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Theresa M. Lowe
James P. Dobrowolski
Abstract-Maturejuniperwoodlands are characterized by spatial variability in hydrological conditions and microtopography. Coppice dunes (syn-hummocks or mounds) often occur beneath trees.
These microtopographic features, sometimes reaching elevations of greater than one meter above the surrounding interspaces, typically are characterized by superior organic matter content and relatively fine-textured soils. This research is an attempt to identify the mechanisms involved in the production of the microtopographical differences. Differences in soil morphology and plant distribution between coppice dunes and interspaces were observed in and around backhoe trenches exposing soils in the coppice dunes and interspaces. potential flow paths will be made. The specific objectives include:
1. To describe the soil morphology beneath the juniper trees and within the interspaces and the relationship to the vegetation.
2. To survey the hillslope surfaces for small scale elevation differences between tree coppice dunes and interspaces.
When juniper canopies begin to mature and close, microtopographic elements of a hillslope become more pronounced. Beneath trees, mounds or "coppice dunes" are evident. These coppice dunes appear to decrease in elevation from the tree trunk outward and they are composed of relatively fine-textured soils with incorporated leaf litter.
Within interspaces, soil surfaces can be as much as one meter (3.25 ft) lower than at the tree trunk and are covered by gravel. Heede (1987) found that the microtopography produced by tree coppices absorbed the energy of flowing water and restricted the sediment delivery downslope. With the inability to effectively measure erosion, little erosion data exists to refute or substantiate the philosophical differences involving claims of site degradation and soil loss (Price and Ridd 1991). Do sites that are dominated by mature juniper trees represent degraded or degrading systems?
Researchers have postulated that juniper succession trajectories are currently in place and are likely to continue for future centuries due to tree longevity, resulting in a selfdestructive system (Carrara and Carroll 1979; Evans 1988;
West and others, 1979).
The general objective of this study is to examine the processes occurring in a juniper ecosystem to identify sediment source or sink relationships towards answering the need for custodial or active management. It will begin with the attempt to identify the formation properties of juniper coppice dunes and how they differ or relate to the tree interspaces. The surface morphology of the juniper-covered hillslopes will be described and an attempt to model the
In: Monsen, Stephen B.; Stevens, Richard, comps. 1999. Proceedings: ecology and management of pinyon-juniper communities within the Interior
West; 1997 September 15-18; Provo, UT. Proc. RMRS-P-9. Ogden, UT: U.S.
Department of Agriculture, Forest Service, Rocky Mountain Research
Station.
Theresa M. Lowe is a Graduate Research Assistant and James P.
Dobrowolski is an Associate Professor of Rangeland Resources, Department of Rangeland Resources, Utah State University, Logan, UT 84322-5230.
The Clover Creek Watershed is located in northeastern
Tooele County approximately 32 km (20 miles) south of
Tooele, Utah (St. John Quad, Sect. 35, T.6S, R.6W). Two
3.24 ha (8-acre) exclosures were established on land leased by cooperator Darrell Johnson to investigate differences in soil chemical, physical and biological characteristics beneath juniper trees and in tree interspaces. The study area straddles the semi-desert and upland climatic zones. Precipitation averages 30.98 cm (12 inches) each year with approximately 71 percent coming as snow and 29 percent as spring and summer thunderstorms. Temperatures range from -7 to 38°C (-19 to 101°F) throughout the year (Utah
Climate Center, Johnson Pass, 1996). Soils were formed from alluvial deposits derived dominantly from limestone and were mapped as loamy-skeletal, carbonatic, mesic, shallow Petrocalcidic Palexerolls (formerly Aridic Petrocalcic
Palexerolls) of the Borvant series (Soil Survey Staff, 1996;
TrickIer and others, in press). The vegetation type is a juniper woodland integrated with a shrub steppe. The overstory is dominated by Utah juniper (Juniperus osteosperma) with an understory composed of microbiotic crusts and various grasses. Tree interspace can be divided into two categories. One type had dominants that include Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) and gray rabbitbrush (Chrysothamnus nauseosus) with over 50 percent cover and the understory composition similar to the juniper understory. The second interspace type had sparse vegetation with various grasses, microbiotic crusts and gravel.
Analysis of Soil Morphology
Four clusters of five soil pits (twenty soil pits) were established immediately outside of the exclosures. The exclosures will have long term experiments and would have been severely disturbed by the excavation of the pits within the exclosure. In each soil pit cluster, two pits were excavated in coppice dunes after tree removal, two pits were cut into adjacent interspaces and one pit was established in a nearby sagebrush stand. Some interspaces contained living and dead sagebrush plants. Sagebrush also appeared to occur in small coppice dunes. However, coppice dunes of
200 USDA Forest Service Proceedings RMRS-P-9. 1999

dead sagebrush were observed to be eroding apparently by wind, water or both.
Surface topography and geomorphology of the two exclosures were characterized using a GTS-3D Geodetic
Total Station. Vertical resolution with this instrument was approximately 0.001 m, with spatial resolution of 0.005 m
Where visible, microtopography reflecting coalescence of surface runoff was be noted on maps (fig. 1).
Soil characteristics such as depth of each horizon, depth to petrocalcic layer, petrocalcic layer thickness, pore sizes and abundance were recorded. Changes in soil color, structure and particle sizes were used to detect differences in horizons.
Field and laboratory analysis ofthe chemical characteristics such as pH by color indicators and calcium carbonate equivalen t will be cond ucted . Vegetation analysis will be cond ucted to determine percent coverage.
Detailed surface mapping (fig. 1) illustrated the interfluve surfaces with juniper trees and fluvial deposits covered primarily by living and dead sagebrush. In figure 1, the sagebrush interspaces, which will be called fluves, are found in the linear depressions identified by the solid arrows.
Small-scale changes in elevation and individual coppice dunes were visible. Field observations during rainfall-runoff events and the presence oflitterdams suggested that visible micromorphological depressions provide paths for water flow across the landscape. The next step will be to model the overland flow on these exclosures with varying water depth.
Soils were highly variable in the study area. In general, the soil under the juniper trees had an organic horizon
(table la) that was absent in the interspace and the fluve.
There was a petro calcic horizon that appeared to restrict the downward growth of roots and impede water percolation and vertical nutrient flux. This horizon was present in the three pedons but at different depths. The sparsely vegetated interspace had the petrocalcic horizon starting at 26 cm and extending to 149 cm (table lc). The petrocalcic horizon under the juniper coppice dune was deeper, starting at 37.5 cm and extending to 106.5 cm (table la). The sagebrush fluve hada weakpetrocalciclayerextendingfrom 68 to 87 cm with roots occurring in horizontal fractures throughout the horizon (table Ib). The differences in depth indicate that water will most likely infiltrate deepest in the fluve with the best possibility of vertical distribution of nutrients , depending on the amount of rain and the intensity of the storm.
The A horizon was shallowest in the interspace (13 cmtable lc) while the A horizon extended 14 cm and 30 cm under thejuniper and in the fluve, respectively (table la,b).
Soil color helped to distinguish between horizons and assisted in the identification of the differences in horizon properties between coppice dunes and tree interspaces. The pits in the sagebrush fluves had a deeper soil with evidence of multiple stages of deposition. The soil had a calcic or weakly developed petrocalcic horizon. Although Davenport and others (1996) concluded that pinyon and juniper trees had no significant influence on the soil morphology in New
Mexico, it appears from the preliminary findings that horizonation is different between coppice dunes, interspaces and the fluves in the Great Basin. This difference might influence the distribution of vegetation. Further investigations of the linkages between soil morphology, specifically the properties of the petrocalcic layers in relation to plant establishment and erosion potential are being conducted.
Figure 1Three-dimensional surface plot of coppice dunes, interspaces and fluves. Arrows indicate fluves with sagebrush. Individual coppice dunes are evident in the lower right.
USDA Forest Service Proceedings RMRS-P-9. 1999 201

Table 1 a-The representative soil pedon description for Plot 1-301 juniper coppice dune observed on 9/4/97.
The pedon for plot 1-301 is located under a juniper tree in St. John Quad, NE 1/4 of NE 1/4 sec. 35, T.6S, R.6W at an elevation of 5580 ft. The landform is a dissected fan composed of alluvium from limestone. There are no surface stones or rock fragments at this site. The slope is 5 percent with a northeast aspect. This pedon is well-drained with a water table that is deep. The site has a climate of aridic/mesic and supports vegetation such as: juniper and perennial grasses. Colors are for dry soil unless otherwise noted.
This soil is classified as a loamy-skeletal, carbonatic, mesic, shallow Petrocalcidic Palexeroll
Oi 3-0 centimeters; black (1 OYR 2/1) moist; partially decomposed root mat; loose; many fine and very fine roots; violently effervescent with a pH of 7.7; abrupt, smooth boundary.
A
AB
0-6.5 centimeters; grayish brown (10YR 5/2) sandy loam, very dark brown (1 OYR 2/2) moist; moderate fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; few medium, common fine and many very fine roots; many very fine, common fine and few medium tubular pores; gravel 5 percent; violently effervescent with a pH of 8.1; clear, smooth boundary.
6.5-14 centimeters; grayish brown (10YR 5/2) sandy loam, dark brown (7.5YR 3/2) moist; moderate medium subangular blocky structure; soft, friable, slightly sticky and slightly plastic; common coarse, medium, very fine and fine roots; common very fine, fine, medium and coarse tubular pores; gravel 1 percent; violently effervescent with a pH of 8.3; clear, smooth boundary.
BA
Bk
14-21 centimeters; brown (10YR 5/3) sandy loam, dark brown (1 OYR 3/3) moist; moderate medium subangular blocky structure; soft, friable, slightly sticky and slightly plastic; few coarse, medium, fine and very fine roots; common very fine, fine and medium tubular pores, few coarse tubular pores; gravel 10 percent with calcium carbonate seams (5 percent by voL); violently effervescent with a pH of 8.4; clear, smooth boundary.
21-37.5 centimeters; light brownish gray (10YR 6/2) very cobbly sandy clay loam, brown (10YR 4/3) moist; moderate medium subangular blocky structure; hard, very firm, sticky and plastic; common coarse, medium, fine and many very fine roots; many very fine tubular pores, common fine, medium and coarse tubular pores; gravel 10 percent with calcium carbonate in pores and on rock faces (5 percent by voL); violently effervescent with a pH of
8.3; clear, smooth boundary.
Bkm1
Bkm2
37.5-74 centimeters; white (10YR 8/1) very cobbly loamy sand, very pale brown (10YR 7/3) moist; massive; extremely hard, extremely firm, indurated; common coarse, medium, fine and many very fine roots; many very fine and fine tubular pores, common medium and coarse tubular pores; gravel 25 percent and cobbles
30 percent; violently effervescent with a pH of 8.1; clear, smooth boundary.
74-106.5 centimeters; white (10YR 8/1) very gravelly coarse sand, very pale brown (10YR 7/3) moist; massive; extremely hard, extremely firm, indurated; few very fine, fine and medium roots; common very fine pores; common very fine tubular pores; gravel 55 percent with calcium carbonate seams and coating rock faces (30 percent by voL); violently effervescent with a pH of 8.8; clear, smooth boundary.
2Bkm3 106.5-121 centimeters; white (1 OYR 8/1) gravelly coarse sand, pale brown (1 OYR 6/3) moist; moderate medium platy structure; extremely hard, extremely firm, indurated; few fine roots; many very fine tubular pores; gravel 25 percent and cobbles 1 percent with calcium carbonate seams and on ped faces (25 percent by vol.); violently effervescent with a pH of 9.2; clear, smooth boundary.
The diagnostic characteristics of this pedon include: petrocalcic horizon (37.5-106.5 cm); mollic epipedon.
202
Table 1 b-The representative soil pedon description for Plot 1-3Ew sagebrush fluve observed on 8/11/97.
The pedon for plot 1-3Ew is located in a sagebrush fluves in St. John Quad, NE 1/4 of NE 1/4 sec. 35, T.6S, R.6W at an elevation of 5580 ft. The landform is a dissected fan composed of alluvium from limestone. The surface stone and rock at this site is 10 percent gravel. The slope is 5 percent with an easterly aspect. This pedon is well-drained with a water table that is deep, >228 cm. The site has a climate of aridic/mesic and supports vegetation such as: dying big sagebrush and perennial grasses. Colors are for dry soil unless otherwise noted.
This soil is classified as a loamy-skeletal, carbonatic, mesic Xeric Petrocalcid
A
BAtk
0-8 centimeters; brown (1 OYR 5/3) fine sandy loam, dark brown (10YR 3/3) moist; weak fine granular structure; soft, very friable, slightly sticky and nonplastic; common very fine, fine, few medium and coarse roots; many fine interstitial pores; gravel 1 percent; violently effervescent with a pH of 8.2; abrupt, smooth boundary.
8-30 centimeters; light brownish gray (1 OYR 6/2) loam, dark brown (1 OYR 3/3) moist; weak medium to fine subangular blocky parting to granular structure; soft to slightly hard, friable, slightly sticky and slightly plastic; common very· fine and fine, few medium and coarse roots; common very fine and fine tubular pores, few medium and coarse tubular pores; gravel 2 percent; violently effervescent with a pH of 8.3; clear, smooth boundary.
Bk
2Bkm
30-68 centimeters; light gray (1 OYR 7/2) loam, pale brown (10YR 6/3) moist; massive; extremely hard, friable, slightly sticky and slightly plastic; few fine, medium and coarse roots; few fine, medium and coarse tubular pores; gravel <1 percent; violently effervescent with a pH of 8.4; clear, smooth boundary.
68-87 centimeters; very pale brown (10YR 8/2) very gravelly; pale brown (10YR 6/3) moist; massive; indurated; common very fine, fine and few medium roots; common fine tubular pores; gravel 40 percent; roots between Bkm fractures mostly horizontal; violently effervescent with a pH of 9.3; abrupt, wavy boundary.
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2Bk
3BCk1
87-175 centimeters; very pale brown (10YR 7/3) loamy sand, dark yellowish brown (10YR 4/4) moist; massive; hard, firm, nonsticky and nonplastic; few fine roots; many very fine and fine interstitial pores and few fine tubular pores; gravels 5 percent with thin calcium carbonate seams (1 percent by voL); violently effervescent with a pH of
9.9; clear, smooth boundary.
175-183 centimeters; very pale brown (1 OYR 7/3) extremely cobbly loamy coarse sand, yellowish brown (10YR 5/
4) moist; massive; slightly hard, friable, nonsticky and nonplastic; few fine roots; few fine tubular pores; gravels 30 percent and cobbles 40 percent with clay/silt balls (2-3 mm, <1 percent by voL); violently effervescent with a pH of
9.7; clear, smooth boundary.
4BCk2 183-206 centimeters; very pale brown (10YR 7/3) sandy loam, yellowish brown (10YR 5/4) moist; massive; slightly hard, very friable, nonsticky and nonplastic; few fine roots; few fine tubular pores; gravel 1 percent with calcium carbonate seams (1 mm, 5 percent by voL); violently effervescent with a pH of 9.8; abrupt, smooth boundary.
5BCk3 206-228 centimeters; pale brown (1 OYR 6/3) extremely cobbly loamy sand, dark yellowish brown (1 OYR 4/4) moist; single grain; loose, nonsticky and nonplastic; few fine roots; common fine pores; gravel 50 percent and cobbles 35 percent; violently effervescent with a pH of 9.2.
The diagnostic characteristics of the pedon include: petrocalcic horizon (68-87), ochric epipedon.
Table 1 C-The representative soil pedon description for Plot 1-312 sparsely vegetated interspace observed on 8/11/97.
The pedon for plot 1-312 is located in the sparsely vegetated interspace in St. John Quad, NE 1/4 of NE 1/4 sec. 35, T.6S,
R.6W at an elevation of 5,580 ft. The landform is a dissected fan composed of alluvium from limestone. The surface stone and rock at this site is 50 percent gravel. The slope is 5 percent with a northeast aspect. This pedon is well-drained with a water table that is deep, > 149 cm. The site has a climate of aridic, mesic and supports vegetation such as: cryptograms, perennial grasses and sparse sagebrush. Colors are for dry soil unless otherwise noted.
This soil is Classified as a loamy-skeletal, carbonatic, mesic Xeric Petrocalcid
A 0-5 centimeters; pale brown (1 OYR 6/3) very gravelly loam, brown (1 OYR 4/3) moist; weak medium platy parting to granular structure; hard, friable, Slightly sticky and slightly plastic; few very fine roots; few very fine and fine tubular pores; many very fine interstitial pores; upper 1-2 cm very few fine and very fine tubular and vesicular pores; gravel 40 percent; violently effervescent with a pH of 8.3; clear, smooth boundary.
BA 5-13 centimeters; light brownish gray (10YR 6/2) loam/silt loam, brown (10YR 4/3) moist; weak medium subangular blocky parting to very fine granular structure; hard, friable, slightly sticky and slightly plastic; common fine, medium, few coarse and very few very coarse roots; common fine and medium tubular pores, few very coarse and coarse tubular pores; gravel 1 percent; violently effervescent with a pH of 8.2; clear, smooth boundary.
Bw 13-19.5 centimeters; pale brown (10YR 6/3) loam/silt loam, brown (10YR 5/3) moist; moderate medium to fine subangular qlocky structure; hard, friable, slightly sticky and slightly plastic; common fine, few medium and coarse roots; common fine, few medium and coarse tubular pores; gravel 5 percent; petrocalcic fragments 1 percent; violently effervescent with a pH of 8.2; clear, smooth boundary.
Bw2
Btkm
Bkm1
Bkm2
2Bkm3
2Bkm4
19.5-26 centimeters; very pale brown (10YR 7/3), loam/silt loam, brown (1 OYR 5/3) moist; very hard, friable, slightly sticky and slightly plastic; common fine roots, few medium and coarse roots; few fine, medium and coarse tubular pores; violently effervescent with a pH of 8.2; abrupt, smooth boundary.
26-37.5 centimeters; white (1 OYR 8/1), very pale brown (1 OYR 7/3) moist; platy crumbling to fine subangular blocky structure; weakly cemented; very hard, firm; few fine roots; few fine tubular pores; gravel 5 percent; root layer at boundary; violently effervescent with a pH of 8.4; abrupt, smooth boundary.
37.5-68.5 centimeters; white (1 OYR 8/1), very pale brown (1 OYR 7/3) moist; platy crumbling to medium subangular blocky structure; weakly cemented; extremely hard, extremely firm; few fine, few medium and few coarse roots; few fine, few medium and few coarse tubular pores; roots in pores and fractures; root layer of few medium and very fine roots at boundary; gravel 10 percent; violently effervescent with a pH of 8.5; abrupt, smooth boundary.
68.5-77.5 centimeters; white (10YR 8/2), very pale brown (10YR 7/3) moist; massive; extremely hard, extremely firm, indurated; gravel 10 percent; root layer of few medium, coarse and many fine roots at boundary; violently effervescent with a pH of 9.0; clear, smooth boundary.
77.5-92 centimeters; white (10YR 8/2), light gray (1 OYR 7/2) moist; massive; extremely hard, extremely firm, indurated; gravel (fine, medium and a few coarse) 40 percent; violently effervescent with a pH of 9.0; clear, smooth boundary.
92-149 centimeters; white (10YR 8/1), very pale brown (10YR 7/3) moist; massive; extremely hard, extremely firm, indurated; gravel (coarse) 50 percent; violently effervescent with a pH of 9.3.
The diagnostic characteristics of this pedon include: petrocalcic horizon (26-149 cm), ochric epipedon.
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203

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204 USDA Forest Service Proceedings RMRS-P-9. 1999