AN ABSTRACT OF THE THESIS OF
Steven J. Zucker
for the degree of Master of Science in Fisheries and Wildlife
presented on August 19, 1993.
Title: Infuence of Channel Constraint on Primary Production. Periphyton Biomass,
and Macroinvertebrate Biomass in Streams of the Oregon Coast Range.
Abstract approved:
Redacted for privacy
5(3LiTaZ;R. Sedell
Differences in primary production and periphyton and macroinvertebrate
biomass between pairs of constrained (valley floor width of less than twice the active
channel width) and unconstrained reaches were investigated in Elk River and four
tributaries in southwest Oregon. In August 1991, macroinvertebrates were sampled
from individual cobbles, and rocks were collected to determine periphyton biomass.
In August 1992, gross primary production was estimated in the four tributaries using
closed, non-circulating chambers. Unconstrained reaches received approximately
twice as much direct solar radiation (measured with a Solar Pathfinder) as constrained
reaches. Gross primary production in unconstrained reaches was double that of
constrained reaches. Periphyton biomass did not differ between reach types. Total
macroinvertebrate biomass was 38% greater in unconstrained reaches, where scraper
biomass was 2.4 times that of constrained reaches. When regressed across streams,
gross primary production, macroinvertebrate biomass, and scraper biomass were
positively associated with solar radiation. Greater solar radiation in unconstrained
reaches is the most apparent causal mechanism for greater gross primary production,
which in turn may cause greater macroinvertebrate biomass in unconstrained reaches.
Greater invertebrate consumption in unconstrained reaches may limit periphyton
accrual, keeping standing crops at levels similar to those found in constrained reaches.
When identifying variables that shape biotic communities and determine productive
potential, channel constraint is important.
Influence of Channel Constraint on Primary
Production, Periphyton Biomass, and Macroinvertebrate
Biomass in Streams of the Oregon Coast Range
by
Steven J. Zucker
A THESIS
submitted to
Oregon State University
in partial fulfillment of
the requirements for the
degree of
Master of Science
Completed August 19, 1993
Commencement June 1994
APPROVED:
Redacted for privacy
Wildlife in charge of major
Redacted for privacy
Head of department of Fisheries and Wildlife
Redacted for privacy
Dean of Graduate Sch
Presented
August 19.1993
Typed by Steven J. Zucker
ACKNOWLEDGEMENTS
I received a great deal of assistance and support in this endeavor. I would like
to publicly thank some of the people without whom I would not have succeeded. I
appreciate the latitude that Jim Sedell, my advisor, permitted me in developing ideas
and pursuing them. Stan Gregory provided guidance and was instrumental in keeping
me in touch with some form of reality. Gordie Reeves generously provided
unpublished data that strengthened my discussion and was helpful throughout the
development of my project. Others who were very helpful include Judy Li, Bruce
Hanson, Kelly Burnett, Randy Wildman, Linda Ashkenas, Mark Harmon, Dave
McIntire, Donna D'Angelo, and Steve Fieth
TABLE OF CONTENTS
Page
INTRODUCTION
1
METHODS
4
Study Sites
4
Periphyton Biomass
4
Macroinvertebrates
8
Physical variables
8
Gross Primary Production
9
Data Analysis
11
RESULTS
12
Physical Variables
12
Gross Primary Production and Periphyton Biomass
12
Macroinvertebrates
19
DISCUSSION
32
LITERATURE CITED
39
APPENDIX
43
LIST OF FIGURES
Figure
Page
1. Location of study reaches
6
2. Summer direct solar radiation in constrained and unconstrained reaches
of five streams in the Elk River basin in summer 1991.
13
3. Summer direct solar radiation in constrained and unconstrained reaches
of five streams in the Elk River basin in summer 1992.
14
4. Mean substrate size class in constrained and unconstrained reaches of
five streams in the Elk River basin in August 1991.
15
5. Gross primary production in constrained and unconstrained reaches of five
streams in the Elk River basin in August 1992.
16
6. Relationship between gross primary production and direct solar radiation
in the Elk River basin.
17
7. Relationship between gross primary production and direct solar radiation
in constrained and unconstrained reaches in the Elk River basin
18
8. Total periphyton ash-free dry weight in constrained and unconstrained
reaches of five streams in the Elk River basin in August 1991.
20
9. Total periphyton ash-free dry weight in constrained and unconstrained
reaches of five streams in the Elk River basin in August 1992.
21
10. Total macroinvertebrate ash-free dry weight in constrained and unconstrained
22
reaches of five streams in the Elk River basin in August 1991.
11. Total macroinvertebrate density in constrained and unconstrained reaches
of five streams in the Elk River basin in August 1991.
23
12. Scraper ash-free dry weight in constrained and unconstrained reaches
of five streams in the Elk River basin in August 1991.
26
13. Collector ash-free dry weight in constrained and unconstrained reaches
of five streams in the Elk River basin in August 1991.
27
14. Relationship between total macroinvertebrate ash-free dry weight and
direct solar radiation in the Elk River basin.
28
15. Relationship between total macroinvertebrate density and direct solar
radiation in the Elk River basin.
29
16. Relationship between scraper ash-free dry weight and direct solar
radiation in the Elk River basin.
30
Figure
Page
17. Relationship between collector ash-free dry weight and direct solar
radiation in the Elk River basin.
31
LIST OF TABLES
Table
Page
1. Size of streams sampled and percent of basins harvested.
5
2. Physical characteristics of reaches sampled.
5
3. Macroinvertebrate diversity in constrained and unconstrained reaches.
24
4. Absolute and relative biomass on macroinvertebrate functional feeding
groups in constrained and unconstrained reaches.
24
Al. Data from individual channel units in 1991.
45
A2. Data from individual channel units in 1992.
48
INFLUENCE OF CHANNEL CONSTRAINT ON PRIMARY PRODUCTION,
PERIPHYTON BIOMASS, AND MACROINVERTEBRATE BIOMASS IN
STREAMS OF THE OREGON COAST RANGE
INTRODUCTION
Connections between physical features and the flora and fauna of streams have
long been a topic of interest to stream ecologists. Biota undoubtedly depend on the
physical template of stream channels and flowing water, but the mechanisms of
interactions are not thoroughly understood. Several studies have investigated physicalbiological links by examining influences of geomorphic and hydraulic factors on
habitat suitability of stream organisms (e.g., Platts 1979, Brussock et al. 1985, Lanka
et al. 1987, Moore and Gregory 1989, Benda et al. 1992). Less work has related
abundance and distribution of stream animals to physical factors through food
availability and production constraints (Culp et al. 1983, Wilzbach 1985, Coleman and
Dahm 1990). Valley landforms may play an important role in establishing habitat and
the productive potential of streams.
Investigations into the relationship between physical attributes and the biota of
streams can be conducted at several spatial scales. Clearly identifying the scale at
which processes are functioning helps us understand the applicability and universality
of those processes. Frissell et al. (1986) developed a hierarchical system to delineate
a stream network. In order of ascending spatial scale, there are microhabitats, channel
units, reaches, segments, sections, and entire stream networks. At different scales,
different physical processes assert varying degrees of influence (Frissell et al. 1986,
Gregory et al. 1991). At a broad spatial scale, the River Continuum Concept
(Vannote, et al. 1981) provided a framework for relating physical and biological
2
characteristics from headwaters to large rivers, primarily at the level of sections or
segments of streams. Other studies have focused on how physical processes at the
channel unit scale influence biota (e.g., Culp et al. 1983, Huryn and Wallace 1987).
Little attention has been given to the spatially intermediate scale of stream reaches.
To understand the physical-biological link, one must first identify the physical
attributes that may be important in structuring biotic communities. A reach is made
up of a group of continuous channel units (e.g., pools, riffles, rapids, etc.) that share
a common valley landform pattern (Grant et al. 1990). The length of a reach can
range from several meters to many kilometers, depending on the size of the stream,
topography, geology, and climate. Reaches are classified by the degree to which the
channel is constrained by its valley walls and by the mechanism of constraint, such as
bedrock walls, alluvial fans, or earthflows (Grant et al. 1990). A reach that has a
valley floor wider than twice the active channel width is operationally defined as
"unconstrained" (Gregory et al. 1989). The term "constrained" is illustrated by
examples such as canyon gorges or steep, cascading mountain streams bounded by
bedrock and strewn with boulders. Unconstrained channels are represented by broad
alluvial floodplains, alpine meadows, or sinuous lowland rivers. These examples are
extremes; differences between reach types are often less pronounced. Valley
landform patterns are seldom constant throughout the length of a stream section.
Localized areas of each reach type can be found in almost every kind of stream.
Biological significance of the categorical distinction between reach types needs
to be explored. A stream channel in steep montane regions is usually constrained
throughout much of its length, but often has areas where the valley walls are farther
apart, allowing shifting of the channel and development of restricted floodplains.
Unique physical qualities of these unconstrained reaches may be significant to stream
biota. Differences between reach types in the biological components of streams must
3
first be identified, and then causes for these differences can be explored to determine
the role of channel constraint in shaping stream communities.
Solar radiation may be a primary intermediate through which channel
constraint influences the productivity of a stream. The wider valley floors of
unconstrained reaches potentially permit more light to reach the stream channel due to
less topographic shading than in constrained reaches, the channels of which are
partially shaded by the impinging valley walls. Greater solar radiation in
unconstrained reaches would be likely to cause greater primary production (Gregory
1980, Hill and Harvey 1990) and greater macroinvertebrate abundance (Towns 1981,
Behmer and Hawkins 1986). The extent to which solar radiation is dependent on
channel constraint and the effects of solar radiation on biota in the context of different
reach types warrant investigation.
This study assesses the reach scale response of biotic variables to differences in
geomorphic channel constraint in streams of a 200-km2 basin in southwest Oregon.
Gross primary production, periphyton, and macroinvertebrates were examined in pairs
of constrained and unconstrained reaches of Elk River and four tributaries.
4
METHODS
Study Sites
Elk River is a sixth-order stream with a 200 -km2 drainage area in the Coast
range of southern Oregon. Over three-quarters of this steep, highly dissected basin is
within the Siskiyou National Forest. Less than 20% of the total length of stream
channel is unconstrained. Hills lopes are vegetated predominantly by Douglas fir
(Pseudotsuga menziesii), and riparian vegetation is primarily red alder (Alnus rubra),
with some areas of bigleaf maple (Acer macrophyllum) and willow (Salax spp.).
Oregon myrtle (Umbelluleria califomica) occasionally are interspersed with the more
prevalent species. Elk River supports winter steelhead (Oncorhynchus mykiss), fall
chinook (0. tshawytscha), and coastal cutthroat trout (0. clarki clarki). Climate is
generally wet and mild, with 80% of the 230 cm of annual precipitation falling
between October and March, mostly as rain (McHugh 1986). Dominant land use is
logging; approximately 25% of the basin has been harvested (Table 1).
A pair of constrained and unconstrained reaches were identified in each of four
tributaries and the mainstem (Figure 1, Table 2). The two reaches were immediately
adjacent only in Anvil Creek. In the other four streams, areas of intermediate
constraint occurred between the constrained and unconstrained reaches.
Periphyton Biomass
In August 1991, three pools and three riffles from each reach were randomly
selected. From each channel unit, two sets of three rocks were systematically chosen
by laterally and longitudinally stratifying the unit into thirds, and using a randomized
5
Table 1. Size of streams sampled and percent of basin harvested (adapted from Ryan
and Grant 1991).
DRAINAGE AREA
STREAM
ORDER
(km)
% OF BASIN
HARVESTED
Anvil Creek
3
7.1
10
Mainstem Elk River
6
200
25
North Fork Elk River
4
24.5
8
Panther Creek
5
23.6
35
Red Cedar Creek
4
7.7
0
a VFWI (valley floor width
Table 2. Physical characteristics of reaches sampled.
index) is valley floor width/active channel width; water temp is maximum
September water temperature; c unavailable due to equipment malfunction.
STREAM
REACH
WETTED
CHANNEL GRADIENT
VFWIa
WIDTH (m)
(%)
Anvil Creek
Constrained
Unconstrained
2.59
Mainstem Elk River
Constrained
Unconstrained
North Fork Elk River
Constrained
Unconstrained
WATER
TEMP
(oc)o
3.77
5.77
5.8
2.6
15.0
17.0
11.28
12.48
1.5
3.87
2.1
18.0
18.0
1.36
4.04
8.27
7.80
3.2
2.4
--c
18.0
1.33
7.37
7.98
2.0
2.4
18.5
18.0
3.75
4.43
2.2
2.1
17.0
18.0
1.43
1.25
Panther Creek
Constrained
Unconstrained
2.93
Red Cedar Creek
Constrained
Unconstrained
2.76
1.08
Constrained Reach
0 Unconstrained Reach
0
I
1
2
N
I
Miles
Red
Cedar
-----
Port
Orford
......
........... -----------------------------
Figure 1. Location of study reaches.
CIN
starting point. One set of three rocks was placed in an opaque plastic bag, and the
other set of three rocks was scraped with a stiff brush to remove periphyton. At the
end of the day, the rocks were frozen and the periphyton scrapings were
homogenized. One aliquot from each periphyton sample was vacuum filtered through
a pre-weighed Whatman GFF filter, and another equal aliquot was filtered through a
Millipore membrane filter. The filters were then frozen.
Chlorophyll and biomass were measured within two weeks of collection. GFF
filters were dried at 55°C for 24 h, weighed to the nearest 0.1 mg., combusted at
550°C for 8 h, and then reweighed. Millipore filters were dissolved in 95% basic
acetone and analyzed for chlorophyll content using the trichromatic method
(Strickland and Parsons, 1968). A ratio of periphyton biomass to chlorophyll a was
calculated for each channel unit. Frozen rocks were soaked in 95 % basic acetone for
24 h in the dark at 5°C.
Total chlorophyll content of each set of three rocks was
determined by trichromatic analysis of the acetone solution. Total periphyton biomass
was computed by multiplying total chlorophyll a by the corresponding biomass to
chlorophyll ratio.
Surface area of each rock was extrapolated from the length, width and height,
using a regression equation developed from 36 rocks from different reaches. The
equation developed is surface area = -0.888 + 0.065*length + 0.108*width +
0.134*height. Surface area of each of the 36 rocks was estimated by covering the
rock with a single layer of aluminum foil and then weighing the foil (Lamberti et al.
1991). In computing total biomass per m2 at each site, the total surface area was
divided by two, since approximately half of each rock was available for periphyton
colonization.
8
Macroinvertebrates
At the same time periphyton was sampled, benthic macroinvertebrates were
sampled using individual rocks (approximately 7 to 15 cm in diameter) as the
sampling unit (Wrona et al. 1986). Three rocks were selected from each channel unit
using the same scheme as used for the periphyton. A Surber sampler with 0.25-mm
mesh was placed downstream of each rock to catch organisms dislodged as the rock
was lifted off the stream bottom. Invertebrates were brushed from the rock by hand
and rinsed into the Surber sampler. Invertebrates and debris from the three rocks
were rinsed through a 0.25-mm sieve and preserved in the field using 95% ethanol.
Mean length, width and height of each rock were measured for later estimation of
surface area using the regression developed from rocks used for periphyton analysis.
Macroinvertebrates were identified to genus (except for chironomidae and any pupae,
which were identified to family), counted, and measured to the nearest 0.2 mm of
total body length. Regression equations from Smock (1980) were used to estimate
biomass from lengths. Each taxon was assigned to a functional feeding group
following Merritt and Cummins (1984) and Hawkins and Sedell (1981). Community
diversity of the rock samples was computed for each reach using Simpson's Index
(1/D).
Physical variables
Energy from direct sunlight was estimated using a Solar Pathfinder at each
channel unit. Amount of photosynthetically active radiation that penetrates a partial
canopy depends on both the size and orientation of canopy openings (Chazdon and
Pearcy 1991, De Nicola et al. 1992). A Solar Pathfinder incorporates the sun angle
with the south-facing canopy to account for direct solar radiation, but does not
measure diffuse light. By tracing an overlay of canopy opening onto a grid of
daylight hours and months of the year, average daily Megajoules per square meter
were calculated for each month of the year. Values for the summer months of May
through August were averaged to give a single estimate of summer direct solar
radiation for each channel unit.
Several other physical parameters were measured in 1991. Average gradients
of each reach were measured with a clinometer. Maximum-minimum thermometers
were placed in each reach for three weeks in late summer. Widths of wetted channel
(summer low flow), active channel (estimated highest annual flow), and valley floor
(surfaces up to 2 m higher than the active channel) were measured. Substrate
composition was determined at each channel unit by visually estimating percentages of
different size classes, and computing an index of mean substrate size class.
Gross Primary Production
In August 1992, gross primary production was estimated in the same reaches
of the four tributaries. Due to time limitations, gross primary production was not
measured in the mainstem. Many of the channel units sampled in 1991 were used
again in 1992, but some new channel units had to be selected to minimize travel time
among units that were being sampled simultaneously. Clear, 3.8-liter polyethylene
containers were used as closed, non-circulating production chambers. Each container
had a 25-mm hole drilled in one side near the bottom. The hole was sealed with a
cork during production runs, but permitted the insertion of a YSI dissolved oxygen
probe with minimal air contact. Three rocks were selected from each channel unit
and placed in a container, which was filled with stream water. Initial dissolved
10
oxygen was measured with a YSI model 57 oxygen meter and then the container was
submersed in a horizontal position in the center of the channel unit, or in the nearest
location that was deep enough to cover the chamber (approximately 20 cm).
Gross primary production (GPP) was measured in paired reaches within each
tributary on successive sunny days. Net primary production (NPP) was measured by
changes in dissolved oxygen during daylight incubations. Community respiration
(CR) was measured by changes in dissolved oxygen during nighttime incubations.
GPP was estimated by summing NPP and CR for the photoperiod. Lack of
circulation in production chambers probably resulted in an underestimate of GPP
(Rodgers et al. 1978). Consistency of measurement technique should allow relative
comparisons of metabolic rate estimates between reaches. Incubations were run
concurrently in all six channel units of each reach, with a 10 minute delay between
each channel unit. In each of the two reaches in Red Cedar Creek, two successive
light trials of 2.0 h each were run during the middle of the day. Three successive
midday trials of 1.5 h were used in all other reaches. At the end of each 1.5 or 2.0-h
trial, the container was brought to the edge of the stream where the disolved oxygen
of the water in the chamber was measured. The chamber was returned to the center
of the stream and the lid was removed underwater. The open container was left on
the stream bottom for two minutes of mixing with fresh stream water. Water
appeared to circulate well, entering the open end facing upstream and exiting through
the hole in the top at the downstream end. The lid was replaced, the dissolved
oxygen of the water in the chamber measured, and the chamber returned to the stream
bottom. Following the final light trial (in late afternoon), the chamber was double
wrapped in a dark, opaque plastic bag before being returned to the stream. The
"dark" chamber was left in the stream overnight. The following morning the chamber
was removed and the dissolved oxygen measured. Rocks were then removed and
11
placed in opaque plastic bags with as little disturbance as possible. Bagged rocks
were placed in a shaded part of the stream until later in the day, when they were
removed and frozen. Another set of three rocks from each channel unit were scraped
of periphyton to determine a biomass to chlorophyll ratio, and total periphyton
biomass was determined from the rocks used in the primary production incubations.
Data Analysis
Because the scale of interest was the reach, channel units were treated as
stratified subsamples. Values from the six channel units were averaged to give one
value for each reach. Data from individual channel units can be found in the
appendix. A randomized block design (Sokal and Rohlf, 1969) was used, with stream
as the block and reach type as the treatment. Analyses of variance (ANOVAs) were
run using SAS to test differences between reach types for biological measures and
physical variables. Regressions were used to examine associations between physical
parameters and biotic components. Analysis of covariance was performed for GPP
with solar radiation as the covariate to test for reach effects other than solar radiation.
12
RESULTS
Physical variables
Unconstrained reaches received greater direct solar radiation than constrained
reaches. At the 1991 sample sites, solar radiation in unconstrained reaches was 2.6
times that in constrained reaches, but the range was from 62% in Panther Creek (less
light in unconstrained reaches) to 690% in Red Cedar Creek (Fig. 2, p = 0.091).
Data from 1992 revealed a similar trend; solar radiation in unconstrained reaches was
1.8 times that of constrained reaches (Fig. 3, p = 0.073).
Other physical variables measured did not display dramatic differences
between reach types. Gradient and maximum water temperature in September did not
differ significantly between reach types (Table 2). Mean substrate size class was
significantly larger in constrained reaches, but this difference was minor, and all ten
reach means were between the large gravel (11-100 mm in diameter) and cobble (101-
300 mm in diameter) categories (Fig. 4, p = 0.045).
Gross Primary Production and Periphyton Biomass
Gross primary production in unconstrained reaches was twice that of
constrained reaches (Fig. 5, p = 0.099), displaying a pattern similar to that of solar
radiation. There was a significant positive relationship between gross primary
production and direct solar radiation (Fig. 6). Analysis of covariance (ANCOVA) did
not reveal any significant differences between reach types in the relationship between
GPP and solar radiation (Fig. 7, p = 0.203).
Despite greater solar radiation and greater gross primary production in
14
4,
4
12
Constrained
Unconstrained
10
8
6
Col
0
4
2
0
Anvil
Mainstem
North Fork
Panther
Red Cedar
Figure 2. Summer direct solar radiation in constrained and unconstrained reaches of five
streams in the Elk River basin in August 1991. Bars represent one standard error; n = 6.
8
P.,
4...* 4
MN
Constrained
Unconstrained
6
.-411.4-
, * 4, ,
.41.****.
.
414,4
,
.
,40.41.*
41.41.1 0,
.
.
.41.
.**,
.4
.
,
'i 4..
0
Anvil
*****
4 .
.4 .*.
North Fork
fr* *
Panther
Red Cedar
Figure 3. Summer direct solar radiation in constrained and unconstrained reaches of five
streams in the Elk River basin in August 1992. Bars represent one standard error; n = 6.
Boulder 8
(> 300 mm)
Constrained
Unconstrained
Cobble 7
(101no
,1
.4
Lg. gravel 6
(11-100 mm)
Sm. gravel 5
(3-10 mm)
0
4
1
4
4
1,404
0
4
,4
1
4
0
1
4
4
4
4
0
4
0
4
0
4
0
4
0,4
+4
4
1.44
0 41 ,4
144
0
4
0
4
1
0
4
0
4
4
0
4
4
1
4
.404
10
4
0
4
0
4
1
41, 1
0
4
1
4
1
4
1
4
t.
ii
4
1 41a4
41-4
4
-.4
4
410,4
4
4
,4
0
4
4
4
4
I 41
.4
4
0
4
4
4
4
0..4
1
,,4
4
4
4
4
Sand 4
4
1
0 41.4
,
04
1.
1
.4
0
4
4
1
4
41,1
I
4
41
41
(< 3 mm)
Anvil
Mainstern
North Fork
Panther
Red Cedar
Figure 4. Mean substrate size class in constrained and unconstrained reaches of five
streams in the Elk River basin in August 1991. Bars represent one standard error; n
6.
100
40
..4
0"
0
80
60
0
O
C.
Constrained
Unconstrained
40
1.4
:****
**V
20
I,,
--
c.
0
Anvil
:0
V,
***
North Fork
:
Panther
Red Cedar
Figure 5. Gross primary production in constrained and unconstrained reaches of five streams
in the Elk River basin in August 1992. Bars represent one standard error; n = 8.
2
3
4
5
6
7
Direct Solar Radiation (Mjoules /m2 /Summer Day)
Figure 6. Relationship between gross primary production and direct solar radiation in the Elk
2
River basin. y = 16.2 + 8.0x; r = 0.58.
Constrained reaches;
V Unconstrained reaches.
80
771
ck)
0
70
V
V
60
V
50
7_1
40
s.
30
20
0
10
0
1
0
1
2
3
4
5
7
6
Direct Solar Radiation (Mjoules /m2 /Summer Day)
Figure 7. Relationship between gross primary production and direct solar radiation in constrained
and unconstrained reaches of the Elk River basin.
Constrained reaches (solid line), y = 13.3 +
2
2
6.7x, r = 0.85; y Unconstrained reaches (dashed line), y = 35.5 + 5.1x, r = 0.32.
19
unconstrained reaches, periphyton biomass was similar in the two reach types.
Periphyton biomass did not significantly differ in 1991 (Fig. 8, p = 0.700) or in 1992
(Fig. 9, p = 0.331).
Macroinvertebrates
Unconstrained reaches also supported greater macroinvertebrate abundance
than constrained reaches. Total macroinvertebrate biomass in unconstrained reaches
was 1.4 times that of constrained reaches (Fig. 10, p = 0.069). Total
macroinvertebrate density did not differ significantly between reach types (Fig. 11, p
= 0.224), though there were more macroinvertebrates per square meter in
unconstrained reaches of four of the five streams. Panther Creek had twice as many
organisms, but less biomass in the constrained reach. Much of this difference can be
attributed to many early instar Baetis spp. and Heptageniidae in the constrained, and
more final instar Glossosomatidae and large Perlidae in the unconstrained reach.
Diversity of macroinvertebrates associated with rocks did not significantly
differ between reach types (Table 3, p = 0.260). This does not necessarily reflect
total community diversity because my sampling method focused on individual rocks.
Although habitats sampled represented most of the stream bottom, habitats not
sampled (sediments, interstitial areas, organic debris, bedrock, sand) may contribute
taxa not collected in the rock samples. Without accounting for genera of
Chironomidae, the average number of taxa in each reach type was 36.8 (Table 3).
Both reach types had similar invertebrate communities associated with rocks.
Biomass was dominated by large predatory stoneflies; Calineuria californica,
Hesperoperla pacifica, and Perlinodes spp. made up 30% of total biomass.
Chironomidae comprised 13% of the biomass, Glossosomatidae (Glossosoma sp. and
12
4.14
10
Constrained
Unconstrained
cv
ap
0
Cs
0 10 4
4
4
4
411.4
04
0
4
0
0
4
41
0, II.
0.11'4
4
0 410. 1
1
40.4
0
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1
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4
41741
4114
"C.
cv
111.4
0
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I
0
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I
4
41, 4
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40'1
41.4
0 4074
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Mainstem
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North Fork
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.4
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/,
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.1
4
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4
0
4
0 4 l4
4
04
0
4
.4
4
0
1
0
4
01
Panther
Red Cedar
Figure 8. Total periphyton ashfree dry weight in constrained and unconstrained reaches of
five streams in the Elk River basin in August 1991. Bars represent one standard error; n = 6.
12
,.. .1 I
0.11'4.4
10
Constrained
Unconstrained
8
',
...
.
4
0
Anvil
North Fork
Panther
Red Cedar
Figure 9. Total periphyton ashfree dry weight in constrained and unconstrained reaches of
five streams in the Elk River basin in August 1992. Bars represent one standard error; n = B.
i-A
Constrained
Unconstrained
oo
(15
0
c.
1.4
a)
I
4
I
4
I
4
4
0
1
.4
4
V
I
4
41 4
4
4
I4
4
0
11
41
41
4
4
0
I
I
4
Anvil
Mainstem
4
North Fork
Panther
Red Cedar
Figure 10. Total macroinvertebrate ashfree dry weight in constrained and unconstrained reaches
of five streams in the Elk River basin in August 1991. Bars represent one standard error; n = 6.
1174
30000
Constrained
Unconstrained
a
20000
10000
0
Anvil
Mainstem
North Fork
Panther
Red Cedar
Figure 11. Total macroinvertebrate density in constrained and unconstrained reaches of five
streams in the Elk River basin in August 1991. Bars represent one standard error; n = 6.
24
Table 3. Macroinvertebrate diversity in constrained and unconstrained reaches.
aCONST is constrained reach; UNCON is unconstrained reach.
STREAM
NUMBER OF TAXA
DIVERSITY (1/D)
CONSTa UNCON'
CONSTa UNCONb
Anvil Creek
32
36
4.20
4.50
Mainstem Elk River
37
38
5.62
6.59
North Fork Elk River
39
40
5.32
3.97
Panther Creek
41
33
6.42
8.96
Red Cedar Creek
35
37
3.49
5.52
Table 4. Absolute and relative biomass of macro-invertebrate functional feeding
groups in constrained and unconstrained reaches. Reach means were normalized by
gream to account for differences between streams. aCONST is constrained reaches;
'UNCON is unconstrained reaches.
BIOMASS (g/m2)
CONSTa
UNCONb
% OF TOTAL
BIOMASS
CONSTa
UNCONb
Total
1.281
1.716
100
100
Scraper
0.197
0.422
16.3
25.6
Collector
0.388
0.609
29.8
28.6
Predator
0.625
0.482
43.6
28.6
Shredder
0.020
0.038
1.7
2.4
Filterer
0.087
0.063
7.0
2.0
Other
0.028
0.038
1.5
3.5
25
Agapetus sp.) accounted for 10%, and Heptageniidae (mostly Heptagenia sp.) made
up 9%. Density in both reach types was dominated by smaller individuals of
Chironomidae, Micrasema sp., Baetis spp., Heptageniidae, and Hydracarina.
Macroinvertebrates were categorized by functional feeding groups, and only
scraper biomass significantly differed between reach types (Fig. 12, p = 0.044).
Unconstrained reaches had 2.4 times the scraper biomass of constrained reaches.
Proportion of total macroinvertebrate biomass comprised of scrapers (relative biomass
of scrapers) was greater in the unconstrained reaches of all five streams, but this
difference was not statistically significant (Table 4, p = 0.163). Biomass of
collectors in unconstrained reaches averaged 1.7 times that of constrained reaches, but
this difference also was not statistically significant (Fig. 13, p = 0.139). Shredders
and filterers were minor components of the samples and did not display significant
trends.
Total macroinvertebrates, scrapers, and collectors were positively associated
with solar radiation. Regressions of macroinvertebrate biomass (Fig. 14) and
macroinvertebrate density (Fig. 15) on direct solar radiation resulted in significant
positive relationships. Scrapers (Fig. 16) and collectors (Fig. 17) were the only
functional feeding groups that were significantly related to direct solar radiation.
1.5
.4
Constrained
Unconstrained
I
0
V2
0.0
Anvil
Mainstem
North Fork
Panther
Red Cedar
Figure 12. Scraper ashfree dry weight in constrained and unconstrained reaches of five
streams in the Elk River basin in August 1991. Bars represent one standard error; n = 6.
2.0
.
Constrained
Unconstrained
1.5
Ckl
0
0
1 .0
ca
ti
0
I
6>
78
C.)
0.5
:4,44
4
I,
4
I
4
4
4.4
.4
0.0
Anvil
Mainstem
North Fork
Panther
Red Cedar
Figure 13. Collector ashfree dry weight in constrained and unconstrained reaches of five
streams in the Elk River basin in August 1991. Bars represent one standard error; n = 8.
2.5
2.0
V
Fi
OD
1.5
0
V
1.0
ti
0.5
0.0
0
2
4
6
8
10
12
Direct Solar Radiation (lijoules/m2/Summer Day)
Figure 14. Relationship between total macroinvertebrate ashfree dry weight and direct solar radiation in
the Elk River basin. y = 0.87 + 0.13x; r 2 = 0.61.
Constrained reaches;
y Unconstrained reaches.
25000
V
20000
cs/
15000
c3)
Y.
10000
0
S
V
5000
0
0
2
4
6
8
10
12
Direct Solar Radiation (Mjoules /m2 /Summer Day)
Figure 15. Relationship between total macroinvertebrate density and direct solar radiation in the Elk
River basin. y = 4216 + 1269x; r2 = 0.52.
Constrained reaches;
y Unconstrained reaches.
0.8
0.7
0.6
0.5
130
03
0$
ti
0.4
V
V
0
cn
ri)
R.
0.3
0
ri)
0.2
0.1
0.0
0
I
I
I
I
I
2
4
6
8
10
1
12
2
Direct Solar Radiation (ifjoules/m / S u mm e r Day)
Figure 16. Relationship between scraper ashfree dry weight and direct solar radiation in the Elk
River basin. y = 0.13 +0.04x; r2 = 0.36.
Constrained reaches;
y Unconstrained reaches.
1.6
1.4
1.2
1.0
rn
0.8
O
CQ
O
0.6
V
O
0.4
V
0.2
0.0
1
0
2
4
6
8
10
12
2/Summer
Direct Solar Radiation (Kjoules/m
Day)
Figure 17. Relationship between collector ashfree dry weight and direct solar radiation in the Elk
River basin. y = 0.11 +0.08x; r2 = 0.50.
Constrained reaches;
y Unconstrained reaches.
32
DISCUSSION
In the Elk River drainage, one of the most distinct connections between
channel constraint and stream biota was through availability of light to the wetted
channel.
Solar radiation is a primary source of energy to the biota of a stream.
Even in small streams with dense riparian canopies, autochthonous production may be
more important than allochthonous inputs (Minshall 1978, Mayer and Likens 1987).
Valley walls adjacent to the stream channel limited solar energy available to primary
producers. Greater solar radiation in unconstrained reaches increased gross primary
production, which then potentially influenced macroinvertebrate primary consumers.
The relationship across streams between macroinvertebrates and solar radiation
suggests that light may be a primary link between channel constraint and
macroinvertebrates.
Valley landform plays a prominant role in determining the amount of light that
reaches the stream. Unconstrained reaches received more solar radiation because of
less topographic shading and wider active channels, resulting in greater distance
between the wetted channel and the riparian canopy. Local topography and riparian
vegetation determine the degree of attenuation of incident solar radiation.
Topographic shading is a primary factor limiting solar radiation in constrained reaches
in the Elk River drainage. Hills lope vegetation and bedrock walls that usually shaded
constrained channels were set back farther from unconstrained channels, permitting
riparian vegetation to play a more prominent role in limiting solar radiation inputs to
the wetted stream channel.
Constrained reaches were fairly consistently shaded, but there was a wide
range of solar inputs to unconstrained channels, where incident light was limited
primarily by riparian vegetation. Using a series of air photos, Ryan and Grant (1991)
33
investigated the persistence of canopy openings over a twenty-three year period in the
Elk River basin. Sections of stream channels that corresponded with unconstrained
reaches displayed some persistently open areas and some areas of dynamic changes in
canopy opening through time. Constrained reaches seldom had large canopy openings
and the canopy closure was more stable through time (Ryan and Grant 1991).
Floodplains permit the development of diverse and variable vegetation (Osterkamp
and Hupp 1984, Gregory et al. 1991). Riparian vegetation can reduce incident solar
radiation to as low as 5% of full sunlight (Hill and Harvey 1990). In the Elk River
basin, large deciduous trees (usually red alder and bigleaf maple) sometimes
effectively shaded unconstrained reaches by extending over the channel. Wetted low-
flow channels were seldom in the center of unconstrained valley floors. Often they
were adjacent to one hillslope, which increased topographic shading on one side of the
stream to levels similar to that of constrained reaches.
Though more variable, solar
radiation in unconstrained reaches was double that of constrained reaches.
Greater solar radiation in unconstrained reaches resulted in greater gross
primary production. Light is often the major factor limiting primary production in
shaded and partially shaded streams (Gregory 1980, Lowe et al. 1986, Hill and
Harvey 1990, DeNicola et al 1992). Many of the sample sites in the Elk River basin
were moderately to heavily shaded, suggesting GPP was probably light limited. Even
in the more open unconstrained reaches, solar radiation was likely to be limiting
during some hours of the day. The strong relationship between direct solar radiation
and GPP across streams suggests that light was an important factor influencing the
rate of gross primary production.
The positive association between solar radiation and macroinvertebrate
biomass implicates light as a possible causal mechanism for greater macroinvertebrate
biomass in unconstrained reaches. Macroinvertebrates have been shown to be more
34
abundant in reaches with greater solar radiation (Towns 1981, Hawkins et al. 1982,
Behmer and Hawkins 1986, Robinson and Minshall 1986). Greater absolute and
relative biomass of scrapers in unconstrained reaches was probably a result of greater
GPP. Collector biomass may also be related to GPP. Periphyton is a higher quality
food source than allochthonous detritus (Minshall 1978, Anderson and Cummins
1979, Gregory 1980) Increased availability of a high quality source of food may
account for greater total macroinvertebrate biomass in unconstrained reaches, which
had higher solar radiation (Hawkins et al. 1982, Behmer and Hawkins 1986).
Effects of greater solar radiation in unconstrained reaches may influence
higher trophic levels as well. In the Elk River basin, unconstrained reaches made up
15% of the wetted channel area, but supported 31% of the total salmonid abundance
(G. H. Reeves, USFS PNW Research Station, Corvallis, Oregon, personal
communication). Fish densities in unconstrained reaches were consistently greater
than those of constrained reaches in each of the eight years sampled (G. H. Reeves,
personal communication). In Lookout Creek in the Oregon Cascades, unconstrained
reaches supported greater trout densities than constrained reaches (Moore and Gregory
1989). Greater fish densities in unconstrained reaches may be due to increased
productivity of lower trophic levels. Murphy et al. (1981) attributed greater
vertebrate predator abundance in unshaded stream reaches to greater prey abundance.
In the Elk River basin, channel constraint, through its influence on solar radiation,
may affect biotic productivity at trophic levels from primary producers all the way up
to fish.
Though the standing crop of algal material was not greater in the open,
unconstrained reaches in this study, more periphyton was being produced. Periphyton
biomass can be affected by several factors, including production, consumption,
export, taxonomic composition and physiological state of the algal community. In
35
this study, discrepancy between increased production but similar biomass can be
attributed to greater invertebrate consumption in the unconstrained reaches. Several
studies have demonstrated the ability of grazers to limit algal accrual in artificial
channels (e.g., Lamberti et al. 1989a, DeNicola et al. 1991) and in the field (e.g.,
Hill and Knight 1987, Winterbourn and Fegley 1989). In open reaches of Big
Sulphur Creek in California, for example, grazers limited periphyton accrual, and
standing crop of algae was similar to that of shaded reaches (Feminella et al. 1989).
This phenomenon may be occurring in Elk River and its tributaries. Greater scraper
biomass in unconstrained reaches is likely to exert a greater influence on periphyton
biomass than in constrained reaches that support less scraper biomass. Although more
algal material is being produced in unconstrained reaches, more is also being
consumed, resulting in periphyton standing crops similar to those of constrained
reaches.
Increased productivity in unconstrained reaches may be due to more than just
increased solar radiation. Analysis of covariance did not reveal significant differences
between constrained and unconstrained reaches in the response of GPP to solar
radiation, but statistical power was low due to small sample size (four pairs of
reaches). The data suggest, however, that unconstrained reaches may support greater
gross primary production than constrained reaches at similar levels of solar radiation
(Fig. 7). Channel constraint may influence gross primary production (and
consequently higher trophic levels) through other factors, in addition to solar
radiation.
Other factors that may affect rates of primary production include water
temperature (Rounick and Gregory 1981) and nutrients (Gregory 1980, Hill and
Knight 1988). In this study, reach types did not significantly differ in maximum
September water temperature. Greater solar radiation in unconstrained reaches,
36
however, is likely to increase water temperature (Brown and Krygier 1970, Beschta
and Taylor 1988), although this effect could be minor or offset by other factors. In
four of the five streams sampled, unconstrained reaches were upstream of constrained
reaches. In Anvil Creek the constrained reach was upstream of and 2°C cooler than
the unconstrained reach.
Channel constraint can influence the availability of nutrients to stream biota.
Unconstrained reaches of Lookout Creek in the Oregon Cascades had greater
hydraulic and particulate retention than constrained reaches (Lamberti, et al. 1989b).
Greater hydraulic retention would tighten nutrient spiralling (Newbold et al. 1981),
giving primary producers more opportunity to utilize potentially limiting nutrients.
Particulate organic matter must be physically retained before it can be broken down to
release nutrients for the potential use by stream biota (Newbold et al. 1981, Lamberti
et al. 1989b). Greater retention in unconstrained reaches could enhance GPP through
nutrient availability.
Differences in hyporheic patterns between the two reach types may also
influence the availability of nutrients to primary producers. Hyporheic zones can
influence productivity of surface water by modifying cycling of nutrients (Grimm and
Fisher 1984, Triska et al. 1989, Valett et al. 1990). Reaches constrained by their
valley walls have very little opportunity for hyporheic exchange. Terraces and
floodplains of unconstrained reaches offer much more potential for lateral hyporheic
flow. Potentially greater hyporheic flow and more active exchange with surface water
may augment the effects of solar radiation on GPP in unconstrained reaches.
Valley landform may affect macroinvertebrate abundance in ways other than
through solar radiation and primary production. Periphyton is not the sole food
source of stream macroinvertebrates. Unconstrained reaches may receive greater
allochthonous inputs from floodplain vegetation. Greater particulate retention in
37
unconstrained reaches (Lamberti, et al. 1989b) increases food available to shredders
and collectors. Differences in retention may affect macroinvertebrates more
profoundly during and after autumn leaf fall.
Habitat suitability also can significantly influence macroinvertebrate distribution
(Culp et al. 1983, Statzner and Higler 1986, Huryn and Wallace 1987). Differences
between reach types in macroinvertebrate and fish habitat may become more
pronounced during the higher flows of winter. Constrained reaches with abrupt
margins do not have as much room for lateral channel expansion. Unconstrained
reaches with gradually sloping margins and floodplains have much more extensive
areas of low velocity that may be important as refugia for invertebrates and fish during
high flow events (Gregory et al. 1989, Sedell et al. 1990). Unconstrained reaches
distributed within a generally constrained segment of stream may be important as flood
refuge and sources of post-flood recolonization.
Reach type diversity may influence the biotic potential of the stream as a
whole. In steep, highly dissected regions unconstrained reaches usually comprise a
smaller proportion of total stream length than constrained reaches (less than 20% in
Elk River). Interactions between reaches and the relative contribution of
unconstrained reaches to the functioning of the entire drainage network need to be
further explored to determine how biological differences between reach types influence
ecosystem function.
In the Elk River basin, reach scale geomorphology was fundamental in shaping
biotic communities and determining productive potential. Through its effects on solar
radiation, channel constraint influenced stream biota at each trophic level measured.
Greater energy inputs (solar radiation) in unconstrained reaches were transferred from
primary producers to consumers. Stream biota responded consistently to differences in
reach scale channel constraint.
38
A primary goal of stream ecology is to explore the mechanisms by which the
heterogeneous biotic patterns found in natural streams are shaped by measurable
physical attributes. Many theories exploring the dependence of biota on their physical
environment in entire stream systems, such as the River Continuum Concept (Vannote
et al 1980), do not effectively incorporate reach scale patterns. Variables at spatial
scales of individual channel units and lower are useful in describing local phenomena,
but it is difficult to describe an entire stream using channel units. By treating reaches
as functional units it is easier to assemble models and theories of entire stream
networks. Distinct physical characteristics of different reach types correspond to
distinct biological characteristics. Patterns observable at the reach scale are useful as
building blocks of patterns in larger segments of streams. Viewing streams as
longitudinal series of reaches can help explain ecological patterns of entire stream
networks.
39
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Journal of Fisheries and Aquatic Sciences 42:1668-1672.
Winterbourn, M. J., and A. Fegley. 1989. Effects of nutrient enrichment and
grazing on periphyton assemblages in some spring-fed, South Island streams. New
Zealand Natural Sciences 16:57-65.
Wrona, F. J., P. Ca low, I. Ford, D. J. Baird, and L. Maltby. 1986. Estimating the
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Fisheries and Aquatic Sciences 43:2025-2035.
APPENDIX
Table Al. Data from individual channel units in 1991. aCon is constrained and Unc is unconstrained; bChlor.a is
Chlorophyll a.
Macroinvertebrate
Periphyton
Bion ss
(g/m )
Bio
Stream
Reacha
Channel
Unit
Anvil
Anvil
Anvil
Anvil
Anvil
Anvil
Con
Con
Con
Con
Con
Con
Riffle
Riffle
Riffle
Pool
Pool
Pool
Anvil
Anvil
Anvil
Anvil
Anvil
Anvil
Unc
Unc
Unc
Unc
Unc
Unc
Riffle
Riffle
Riffle
Pool
Pool
Pool
0.34
2.42
Mainstem
Mainstem
Mainstem
Mainstem
Mainstem
Mainstem
Con
Con
Con
Con
Con
Con
Riffle
Riffle
Riffle
Pool
Pool
Pool
5.46
3.19
Mainstem
Mainstem
Mainstem
Mainstem
Mainstem
Mainstem
Unc
Unc
Unc
Unc
Unc
Unc
Riffle
Riffle
Riffle
Pool
Pool
Pool
1.82
Densty
ss
( # /m)
(g/m )
8282
6811
6280
8949
5071
2216
15.28
6.91
10.87
1.43
11213
18248
4971
12653
10942
0.65
4212
7.84
5.38
9.90
6.06
5754
10.37
10213
21061
1.54
1.06
0.45
1.27
0.55
0.19
1.79
0.40
1.00
1.52
0.41
0.70
0.75
4.07
1.68
1.69
1.50
4657
5352
2095
14592
10714
10381
6320
10538
5517
Chloiab
(g/m )
Direct Solar
Radiatj2n
(MJ/mL/d)
Substrate
Index
7.0
7.5
6.8
6.8
0.0210
2.24
2.71
2.00
2.01
0.88
0.94
0.0527
0.0624
0.0389
0.0380
0.0490
0.0291
1.69
6.70
7.02
2.05
3.19
2.98
6.4
6.3
6.2
6.3
6.3
5.9
5.78
11.14
7.33
8.55
6.72
0.0692
0.0362
0.0602
0.0397
0.0348
0.0346
4.78
6.40
7.02
6.58
5.96
7.55
6.9
6.9
6.5
6.6
6.7
10.64
3.72
5.51
6.62
10.72
3.75
0.0606
0.0259
0.0370
0.0286
0.0358
0.0191
12.85
15.14
17.43
1.95
6.9
7.0
6.3
6.5
6.7
2.39
6.1
7.03
8.22
6.90
5.64
8.07
0.0499
0.0471
0.0435
0.0247
0.0348
3.42
7.1
6.7
6.1
,I=.
(A>
Table Al. Data from individual channel units in 1991 (continued).
Macroinvertebrate
Demty
Stream
Reacha
Channel
Unit
North Fork
North Fork
North Fork
North Fork
North Fork
North Fork
Con
Con
Con
Con
Con
Con
Riffle
Riffle
Riffle
Pool
Pool
Pool
0.39
North Fork
North Fork
North Fork
North Fork
North Fork
North Fork
Unc
Unc
Unc
Unc
Unc
Unc
Riffle
Riffle
Riffle
Pool
Pool
Pool
1.57
0.83
2.63
28249
1.35
11159
13699
39483
Panther
Panther
Panther
Panther
Panther
Panther
Con
Con
Con
Con
Con
Con
Riffle
Riffle
Riffle
Pool
Pool
Pool
2.54
0.92
Panther
Panther
Panther
Panther
Panther
Panther
Unc
Unc
Unc
Unc
Unc
Unc
Riffle
Riffle
Riffle
Pool
Pool
Pool
Bio
ss
(g/m )
0.71
2.37
1.28
1.56
2.25
3.07
3.50
(#/m`)
12215
19671
20495
8292
8136
9404
16408
36236
Periphyton
Biorriss
(g/m )
Chlo&ab
Direct Solar
Radiation
(g/m`)
(MJ/m/d)
4.98
4.24
5.31
3.08
4.46
9.38
0.0356
0.0254
0.0305
0.0174
0.0303
0.0359
4.37
7.46
7.42
2.75
5.88
4.86
6.9
7.4
7.0
6.8
7.2
6.2
5.86
4.97
9.47
9.57
10.24
12.00
0.0294
0.0323
0.0377
0.0323
0.0274
0.0520
8.63
6.31
11.65
11.16
5.66
18.29
6.7
6.2
6.9
5.8
6.5
5.9
0.0506
0.0558
0.0352
0.0195
0.0205
0.0266
0.77
6.04
6.80
3.70
6.5
7.2
7.0
6.9
6.6
6.7
0.0329
0.0212
0.0346
0.0236
0.0254
0.0291
0.75
1.68
11012
18879
13429
1.61
6806
0.64
1.79
5391
9855
6.02
8.45
5.61
5.23
6.30
4.49
2.30
0.45
2.83
0.73
2.38
2.28
6267
6221
8454
3846
3382
3210
5.48
3.43
4.54
5.16
6.00
6.14
1.12
4.65
1.74
0.81
2.09
5.15
3.77
Substrate
Index
6.7
6.9
6.7
6.3
6.7
6.7
Table Al. Data from individual channel units in 1991 (continued).
Macroinvertebrate
Periphyton
Bio
Chlo.ab
(#/m`)
Biorr ss
(g/m )
Dens4
Direct Solar
Radiati9n
(MJ/mL/d)
Substrate
Index
Stream
Reacha
Channel
Unit
Red Cedar
Red Cedar
Red Cedar
Red Cedar
Red Cedar
Red Cedar
Con
Con
Con
Con
Con
Con
Riffle
Riffle
Riffle
Pool
Pool
Pool
0.55
0.50
1.57
0.27
0.54
0.88
8593
8810
10282
6049
8307
4824
4.63
4.36
4.50
4.23
8.83
4.69
0.0391
0.0348
0.0315
0.0228
0.0339
0.0351
0.61
1.10
0.25
1.36
0.05
6.5
6.7
7.0
7.3
6.5
6.9
Red Cedar
Red Cedar
Red Cedar
Red Cedar
Red Cedar
Red Cedar
Unc
Unc
Unc
Unc
Unc
Unc
Riffle
Riffle
Riffle
Pool
Pool
Pool
1.48
16268
3852
10098
11653
3638
10205
4.36
4.64
8.29
4.64
9.06
9.46
0.0395
0.0268
0.0341
0.0380
0.0533
0.0521
9.77
6.7
1.15
6.1
6.14
0.45
6.37
10.33
6.7
7.0
5.7
6.3
ss
(g/m )
0.39
0.81
2.52
1.85
0.99
(g/m )
1.51
Table A2. Data from individual channel units in 1992. aCon is constrained and Unc is unconstrained; bChlor.a is chlorophyll a.
Stream
Reacha
Channel
Unit
Periphyton
Biomass
Chlor.au
(g/m )
(g/mL)
Gross Primary
Production,
(mg 02/m /h)
Direct Solar
Radiaticn
(MJ/mL/d)
Anvil
Anvil
Anvil
Anvil
Anvil
Anvil
Con
Con
Con
Con
Con
Con
Riffle
Riffle
Riffle
Pool
Pool
Pool
7.65
4.17
5.90
4.44
6.22
4.62
0.0326
0.0402
0.0297
0.0188
0.0199
0.0186
60.46
23.98
21.86
35.74
28.16
36.88
5.362
0.321
1.783
2.950
0.154
2.285
Anvil
Anvil
Anvil
Anvil
Anvil
Anvil
Unc
Unc
Unc
Unc
Unc
Unc
Riffle
Riffle
Riffle
Pool
Pool
Pool
3.92
5.20
5.30
3.80
4.39
7.16
0.0487
0.0304
0.0349
0.0291
0.0335
0.0222
20.33
32.40
55.81
47.03
39.52
25.72
1.688
0.511
5.721
2.047
3.192
1.841
North Fork
North Fork
North Fork
North Fork
North Fork
North Fork
Con
Con
Con
Con
Con
Con
Riffle
Riffle
Riffle
Pool
Pool
Pool
2.99
8.48
3.97
6.40
5.75
9.03
0.0199
0.0431
0.0324
0.0363
0.0344
0.0509
31.57
25.30
55.44
36.61
53.56
84.37
2.281
4.248
7.421
5.719
5.881
4.861
North Fork
North Fork
North Fork
North Fork
North Fork
North Fork
Unc
Unc
Unc
Unc
Unc
Unc
Riffle
Riffle
Riffle
Pool
Pool
Pool
14.27
0.0869
0.0548
0.0403
0.0405
0.0318
0.0317
66.17
88.20
83.52
65.02
54.76
52.78
7.100
3.181
5.87
5.60
7.26
8.44
6.84
12.848
4.714
3.273
3.077
Table A2. Data from individual channel units in 1992 (continued).
Stream
Reacha
Channel
Unit
Periphyton
Chlor.g
Biom s
(g/m )
(g/m`)
Gross Primary
Production,
(mg 02 /m /h)
Direct Solar
Radiatipn
(MJ/mL/d)
4.153
4.540
3.247
3.699
Panther
Panther
Panther
Panther
Panther
Panther
Con
Con
Con
Con
Con
Con
Riffle
Riffle
Riffle
Pool
Pool
Pool
8.27
7.05
8.15
3.36
4.01
4.48
0.0525
0.0558
0.0537
0.0149
0.0159
0.0245
37.03
43.89
51.93
41.09
6.128
Panther
Panther
Panther
Panther
Panther
Panther
Unc
Unc
Unc
Unc
Unc
Unc
Riffle
Riffle
Riffle
Pool
Pool
Pool
6.24
7.43
3.88
6.21
3.82
5.28
0.0529
0.0554
0.0401
0.0383
0.0204
0.0332
65.17
83.40
40.56
46.72
58.62
51.18
7.997
4.265
0.810
10.242
5.956
5.505
Red Cedar
Red Cedar
Red Cedar
Red Cedar
Red Cedar
Red Cedar
Con
Con
Con
Con
Con
Con
Riffle
Riffle
Riffle
Pool
Pool
Pool
6.95
3.60
7.95
2.76
3.63
3.92
0.0662
0.0375
0.0375
0.0225
0.0267
0.0260
34.86
1.684
1.104
1.717
18.40
4.23
0.253
1.359
0.051
Red Cedar
Red Cedar
Red Cedar
Red Cedar
Red Cedar
Red Cedar
Unc
Unc
Unc
Unc
Unc
Unc
Riffle
Riffle
Riffle
Pool
Pool
Pool
6.26
0.0400
0.0452
0.0525
0.0523
0.1010
0.0914
75.73
64.88
76.40
46.92
60.44
86.61
7.873
1.147
4.744
0.253
1.425
4.864
7.41
9.10
7.53
11.71
13.49
17.05
18.81
14.47
17.11
9.10
1.118