large diameter trees (50 cm DBH) were placed into two categories (<40 and >40 trees/ha) for additional analysis. Species specific equations developed by the U.S.D.A Forest Service (1967) were used to calculate tree volume using DBH. LARGE WOODY DEBRIS MEASUREMENTS Large woody debris (0.1 m in diameter and 1 in in length) was inventoried within or in contact with the floodprone area. Large woody debris was categorized into four diameter classes: 10-15 cm, 15-30 cm, 30-50 cm, and 50 cm liiselt 1)CI1 I %-IIaII1ILI IJCIL I -"- Figure 3. Riparian stand inventory within two belt widths from the bankfull channel (0-15 m) and (15-30 m). 21 The maximum and minimum diameters for additional analysis. of a LWD and its length were used to estimate the volume according to the following formula by Lienkaemper and Swanson (1987): 3.14 (D12 + D)L Volume = 8 where D1 and D2 are end diameters (m) and L is length (m). Large woody debris diameter was measured and length was estimated. Every tenth LWD length estimate was measured to establish a correction factor for each study site (Appendix Al). The relative proportions of each debris piece within four hydraulic zones were estimated using a technique described by Robison (1987). Zone 1 included that percentage of the debris submerged during summer low flow, Zone 2 in the bankfull flow, and Zone 3 in the area directly above Zones 1 and 2. 1, 2, or 3 (Figure 4). Zone 4 includes the LWD outside Zones Each LWD piece was characterized as: an individual piece, loosely associated but touching other pieces, or tightly associated (i.e., piled debris jam). It was also noted if the piece of wood had an attached root wad. Horizontal orientation of each piece relative to the left and right bank (Robison and Beschta 1990; Figure 5) were also determined for sites 1-5, 10, and 13-15. Figure 4. Theoretical riparian area showing four hydraulic zones used for classification of LWD. Adopted from Robison (1987). Ni 23 of Flow horizontal orientation Figure 5. Method for characterizing LWD in relation to the channel. 24 Large woody debris delivery mechanisms were categorized into three areas: fluvial, erosion, and windthrow. Fluvial is defined as pieces floated or repositioned via fluvial processes. For example, if the LWD was recruited by another delivery mechanism (i.e., windthrow or erosion) and then moved or repositioned, it was categorized as fluvial. The erosion delivery mechanism is defined as pieces recruited by bank erosion but have not floated or repositioned by fluvial processes. Windthrow includes all other delivery mechanisms (e.g., tree mortality due to disease, fire, and windstorms). The role of LWD was evaluated at each pool habitat Unit. Large woody debris function was separated into four categories: 1) formed pool, 2) physically enhanced pooi size or depth, 3) provided overhead cover for fish (LWD lO cm vertical distance from the low-flow water surface), and 4) no direct influence. DATA ANALYSIS Data were first separated into four categories: 1) geomorphic features, 2) riparian forests, 3) large woody debris, and 4) pools. Geomorphic features were analyzed first to help define the differences between reach types (analysis is included in Appendix B for reference). Geomorphic features were then related to riparian forests, large woody debris, and pools. In general, data analysis consisted of computing and comparing summary statistics, 25 frequency distributions, correlations, regressions and More analysis of variance for different study sites. specifically, correlation analysis was used to investigate associations and covariance among the main variables across Simple and multiple regressions were used to all sites. describe specific relationships between geoinorphological features, debris, and stand characteristics. Statgraphics 5.0 was the statistical package utilized during the analysis. Trees were identified to species, but only lodgepole pine, western larch, and ponderosa pine were analyzed separately. delineated as The remaining tree species were grouped and Fir" due to the low confidence in accurate species identification between grand fir, Douglas-fir, and Englemann spruce during stand tallies. Large woody debris enhancing or providing cover for fish were combined to increase the sample size for regression analysis. One-way analysis of variance was used to make inferences about population parameters for various levels of channel constraint and large tree densities. The validity of the equal variance assumption was examined by constructing scatter plots of residuals versus the predicted values. Graphical tests were employed to determine the normality of the data distribution for all variables. Data were transformed as needed to induce normality (Appendix A2). Significance was determined at P<0.05. Significance levels of correlations, regressions, and analysis of variances are reported in the text where necessary. and 11 did not classify as old-growth (>25 trees/ha, DBH). Site 9 5O cm See Tables A3-4 for raw riparian, LWD, and pool data. 27 4 RIPRThI FOREST The six principal tree species within 30 in of bankfull for all channel types were Engelmann spruce, Douglas-fir (Pseudotsuga menziesii), grand fir, lodgepole pine, western larch, ponderosa pine and Pacific yew (Taxus brevifolia). Among all sites, the riparian stand tallies included only seven hardwood trees (black cottonwood, (Populus trichocarpa)) larger than 10 cm DBH. Hardwood shrubs were common streamside vegetation and included red-osier dogwood, and mountain alder. The frequency of each conifer species within zones A (0-15 in) and B (15-30 in), were variable among and between sites although stand density remained approximately the same (Appendix A5). For all sites, mean stand density for zones A and B were 471 and 458 trees/ha, respectively (Appendix A5). The mean composition of western larch and ponderosa pine ranged from 42 trees/ha in zone A to 67 trees/ha in zone B for all channel types (Appendix A5). Mean stand density and species composition did not vary between zones A and B (Figure 6). Mean volume of individual western larch and ponderosa pine generally decreased and increased, respectively, as you moved from zone A to B (Table 5; Figure 6) Riparian stands were commonly two-storied with shade tolerant species (e.g., grand fir) dominating the Due partially to the understory composition understory. (e.g., grand fir), mean volume for shade tolerant species was significantly less (P<0.Ool, two-sample t-test) than the shade intolerant trees that were limited to the overstory (i.e., western larch and ponderosa pine). Snag frequency ranged from 0 to 20.9 trees/ha and averaged 5.8 trees/ha for all sites. Percent snag composition for all trees greater than 30 cm DBH ranged from 0.6% to 8.9% and averaged 3.4% for all sites. Variation in microtopography (e.g., slope, aspect, floodplain width), fire return interval, and mortality from disease, has developed a patchy riparian stand. For all sites, mean stand basal area was 38.7 m2/ha (SD=17.4; Appendix A6). Zone A and B exhibited similar stand basal areas of 39,8 m2/ha (SDl6.9) and 37.3 m2/ha (SD=l9.8), respectively. Approximately 83% of the basal area was provided by two tree size categories, 30-50 cm DBH and >50 cm DBH. Basal areas of the two largest size categories were at near equal proportions (Appendix A6). Site 6 had the greatest basal area (71.7 m2/ha) and the highest density of trees (299.3/ha) greater than 30 cm DBH within 30 m of the bankfull channel (Appendix A6 and A7). Site 11 had the 29 Table 5. Riparian stand characteristics (trees >10 cm DBH) for zone A (0-15 in) and zone B (15-30 in). Snags per hectare (ha) and percent snags within the riparian stand (trees > 30 cm DBH). Data are means and included all study sites. ttFirtt trees include: Englemann spruce, Douglas-fir, and grand fir. LP= lodge pole pine; WL= western larch; PP= ponderosa pine. Riparian Stand Character Fir Mean Volume! Species 19.7 Mean Volume/ ha Mean Diameter 7320 25.5 Riparian Stand Character Fir Mean Volume/ Species 22.1 Zone A 0-15 in LP WL 12.5 1160 22.1 103.4 2610 47.8 Total PP 56.2 930 42.6 Zone B 15-30 in LP WL 10.0 79.6 -- 12,020 -- Total PP 91.9 -- Mean Voluine/ ha Mean Diameter 6860 25.3 Riparian Stand Character 1130 21.7 2790 44.5 2680 47.4 Zones A and B 0-30 rn Snags/ha 5.8 Percent Riparian Composed of Snags 3.4 12,960 -- Species Composition (#) Vo!ume/ha 500 10 400 8 . . .r.i.i.r.i 300 6 200 4 100 '" 2 S S 0 E I-' I! 'Is] 500 10: 400 300 200 100 0 > 5 P1IIIiIIIPI :': : tTrsisi: W1tisu uuia 7Tttsi*ui sr Figure 6. Species composition (trees/ha) and volume/ha withn zones A and B (0-15 m and 15-30 m from bankfull). 31 lowest basal area (8.5 m2/ha) and the lowest number of trees per hectare greater than 30 cm DBH (32.3/ha; Appendix A6 and A7). Site 11 exhibited sparsely forested sedge-dominated meadows (Carex spp.) immediately adjacent to the bankfull With the exception of sites 9 and 11, all study channel. sites exhibited A or B. 25 trees/ha greater than 50 cm DBH in zones Mean stand basal area within zones A and B were similar between channel types (Appendix A6). Similar to basal area, stand volumes (developed from species specific tree volume equations) between zones A and B exhibited similar volumes of 11,639 m3/ha (SD=5,978) and 12,308 m3/ha (SD=7,496), respectively (Appendix A8). However, mean stand volume of seral species (lodgepole pine, western larch, and ponderosa pine) within MC and UC channels (zones A and B), were approximately 2.5 times greater than HC channels (Table 5). 32 LARGE WOODY DEBRIS Dimensions and Frequency Distributions of LWD diameters and lengths were skewed toward smaller pieces (Table 6; Figures 7a and 7b). The smallest LWD category (i.e., <15 cm diameter) were the most frequently encountered. At each progressively larger LWD size category the frequency of encounters diminished. The two largest diameter categories (i.e., >50 cm and 30-50 cm) averaged 20% of the total mean LWD frequency (Table 6). Percent LWD composition of pieces >50 cm diameter averaged 10% and ranged from 2% to 19%. Appendix A9 shows the total LWD frequency within all study sites. Large woody debris frequency was greatest in site 13 and least in site 5. Highly constrained channels exhibited the least mean frequency on all LWD size categories, but UC channels exhibited the greatest mean frequency in all size categories. The greatest differences between HC and UC channels were at the larger size categories where mean LWD diameters 15 cm were twice as frequent in UC channels (Table 6). Variability within channel types precluded any significant relationships with the given sample sizes. Vo itune Large woody debris volume varied among study sites and was skewed to the larger pieces. Large woody debris 50 cm diameter exceeds 60% of the total volume in 11 of 15 sites Table 6. Large woody debris frequency per 100 m and percent volume separated into piece size categories. Size categories were: 1) 50 cm diameter, 2) 30-50 cm diameter, 3) 15-30 cm diameter, and 4) l0-l5 cm diameter. Diameters are measured at the large end. Means and standard deviations (SD) are given for major categories. Site Piece Frequency/l00 m 1 2 3 4 Percent Volume (%) Total 1 2 3 4 Highly Constrained 1 2 3 4 1.0 0.9 2.2 1.1 1.7 1.7 9.3 2.4 2.3 2.6 14.8 6.9 7.3 9.2 10.7 9.5 12.3 14.4 37.0 19.9 63 77 62 79 29 19 26 16 1.4 2.4 6.4 0.6 0.4 0.8 2.6 4.2 1.4 1.0 3.0 1.1 1.6 7.2 5.0 10.0 4.8 12.1 4.2 9.7 7.8 15.4 4.8 13.4 9.8 23.5 20.6 27.0 13.0 27.4 78 67 87 41 1.9 1.4 3.2 1.5 5.2 2.4 2.0 4.1 2.2 3.6 7.5 11.6 13.6 4.0 9.1 6.5 13.7 18.7 7.2 9.1 18.3 28.7 39.0 14.9 27.0 57 60 61 62 74 12 <1 <1 <1 4 1 19 24 3 <1 8 1 8 4 26 64 47 29 21 38 1 4 24 17 19 13 <1 6 2 <1 8 4 Moderate lv Constrained 5 6 7 8 9 10 15 12 <1 3 Unconstrained 11 12 13 14 15 20 26 27 24 2 1 5 '4 Table 6. Continued. Piece Freguency/100 Site 1 Highly Constrained median 1.0 mean 1.0 SD 0.1 3 4 Total 1 2 3 4 1.7 1.9 0.4 2.6 3.9 2.6 9.2 8.7 1.2 14.4 15.5 3.9 70.0 70.2 9.0 22.5 22.5 6.0 6.0 7.0 3.8 0.0 0.2 0.5 1.4 7.2 7.2 4.1 9.7 10.1 4.4 23.5 21.7 7.2 67.0 57.0 30.5 24.0 24.8 14.2 8.0 16.4 16.0 1.0 1.7 1.5 2.4 2.9 0.9 9.1 9.0 3.5 9.1 11.0 5.1 27.0 25.6 9.5 61.5 61.2 6.6 25.0 24.2 3.1 9.5 10.0 7.5 0.5 1.1 1.7 2.2 2.3 1.1 7.2 7.1 3.9 9.2 10.1 4.1 20.6 21.8 8.1 63.0 63.3 19.3 24.0 23.9 8.9 8.0 11.5 11.0 0.5 1.1 1.7 Moderately Constrained median 1.4 1.4 mean 2.3 2.1 SD 2.4 Unconstrained median 1.9 mean 2.6 SD All Sites median mean SD 1.6 1.4 2.1 1.8 Percent Volume (%) in 2 (4 600 500 400 300 WA. Diameters (cm) 7a 400 290 300 200 110 100 0 7b Lengths (m) Figure 7. Large woody debris diameter for all pieces measured (A), and length frequencies for all pieces measured (B). U' 36 (Table 6). The greatest total volume (zones 1-4) was within site 3, which had 11.5 pieces/lOO m 30 cm diameter (over 2.5 times greater thanthe mean; Table 6). Large woody debris mean large-end diameter ranged from 24.8 cm to 42.9 cm between sites (Table 7). Of the four HC channels, three exhibited the shortest mean LWD lengths when compared to all study sites (Table 7). Mean LWD volume per 100 m of stream was 26.6 m3 which includes all LWD zones of influence (i.e., areas within and outside the bankfull channel; zones 1 Table 8). - 4; The proportion of LWD volume lying outside of bankfull (zone 4) was significantly higher than the other three zones of influence (Table 8). The proportion of the volume within the bankfull channel (zones 1 and 2) averaged 33% (Table 8). Mean LWD volume per hectare was 156 m3/ha within the bankfull channel (zones 1 and 2) and 237 m3/ha within and above the bankfull channel (zones 1-3), respectively (Appendix AlO). Similar to total volume, sites 3 and 9 exhibited the greatest and least LWD volume/ha, respectively. Although relative abundance and volume of woody debris varied within and among zones of influence, abundance and volume of LWD was not found to be related to channel entrenchment. For all sites, bankfull width was positively related with total LWD volume per 10 bankfull widths (Appendix All). Only in MC channels was bankfull depth Table 7. Large woody debris frequency, mean dimensions, and mean volume (VOL) associated with the four hydraulic influnece zones ("Z" 1-4). Means and standard deviations (SD) are given for major categories. Site Number of LWD Measured Mean Length Mean Large Diameter VOL/ Piece Total VOL/100 in Stream Length (in3) Z:1-4 Z:1-2 0.8 1.0 1.4 0.6 11.1 14.6 74.6 14.1 2.4 4.4 32.3 5.0 42.9 35.1 35.1 24.8 29.1 23.7 1.8 1.2 1.3 0.7 0.5 0.4 18.7 35.2 23.0 19.0 6.6 10.7 11.8 26.0 6.6 9.9 1.0 4.2 30.8 28.1 28.1 35.9 42.5 1.1 1.0 0.8 1.0 1.8 31.4 38.2 32.7 15.7 50.7 15.5 11.0 7.5 22.1 (m) (cm) (m3) 7.8 7.1 13.1 8.6 34.9 38.4 36.9 30.8 11.5 11.4 9.4 10.9 10.1 10.5 14.8 12.6 10.8 8.9 12.5 Hiahlv Constrained 1 2 43 53 3 128 117 4 Moderately Constrained 5 6 7 8 9 10 44 146 27 165 28 102 Unconstrained 11 12 13 14 15 146 121 99 113 72 6.3 Table 7. Continued. Mean Length Site Highly Constrained median mean SD Unconstrained median mean SD All Sites median mean SD VOL/ Piece Total VOL/l00 in Stream Length (m3) Z:1-4 Z:l-2 0.9 1.0 0.3 14.3 28.6 30.7 4.7 11.0 15.2 0.8 32.1 31.8 7.3 1.0 1.0 0.5 18.9 18.9 10.0 8.3 9.9 8.8 12.5 11.5 2.2 30.8 33.1 6.2 1.0 1.1 0.4 32.7 33.7 12.6 11.0 12.5 6.5 10.8 10.7 2.1 34.9 33.1 5.8 1.0 1.0 0.4 19.0 26.4 18.1 7.5 11.1 9.2 (in) (cm) (m3) 8.2 9.2 2.7 35.9 35.3 3.3 Moderately Constrained 10.7 median 10.6 mean SD Mean Large Diameter Table 8. Large woody debris volume per 100 in for each size category within each of the four hydraulic influence zones: Zone 1 includes the percentage of the debris submerged during summer flow, Zone 2 within the bankfull flow cross-sectional area, and Zone 3 in the area directly above zones 1 and 2. Zone 4 includes the percentage of the LWD outside zones 1, 2, or 3, but in contact with the flood-prone area (Figure 4). Total volume within the l0-l5 cm diameter category was insignificant (<1%) and not included in the table. Diameter was measured at the large end. Means and standard deviations (SD) are given for major categories. >50 cm dia. 30-50 cm dia. (ms) Site zonel zone2 15-30 cm dia. (ms) zone3 zone4 (ms) zonel zone2 zone3 zone4 zonel zone2 zone3 zone4 0.3 0.4 1.6 0.4 0.2 0.2 4.6 0.5 Highly Constrained 1 2 3 4 0.3 0.8 10.0 0.4 0.9 2.5 13.6 1.4 1.5 3.5 7.3 1.3 4.3 4.5 14.8 27.2 0.1 0.1 1.4 1.0 0.7 0.8 4.8 1.4 0.7 0.9 5.4 0.7 1.8 0.8 8.5 3.1 <.1 0.1 0.7 0.3 0.2 0.1 1.9 0.4 1.7 4.4 8.2 8.5 10.3 25.5 0.4 0 1.1 2.5 1.6 1.4 0.6 1.3 0.5 0.3 1.8 0 0.4 0.1 <.1 1.1 0.4 0.1 0.5 0.3 1.6 0.2 0.6 0.1 0.7 0.3 0.4 0.9 0.4 3.9 5.9 3.3 1.2 0.3 1.7 1.1 0.1 0.7 3.6 1.1 0.5 0.4 0.8 0.5 0.1 3.0 4.3 1.5 0.2 Moderately Constrained 5 6 7 8 0.1 2.2 0.8 0.8 0.2 0.6 Unconsta med 9 10 11 12 13 14 15 0.7 4.0 1.2 0.9 2.8 4.2 6.7 3.4 2.9 0.3 0.2 2.8 5.5 3.4 3.2 15.3 0 3.6 2.7 1.5 5.2 3.5 3.0 8.5 0.4 0.4 9.8 18.4 12.0 3.0 15.6 0.6 0.3 0.5 0.1 1.0 0.5 1.2 2.4 0.8 0.7 0.2 0.8 0.9 0.7 1.2 2.7 1.7 1.8 0.6 1.1 0.9 0.6 3.0 1.3 3.3 2.3 2.5 2.5 0.1 <.1 0.8 0.4 0.3 0.3 0.7 0.3 1.6 0.7 2.1 0.2 Table 8. Continued. 30-50 cm dia. >50 cm dia. (mi) Site zonel zone2 Highly Constrained 0.6 2.0 median 4.6 mean 2.9 SD 4.8 6.0 (ms) zone3 2.5 3.4 2.8 Moderately Constrained 3.2 0.7 3.2 median 3.0 3.4 mean 0.8 SD 0.8 Unconstrained median 1.2 mean 1.9 SD 1.4 All Sites 0.8 median mean 1.7 SD 2.5 15-30 cm dia. (ms) zonel zone2 zone3 zone4 zonel zone2 zone3 zone4 9.6 12.7 10.8 0.6 0.6 0.7 1.1 1.9 1.9 0.8 1.9 2.3 2.4 3.6 3.4 0.2 0.2 0.1 0.2 0.2 0.1 1.8 2.2 0.7 0.4 0.4 0.1 0.4 0.4 0.4 1.2 1.3 0.8 0.6 0.7 0.4 2.1 1.9 1.0 0.1 0.3 0.2 0.6 0.6 0.5 0.3 0.4 0.2 0.9 1.1 0.7 zone4 2.5 2.8 4.4 7.6 9.3 3.4 6.0 5.3 3.4 4.3 2.7 12.0 11.8 5.9 0.8 1.1 0.8 1.8 2.1 0.8 0.9 0.9 0.3 3.3 3.4 1.7 0.3 0.6 0.7 0.7 1.3 1.4 0.4 0.4 0.3 1.5 1.8 1.8 3.2 4.4 4.4 3.4 3.5 2.8 9.8 10.3 8.7 0.6 0.7 0.6 1.4 0.7 1.1 0.7 1.1 1.2 2.5 2.8 2.1 0.2 0.4 0.5 0.5 0.9 0.9 0.4 0.4 0.4 0.7 1.4 1.5 0 41 related with LWD volume (Appendix All). However, HC channels consistently exhibited the least total mean volume, volumes for zone 1 and 2, and total volumes within different LWD size categories (e.g., 50 DBH; Tables 7 and 8). Unconstrained channels consistently exhibited the greatest mean volume among these variables. For large woody debris within or above the bankfull channel (zones 1-3), mean volumes for UC channels averaged 18.6 m3/lOO m, more than twice the volume of HC channels (7.0 m3/100 m; Table 7). Mean volume of LWD >50 cm diameter within or above the bankfull channel (zones 1-3) averaged 4.2 and 12.2 m3/lOO in for HC and UC channels, respectively. Moderately constrained channels often split the difference between HC and UC channels with an average of 7.3 m3/iOO in (Table 8). Recruitment The method of LWD recruitment was consistent between channel types (Table 9). Windthrow averaged 54% of the total LWD recruitment to the channel. Large woody debris transported or repositioned accounted for 25% of the total. The balance (21%) of the LWD was fluvially recruited to the channel. The proportion of LWD pieces with rootwads ranged from 7% to 55% and averaged 26%. Assuming that all pieces that were fluvially recruited retained their rootwads, an average of 84% of the pieces with rootwads were eroded into the channel. The dimensions of LWD pieces transported or 42 Large woody debris association with other pieces Table 9. Proportion of LWD associations: and delivery mechanism. single piece, groups of 2 or 3, and small debris jams in the channel (zones 1-4), and the proportion of LWD delivery mechanisms: floated, windthrow "WT", and fluvial. Means and standard deviations (SD) are given for major categories. Delivery Mechanism Pieces Association Single >2 pieces Site (%) (%) Jam Float (%) (%) WT Rootwad Fluvial with w/out (%) (%) (%) (%) 21 32 24 17 49 42 44 68 30 26 32 15 53 19 36 47 81 20 80 39 34 26 32 54 63 44 49 88 68 7 3 30 20 11 15 55 10 26 22 45 90 74 78 93 81 73 64 12 11 21 45 45 33 31 27 31 28 35 79 93 69 72 65 38 32 16 72 68 16 Highly Constrained 1 2 3 4 82 76 56 79 9 15 16 5 9 9 28 16 64 Moderately Constrained 5 6 7 8 9 10 77 67 97 63 79 79 14 23 10 9 2 1 29 20 8 1 5 16 17 13 25 26 23 24 5 5 15 25 24 38 28 1 7 19 Unconstrained 11 12 13 14 15 82 70 62 67 65 Highly Constrained median 77 12 11 mean 73 SD 12 5 Moderately Constrained 18 median 78 17 mean 78 SD 13 Unconstrained median 67 mean 69 SD 10 24 22 8 5 All Sites median 76 mean 74 16 17 SD 11 8 12 10 11 39 7 12 16 22 24 46 51 28 26 9 6 12 8 6 5 4 28 25 14 58 61 16 13 14 10 21 23 17 80 77 17 10 25 26 8 45 51 18 27 24 12 28 24 11 72 76 11 25 25 10 49 54 16 20 21 11 22 26 14 78 74 14 9 3 9 9 7 43 repositioned averaged 26.2 cm diameter and 5.8 m in length, significantly smaller and shorter than the average for all LWD pieces (34.9 cm diameter; 10.8 m; P < 0.05 two-sample t test). Large woody debris delivery mechanisms were not significantly different between channel types. When comparing the means, both HC and uc channels exhibited similar proportions between the three delivery mechanisms (i.e., fluvial, windthrow, and erosion; Table 9). Association with other Debris Twenty-six percent of the LWD within the channel were associated with other pieces (Table 9). Large woody debris frequency and volume was negatively related with the percent LWD classified as an "individual", however, LWD classified as being within groups or jams were not related with LWD frequency or volume (Appendix Al2). Geomorphic variables were not found to be related with the percentage of LWD pieces within individual, or group associations (Appendix Al2). Jam associations were positively related with the interaction term (bankfull width x gradient), a likely indicator of stream power. Large woody debris classified as individuals exceeded 60% within all sites but site 3, which also exhibits the greatest total LWD volume and the greatest percentage of LWD associated with jams. Unconstrained channels had the lowest proportion of individual LWD and the 44 highest proportion in a clumped association. The proportion of LWD within a jam association averaged 10.6% for all sites (Table 9). Horizontal Orientation The greatest proportion of LWD was positioned approximately perpendicular to the channel (70 - 110 degrees; mean 44.1%; P<0.005, two-sample t-test). Downstream (110 - 180 degrees) and upstream (0 - 70 degrees) orientations average 34.0% and 22.1%, respectively (Figure 8). Orientation showed no significant relationship with gradient, channel type, or LWD dimension (P>0.05, Tukey multiple comparison test). Association with Large Tree Density The variability in large diameter tree density within old-growth grand fir stands did not significantly influence LWD density within the channel or flood-prone area. Conversely, LWD volume/l00 m within the ban]cfull channel (zones 1-2) was related to the number of large trees/ha (50 cm DBH) within 0-15 m and 0-30 in from the bankfull channel (r2=37, P=0.022 and r2=45, P=0..009, respectively; Figure 9a). However, LWD volume within the flood-prone area (zones 1-4) was related to the number of large trees within 15-30 m from the bankfull channel (r2=35, P=0.025; Figure 9b), and not to the number of trees within 0-15 in or 350 319 300 250 > C C 200 iso 103 100 7 6 50 :ii 0 deg. 45 deg. 90 deg. 135 deg. Degree Categories Figure 8. Horizontal orientation for all measured large woody debris (n=719). Where 0 degrees and 45 degrees are oriented up-stream. 180 deg. -.- b 4 4 3 C,, 3 0 N E 2 2 E 1 I I I A 0 20 40 60 80 Trees/ha >50 cm DBH (0-30 m) 100 A 0 20 40 60 80 Trees/ha >50 cm DBH (15-30 m) Figure 9. Relationship of LWD volume/lOO in (zones 1-2) and trees/ha 5O cm DBH from 0-30 in (A), and relationship of LWD volume! 100 in (zones 1-4) and trees/ha >50 cm DBH from 15-3 0 in (B). 100 47 0-30 in Of the 13 old- from the bankfull channel (P>0.05). growth study sites, 8 sites exhibited a stand with more than 40 trees/ha (>50 cm DBH), and two or more sites exhibited stands with more than 40 trees/ha (>50 cm DBH) within each of the three channel types (Appendix A7). The density of large diameter trees were not correlated to drainage area, channel gradient, channel type, or base elevation of the site. Mean total frequency of LWD 2.3/100 in 50 cm diameter averaged and 1.1/100 m for stands with more than and less than 40 trees/ha (>50 cm DBH), respectively. Similarly, mean total LWD volume/100 in (all zones of influence) averaged 33.0 m3 for sites with 40 trees/ha (50 cm DBH) and 18.9 in3 for sites with <40 trees/ha (>50 cm DBH). However, significant differences for frequency and volume were only found at the 90% confidence interval when comparing sites with more than and less than 40 trees/ha (>50 cm DBH; P<0.1; Tukey multiple comparison test). The composition of each size category within the riparian stand (for all sites) closely resembled the size composition of LWD (Figure 10). However, larger size categories of LWD were significantly more likely to form pools. For example, 5% of the pieces forming poois were 10-15 cm in diameter, although 44% of the pieces measured were within this size category. In contrast, 17% of the pieces forming pools were >50 cm in diameter, although 8% of the pieces measured were within this size category (Figure 10). Riparian Stand Composition LWD Composition 10-15 cm DBH 4982 (33%) 15-30 cm DBH 4316 (28%) Forming Pools 10-15 cm dia. 15-3 0 cm dia. 252 (47%) 10-15 cm dia. >5OcmDBH >50 cm dia. 1322 (9%) 110 (8%) 15-30 cm dia. 30-50 cm DBH 4601 (30%) 506 (36%) 25 (5%) >50 cm dia. 30-50 cm dia. 178 (13%) 30-50 cm dia. 91(17%) 169 (31%) Figure 10. Riparian stand composition, total LWD pieces measured, and LWD forming pool habitats by size category. 49 POOLS Association with Large Woody Debris A total of 262 primary pools were measured in the 15 study sites, of which 63% (n=165) were formed by LWD. Primary pools formed by LWD reacted differently to geomorphic variables than pools not formed by LWD. frequency of pools (per 100 m) formed by related to channel gradient. pools not formed by LWD LWD The was negatively In constrast, the frequency of were positively related to channel gradient (Appendix A13a, A13b, and A14). Similarly, LWD/100 m was positively related to the number of pools formed by LWD (Figure 11). Entrenchment, channel gradient, bankfull depth, and the interaction term were the most common variables to be related to pool frequency and the spacing between pools (Appendix Al4-A16). Pool frequency and spacing were best predicted by the frequency of m; Appendix A14-Al6; P<O.01). LWD (per 100 The pool frequency and spacing relationship with channel gradient, bankfull depth and the interaction term was less precise (Appendix Al4Al6). However, only pool frequency and spacing not formed by were related to entrenchment (Appendix A14-A16). LWD A comparison of primary pools/100 m formed and not formed by LWD for HC, MC, and UC channels are displayed on Figures 12a, 12b, 12c and 13). Geomorphic and LWD relationships with primary pools are summarized in Figure 14. 50 8 6 >1 a) 0 cl-4 0 0 ri:i 0 0 %14 e 10 20 30 40 50 8 LWD/100 in Figure 11. Relationship of pools formed by LWD and LWD/lOOin. 8 Pools Formed by LWD 7 7 6 6 7 6 S 0 C 5 4 4 3 2 2 1 1 3 2 1 n HC 12a MC a UC HC 12b MC UC HC MC UC 12c Figure 12. Relationship of channel constraint on all primary pools (A), pools formed by LWD (B), and pools not formed by LWD (C). The width of the box is one interquartile range. The horizontal line is the mean. Ui H Highly Constrained Formed by LWD 27 (40%) Moderately Constrained Unconstrained Formed by LWD 643°h) Formed by LWD -s . + + . + + + + + , , , J. + + , , + + + + , %_ 74(80%) #+,+ + , + + + + + + ,, + , , , , + , + + + + 4 + 0 4 4 4 +... -,.,+ + 4 + 4 0 0 4 + + I'. 4 4 4 + + 0 + + + 1+ + + + + + + 0 + + + + 1+ 0 + + 4 4 + + + + + + + 4 + 0+4+4 +0+4+ + + . 0 + 0 4 + + ++ +0++4 +++, + + 0 + + + + 0+ '_ 0 0+ 0 _+_+_+ Not Formed 40 (60%) Not Formed 38 (37%) Total primary pools formed and not formed by LWD. Figure 13. percentage are given. Not Formed 19 (20%) A total number and Ui 53 Total Primary Pools (n=262) BFD (+) BFW (-) Formed by LWD Not Formed by LWD (n=165) i (n=97) Entrenchment (+) BFW LWD Volume (+) (-) LWD Basal Area (+) LWD Abundance () BFD (+) Entrenchment (+) Gradient (+) BFW (-) BFD (-4-) LWD Abundance (+) BFW INT (+) Scour (n=75) Plu] (n=l5) [ Dammed Scour (n=4) (n=64) riunge Dammed (n=50) (n=51) Hierarchical structure and statistically Figure 14. significant correlations (P<O.05) of the primary pool analysis. The slope of the linear regression line is Bankfull width, denoted as positive (+) or negative bankfull depth and the interaction term (Bankfull width x gradient) are denoted as BFW, BFD, and BFW INT, respectively. (-). 54 Large woody debris was an important formative agent for pools in all channel types. An average of 11% (range: 4- 17%) of the 1404 LWD pieces functioned to form pools (Table 10). An additional 3.3% (range: 0-13%) of the total LWD pieces functioned to enhance pools or provide overhead cover for fish. The percentage of LWD functioning to form pools was primarily related to entrenchment, gradient and bankfull depth (Appendix A17). The percentage of LWD forming pools declined with increasing gradient, and bankfull depth, but increased with entrenchment indicating that more of the LWD in UC channels formed pools (Appendix A17). Contrary to the LWD which formed pools, the percentage of LWD physically enhancing pool size or depth or providing overhead cover for fish, was positively correlated to gradient and bankfull depth (Appendix A17). Pools formed by LWD were similar in size to pools formed by other processes. The function of LWD associated with pools habitats were influenced by channel constraint. Appendix A18 lists the function of LWD associated with primary pools. Highly constrained channels exhibited the smallest proportion of LWD formed pools, and the greatest proportion of LWD (associated with the pool) having no influence (Figure 15). Compared to UC channels, the proportion of LWD with no influence was three and five times higher in MC and HC channels, respectively. The mean size of primary poois were nearly 40% larger in UC channels than HC or MC channels. 55 Table 10. Function of LWD within the channel. Percent LWD forming pools, enhancing pools, or providing cover for fish. Large woody debris forming or enhancing pools also provided cover for fish. Pools listed are primary pools only (Pool area Medians, means and standard Wetted width2). deviations (SD) are given for major categories. Formed Pools Site Enhanced Pools (%) (%) Provided Number of Measurements LWD Pools Fish Cover (%) (#) (#) jjqh1y Constrained 1 2 3 4 2 4 6 14 7 0 13 11 2 3 2 2 13 16 11 28 43 53 128 117 20 22 146 Moderately Constrained 5 6 7 8 9 10 16 10 11 14 11 14 5 2 7 1 4 1 4 1 4 1 44 6 27 31 165 28 102 4 5 0 18 1 1 1 6 1 0 1 23 3 0 1.5 2.5 3.1 2.0 3.8 4.9 Unconstrained 11 12 13 14 15 12 17 9 16 11 Hiqhly Constrained median 5.0 mean 6.5 SD 5.3 Moderately Constrained median 12.5 1.0 mean 12.7 1.7 SD 2.3 Unconstrained median 12.0 mean 13.0 SD 3.4 All Sites median 11.0 mean 11.1 SD 4.4 3 21 10 29 10 1.5 2.5 2.3 1.9 2.0 1.8 1.8 1.0 1.0 1.2 --- 1.0 1.7 2.0 1.0 2.3 2.8 --- 146 121 99 113 72 Form Enhance ECover No Influence 100 80 20 I )0 00' + 0 .1+ + HC )0000 ....... . _______ :>;. 0000 MC .-.- - .-.- ...... ________ UC Channel Constraint Function of LWD within pools for different levels of channel constraint. Figure 15. Highly constrained = HC, moderately constrained = MC, and unconstrained = UC. The vertical bars show the standard error. - 57 Pool Size Table 11 lists the average primary pool area and volume associated with each study site. Site 9 exhibited the lowest pool frequency and the greatest spacing between pools (also with the least total LWD volume within the bankfull channel; Table 11). Site 12 exhibited the greatest pool frequency and lowest spacing between pools. Due to the size of the channel in site 10 (2.1 m), pocket pools were difficult to distinguish and were not delineated when surveyed. Mean pool area of UC channels were 58% and 65% larger than MC and HC channels, respectively (Table 10). Regressions were undertaken using geomorphic variables and average pool area and volume (Appendix A19) . and volume were related to basin area. Both pool area Although pooi area was also related to both entrenchment and gradient, these variables were not related to pool volume. Pool area and volume were not related to LWD frequency or volume within the channel per 10 bankfull widths (Appendix Al9). Frequency Table 10 lists the frequency and average spacing of primary pools within all 15 study sites. Primary pooi frequency per 100 m was not related to entrenchment, gradient, basin area or the interaction term (bankfull width x gradient; Appendix A20). Similarly, primary poo1 frequency was not different between HC, MC, or UC channels. Table 11. Pool frequency, spacing, mean residual pool area, mean residual volume, and pooi to riffle ratio (% of total wetted area). Bankfull width and wetted width are denoted as wetted width2). Pocket pools = (l/2 wetted width2 but "BFW" and "WW", respectively. Medians, means and standard deviations (SD) are given for major categories. Site Primary Pools 10 BFW 10 WW Area Volume P:R Ratio Pocket Pools Total 10 WW Total 100 m (/1) (#) (#) (#) (m2) (ms) (%) 4.3 4.3 4.1 3.7 3.3 2.8 3.1 2.1 1.5 1.7 1.3 1.5 21.0 30.2 13.2 9.3 11.3 20.9 5.5 3.9 26:74 39:61 21:79 17:83 0.5 0.1 0.3 0.6 2.6 2.6 2.7 2.8 2.2 3.6 5.2 3.4 1.8 3.3 1.1 1.8 1.8 2.0 1.8 2.5 0.7 1.0 19.2 24.2 27.7 19.0 18.3 6.9 7.6 9.4 12.1 6.9 8.3 1.9 24:76 23:77 25:75 22:78 14:86 16:84 0.5 0.8 0.3 0.9 0.2 23 29 14 3.6 6.8 3.2 3.3 4.0 3.1 7.3 1.9 2.5 2.7 1.7 2.8 1.8 1.6 1.2 35.9 34.3 15.9 42.3 22.9 15.8 9.9 7.3 19.6 9.0 46:54 65:54 18:82 47:52 32:68 0.2 0.4 0.3 0.2 0.1 12 12 17 12 (#) (%) Highly Constrained 1 2 13 16 3 11 28 4 24 6 21 28 Moderately Constrained 5 6 7 20 22 8 31 9 5 10 18 6 -- 26 29 -- Unconstrained 11 23 12 13 14 15 21 10 29 10 9 U, Table 11. Continued. 100 m Site (#) Highly Constrained 4.2 median 4.1 mean SD 0.3 Moderately Constrained 2.6 median mean 2.8 SD Unconstrained median mean SD All Sites median mean SD 10 BFW Primary Pools 10 WW Area Volume P:R Ratio (%) Pocket Pools 10 WW Total (%) (#) (/1) (m2) (ms) 3.1 2.9 0.5 1.5 1.5 0.2 17.1 18.4 9.2 8.4 10.4 7.7 24:76 26:74 9.6 0.4 0.4 0.2 22.5 19.8 9.6 2.6 2.7 19.1 19.2 7.1 8.0 7.7 3.4 22:78 21:79 4.5 0.5 0.5 0.3 26.0 24.2 (#) 0.5 .1.6 1.8 1.8 0.5 3.6 4.2 1.5 2.5 2.8 1.1 1.5 1.6 0.5 34.3 30.3 10.6 9.9 12.3 5.2 46:54 42:58 17.6 0.2 0.2 0.1 12.0 12.4 2.9 3.6 3.6 1.1 2.7 2.8 1.2 1.5 1.6 0.5 21.0 22.7 10.0 9.0 10.0 5.4 24:76 29:76 14.0 0.3 0.4 0.3 17.0 17.5 9.1 8.3 U, However, when pocket pools were included, a model with bankfull width and bankfull depth as independent variables, was related to the number of pools per 100 In (r2=0.51, Individually, bankfull width and bankfull depth PcZO.0l). were not related to pool frequency. The frequency of pocket pools within HC or MC channels are approximately two times that of UC channels (Table 11). Spacing Primary pool spacing per 10 bankfull widths, was related to mean bankfull width (r2=0.67, P<0.00l) and LWD volume (r2=O.39, P=0.0l2) within the bankfull channel (Appendix A20). The spacing of primary pools per 10 wetted channel widths related only to the LWD volume within zones 1 and 2. The primary pool spacing (average pool spacing per average 10 bankfull channel widths and 10 wetted channel widths) was not related to basin area or entrenchment. Again, when pocket pools are included, pool frequency per 10 bankfull widths was related to mean bankfull depth (r20.58, P<0.00l). Percent Pool Area The percentage of stream area in pools (summation of pool area per total stream area x 100) decreased as the average channel slope increased (r2=0.28, P<O.05). The average proportion of total wetted area classified as pools 61 was 29% (range: 16-65). Riffles, on average, comprised 71% of the total wetted area. Mean percent area in pools was greater in UC channels (42%) than in HC (26%) or MC channels (22%), respectively. When comparing the means, UC channels had a statistically greater percentage of their area in pools, compared to MC channels (F=4.71, P=O.031; Tukey's One Way Analysis of Variance). Basin area, entrenchment, LWD frequency, LWD volume, or the interaction term (bankfull width x gradient) were not related to percentage of stream area in pools (P<O.05, Simple Linear Regression). Slow-water Habitats: Scour, Plunge, and Dammed Large woody debris disproportionately favored the formation of plunge and dammed pool habitats. Plunge pools were most likely to be formed by LWD (91%), followed by dammed pools (76%), and scour pools (46%). Of the 96 pools not formed by LWD, scour pools made up 79% of the total, dammed pools 6%, and plunge pools 4% (Table 12; Figure 16). Appendix A2l, A22, A23 and A24 lists the relationships of LWD and geomorphic variables on slow-water habitats. Frequency and size of scour pools not formed by LWD decreased as LWD frequency (per 100 m) increased. Frequency, size, and spacing of scour pools formed by LWD were not related to LWD frequency, but were best predicted by the entrenchment, gradient and the interaction term. frequency of plunge pools (per 100 m) formed by LWD was The Slow-water Table 12. The percentage of slow-water habitats formed and not formed by LWD. habitats include scour pools, plunge pools and dammed pools. Medians, means and standard deviations (SD) are given for major categories. Not Formed by LWD Formed by LWD Site Number of Pools Dammed (%) Plunge (%) Scour (%) Number of Pools Dammed Plunge Scour (%) (%) (%) (n=ll) (n-14) (n= 3) (n=12) 0 7 0 0 27 50 67 25 73 43 33 (n=l3) (n= 8) (n= 3) (n= 8) 0 0 0 0 100 12 33 12 2) 50 Highly Constrained 1 2 3 4 (n= 1) (n= 2) (n= 8) (n=l6) 0 0 0 100 100 38 25 62 0 0 25 50 42 29 33 39 33 36 29 29 33 67 28 (n (n= 4) 0 0 0 11 52 22 17 17 19 44 72 29 34 (n= 5) 27 0 0 56 100 (n=11) (n= 2) 0 0 0 0 0 0 0 0 0 0 75 Moderately Constrained 5 6 7 8 9 10 (n= 7) (n=14) (n= 3) (n=23) (n= 3) (n=l4) 29 42 33 52 0 36 9 12 88 67 76 50 100 Unconstrained 11 12 13 14 15 (n=18) (n=21) (n= 9) (n=18) (n= 8) (n (n 0) 1) 100 0 100 100 100 Table 12. Continued. Formed by LWD Dammed Site Highly Constrained median mean SD Scour Dammed (%) (%) (%) (%) 12.5 15.8 18.9 43.5 46.8 43.7 25.0 37.5 47.9 17.6 34.5 35.3 4.7 29.0 32.5 18.9 17.0 20.4 19.5 19.0 21.4 16.0 56.0 58.2 29.1 0 0 0 25.0 23.8 18.6 33.0 42.4 31.6 33.0 42.4 31.6 0 Moderately Constrained median 34.5 mean 32.0 SD Uncontrained median mean SD All Sites median mean SD Plunge Not Formed by LWD 0 1.8 3.5 12.0 17.8 19.8 7.6 14.8 Plunge Scour (%) (%) 38.5 42.2 20.0 58.0 56.0 21.2 0 2.0 4.8 82.0 80.2 19.7 0 0 0 100.0 80.0 44.7 0 76.0 73.7 30.5 12.1 21.2 Formed by LWD Not Formed by LWD Dammed 51 (31%) _T7 _, + 4 + 4 4 + +4,4+,, Plunge 49 (30%) Plunge 16 (16%) 00000 ::: 0000 +4+,,,,, + ' + ,,. ,_+_+_+_,_, +,,,,,+,++, + )0000c' 4444+44+44+4+ 4 + 4 + 4 4 4 + + + + + 4 + ' Dammed A (Aol ++++++,+.+ 1 I?fO .++,+,,,.,.,,.., ,,,,,,.,,.++++ A + +4+ + 4++ + + 4 + + , + +4 + + 4+4 + + 4 + + +1 44++ + 44+4 + + jfr + + 4 4 + 4 4 4 4 4 4 4 +4 ++ ++4 ++ 4 + 4+4+ + + ,++,++++, + +4+4+ + ,++,+,,,++ 4,, 4 + + 4 4 + 4 ++,++,+4 + , 4 + . Scour 79 (80%) +4,44,4+4+ '.4+,.. Scour 62 (38%) Figure 16. Number of slow-water habitats formed and not formed by LWD for all sites. Pies are proportional to the number of primary pools. 65 related exclusively to LWD frequency. Pool frequency and spacing formed by LWD were not related to entrenchment, gradient or the interaction term. was related to basin area. However, plunge pool size The spacing between plunge pools (per 10 bankfull widths) formed by LWD decreased as LWD volume within the bankfull channel increased. Since plunge pools not formed by LWD were nearly an exclusive feature of HC channels (Figure l7a), all but bankfull width and basin area of the geomorphic variables were not related. Similar to plunge pools, the frequency of dammed pools formed by LWD was related exclusively to LWD frequency (Figure 17b). Dammed pool size formed by LWD was similarly related to basin area, however, additional relationships with channel gradient, and the interaction term were also found. The spacing between dammed pools formed by LWD were related to LWD frequency and volume within the bankfull channel. Due to the small sample size (n=5), a statistical analysis was not pursued for dammed pools not formed by LWD. Association of Slow-water Habitats with Channel Constraint Channel constraint was a key factor for determining primary pool frequency, spacing and size for specific slowwater habitats. Table 13 compares selected mean pooi frequency, spacing, size, and pool area between HC, MC, and tJC channels for each slow-water habitat. Highly constrained and UC channels both exhibited a significantly greater 17a 100% 80% 60% cL) 0 cL) -( 40% 20% 0% Not Formed by LWD +44+4+0 4+44.0+4 +4+4+4+ +++++++ +40+4++ +0444++ ++++,, 04+444+ +4+4+,, +400+4+ +o4 +0+4+++ +4,,,,, 44++++ +0+40++ 0+44+++ +.+++,+ 0+4++++ +40444+ ,,.,,,+ +0+++++ 44+4++ +4+4+4+ +44++0 +040+0+ +4+4+++ 04+4+++ 0+4+4+ +++++++ 00+4+4+ +4+49++ ,+,++ 9+4++++ +40+04+ ,+,++,+ ++,,++ 0++++++ +,,,,,+ +4+4+.. 4+444+4 +400+++ +04+44+ +44+,,, ,++4+, 0+4*9+0 +40+400 +0+4+4+ 0+4++++ 004+444 4++++ 4+40+0+' +040+40 +4+00+4 +40+44+ +044+44 44444 0000+++ #4+00 +4+49+4 4+0+44+ 4404+ +4+4+++ ,+,,+++ 400+0+ ++++++, 44+4+4 +4004+4 +++,++ 4,,,,., 4+0+9+4 +44++++ +4+4+4+ +4+4+4+ +0+++4+ 4+4+40+ ++++,+, 4+4++++ 040+04+ +,+,+++ 4,..,,, +44+4+9 4+,,,,, +44+4+0 +4++.++ 9+4+4+4 4+44+4+ 0+4+44+ +4+,,,, 00+0+44 4++0+++ ,,+++,4 +4+0000 +44+44+ +44+9+4 +4+0+4+ 4+4+0++. +4+4,4+ +++++++ 4+4++++ +4++4++ +4+0+9+ +440+9+ 4+4+44+ +4+4+4+ +0+4+4+ 4+9++++ 444++ 4+9+0++ +44+44+ +4+4+4+ +4+++++ 44+4+9+ 4+4+9+4 +4+0+9+ 4+++4++ 9+++++ +4+,,,, +4+.,,. ,+,,++ +4,4,4+ +4+94+4 4+4+44+ +44++++ +0+4+++ ,,,,,+, 4+,,,., +4+9+4+ 4+++++ 4+94+4+ ++,4,+, +4+,,.. 4+,,.,, 4+4+4++ +4+4+4+ +4+4+++ ,,+,,, .9+4+,, 4+4+44+ 4++4+++ 4++++4+ +444+44 4+4+94+ +9+4+4+ +4+0+4+ +4+4+4+ 44+9+44 +4+4+4+ 404+440 +4+0+44 +4+44+4 4+4+,,, +4+4+0+ 4+0+4+4 4+4+4+4 04+4+4+ 4+0+4+4 4+4+9+4 004+4++ 4,,,,,, 4,9+4,, +4+4+4+ 0++++++ +44,4,, 4+4+0++ 4+9+4+4 +4+4+4+ +0+4+4+ +0+4+4+ 4+0+4+4 .4+4+,. 4+,,,,, +44+4+, +,+++++ 0++0+++ +044+4+ +++++0 4+0+9++ +4,,,,, +44,4,, 4+4+4+4 0++++++ 44+4++4 0++++++ 0++++4+ 0+4+4+4 40+++++ 4+++++ +0+0+++ 00+4+0+ +4+,,,, 40+0404 +4+,,., +4+94+0 4+0++++ +4+++94 .4+4+44 UC HC MC ++++ 17b 100% Formed by LWD 4+444 4+,,,,. ,,,,+,+ ++++++ 4.4+,,, +4+4+++ .4,,,,, +4,,,,, 4+,,,,, ++,4++, 4,,,,,, 4+44+4+ 4,,,,,, 4+,..,. 0++++4++ 80% 44+4444 4,,,,,, +++4+++ ++++ +44+4+4 ++++4+ + + + + . + + 4 + 4 + + +++ 4+++44+ 4+4+4+4 44+444+ .4,,.,, 4+4+44+ ++++4+ +++4++ 4,,,,,, 4+44+4+ +44+44+ +4+44+4 4+44+4+ 4+++++ +4+.,,, .4,,.,, +4+4+4+ 4,..... +4+,., +4.,,,. '''4.., '4,.,,, 4+4+++ ''+4,,. '''''+4 '.4,,,, ''4+,,, 4+.,.,, 4+,,,,,. 4+++4+ +4++4++ +4+++++ 44++++ .4,,,,, 4++++++ 4,,,.., 4,,,,., '''.4,, 4,,..,, 4 4+,,,,, 44+4+44 +4.,,,, 4+,,,,, .4,,,,, +4+4+4+ +4.,,,, +4,,,., +++4+++ 4+..,,, +++++ 44+++++ 4,4+44+ +4,,,,, +4444+4 +4,,,., 4.,,,., +,,,., 4+,,,,, 60% 40% 20% 0% FTC MC Percent mean frequency of slow-water habitats not formed (A), and Figure 17. formed (B) by LWD. Highly constrained = FTC, moderately constrained = MC, and unconstrained = UC. UC 67 Table 13. Differences in slow-water habitats (primary Results of pools) between degrees of channel constraint. Tukey's One Way Analysis of Variance. Sites 1-4 were highly constrained = "HC", sites 5-10 were moderately constrained = "MC", and sites 11-15 were unconstrained = "UC". An "S" indicates that the mean is significantly different from the corresponding level (P<0.05). Pools/100 m Level HC MC UC Pools/lOO m Not Formed by LWD MC Level HC HC . S . HC . MC S . S NC . UC . S . UC S Plunge Pools/lOO m Not Formed by LWD Level HC MC UC Plunge Pools/lO BFW Not Formed by LWD NC HC Level HC . S S HC . MC S . . MC S UC S . . UC S Scour Pools/i.00 m Formed by LWD Level HC MC UC . Scour Pools/b Formed by LWD HC Level S UC S UC S BFW MC UC HC . . S HC . . S MC . . S MC . . S UC S S . UC S S Percent Total Stream Area in Pools Level HC MC UC Scour Pool Area (m2) Formed by LWD MC Level HC UC HC . . . HC . . S MC . . S MC . . S UC . S . UC S S frequency of primary pools than MC channels. However, for primary pools not formed by LWD, HC channels exhibited a significantly greater frequency than UC channels. In contrast, LWD formed 31 and 27% of the scour pools within HC and MC channels, and 68% within UC channels (Figure 17b). Relationships between entrenchment and pools were most evident for plunge pools (not formed by LWD) and scour pools (formed by LWD; Appendix A20-A24). Within HC channels, 42% of plunge pools were the result of LWD. Of the 40 total plunge pools within NC and UC channels, all but one was formed by LWD. Scour poois formed by LWD were significantly larger and more abundant in UC channels than the other two channel types (Table 13). were formed by LWD. Of the 56 dammed pools, all but 5 Dammed and plunge pools were exclusively formed by LWD within tIC channels. DISCUSSION INFLUENCE OF RIPARIAN VEGETATION ON LARGE WOODY DEBRIS Contrasts in conditions of stream debris in different forest types reflect differences in stand density, stand composition, rates of LWD decay, and successional dynamics of the forest ecosystems supplying LWD to streams (Swanson et al. 1984). Grand fir climax stands along eastern Oregon streams, for instance, tend to carry lower biomass than western hemlock forests in western Oregon because the stocking density of large (greater than 60 cm) stems is less in eastern Oregon streams (Cf. Swanson et al. 1984). In terms of tree growth rites and biomass production within eastern Oregon forests, grand fir stands are very productive, particularly those within riparian systems that often are characterized by deep soils and high-moisture regimes (U.S.D.A. and U.S.D.I. 1994). However, largely due to historically frequent small low-to-moderate intensity fires, grand fir climax associated stands often exhibit a lower overall stem density, but a greater seral species component (e.g., western larch) within the overstory (Brown et al 1994; Harvey et al 1994). Fire not only influences LWD recruitment by manipulating stand composition and structure (Agee 1990; Kauffman 1990; Baker 1992), but also by providing f ire- 70 killed trees (Minshall et al. 1989; Young 1994). In addition, low order streams would likely be affected more severely than higher-order ones because fire is more likely to burn an entire low order drainage (Minshall and Brock 1991). Minshall et al. (1990), found that long-term fire recovery of low order forested streams can largely be dependent on elevated LWD recruitment from fire-killed trees within an 30 m corridor. The 15 streams sampled in undisturbed grand fir climax stands contained an average of 156.1 m3/ha of LWD within the bankfull channel (zones 1 and 2) and 237.0 m3/ha within and above the bankfull channel (zones 1-3), respectively. These results are similar to other low order old-growth stream studies (Table 14), including streams in southeast Alaska where LWD within the bankfull channel averaged 183 m3/ha (Robison and Beschta 1990b). At higher elevations, 11 Colorado streams associated with old-growth Engelmann spruce and subalpine fir (Abies lasiocarpa) were also similar exhibiting 263 m3/ha within and above the bankfull channel (Richmond 1994). Higher LWD volumes were found in undisturbed reaches of 11 northeastern Oregon streams which averaged 379 m3/ha within and above the bankfull channel (Carison et al. 1990; Table 13). However, Carlson et al. (1990) also found that an average of 14% of their unmanaged stands were composed of snags. In contrast, snag Table 14 (1 of 4). Comparison of volumes and densities of large woody debris (LWD) in selected low-order streams similar in size to this study (2-11 in bankfull channel widths) flowing through undisturbed forests. This list includes drainage basin area, bankfull channel width, channel gradient. Basin Area Forest Type and Location (ha) Age mean(range) Abies grandis Blue Nts, OR. Old 2360(809-4047) Abies cirandis/Picea engelmannii Northeasten OR. Old 1445(700-2500) Hardwood Smokey Mts, TN. Bankfull Channel Width (m) mean(range) 6.3(3.8-11.0) 4.0(2.3-6.1) 200 71(44-96) 5.5(4.6-6.5) 200 46(21.70) 4.8(3.4-6.2) Stream Gradient (%) inean(range) 11.3(0.5-7.1) 4.8(2.0-7.1) Picea-Abies Sinokey Mts, TN. Picea engelmannii Idaho 200 965(900-1030) Northeastern CO. Old 1248(240-2910) Picea sitchensis Southeast AK. 300-500 -Picea sitchensis/Thu-ja plicata Western WA. Old 2486 (400-8700) Picea sitchensis/Tsuga heterophylla Coast Range OR. Old -Southeast AK. old 91(50-153) Pinus Idaho 200 6710(6670-6750) 3.0(2.3-3.7) 5.3(3.7-10.0) 2.6(0.5-6.0) 3.5(2.1-4.8) 6.5(3.6-9.0) 11.3 (1.0-18.0) 4.5(2.0-7 .3) 9.0(2.8-22.6) 2.1(1.6-2.5) 6.1(4.6-8.8) 6.0(4.7-7.3) -4 Table 14 (2 of 4). Continued. LWD Volume Forest Type m3(ha) and Location inean(range) Abies grandis Blue Mts, OR. 156(29-475) Abies grandis/Picea encielmannii Northeasten OR. 379(232-550) Hardwood Smokey Mts, TN. Picea-Abies Smokey Mts, TN. Picea encielinannii Idaho Northeastern CO. Picea sitchensis Southeast AK. Pinus Idaho #/100 m mean(range) Sample Size (1) Reference 27(10-57) 15 8 16(8-36) 11 5 4 1 2 1 2 158(60-300) -- 180(140-220) --- 69 (50-88) 263 (130-536) 43(18-64) 11 1 6 166(55-240) -- 4 1 -- 43(17-77) 14 7 269(175-361) 183(140-250) 29(24-34) 30(25-41) 4 2 3 3 2 1 Picea sitchensis/Thula plicata Western WA. Picea sitchensis/Tsuga heterophylla Coast Range OR. Southeast AK. LWD Density 61(2-120) -- -.4 Table 14 (3 of 4). Forest Type and Location Continued. Basin Area (ha) Age mean(range) Bankfull Channel Width (m) mean(range) Pseudotsuqa menziesii Cascade Mts, OR. 250-500 Kiamath Nts, CA. 300 2 00(7-640) 4.7(2.6-9.1) 3.9(2.6-7.2) Sequoiadendron qiqantia Sierra NV. Mts, CA.300 175(160-190) 4.8(4.7-5.0) Sequoia seinpervirens California 500 455(50-1120) 5.5(2.3-9.6) 749 (287-1500) 7. 0 (5. 7-10. 0) 800(110-1350) 7.4(3.8-10.5) Tsuqa heterophylla Coast Range, OR. Western WA., WA. 290-410 - 102 (8-53 6) Stream Gradient (%) mean(range) 1.1(0.9-2.0) 3.8(0.7-10.4) L) Table 14 (4 of 4). Continued. LWD Volume Forest Type and Location Pseudotsuga menziesii Cascade Mts, OR. Kiamath Nts, CA. Seguoiadendron gigantia Sierra NV. Mts, CA. Sequoia sempervirens California Tsuga heterophylla Coast Range, OR. Western WA., WA. LWD Density m3(ha) #/100 in mean(range) mean(range) 660(18-1400) (1) Sample Size Reference --- 13 122 (7-460) 10 1 1 775(550-1000) -- 2 1 1699(240-4500) -- 10 1 401(258-582) 59(47-81) 24(5-54) 5 28 4 9 -- (1) Data adapted from the following authors and includes LWD size category, and channel area surveyed when available (modified from Ursitti 1991). 1. 2. 3. 4. 5. 6. 7. 8. 9. Harmon et al. 1986 Froehlich 1987 Robison and Beschta 1990b Ursitti 1991 Carlson et al. 1990 Richmond 1994 Bilby and Ward 1989 This Study Ralph et al. 1994 >10 >10 >20 >10 >10 >10 >10 >10 >10 cm cm cm cm cm cm cm cm cm dia. dia., dia., dia., dia., dia., dia., dia., dia., >1 in >1.5 >1 in >1 in >1 m long m long long long long >2 m long >1 in long > in long within 10 m of channel center line within the bankfull channel within the bankfull channel within 10 in of channel center line within the bankfull channel probably includes zones 1-3 within the bankfull channel in and above the bankfull channel. 75 composition within this study averaged 3.4% for all the study sites. The disparity in snag composition is likely due to differences in disease and insect activity between the study areas. Large woody debris volumes per hectare of this study were 41% and 44% of mean values reported within the bankfull channel of old-growth western hemlock (Tsuga heterophylla) and Douglas-fir climax stands in western Oregon, respectively (Ursitti 1991; Lienkaemper and Swanson 1987). These much higher instream volumes are likely the result of very large trees which often exceed 120 cm and 35 m in length (Ursitti 1991). Wood volumes in eastern Oregon streams more closely resembled wood volumes in seven streams flowing through second growth western hemlock stands (80-150 years old) averaged 190 m3/ha within the channel (Ursitti 1991) Large woody debris in eastern Oregon streams were smaller in diameter but longer than other Pacific Northwest streams. On average, mean LWD diameter was 34.9 cm and mean length 10.8 m in eastern Oregon, compared to 39 cm mean diameter and 5.2 m mean length in six western Oregon streams (Ursitti 1991). Mean LWD length may be influenced by the likelihood of breakage at the time of recruitment (Van Sickle and Gregory 1990), on site decay rates, or the ability of the channel to transport LWD. Bilby and Wasserman (1989) hypothesized that hydrologic conditions in eastern Oregon and Washington probably dispay smaller 76 extremes and therefore, less capable of transporting LWD than on the west side, due to the fact that most high discharges in eastern Oregon and Washington are governed by snowmelt runoff, versus heavy winter rains or as rain on snow events west of the Cascades. In addition, LWD in five southeastern Alaska streams had a average diameter of 53 cm and average length of 7.4 in (LWD >20 cm diameter, >1.5 in length; Robison and Beschta 1990b). Unlike Oregon streams, LWD within Colorado streams were smaller in median diameter (19 cm) and median length (3.3 m), which is likely due to differences in stand structure and species composition. One piece of LWD had an average of 1.0 in3 in eastern Oregon streams compared to an average of 0.13 in3 in 11 Colorado streams (Richmond 1994). Large woody debris volume for western Oregon and southeast Alaska both averaged 1.7 in3 (Ursitti 1991; Robison and Beschta 1990b). The variability of tree densities 50 cm diameter influenced LWD volume associated with the channel. The average LWD piece volume within old-growth stands with 50 trees over 50 cm DBH within 15 in of the bankfull channel was 1.3 in3. Conversely, average LWD piece volume within old- growth stands with less than 25 trees over 50 cm DBH within 15 m of the channel was 0.7 in3. Although overall frequency of large diameter trees within 30 in of the channel exceeded 27/ha, the density of large diameter trees within 15 in of the channel was more important for maintaining greater LWD 77 piece volume. Similarly, Van Sickle and Gregory (1990) and Robison and Beschta (1990c) found that LWD recruitment is largely influenced by riparian stand composition, density, and distance of the tree from the stream relative to its height. Large woody debris was primarily recruited from either erosion or windthrow, since the sites within this study did not have the capacity to move LWD longer than the bankfull width. Although eastern Oregon old-growth stand characteristics (i.e., frequency of trees 50 cm DBH) were significantly related to LWD volume within the bankfull channel (Figures 9a and 9b), no relationship was found with LWD frequency. Eastern Oregon streams average abundance (21.3 stems/100 m) was generally less than Colorado (42 stems/ 100 m), western Oregon (58 stems/lOO m), and Alaska old-growth streams (33 stems/l00 m). In this study, 53% of the total LWD abundance were pieces 10-15 cm in diameter. Large woody debris greater than 30 cm diameter averaged 23% of the total abundance but 86% of the total volume. The abundance of large diameter pieces not only disproportionately influences LWD volume within the channel, but provides pieces with slower decay rates which probably favor accumulation over time. Large woody debris frequencies and volumes may be more dependent on the condition of a specific conifer species component within the riparian stand than over-all stand structure. Since susceptibility to insects, disease, and fire are different for each conifer species, a schedule for mortality would vary between species (Spurr and Barnes 1980). For example, heavy mortality of the lodgepole pine component within site 10, can explain the low volume per LWD piece because lodgepole pine exhibited the smallest mean diameter and least mean volume per piece (Table 5). INFLUENCE OF CHANNEL CONSTRAINT ON LARGE WOODY DEBRIS Large woody debris frequency and volume was related to channel constraint and its effect on riparian stand characteristics. Mean LWD frequency generally increased in streams with larger entrenchment ratios. This is most likely due to higher entrenchment ratio's exhibiting wider flood-prone widths and a greater overall area available for LWD recruitment. The dynamics of valley floors differ substantially between constrained and unconstrained areas because of contrasts in the degree of landform control (Swanson 1979; Swanson et al. 1988). Ursitti (1991) found that riparian stand characteristics (i.e., stem density and basal area) were dependent on the geomorphic landform they occupied. For example, tJrsitti (1991) found that the mean hillslope basal area (59 m2/ha) was significantly greater than the mean floodplain basal area (37 m2/ha). Graham (1982) and Mckee et al. Conversely, (1982) found that lower 79 terraces were more productive exhibiting trees and boles larger in diameter than on upper terraces in the South Fork Hoh River. Bedrock outcrops and steep side slopes create constrained, steep channels which often alters the surrounding riparian stand, the magnitude of shading, litter production, and LWD recruitment (Swanson et al. 1990). Since availability and extent of more productive streamside landforms, such as terraces, change with the level of channel constraint, a vegetative response would be expected. With this study, the frequency of large trees (>50 cm DBH) within 15 in of the three channel types (HC, MC, and tJC) were similar. However, HC channels exhibited nearly 40% fewer large trees 15-30 in from bankfull than the other two channel types. The frequency of large diameter trees was largely dependent on the frequency of western larch. The width of the valley floor including stream-adjacent geomorphic surfaces within HC channels and the steeper moisture gradient, are likely agents responsible in changing the physical and biological character of the riparian stand. The distribution of LWD within the four hydraulic zones of influence were related to channel constraint. Channel constraint, which influences not only channel morphology but fluvial processes, can change the distribution of LWD within and above the bankfull channel (Ursitti 1991). Grant (1988b) found the level of channel constraint to have a profound influence on the placement and function of large roughness elements such as LWD. For LWD within and above the bankfull channel, HC channels exhibited the largest proportion of their LWD volume above the bankfull channel (zone 3), and the lowest proportion within the bankfull channel (zones 1 and 2). The diameter of LWD was related to its placement within the channel. Moderately constrained and UC channels had over 2 x the volume of smaller LWD (15-30 cm diameter) within the bankfull channel than was observed in HC channels, which is likely due to the greater mobility and shorter retention time of smaller LWD within channels of greater stream power. Bull (1979) and Grant et. al (1990) recognized that stream power and the ability of the stream to transport its sediment load or overcome large roughness elements is related to the degree of channel constraint. Gurtz et al. (1988) and Benke and Wallace (1990) reported that stream power, and not stream size, was found to be the determining factor in LWD frequency, distribution, or position within the channel in southeastern U.S.A. streams. Distribution of LWD along the channel was relatively even throughout all study sites. Large woody debris tended to stay where they fell because flows in low order streams were generally inadequate to move them (Bisson et al. 1987, Robison and Beschta l990a, Richmond 1994). The percentage of LWD classified as individual did, however decrease in streams with higher LWD frequency and volume, but no relationship was found with channel constraint. The percentage of LWD associated as groups and jams were weakly related to the width to depth ratio and gradient, respectively (Appendix Al2). Lienkaemper and Swanson (1987) reported that when LWD piece length exceed channel width, pieces are more likely to become anchored on both stream banks and, therefore, more likely to remain stable through high flow events. Only in site 1 did mean bankfull width exceed mean LWD length. In eight of the 15 sites, mean LWD length was approximately 2 times the mean bankfull width. The abundance of large more stable LWD are important in providing channel stability (Bilby 1984), and habitat for fish and other aquatic organisms (Carison et al. 1990). INFLUENCE OF LARGE WOODY DEBRIS AND CHANNEL CONSTRAINT ON POOL FORMATION Many researchers have found LWD to play an important role in pool formation across other regions (Swanson et al. 1984; Sedell et al. 1984; Sedell and Swanson 1984; Lienkaemper and Swanson 1986; Bilby and Ward 1989; Kozel et al. 1990; Robison and Beschta 1990a; Sedell et al. 1990). Sixty-three percent of the pools were formed by 11% of the total LWD pieces measured (n=1404). Carison et al. (1990) in northeastern Oregon found a nearly identical relationship with 64% of the pools formed by 11% of the total LWD measured. Similarly, Richmond (1994) found that 10% of the 82 LWD formed 81% of pools in undisturbed streams in northeastern Colorado. Channel constraint and the surrounding landforms influence patterns of LWD distribution and function within the bankfull channel. Large woody debris within MC and tJC channels were twice as likely to form pools than LWD within HC channels. In addition, as channel constraint increased, the dominant substrate size and interaction term (bankfull width x gradient) also increased. Since HC channels are more likely to generate higher stream power than UC channels (Lisle 1987), the function of LWD within different channel Grant (1990) types could be expected to change accordingly. reported that although LWD was abundant within two HC-high gradient channels of the McKenzie River basin, LWD played only a minor role in creating slow-water habitats. In constrast, Lisle (1982) found that pools within gravel bed streams were more likely to be formed by LWD. Anderson et al. (1978) and Speaker (1984) recognized that the differences in LWD function were often dependent on channel constraint and its relation to channel morphology, hydrologic characteristics, and substrate types. The ability of LWD to form specific slow-water habitats was influenced by the constraint of the channel. Slow-water habitats most dependent on LWD were plunge and dammed pools. Within HC channels, LWD was less likely to form plunge and scour pools than other channel roughness elements (e.g., 83 boulders). However, within Mc channels, only scour pools were more likely to be formed by channel roughness elements other than wood. All slow-water habitats within UC channels were more likely to be formed by LWD. Grant (1988b) recognized differences in pool forming processes between constrained and unconstrained channels. However, Grant (l988b) also suggested that pools within unconstrained channels were formed primarily by bedforms and channel bars. This was not the case for this study, where LWD formed 80% of all the slow-water habitats within UC channels. The local abundance or absence of LWD may be more important in determining processes of pool formation than channel constraint alone. The character of dammed, plunge, and scour pools were often dependent on the function of LWD and degree of channel entrenchment. Plunge pools formed by LWD within HC channels were two times larger in surface area than plunge pools within UC channels. Grant (1990) reported that plunge pools and step-pool sequences within HC channels are important for energy expenditure, and increase in frequency and size with increasing channel slope. Therefore, the effect of gradient can often introduce a bias in pooi frequency and size complicating the role of channel entrenchment. Cupp (1989) and Ursitti (1991), both suggested that changing relationships between LWD and channel slope with channel constraint could influence pool size and character. Richmond (1994) also suggests that geomorphic and fluvial characteristics and not LWD exert primary control on individual pools size and type. Contrary to plunge pools, scour pools formed by LWD within tIC channels were 1.5 times larger than scour pools within MC and HC channels. In addition, the percentage of stream area as pools was greatest in UC channels. Stack (1988) found channel slope inversely related to pools size, which would allow a single LWD piece to influence a larger surface area within channels of lower channel slope. MANAGEMENT IMPLICATIONS The entrenchment ratio clearly defines the relative conditions needed to change the mode of LWD character and function within the stream channel. The entrenchment ratio was found to occupy a key position in the complex interactions of other geomorphic features and fluvial processes. In addition, this study showed that LWD influenced channel morphology differently within an unconstrained stream reach than a highly constrained stream reach. For example, LWD was more likely to form pools (especially scour pools) within unconstrained stream reaches. These two stream reaches differ predictably in other geomorphic attributes (e.g., gradient), and likely respond differently to land management activities. Another measure of constraint is the valley floor width index (VFWI), where constrained reaches exhibit a valley floor narrower than two bankfull widths (Gregory et al. 1991). Constrained reaches determined by the VFWI, were generally analogous to highly constrained reaches determined by the entrenchment ratio (Table 15). The three study sites which VFWI classified as constrained (sites 1, 2, and 4), The other were streams flowing through V-shaped landforms. study sites (classified as hmunconstrainedtt by the VFWI) include one or more terrace within moderate sloped landforms. The VFWI which includes the entire valley floor, may include landforms accessible to only rare flood events. This may make the VFWI less representative of active geomorphic surfaces related to the present bankfull discharge. Some of the streamside geomorphic landforms less accessible to flooding may be remnant features developed by higher flow regimes during the Pleistocene (Schuinm and Lichty 1964), or areas of ash deposit resulting from the Mazama eruption. Some stream reaches may have been influenced by beaver, however, no present or past beaver activity was evident in any of the study sites. The entrenchment ratio which represents a relatively more frequently flooded area (<50 year return period), may be a more reliable measure of constraint in eastern Oregon physiographic zones. Table 15. Comparison of valley floor width index and the entrechment ratio. The Rosgen (1994) reach classification is also given for reference (which includes the entrechment ratio and other geomorphic and subtrate parameters - see text for details). Site Entrenchment Ratio Valley Floor Width Index Rosgen Stream Classification Highly Constrained 1 2 3 4 1.2 1.4 2.6 1.7 A2 A2 A2 A3 1.6 1.6 2.1 1.5 1.9 1.8 2.0 4.1 4.6 4.6 4.9 4.1 B2 B3 B3 B3 B3 B4 3.7 2.6 3.4 3.6 3.2 5.7 4.1 5.4 13.2 4.2 C4 C4 C3 C3 C3 1.1 1.4 1.4 1.3 Moderately Constrained 5 6 7 8 9 10 Unconstrained 11 12 13 14 15 Hicihlv Constrained median mean 1.4 1.3 0.1 SD Moderate lv Constrained median 1.7 mean 1.8 SD 0.2 Unconstrained median 3.4 mean 3.3 SD All Sites median mean SD 1.5 1.7 0.6 4.4 4.1 1.1 0.4 5.4 6.5 3.8 1.8 2.1 0.9 4.1 4.2 2.9 87 Spatial variation in LWD and physical habitat parameters may obscure effects of land-use or stream restoration efforts if the available reference data sets (i.e., baseline data) are inadequate to provide a basis for reliable site specific objectives. Site specific objectives are necessary to measure change within a stream reach. This study established the variability and heterogeneous nature of LWD character and function, and illustrates a need for reach stratification to account for variation in reach geomorphology. Huntington (1995) found that grouping surveyed streams by entrenchment (via Rosgen 1985), was an effective method in finding differences between roaded and unroaded areas within forested Idaho streams (Clearwater National Forest). Although not compensating for stream size or basin area, Huntington (1995) found differences in LWD frequency, pool frequency, salmonid abundance, and in fish assemblages between UC, MC, and HC stream reaches. Huntington (1995) found LWD (1O cm diameter) to be most abundant in HC channels (14.5 pieces/lOO m), followed by UC channels (13.6 pieces/lOO m) and MC channels (10.1 pieces/100 m). The frequency of LWD within HC channels are similar to this study, however, this study found UC and MC channels to exhibit over 2x the frequency found by Huntington (1995). In order to compare LWD frequency and function by degree of channel constraint, it may be necessary to first stratify by stream size or basin area (Bilby and Ward 1989). Stratification of reaches by the entrenchment ratio, also allowed for the comparison of the relational differences between LWD and pool formation. 40% of the pools were created by LWD For example, within highly constrained reaches, although an average of 6% of the functioned to form pools. LWD Unconstrained stream reaches followed a similar pattern, with 80% of the pools created by LWD, and an average of 13% of the LWD functioning to form pools. The ability of unconstrained reaches to utilize a greater percentage of their LWD in forming pools, has likely influenced the frequency of pools formed by LWD. the majority of the "surplus" of LWD LWD Although did not form poois (89-94%), this may be providing channel stability, habitat complexity, or future pool forming LWD, which are essential elements to ensure the diversity and stability of aquatic and riparian dependent communities. Due to concern over the economic and ecological health of eastern Oregon forests, different approaches have recently been proposed for the long-term protection and restoration of streams and streamside vegetation. As an interim strategy, federal land management agencies have temporarily adopted the concept of Riparian Habitat Conservation Area widths, which incorporate areas larger than traditional riparian management areas (U.S.D.A. 1992). The Riparian Habitat Conservation Area is a stream buffer which provides a different level of protection for fishbearing streams, permanently flowing non-fish-bearing streams and lakes. These stream buffers will, in the short- term, be an effective method for protecting riparian stands and LWD recruitment for fish-bearing streams. Due to fire suppression and the subsequent decrease in fire frequency, the successional dynamics of many riparian stands may have changed, becoming more densely stocked and less resistent to insects, disease, and stand replacement fires (Arno 1980; However, climatic Agee 1990; Kauffman 1990; Brown 1994). gradients between the riparian and upland sites are frequently sharp in more arid intermountain forests (Youngbood et al. 1995). Within this study, sharp climatic gradients were found to coincide with abrupt changes in riparian stand composition and structure, especially at the ecotone adjacent to a southern exposure. The upland southern exposure was dominated by ponderosa pine within eight study sites (sites 2, 4, 5, 7, 9, 11, 14, and 15) where fire plays a more significant role in forest dynamics. A diversion from a natural riparian disturbance regime may modify riparian stand dynamics and LWD recruitment over the long-term, however, the extent of the modification will be highly dependent on riparian areas historical fire regime, which is often highly site specific. To realign disturbance processes, multiple treatments will likely be needed to regulate vegetation composition and structure. Management strategies should incorporate knowledge of historical and current disturbance regimes, site potentials, and climates (Harvey 1994). Seral species which are often established by historic fire regimes, currently supply an average of 40-52% of the potential LWD recruitment 50 cm diameter within this study. Changes in current riparian management strategies will be required to maintain historic recruitment processes. In some cases, a return to historical norms may be socially or ecologically infeasible due to the cumulative effects of past management within streams, basins, or watersheds. In order to manage riparian ecosystems, a substantial investment in ecological inventory and classification will be required. The Oregon Forest Practices Act (OFPA) water protection rules have adopted a new approach by using live conifer basal area instead of number of trees as the vegetationretention measure. The water protection rules have been formulated by stream size and geographic regions in order to more adequately protect water quality and the recruitment of LWD across the state (Lorensen et al. 1994). Generally, the rules require a no-harvest area within 6.1 m (20 feet) of all fish bearing streams to mitigate a reduction in stream shading and LWD recruitment. Implementation of the OFPA water protection rules would provide an average basal area target of 4.4 m3/ha, for a medium size stream (0.06 m3/s 91 0.28 Ins/s average annual flow) outside the 6.1 in no-harvest area (6.2-23 in (21-70 feet); within the Blue Mountain geographic area). All sites except for site 10 are likely medium size streams as described under the OFPA (an average annual flow greater than 0.06 m3/s but less than 0.28 m3/s; see Table 12). Assuming a direct correlation with basal area and LWD recruitment, and that the no-harvest area (6.1 in) provides 40% of the total LWD loading (Lorensen 1994), a 50% total reduction in potential LWD recruitment would be expected if old-growth grand-fir stands were managed under the OFPA. A reduction of LWD recruitment of this magnitude will establish a gradual decline in LWD frequency and volume from present levels. Pools formed by LWD would likely follow suit and decline proportionately with LWD. An over- all decline in the physical and biological integrity of streams, similar to this study, would likely be a result if additional mitigations were not put in place. In order to meet commitments with the Columbia River Basin Anadromous Fish Habitat Management Policy and Implementation Guide (PIG), many eastern Oregon Forests have developed core sets of minimum numeric standards in an attempt to describe fully functioning aquatic systems (U.S.D.A. 1991, U.S.D.A. 1993, and U.S.D.A. 1995). Implementation of the Umatilla and Malheur National Forests minimum numeric standards (U.S.D.A. 1993 and U.S.D.A. 1994, 92 respectively) would provide 6.6 LWD/l00 in (30 cm diameter) with 20% >50 cm diameter (1.3 LWD/l00 m; Table 16). However, this study indicates that averages of 4.4 LWD/lOO lii (30 cm diameter) and 2.1 LWD/ 100 in 50 cm diameter are typically present in streams flowing through old-growth grand-fir stands. Only 5 of 15 study sites met the Umatilla or Maiheur numeric standard (6.6 LWD/l00 m, >30 cm diameter). Although the frequency of LWD >30 cm diameter was less within this study (all sites combined), the frequency of LWD 50 cm diameter was 38% greater than the numeric standard. However, when comparing highly constrained stream reaches to the numeric standard, the frequency of LWD was slightly less (1.0/100 in). 50 cm diameter Large woody debris 50 cm diameter has often been found to provide habitats more resistent to high stream flows and floods than habitats formed by smaller diameter pieces (Sedell and Swanson 1984; Bilby 1988; Swanson et al. 1990). Although the size distribution of LWD is likely an important element in the physical and biological integrity of the stream ecosystem, the relative importance of LWD within the stream may be dependant on the degree of channel constraint and/or other geomorphic features (Frissell et al. 1986; Grant et al. 1990; Ralph et al. 1994). consequently, it is inappropriate to set numeric LWD standards or thresholds and uniformly apply them to all streams (U.S.D.A. 1993; Ralph et al. 1994). To properly manage a stream ecosystem, the stream 93 Table 16. Comparison of LWD frequency by diameter categories between the minimum numeric standards developed by two eastern Oregon Forests for mix conifer stands (U.S.D.A. 1993, U.S.D.A. 1994), and findings from this study. #/100 m Site >50 cm >30-50 cm >15-30 cm >10-15 cm Umatilla/Malhei ir National Forests Numeric Standards 1.3 5.3 Average of all sites 2.1 within study 2.3 7.1 10.1 Unconstrained Study Sites 2.6 2.9 9.0 11.0 Moderately Constrained Study Sites 2.3 2.1 7.2 10.1 Highly Constrained Study Sites 1.0 1.9 3.9 8.7 94 must be viewed in a watershed context to accommodate natural variability between streams and stream reaches. The species present in a stream, or reach, must also be viewed collectively as part of the watershed, to determine the relative value of a reach type (e.g., unconstrained) for the fishery resource. Cupp (1989) and Huntington (1995) have found fish assemblages to be- often dependent on reach constraint. For example, cutthroat trout (. clarki) were found to dominate highly constrained reaches within a basin (Cupp 1988; Huntington 1995). Other species, such as bull trout, showed no preference to a level of reach constraint (Huntington 1995), but have been found to display a strong preference for cover (Goetz 1989; Sexauer and James 1993), which is often supplied and created by LWD. Bull trout presence and distribution has also been found to be dependent on other variables such as stream temperature or complex habitat formed by LWD (Buckman et al. 1992; Ratliff and Howell 1992). With bull trout populations largely fragmented and isolated in low order streams (Ratliff and Howell 1992), the status of bull trout populations will be largely influenced by the ability land managers to protect and restore bull trout habitat by managing LWD and its future recruitment. The identification of the natural variability of LWD characteristics and function among each level of channel constraint allows valid evaluation of the variable impacts 95 of land management. The effects of land management, such as timber harvest activity, will often affect the character and function of LWD. Large woody debris is largely responsible for the physical, chemical, and biotic characteristics of riparian and aquatic habitats, and its successful management will be an essential component in the protection or restoration of stream ecosystems. BIBLIOGRAPHY Agee, J.K. 1990. The historical role of fire in Pacific Northwest forests. Chapter 3 In; Waistad, J., and Natural and prescribed fire in the others (eds). Pacific Northwest. Oregon State University Press. Anderson, N.H., J.R. Sedell, L.N. Roberts, and F.J. Triska. The role of aquatic invertebrates in processing 1978. The of wood debris in coniferous forest streams. American Midland Naturalist 100(1) :64-82. 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For. Res. 24: 1933-1938. Youngblood, A.P., W.G. Padgett, and A.H. Winward. 1985. Riparian community type classification for eastern Idaho-western Wyoming. R4-Ecol-85-01. U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station. 78 p. 106 APPENDICES 107 APPENDIX A 108 Length correction factors for each stream. Appendix Al. Only one correction factor was developed for Clear Creek and Little Crane Creek although they exhibited both constrained The correction factor x the and unconstraind sites. estimated LWD length = corrected LWD length. Raw data on file at Pacific Northwest Research Station, Corvallis, OR. Site 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Correction Factor 0.96 0.99 1.13 0.92 1.09 0.90 0.97 1.06 0.92 1.27 0.97 1.06 0.99 1.04 1.24 109 Table A2. Select stream variables evaluated at each study site and appropriate transformation used to induce normality when applicable. Logarithmic transformations utilized natural logarithms. Variable Transformation Used GeomorDhic Variables Entrenchment Ratio Gradient (%) Basin Area (ha) Average Bankfull Width (in) Average Bankfull Depth (m) Logarithmic Logarithmic None Logarithmic Logarithmic Riparian Vecietation Trees >50 cm/ha (zone A/zone B) Trees 30-50 cm/ha (zone A/zone B) Trees 15-30 cm/ha (zone A/zone B) Trees 10-15 cm/ha (zone A/zone B) None/None None/Logarithmic Logarithmic/Logarithmic Square-root/Square--root Larcie Woody Debris LWD/100 in LWD length (in) LWD diameter (cm) LWD volume (m3) LWD >50 cm diaxneter/lOO in LWD 30-50 cm diameter/lOU in LWD 15-30 cm diameter/lOO in LWD 10-15 cm diameter/lOO m None None None Logarithmic Logarithmic Logarithmic None Logarithmic Primary Pools Formed and not formed by LWD: Pools/100 in Pool Area (m2) Pool Volume (in3) - Slow-water habitats Formed by LWD: Dammed Pools/l00 in Plunge Pools/lOU in Scour Pools/lOU in Not formed by LWD: Dammed Pools/100 m Plunge Pools/lOU m Scour Pools/laO m None None Square-root Square-root None Square-root Square-root Square-root Square-root Highly Length, LWD, and riparian data of the 15 study sites. Appendix A3. Raw data: Constrained (sites 1-4), moderately constrained (sites 5-10), and unconstrained (sites 1115) Highly Constrained Sites Characteristic 302 Study Site Length (in) 3.7 10 bankfull widths 8.6 10 Wetted widths LWD (#) Association: 35 Individual 4 Group 4 Jam Delivery: 9 Floated 21 Windthrow 13 Eroded Riparian 1.2 Area (ha) Trees/dia. class (#): 55 >10-15 cm 816 l5-30 cm 30-50 cm >50 cm Trees/spp. Fir LP WL PP (#): 2 1 346 5.4 9.6 40 3 244 3.6 9.7 8 5 72 20 36 17 22 14 30 57 41 1.1 0.6 4 536 12.5 18.5 22 6 0 0 25 3 2.0 844 356 445 200 0 115 262 408 58 84 322 56 1543 670 515 0 57 1463 174 31 0 2 0 47 8 0 126 628 75 82 0 Appendix A3. Continued. Moderately Constrained Sites Characteristic Study Site Length (in) 10 bankfull widths 10 Wetted widths 5 424 3.8 11.2 6 506 6.7 11.0 7 8 9 148 3.3 3.6 571 8.9 12.4 225 4.2 7.5 10 365 9.6 17.4 LWD (#) Association: Individual Group Jam Delivery: Floated Windthrow Eroded 34 6 4 98 33 15 17 24 49 92 3 104 47 91 6 82 15 14 19 5 12 51 81 5 8 33 20 79 18 19 68 15 1.6 0.6 27 0 0 7 Ripar ian Area (ha) 1.1 Trees/dia. class (1/): >10-15 cm 239 >15-30 cia >30-50 cm >50 cm 156 115 89 1.7 0.8 0.5 605 456 706 269 438 373 92 76 1343 771 435 158 82 55 76 14 120 220 391 20 1412 265 186 173 532 245 142 60 1495 873 264 75 141 52 478 204 8 78 26 0 Trees/spp. (#): Fir LP WL PP 521 46 28 4 I-. I-a Appendix A3. Continued. Unconstrained Sites 11 12 13 14 15 309 4.4 8.6 246 4.7 6.8 720 11.4 20.0 252 3.7 9.0 Characteristic Study Site Length (Tn) 10 bankfull widths 10 Wetted widths LWD (#) Association: Individual Group Jam Delivery: Floated Windthrow Eroded Riparian Area (ha) Trees/dia. class (#): >10-15 cm >15-30 cm >30-50 cm >50 cm 532 11.3 15.6 120 19 85 30 61 26 7 6 21 107 18 30 77 14 0.9 150 112 47 9 0.3 72 121 70 21 47 17 12 77 17 19 24 44 31 43 40 30 20 24 28 ------ 2.2 8 0.6 485 295 554 193 434 239 312 84 1210 876 113 Trees/spp. (#): Fir LP WL 133 75 101 PP 9 26 216 23 19 ----- 129 113 75 83 6 i-. Appendix A4. Raw data: Large woody debris function and pool data of the 15 study sites. Highly Constrained (sites 1-4), moderately constrained (sites 5-10), and unconstrained (sites 11-15). Pool relationship with LWD includes only pools habitats with LWD present. Highly Constrained Sites Characteristic 1 Pool relationship with LWD (#): Formed 1 Enhanced 3 Cover 0 No Influence 5 Pools Formed by LWD Count (#): Dammed pools 0 Plunge pools 0 Scour pools 1 2 3 4 2 7 0 15 6 6 3 2 0 2 0 3 2 5 0 4 4 8 1. 0 1 Mean pool area (in2): Dammed pools Plunge pools Scour pools - 22.4 Pools Not Formed by LWD Count (#): Dammed pools 0 Plunge pools 3 Scour pools 8 Mean pool area (m2): Dammed pools Plunge pools 33.8 Scour pools 23.4 Pocket Pools (#) 4 - 23.8 17.2 11.8 8.6 13.4 13.1 - - 1 0 0 7 6 2 3 1 9 - - 62.7 32.2 26.8 1 11.3 12.0 3 7.8 8.7 11 Appendix A4. Continued. Moderately Constrained Sites 5 6 7 8 9 10 8 2 1 2 2 1 1 0 13 3 9 1 1 1 0 1 1 1 6 4 4 1 1 1 12 0 1 2 5 5 4 Characteristic Pool relationship with LWD (#): Formed 4 Enhanced 0 Cover 2 No Influence 5 Pools Formed by LWD Count Dammed pools Plunge pools Scour pools Mean pool area (in2): Dammed pools Plunge pools Scour pools 3 (#): 2 3 2 22.1 19.9 12.0 Pools Not Formed by LWD Count (#): Dammed pools 0 Plunge pools 0 Scour pools 13 Mean pool area (m2): Dammed pools Plunge poois Scour pools 24.6 Pocket Pools (/1) 0 6 24.5 13.9 19.3 1 0 7 81.6 - 30.6 9 16.1 23.9 16.1 1 0 2 64.8 - 28.6 1 9 2 23.6 18.4 19.9 1 1 6 51.2 17.1 18.9 11 - 24.6 17.0 1 0 1 14.6 - 18.2 2 5.8 5.7 10.4 0 0 4 - 6.4 0 I- Appendix A4. Continued. Uconstrained Sites 11 12 13 14 15 11 7 13 0 0 0 1 4 0 0 4 8 2 0 0 11 2 4 3 3 Characteristic Pool relationship with LWD (#): Formed 17 Enhanced 2 Cover 1 No Influence 2 Pools Formed by LWD Count Dammed pools Plunge pools Scour pools Mean pool area (m2): Dammed pools Plunge pools Scour pools (#): 2 3 13 47.9 22.9 39.7 Pools Not Formed by LWD Count (#): Dammed pools 0 Plunge pools 0 Scour pools 5 Mean pool area (m2): Dammed pools Plunge pools Scour pools 29.2 Pocket Pools (#) 3 3 4 6 36.8 25.6 35.5 15.4 16.5 16.2 5 10 20.0 27.4 37.0 0 0 8 - 25.3 0 0 0 0 0 1 11 0 2 0 - - - 3 13.8 2 0 0 59.9 4 0 13.6 1 I-a I-a 'i-I Appendix A5. Trees per hectare for four species categories within zone A (0-15 in) and zone B (15-30 in). The total number of trees per hectare is given (0-30 in) denoted by "ALL". "Fir" trees include: Engelmann spruce, Douglas-fir, and grand fir. LP= Lodge pole pine; WL= western larch; PP= ponderosa pine. Means and standard deviations (SD) are given for major categories. Study site 13 was burned by wildfire before the stand survey was completed. Site Fir Trees per Hectares (#) Zone A (0-15 m Zone B LP WL PP Fir LP Hicfhlv Constrained 1 651.2 0 2 379.7 0 3 435.9 0 4 489.8 43.5 6.6 5.4 7.7 34.3 0 29.6 0 17.4 (15-30 Tn') WL PP 0-30 in ALL 611.9 221.7 351.2 258.5 89.3 46.1 19.7 3.6 4.6 7.2 287.2 420.2 399.0 148.8 62.6 431.1 16.7 89.6 236.9 88.5 35.1 208.0 13.2 56.4 157.4 58.7 2.5 83.2 1.8 86.5 60.8 22.7 20.0 65.6 53.8 -- 42.6 247.4 104.6 28.7 -- 8.1 46.6 -- 183.6 509.2 -- 251.3 595.1 24.7 186.6 24.7 40.2 18.4 6.4 342.9 788.1 0 0 0 13.5 0 46.6 644.7 326.2 444.4 471.7 Moderately Constrained 5 6 7 8 9 10 172.2 447.2 430.2 160.5 113.9 474.6 23.7 73.6 143.4 53.5 30.1 175.9 10.5 56.4 65.5 24.4 7.5 47.3 1.8 19.0 34.3 12.8 12.5 44.9 527.1 2.3 21.5 -- 11.5 53.8 -- 32.3 30.6 26.9 53.1 15.3 3.2 0 0 263.6 624.4 768.8 285.0 142.1 710.1 Unconstrained 11 12 13 14 15 87.5 39.4 -- 292.2 661.0 -- -- H C' Appendix A5. Site Continued (includes mean subtotals). Trees per Hectares (# Sub Zone B (15-30 in) PP Total Fir LP WL Zone A (0-15 in) Fir LP WL Highly Constrained median 462.8 0 mean 488.9 10.9 PP Sub Total 0-30 in ALL 8.7 11.8 14.4 525.1 304.8 360.8 176.0 24.1 33.8 42.9 5.9 8.8 7.4 6.8 15.0 22.0 418.4 21.8 7.2 13.5 13.9 458.1 471.8 131.5 Moderately Constrained median 301.2 63.6 299.8 83.4 mean 167.1 62.5 SD 35.8 35.3 24.5 12.6 13.4 12.5 431.9 343.1 291.5 155.2 89.1 112.5 90.4 57.6 61.9 55.7 21.4 32.0 34.5 497.4 454.7 465.7 266.5 Unconstrained median 189.8 mean 270.0 282.8 SD 38.6 158.7 245.7 40.0 36.3 20.8 9.3 13.1 13.6 478.1 158.4 241.4 252.5 114.6 125.3 109.0 34.4 49.6 37.3 13.2 19.9 18.6 436.2 426.1 456.0 258.3 All Sites median 404.4 mean 345.3 203.5 SD 37.9 84.2 137.5 25.6 29.4 22.0 12.6 12.1 22.0 471.0 272.8 297.0 182.6 67.3 93.7 88.8 26.7 43.2 45.4 16.0 23.7 26.6 457.6 458.0 464.2 216.5 SD 117.3 Appendix A6. Basal area (m2/ha) of conifer categorized by four diameter classes witin zones 30-50 cm diameter, A (0-15 m) and B (15-30 m). Size categories were: 50 cm diameter, 2) l5-30 cm diameter, and 4) l0-l5 cm DBH. Diameters are measured at the large end. Study 3) site 13 was burned by wildfire before the stand survey was completed. deviations (SD) are given for major categories. Means and standard Basal Area (iii2/ha) Zone B (15-30 m) Zone A (0-15 m) Site 1 Total 4 3 2 Total 4 3 2 5.9 1.4 0.8 4.2 22.0 16.5 27.2 10.4 14.9 5.0 10.1 10.7 43.4 23.0 39.6 26.9 43.3 31.0 47.0 37.9 15.4 48.0 26.6 16.5 1.5 1.2 31.3 82.2 58.8 36.7 6.7 40.2 26.8 71.7 53.4 44.7 9.3 43.0 Highly Constrained 1 2 3 4 0 0 0.7 13.6 10.9 12.2 22.2 24.4 43.1 39.1 54.3 48.8 0.6 14.2 33.3 22.8 24.2 4.4 10.5 22.3 61.3 43.1 52.8 11.9 45.8 1.5 2.3 4.7 4.9 0.6 0.1 4.3 10.1 12.2 5.2 2.4 4.5 22.5 8.0 12.6 5.6 29.4 0.3 6.0 10.0 21.8 15.3 10.1 4.3 33.0 1.1 9.4 1.0 10.0 0.3 15.8 4.0 36.6 0.6 1.8 3.9 1.5 4.3 8.8 4.2 15.3 13.0 27.5 8.5 32.1 20.9 29.5 35.9 58.5 1.1 5.3 2.6 2.1 12.0 24.3 16.4 29.1 32.1 60.8 34.1 59.6 6.5 2.9 1.8 4.8 25.7 23.8 25.8 16.0 0 1.6 1.6 Moderately Constrained 5 6 7 8 9 10 0.9 2.2 4.9 6.4 0.6 3.6 2.6 3.3 12.5 9.6 1.3 Unconstrained 11 12 13 14 15 1.6 1.5 - 1.8 3.9 Average 0-30 m 1 - 1.0 2.5 - 12.2 22.6 - - - - - - - - Appendix A6. Continued. Basal Area (m2/ha) Zone A (0-15 Site 1 2 Highly Constrained median 0.4 3.8 mean 1.1 4.0 3 Zone B (15-30 in) 4 Total 1 2 3 Average in) 4 Total 0-30 in 24.8 22.8 4.6 17.2 17.4 6.9 46.0 46.3 6.7 1.1 1.0 0.8 2.8 3.1 2.4 19.2 19.0 7.2 10.4 10.2 4.1 33.2 33.2 9.8 40.6 39.8 7.0 Moderately Constrained median 2.9 3.0 10.3 mean 3.1 5.3 13.8 SD 2.3 4.6 10.1 18.5 18.2 10.5 44.4 39.5 18.8 1.9 2.4 2.0 5.6 4.4 4.3 12.7 15.8 10.3 16.0 18.2 17.5 38.4 42.6 25.6 43.8 41.5 21.5 SD 1.8 Unconstrained median 1.7 mean 2.2 SD 1.1 All Sites median 1.7 2.3 mean SD 1.9 2.1 1.8 3.5 4.0 11.1 11.4 8.9 18.4 16.6 12.3 36.2 33.8 22.4 1.4 2.2 2.1 2.4 2.5 1.0 10.4 12.4 8.6 15.8 16.2 10.2 28.9 33.4 20.0 33.1 33.6 20.9 2.8 4.4 3.7 14.3 15.7 9.2 18.4 17.5 9.4 43.1 39.8 16.9 1.6 1.9 1.8 4.1 4.3 13.6 15.7 8.8 15.1 15.4 12.6 34.4 37.3 19.8 40.4 38.7 17.4 3.4 I-. 120 Trees per hectare for four DBH categories. Appendix A7. Large diameter trees (>50 cm DBH) are shown separately at two belt widths distances from bankfull (0-15 m and 15-30 Size categories were: >50 cm DBH (diameter at breast m). height), 2) 30-50 cm DBH, 3) 15-30 cm DBH, and (4) 10-15 cm Means and standard deviations (SD) are given for major DBH. (*) Sites not included in data summaries (did categories. Study site 13 was not qualify for old-growth designation). burned by wildfire before the stand tally was completed. Trees per Hectare (#) 0-30 m 15-30 m 15-30 cm 30-50 cm >50 cm 10-15 cm 0-15 m Site >50cm Highly Constrained 1 2 3 4 27.0 37.7 57.0 71.7 34.4 14.4 29.3 30.7 22.5 0 88.6 216.0 334.2 117.6 64.7 91.1 257.2 183.1 248.0 113.9 30.7 26.0 43.1 51.2 Moderately Constrained 5 6 7 8 9 10 35.1 78.0 49.9 53.5 12.5 32.1 43.0 87.2 68.6 38.4 5.0 3.8 105.0 185.7 341.3 390.6 51.3 113.4 68.5 139.9 290.7 224.2 34.4 208.0 50.5 216.7 71.7 126.5 47.6 369.7 39.1 82.6 59.2 46.0 8.8 18.9 94.4 43.0 -35.9 67.5 86.3 129.1 -108.8 350.0 64.5 216.9 27.1 125.5 47.8 37.6 66.2 192.2 124.3 250.9 43.3 67.5 81.8 55.5 97.1 151.9 104.3 123.4 200.6 215.6 66.5 37.8 36.9 11.5 31.7 185.7 227.2 131.6 208.0 186.3 84.9 126.5 167.0 130.2 46.0 49.2 23.7 43.0 48.8 16.6 129.1 196.0 133.8 192.2 158.4 80.8 125.5 166.9 72.7 46.0 49.5 15.9 37.2 41.4 23.4 121.2 170.9 128.9 166.1 167.8 90.7 154.8 178.2 92.8 43.2 45.4 17.8 Unconstrained 11 12 13 14 15 1.2 32.3 -- 50.7 67.5 Hicthlv Constrained median 48.3 27.2 mean 30.0 47.3 SD 19.9 8.8 Moderately Constrained median 49.9 43.0 mean 49.7 48.2 SD 18.3 Unconstrained median 50.7 mean 50.2 SD 17.6 All Sites median 50.3 mean 49.4 SD 16.9 121 Mean stand volumes per hectare are and zone B (15-30 m). Means and deviations (SD) are given for major categories. 13 was burned by wildfire before the stand tally completed. Appendix A8. zone A (0-15 in) shown for standard Study site was Volume per Hectare (in3) Site 0-15 in 15-30 in 0-30 in Highly Constrained 1 2 3 4 12652 7219 7089 13056 12220 9606 5968 15446 7884 20969 16639 4530 3910 14020 10301 32516 19348 8550 1998 10748 9092 26742 17994 6540 2954 12384 2804 13878 -12920 18927 6540 10932 4672 12405 11788 11992 4846 17834 Moderately Constrained 5 6 7 8 9 10 Unconstrained 11 12 13 14 15 Hicihlv constrained median 11890 mean 11615 SD 5313 10912 10810 4016 10524 13910 10671 10738 12618 8613 6754 11246 13910 10671 12323 12170 6000 12456 11639 5978 10840 12308 7496 12230 11973 6419 6950 Unconstrained median 13399 mean 12132 SD All Sites median mean SD 112241 19362 9936 10004 3296 Moderately Constrained median 10952 mean 11326 SD -- 1156 19798 50 E 30 20 10 [IJ 1 2 3 4 5 6 7 8 9 10 Site Appendix A9. Large woody debris per 100 m for all study sites. 11 12 13 14 15 123 Large woody debris volume within the bankfull Appendix AlO. channel (zones 1-2), and within and above the bankfull channel (zones 1-3). Means and standard deviations (SD) are given for major categories. Site LWD Volume per Hectare (m3) Zone 1-2 Zones 1-3 Highly Constrained 1 2 3 4 57.7 143.2 686.8 170.1 Moderately Constrained 5 76.1 249.4 6 7 8 9 10 28.7 68.6 475.0 114.5 346.8 133.3 40.7 139.9 53.8 170.6 145.6 123.4 17.0 103.8 187.2 370.8 304.8 175.3 473.8 132.4 269.1 210.3 117.5 325.6 Unconstrained 11 12 13 14 15 Hiahlv Constrained median 156.6 mean 264.4 SD 285.6 Moderately Constrained median 136.6 mean 164.4 SD Unconstrained median mean SD All Sites median mean SD 91.5 171.7 205.2 114.2 123.4 119.4 44.3 304.1 302.2 126.0 210.3 211.0 88.6 175.3 237.0 175.1 123.4 156.1 121.8 124 Appendix All. Relationships geomorphic variables between Constrained = HC, Moderately Unconstrained = UC. Results means measured at each study between LWD volume and select Highly channel types. Constrained = MC, and are based on transformations of site. LWD Volume per 10 BFW's Geomorphic Variable HC MC r2(p) r2(p) UC r2(p) All Sites r2(p) Entrenchment .08(0.70) .30(0.26) .43(0.23) .01(0.80) Gradient .53(0.05) .38(0.18) .76((0.05) .00(0.90) BFW .08(0.72) .51(0.11) .70(0.07) .33(0.024) BFD .13(0.35) .73(0.030) .00(0.90) .05(0.49) W:D Ratio .00(0.72) .05(0.46) .00(0.70) .00(0.91) BFW INT .05(0.76) .33(0.23) .50(0.18) .04(0.45) Basin Area .09(0.69) .08(0.59) .65(0.09) .02(0.61) 125 Relationships between LWD association (i.e., Appendix Al2. Large woody individuals, group, or jam) and LWD abundance. debris volume (m3) is given per ten bankfull widths (TBF). Relationships with geomorphic variables are also given. The interaction term bankfull width x gradient is denoted as BFW Results are based on transformations of means measured INT. at each study site (Table Al). Large Woody Debris Association LWD Variable % Individual % Group r2(p) r2(p) % Jam r2(p) [MD/100 m -.39(0.013) .09(0.29) .00(0.58) Jolume/TBF -.33(0.025) .00(0.50) .00(0.86) .00(0.70) .00(0.39) .00(0.48) .00(0.79) .00(0.38) .24(0.06) BFW .04(0.23) .12(0.20) .08(0.29) BFD .00(0.86) .00(0.68) .11(0.22) .00(0.64) .24(0.06) .00(0.69) .00(0.54) .00(0.70) .29(0.039) eomorphic Tar iable Entrenchment radient :D Ratio BFW INT 126 a a 6 -4 a -1 i.e. a 4 0 0 2 a z -9.2 0.3 0.8 i.3 1.8 2.3 1.3 1.8 2. LOG GRADIENT 8 E 6 a -1 0 0 0. 4 a E t. 0 2 0 0 3 I 9.2 0.3 0.8 LOG GRADIENT Appendix Al3. Relationship of pools formed and not formed by LWD and gradient. 127 Relationships of LWD and geomorphic variables Appendix A14. on primary pool frequency (per 100 in) formed and not formed by LWD. Large woody debris volume (in3) is given per ten bankfull widths (TBF; within the bankfull channel). The interaction term (bankfull width x gradient) is denoted as BFW INT. Results are based on transformations of means measured at each study site. Primary Pools/100 in Formed by LWD LWD Variable r2(p) Not Formed r2(p) -.43(0.008) L1WD/100 in .54(0.002) lolume/TBF .16(0.14) .01(0.54) .13(0.18) -.37(0.017) eomorphic 1ariable Entrenchment radient -.29(0.040) 3FW .04(0.49) 3FD -.23(0.025) :D Ratio 3FW INT 3asin Area .02(0.54) -.30(0.034) .00(0.97) .35(0.020) .13(0.19) .64(0.000) .18(0.11) .39(0.008) .00(0.95) 128 Appendix A15. Relationships of LWD and geomorphic variables on primary pool spacing/b bankfull widths (10 BFW) formed and not formed by LWD. Large woody debris volume (m3) is given per ten bankfull widths (TBF; within the bankfull channel). The interaction term bankfull width x gradient is denoted as BFW INT. Results are based on transformations of means measured at each study site. Primary Pools! 10 BFW Formed by LWD LWD Variable r2(p) Not Formed r2(p) LWD/l00 m .43(0.008) -.43(0.008) Volume/TBF .44(0.007) .00(0.96) eomorphic lariable .07(0.23) -.31(0.031) -.26(0.049) .30(0.034) BFW .01(0.60) .27(0.047) 3FD .18(0.11) .62(0.001) .10(0.25) .07(0.32) 3FWINT .17(0.12) .45(0.006) 3asinArea .00(0.73) .00(0.89) Elntrenchment radient :DRatio 129 Appendix A16. Relationships of LWD and geomorphic variables on primary pool spacing/b wetted widths (10 WW) formed and not formed by LWD. Large woody debris volume (m3) is given per ten bartkfull widths (TBF; within the bankfull channel). The interaction term bankfull width x gradient is denoted as BFW INT. Results are based on transformations of means measured at each study site (Table Al). Primary Pools/b Formed by LWD LWD Variable r2(p) WW Not Formed r2(p) -.42(0.008) LWD/lOO iii .42(0.010) Volume/TBF .22(0.07) .01(0.64) .16(0.14) .29(0.039) eomorphic 1ariab1e Entrenchment radient -.42(0.009) .24(0.06) 3FW .02(0.66) .06(0.27) BFD -.36(0.018) :DRatio FW INT 3asinArea .03(0.42) -.40(0.012) .08(0.32) .47(0.005) .14(0.17) .20(0.036) .01(0.64) 130 Appendix A17. Relationships between LWD's role in pool formation and geomorphic variables. Results are based on transformations of means measured at each study site (Table Al). LWD Association with Pool Formation Geomorphic Variable Entrenchment Gradient % Forming r2(p) .26(0.052) -.35(0.020) BFW .00(0.40) BFD -.40(0.011) W:D Ratio .21(0.086) % Maintaining % No influence r2(p) r2(p) .11(0.23) .00(0.41) .23(0.069) .09(0.27) .08(0.30) .00(0.89) .41(0.010) .00(0.92) .02(0.65) .09(0.28) Appendix A18. Pools and the function of LWD associated with them. The relationship between pools and LWD were categorized: Pools formed by LWD, pools maintained by LWD, pools where LWD has provided fish cover, or pools with no direct LWD influnece. Large woody debris forming or maintaining pools also provided cover for fish. Mean pool area of pools formed by LWD and those not formed by LWD, are listed. Pools listed are primary pools only (Pool area > Wetted width2; n=263). Function of LWD Associated with Pools Form Maintain Cover No Influence Site (%) (%) (%) (%) 56 40 Pools Formed w/o LWD with LWD (m2) (m2) 22.4 23.8 13.8 12.5 27.0 32.1 11.5 8.5 18.3 20.0 18.7 21.2 19.5 7.1 24.6 37.0 40.7 22.7 16.4 6.4 Highly Constrained 1 11 33 0 2 13 3 70 75 7 0 5 40 30 10 0 18 14 25 7 4 0 10 Moderately Constrained 5 6 7 8 9 10 36 57 50 81 60 69 6 0 8 25 6 20 0 46 22 0 7 20 23 Unconstrained 11 77 12 13 14 100 15 88 54 80 9 0 0 5 0 9 0 0 17 12 12 17 20 0 0 37.8 34.3 16.2 31.5 25.3 29.2 none 13.8 59.9 13.6 () Appendix A18. Continued. Function of LWD Associated with Pools Form Cover Maintain No Influence Site (%) Highly Constrained median 41.5 42.2 mean SD All Sites median mean SD (%) (m2) (m2) 20.0 20.0 18.2 25.0 26.5 26.0 18.1 18.1 5.8 19.2 19.8 11.5 7.0 8.8 9.5 12.5 12.7 9.7 21.0 19.7 15.9 19.1 17.5 5.2 23.6 24.6 12.8 16.9 9.0 9.2 9.3 5.0 5.8 6.0 5.2 7.7 31.5 29.0 8.5 21.5 29.1 21.8 69.0 61.4 25.7 7.0 9.6 10.2 10.0 12.3 12.1 10.0 16.7 18.2 20.0 21.5 8.3 23.6 24.5 14.7 40.0 15.5 Unconstrained 80.0 median mean 79.8 SD (%) 6.0 11.2 14.8 Moderately Constrained median 58.5 mean 58.8 SD (%) Pools Formed with LWD w/o LWD 0 t..j 133 Appendix A19. Relationships of LWD and geomorphic variables on primary pooi area and volume. Large woody debris volume (m3) is given per ten bankfull widths (TBF; within the bankfull channel). The interaction term (bankfull width x gradient) is denoted as BFW INT. Results are based on transformations of means measured at each study site. Primary Pools LWD Variable Area (m2) Volume (m3) r2(p) r2(p) LWD/100 m .03(0.52) .13(0.19) lolume/TBF .01(0.67) .00(0.43) .28(0.041) .08(0.32) -.33(0.026) .07(0.34) 3FW .00(0.46) .00(0.37) 3FD .00(0.59) .13(0.13) .00(0.43) .00(0.99) -.21(0.09) .03(0.57) 3eomorphic Jariable Entrenchment radient :DRatio 3FW INT 3asin Area .52(0.006) .46(0.006) 134 Appendix A20. Relationships of LWD and Geomorphic variables on primar' pool frequency and spacing. Large woody debris volume (in) is given per ten bankfull widths (TBF; within the bankfull channel). Bankfull width and wetted width are denoted as "BFW" and "Ww", respectively. The interaction term bankfull width x gradient is denoted as BFW INT. Results are based on transformations of means measured at each study site (Table Al). Primary Pool Frequency and Spacing per 100 in LWD Variable per 10 BFW per 10 WW r2(p) r2(p) [MD/lOO in .18(0.12) .00(0.92) .03(0.52) Tolume/TBF .05(0.43) .39(0.012) .26(0.049) ntrenchment .00(0.81) .06(0.37) .02(0.60) radient .00(0.92) .00(0.97) .09(0.29) 3FW .00(0.85) .67(0.000) .12(0.21) 3FD .07(0.35) .16(0.14) .00(0.87) :DRatio .11(0.24) .02(0.62) .00(0.78) FW INT .00(0.88) .07(0.36) .02(0.58) .05(0.4-3) .01(0.75) .25(.059) r2(p) eomorphic fariable 3asin Area Appendix A21. Relationships of LWD and geomorphic variables on primary slow-water habitats size: formed and not formed by LWD. Large woody debris volume (in3) is given per ten bankfull widths (TBF; within the bankfull channel). Bankfull width, wetted width, and the interaction term (bankfull width x gradient) are denoted as BFW, WW, and BFW INT, respectively. Due to sample size (n=5), relationships for dammed poois not formed by LWD were not pursued. Pool Size (in2) Pools Formed by LWD LWD Variable LWD/l00 m o1ume/TBF Dammed Plunge r2(p) r2(p) Pools Not Formed by LWD Scour r2(p) Dammed r2(p) Plunge r2(p) Scour r2(p) .12 (0.20) .04(0.47) .00(0.97) --- .01(0.75) -.26(0.051) .15(0.15) .02(0.64) .00(0.97) --- .01(0.66) .00(0.77) .06(0.38) .49(0.004) --- -.41(0.010) .02(0.62) -.20(0.10) -.59(0.001) --- .54(0.002) .00(0.97) eomorphic Variable 6ntrenchment radient .17(0.12) -.54(0.002) BFW .00(0.84) .00(0.80) .00(0.99) --- .04(0.50) .02(0.58) BFD .06(0.38) .04(0.46) .07(0.35) --- .48(0.004) .13(0.19) .02(0.58) .12(0.21) .16(0.15) --- -.29(0.039) .00(0.93) -.42(0.009) .18(0.11) -.49(0.004) --- .53(0.002) .00(0.92) .12(0.21) --- .04(0.48) .19(0.11) :D Ratio BFW INT Basin Area .35(0.021) .66(0.000) C..) - . --.. Appendix A22. Relationships of LWD and geomorphic variables on primary slow-water habitat frequency: formed and not formed by LWD. Large woody debris volume (m3) is given per ten bankfull widths (TBF; within the bankfull channel). Bankfull width, wetted width, and the interaction term are denoted as BFW, WW, and BFW INT, respectively. Due to sample size (n=5), relationships for dammed pools not formed by LWD were not pursued. Pool Frequency/lOU Pools Formed by LWD Dammed LWD Variable r2(p) Plunge r2(p) in Pools Not Formed by LWD Scour r2(p) Danuued r2(p) Plunge r2(p) Scour r2(p) LWD/lOO in .37(0.017) .49(0.004) .05(0.43) --- .00(0.82) -.45(0.006) Tolume/TBF .17(0.13) .12(0.22) .00(0.76) --- .01(0.71) .01(0.66) .00(0.99) .00(0.77) .57(0.001) --- -.38(0.015) .14(0.17) .14(0.18) .00(0.96) -.32(0.027) --- .63(0.000) .14(0.18) BFW .00(0.73) .03(0.57) .06(0.37) --- .02(0.64) .04(0.34) BFD -.21(0.090) .11(0.22) .12(0.20) --- .57(0.001) .35(0.020) .01(0.71) .00(0.86) .02(0.66) --- -.38(0.015) .10(0.26) -.13(0.18) .00(0.81) -.36(0.019) --- .59(0.001) .18(0.12) .02(0.64) .00(0.82) .00(0.94) --- .04(0.48) .00(0.95) eomorphic Variable Entrenchment radient :D Ratio BFW INT Basin Area I1 Appendix A23. Relationships of LWD and geomorphic variables on primary slow-water habitat spacing per 10 bankfull widths: formed and not formed by LWD. Large woody debris volume (m3) is given per ten bankfull widths (TBF; within the bankfull channel). Bankfull width, wetted width, and the interaction term are denoted as BFW, WW, and BFW INT, respectively. Due to sample size (n=5), relationships for dammed pools not formed by LWD were not pursued. Pool Spacing/b Bankfull Widths Pools Formed by LWD Pools Not Formed by LWD II LWD Variable Dammed Plunge r2(p) r2(p) Scour r2(p) Dammed r2(p) Plunge r2(p) Scour r2(p) WD/100 in .32(0.029) .34(0.024) .00(0.83) --- .00(0.80) -.46(0.005) Jolume/TBF .27(0.048) .30(0.034) .02(0.66) --- .01(0.74) .00(0.86) .00(0.92) .03(0.56) .49(0.004) --- -.37(0.016) .15(0.16) .13(0.19) .00(0.99) -.44(0.007) --- .62(0.000) .11(0.23) 3FW .01(0.75) .04(0.46) .00(0.88) --- .03(0.53) .02(0.60) BFD .13(0.18) .02(0.61) .16(0.14) --- .59(0.001) .43(0.008) 7:D Ratio .03(0.50) .00(0.74) .12(0.20) --- -.35(0.021) .01(0.60) BFW INT .08(0.28) .00(0.80) -.39(0.014) --- .60(0.001) .23(0.09) BasinArea .02(0.58) .00(0.99) .00(0.99) --- .04(0.46) .00(0.86) eoinorphic Variable Entrenchment radient L) -.1 Appendix A24. Relationships of LWD and geomorphic variables on primary slow-water habitat spacing per 10 wetted widths: formed and not formed by LWD. Large woody debris volume (m3) is given per ten barikfull widths (TBF; within the bankfull channel). Bankfull width, wetted width, and the interaction term are denoted as BFW, WW, and BFW INT, respectively. Due to sample size (n=5), relationships for dammed poois not formed by LWD were not pursued. Pool Spacing/b Wetted Widths Pools Formed by LWD Pools Not Formed by LWD II LWD Variable Dammed Plunge r2(p) r2(p) Scour r2(p) Dammed r2(p) Plunge r2(p) Scour r2(p) LWD/lOOm .31(0.032) .34(0.022) .03(0.39) --- .00(0.72) -.46(0.005) lolume/TBF .20(0.10) .15(0.15) .01(0.59) --- .01(0.67) .00(0.83) .00(0.99) .00(0.86) .66(0.000) --- -.37(0.016) .13(0.19) .17(0.12) .00(0.91) -.50(0.003) --- .59(0.001) .07(0.32) BFW .00(0.93) .03(0.51) .02(0.49) --- .01(0.61) .07(0.21) BFD -.20(0.10) .14(0.17) .14(0.18) --- .57(0.001) .32(0.027) .01(0.62) .00(0.92) .02(0.55) --- -.37(0.017) .06(0.36) BFW INT .15(0.16) .02(0.52) -.50(0.003) --- .56(0.001) .13(0.19) Basin Area .06(0.38) .04(0.48) .02(0.55) --- .01(0.55) .00(0.60) eomorphic Variable Entrenchment radient :D Ratio 03 139 APPENDIX B 140 Appendix Bi. A Comparison of Geomorphic Features. Geomorphic attributes were often intercorrelated. Of the 10 constrained stream reaches, four (sites 1 - 4) were narrow, deep, and highly constrained (HC) with gradients ranging from 5.2% to 7.1% (mean 5.8, SD 0.8). Six of these streams reaches (sites 5 - 10), were wide, shallow, and moderately constrained (NC) with gradients ranging from 1.4% to 2.5% (mean 1.9, SD 0.8). The five unconstrained (UC) stream reaches (sites 11 - 15) were slightly entrenched (i.e., well-developed floodplain), wide, shallow, with gradients ranging from 0.5% to 2.0% (mean 1.1, SD 0.6; Table 2). Table B2 lists results of the simple linear regression analysis describing the relationships between geomorphic variables. Channels with a lower ER generally exhibited higher channel gradients and larger substrates. The best predictor of entrenchment was the interaction term (gradient x bankfull width). Dominant substrate size was also best predicted by this interaction term, although, gradient and bankfull width were both individually related to substrate The channels wetted width increased with basin area, size. but decreased with the interaction term (gradient x bankfull width). Variation in physical channel characteristics between levels of entrenchment were evident, although the sample sizes were relatively small. Table B3 shows the differences between the three individual channel types by geomophic 141 variable (H0: HC=MC=UC, Ha: Mean geomorphic variables are not the same in all channel types; Tukey multiple comparison test). Channel gradient between HC and the other two channel types were different (F=4.O1, P<O.001). Similarly, mean bankfull depth was greater in HC channels than the other two channel types (F=7.35, P=O.008). The interaction term (gradient x bankfull width) was also greatest in the HC channels compared to the other two channel types (F=15.85, P<O.001). The width to depth ratio within MC channels was greater than HC channels, but not the UC channels (F=4.02, P=O.046). Mean bankfull width and basin area were not different between channel types (Fl.92, P>O.05 for both). Appendix B2. Relationships between geomorphic variables. The interaction term (Bankfull width x gradient) is denoted as BFW INT. The width to depth ratio is denoted as W:D. Results are based on the trasformations of means to induce normality (Table Al). Geomorphic Variable Gradient Entrechment r2(p) Gradient r2(p) BFW r2(p) BFD r2(p) W:D r2(p) Basin Area r2(p) -.56(0.005) BFW .06(0.40) .01(0.69) BFD .15(0.15) .34(0.022) .30(0.035) W:D Ratio .04(0.48) .16(0.14) .07(0.34) .18(0.12) Basin Area .08(0.31) -.32(0.029) .00(0.84) .00(0.75) .01(0.75) BFW INT .58(0.001) .89(0.000) .18(0.11) .07(0.32) .07(0.32) -.28(0.043) Wetted Width .01(0.76) .09(0.26) .18(0.12) .00(0.72) .01(0.72) .44(0.006) .55(0.001) .37(0.013) .56(0.001) .05(0.40) .04(0.50) Substrate LJ.kLIC -.41(0.010) 143 Appendix B3. Geomorphic differences between degrees of channel constraint. Results of Tukey's One Way Analysis of Variance. Channel constraint measured by a ratio of floodprone area and bankfull width (i.e., entrenchment). The interaction Width:Depth ratio was measured at bankfull. term (bankfull width x gradient) is denoted as BFW INT. Sites 1-4 were highly constrained = "HC", sites 5-10 were moderately constrained = ttMCII and sites 11-15 were unconstrained = "UC". An "S" indicates that the mean is significantly different from the corresponding level (P<0.05) Entrenchment Level HC MC UC Width:Depth Ratio HC MC Level HC . S S HC . MC S . S MC S UC S S . UC . Gradient Level HC MC UC Bankfull Depth Level HC MC UC HC . S S HC . S S MC S . . MC S UC S . . UC S MC UC BFW INT Level HC NC UC Bankfull Width Level HC HC . S S HC . MC S . . MC . UC S . UC . Basin Area Level HC MC HC . . MC . . UC . . UC UC S .
