Understanding the Relationship between Trail-Use, Stream Sedimentation, and Stream Salamander
Densities at Oak Mountain State Park
Éléonore É. Dupal1, Kristin A. Bakkegard2
1
Virginia Polytechnic Institute and State University, Blacksburg, VA, e-mail: [email protected]
3
Department of Biology, Samford University, Birmingham, AL, e-mail: [email protected]
ABSTRACT
The effects of trails on close-proximity streams have not been widely studied. We compared trail-use,
sediment load, salamander density, and stream characteristics of seven stream sites in Oak Mountain
State Park (OMSP) in Alabama. The sites were categorized into three treatments: Control, Hike, and
Bike. Salamanders were measured using two sampling methods: leaf litter bags and quadrat visual
surveys. Leaf litter bags were decided as the best measure for salamander abundance. Sediment load
was measured using ceramic tiles. There was no significant difference between treatments and
salamander abundance. There was a significant correlation between the number of trail-users and
salamander abundance among stream sites when an outlier was removed. Due to study limitations, not
all sediment data collected were analyzed. Despite this, our data showed many trends implying
increases in trail-use may be related to increases in sediment loads and decreases in salamander
abundance in streams.
Key words: Plethodontidae, Desmognathus, Eurycea, macroinvertebrates, hiking, mountain biking
INTRODUCTION
Many streams within Oak Mountain State Park are critical to salamander survival. Trails in closeproximity to these streams may affect their sediment loads, which could affect salamander populations.
Mountain bike trails are especially important to study as bikers shape the trail differently than hikers
(Vandeman, 2008). Bikers leave behind V-shaped indentations, sometimes trapping amphibians that
cannot get out of the groove (Vandeman, 2008). Popular trails risk running over these amphibians and
may crush eggs deposited in the grooves (Vandeman, 2008). Hikers compact the soil, increasing runoff.
Effective placement and management of trails is important in reducing the amount of soil erosion
because these increases in sediment runoff could affect stream ecosystems (Olive and Marion, 2009;
Castelle et al., 1994). Environmental impacts of mountain biking include soil compaction, erosion, loss
and compositional changes in vegetation, and degraded water quality (Marion and Wimpey, 2007).
We are interested in knowing how mountain biking trails, compared to hiking trails, affect
streams within the park because salamanders are important habitat health indicators, similar to how
aquatic macroinvertebrates may reveal stream quality through species diversity (Jung et al., 2005).
Macroinvertebrates in the orders Ephemeroptera, Plecoptera, and Trichoptera are especially sensitive
to increases in turbidity, acidity, and pollution (Lemly, 1982). We expect that if trails are negatively
impacting close-proximity streams, we will observe fewer salamanders and macroinvertebrates.
Salamanders can alter aquatic macroinvertebrate communities, such as maintaining mosquito
populations which can carry diseases to humans (Brodman et al., 2003). The diet of desmognathine
salamanders largely consists of aquatic macroinvertebrates, among other arthropods (Orser and Shure,
1972). Declining salamander numbers could result in increasing pest insect populations (Brodman et al.,
2003).
The biomass of salamanders is often greater than any other vertebrate species living in the same habitat
(Wyman, 1998; Petranka and Smith, 2005; Burton and Likens, 1975). Because of their abundance,
salamanders are an important source of food for other species like birds, snakes, and fish (Wyman,
1998). Maintaining salamander populations may then be considered vital for sustaining the overall
health of forest ecosystems (Wyman, 1998). For example, it has been shown that salamanders act as
keystone species in the Huyck Preserve in New York by exerting a top-down control on energy cycling
and nutrient decomposition (Wyman, 1998). If salamanders were to decline as a result of trails
impacting streams, we could expect energy cycling to become disrupted among forest communities.
Increased levels of sedimentation make streams turbid, increase stream temperatures, and lower
dissolved oxygen levels (Ischinger and Nalepa, 1976). Due to these increases in sediment, salamander
egg clusters may suffocate as they are particularly sensitive to inorganic particles in the water (Orser and
Shure, 1972). Turbidity has been shown to reduce aquatic macroinvertebrate abundance as well (Lemly,
1982). Influxes of sediment in streams may cover aquatic macroinvertebrates’ respiration structures,
challenging their ability to breathe in turbid streams where dissolved oxygen is already low (Wood and
Armitage, 1997).
Salamanders in the family Plethodontidae are lungless and require moist environments to survive
(Petranka and Smith, 2005; Jung et al., 2005). Increasing sediment in streams, where many of these
salamanders live, may fill potential living-spaces for individuals through covering smooth rocks that
would otherwise be unobscured. Plethodontid salamanders of the genus Desmognathus, in particular,
need smooth rocks to live under and for attaching egg clusters (Crawford and Peterman, 2013; Grant et
al., 2005; Price et al., 2012; Jung et al., 2005; Orser and Shure, 1972). Within streams, salamander larvae
may avoid sections where levels of silt are high (Smith and Grossman, 2003). It is important to study
how sedimentation affects vertebrates and invertebrates living in streams because increases in
turbidity, silt, and other inorganic particles may negatively affect these ecosystems.
If hiking and mountain bike trails have an increased erosional effect on sediment load in
streams, then salamander and macroinvertebrate populations should suffer as sediment levels increase.
We tested whether hiking and mountain biking trails increase sediment levels in streams that are ten
meters away from trails versus streams where no recreational trails existed. Because a local mountain
biking organization received a grant to create more mountain biking trails within the park, we wanted to
determine if 1) the presence of hiking and mountain biking trails affect the amount of sediment in closeproximity streams and 2) if the sediment affects population densities of various salamander species
living in those streams.
METHODS & MATERIALS
Study Site
Oak Mountain State Park covers 9,940 acres (Figure 1). There are 30 and 24 miles of biking and
hiking trails, respectively. Often these trails closely follow streams and cross them on bridges. Many of
these streams drain into Buck Creek, a tributary of the Cahaba River, which is one of the most
biologically diverse rivers in the United States (Duncan, 2013).
Our study site includes six streams found throughout Oak Mountain State Park (Figure 1) with
three treatments. Control streams were in located in areas with no trails, hiking and biking trails were
defined by the park. We have labeled treatments; Control (Picnic, Culvert), Hiking (White Trail, BMX),
and Biking (CatDogSnake, Roadside, Red Trail). Control treatments did not have recreational trails within
100 meters of the 30 to 50m plots. Steams designated as Hiking and Biking were within ten meters of
hiking and mountain biking trails, respectively. Stream reaches designated Biking had fewer than three
established 50m plots as the trails eventually moved outside 10m from the streams: Red Trail had one
50m plot. Roadside had one 50m plot and one 30m plot. CatDogSnake had two 50m plots. Because sites
were different sizes, salamander abundance was used in place of total density (Table 2).
For each stream we established three 30m to 50m plots, with the exception of Red Trail,
CatDogSnake, and Roadside (Table 1). For each site near a trail, a game camera was used to monitor
trail-use. We divided each 50m plot into three 15m subplots. Within these subplots, we conducted area
constrained visual surveys for salamanders using two 1 x 0.5m quadrats made of PVC pipe, placing them
on each side of the streams (Jaeger and Inger, 1994). The location for each quadrat was chosen using a
random number generator. For every 15m, 2 random quadrats were sampled (Figure 2). We tallied how
many salamanders were observed within each quadrat, then removed the individuals so as not to
double-count them in future surveys.
Salamanders were also sampled using 50cm x 50cm leaf litter bags filled with between 50g to 60g of leaf
litter (Dodd, 2009). Leaf litter was taken from the surrounding forest floor in each plot. Each 50m plot
contained 6 leaf litter bags spaced 10m apart (Figure 2). Leaf litter bags were in the stream for 12 days
to allow salamanders to colonize them. Leaf litter bags were then collected twice at twelve day intervals
and six days for the final sampling. Leaf litter bags were placed in individually labeled one gallon plastic
bags for sorting and identification of salamanders in the lab. Salamanders were identified to species and
maintained in the lab in species and life stage appropriate conditions, kept with individuals collected
during visual survey samples. For the first two collection days, used bags were replaced in the stream
with new leaf litter bags.
We placed a Moultrie A5 Low Glow game camera (Moultrie, Alabaster, Alabama) at each stream (with
the exception of Culvert as it was in a remote location and we had limited cameras) to measure trail-use.
The cameras were secured approximately two and a half meters off the ground to a tree trunk. Trailusers were categorized as hikers or bikers and tallied per stream. Only humans were recorded as trail
users. The cameras were left for one month, disturbed only when exchanging SD cards.
To measure sediment deposition for each stream, we placed nine ceramic tiles (15.24cmx15.24cm)
within one meter upstream of each 50m plot (Figure 2). Tiles were placed within 10cm of each other.
The tiles accumulated sediment over a period of 30 days. We collected three tiles each using Ziploc bags
(SC Johnson, Racine, Wisconsin) on days ten, twenty, and thirty but due to time constraints, only those
from the first collection were later scraped for organic and inorganic particle analysis. The scraped
particles underwent vacuum filtration to separate excess water, were weighed, then dried for 24 hrs at
105° C, reweighed, then muffled at 500° C for 24 hrs to remove any organic material, then weighed
again (Cambardella et al., 2001).
At the lowermost section of each stream 50m subplot we sampled once for aquatic macroinvertebrates
using methods similar to Lenat (1988). We used a 1x0.5m quadrat made of PVC pipe and placed it
midstream. We placed a kicknet directly downstream of the quadrat, lifting rocks and hand-scraping
them to dislodge aquatic macroinvertebrates. They then flowed into the kicknet. Samples were placed
into one gallon plastic bags and brought to the lab for identification down to species. The number of
macroinvertebrates in the orders Ephemeroptera, Plecoptera, and Trichoptera were used to calculate
percent EPT, a metric for measuring water quality (Barbour et al., 1999).
The water quality parameters pH, temperature, conductivity, and turbidity were measured once using A
Hach pH meter, Hach conductivity meter, and Hach DR/890 Colorimeter (Hach Company, Loveland, CO),
respectively. Stream width, width at bankfull height, bank height, bankfull height, bankfull elevation,
bank slope, thalweg, and distance of thalweg from the right bank were measured using a 2m stick and
50m tape (Barbour et al., 1999). Percent vegetation cover of both banks was estimated. We measured
stream velocity by recording the amount of time it took for a float to travel two meters (Barbour et al.,
1999). The float remained half in/half out of the water and was placed in approximately the middle of
the stream. We took these measurements over two days (July 15th and 16th) due to time conflicts. White
Trail and Picnic were at low flow and CatDogSnake had become dry with the exception of intermittent
puddles.
We estimated salamander density using two measures of catch per unit effort (CPUE). In the
first, we divided the total number of salamanders caught via leaf litter bags (LLB) by the total number of
leaf litter bags collected per stream to equal CPUE_LLB. The second measure used the total number of
salamanders caught via quadrat visual surveys divided by the total number of quadrat visual surveys
conducted per stream (CPUE_VIS) (Table 2).
We also calculated approximate total stream area by multiplying plot length (30m to 50m,
depending on the stream) with stream width (Table 2). With this measurement, we were able to
estimate salamander abundance for each stream reach.
We used a univariate regression test to determine if stream and water quality parameters,
aquatic macroinvertebrate abundance, trail-use, and sediment load had any effect on salamander
density. We used the non-parametric Kruskal-Wallis test to determine if there were any differences
between treatments for stream and water quality parameters, aquatic macroinvertebrate abundance,
trail-use, sediment load, and salamander density.
Results
The numbers of salamander species found were: Eurycea spp. (105), Desmognathus spp. (10),
and Pseudotriton r. ruber (2) (Table 3). Of the genus Eurycea, we were able to identify 29 E. cirrigera and
1 E. guttolineata. Of the genus Desmognathus, we were able to identify 5 D. monticola and 4 D. conanti.
A single Gyrinophilus porphyriticus was found. Two salamander larvae could not be identified. We
captured all the species of salamander that we expected in Oak Mountain State Park. Eurycea spp.
larvae composed the majority of the salamanders sampled (Table 3).
We found no relationship between mean catch per unit effort and Hike, Bike, and Control
treatments (Figure 3). There was a significant correlation between salamander densities and total
number of trail-users per stream site when the data point for Red Trail was removed (R2 = 0.783, p <
0.05) (Figure 4). The game camera at Red Trail did not capture every trail-user we observed. Even if we
added more trail-users to compensate for this error, the data would still be an outlier.
The total number of trail-users captured by camera at each stream site was: White Trail (22),
Bike Moto-Cross Area (50), Red Trail (10), Roadside (478), and CatDogSnake (777) (Figure 5). Hike and
Bike treatments are underestimates of trail-use because we observed people while in the field that were
not captured on our cameras during the study. We know definitively our cameras did not capture every
trail-user at White Trail & Red Trail sites. To confirm that our designated Hike and Bike treatments were
used primarily by hikers and bikers, respectively, we categorized each captured trail-user as either a
Hiker (an individual without a bike) or a Biker (an individual with a bike) (Figure 5). There were no
significant differences between treatments and total number of trail-users (Figure 5).
The total amount of sediment measured from each stream site, in grams, was: White Trail
(25.75), Bike Moto-Cross Area (24.48), Red Trail (4.61), Roadside (110.03), CatDogSnake (30.30), Picnic
(10.08), and Culvert (12.73) (Table 4). Tiles that were out of water or broken were not included. An
outlier from Picnic was also excluded because it was much larger than all the other points combined.
There was no correlation between salamander density and mean sediment load per stream (R2 = 0.303,
p > 0.05). The mean sediment load was not significantly different among Hike, Bike, and Control
treatments (Kruskal-Wallis, p > 0.05; Figure 6). Mean sediment load was not affected by total number of
trail-users (R2 = 0.281, p > 0.05) (Figure 7).
Because stream salamanders depend on aquatic macroinvertebrates for much of their diet, we
measured the total number of aquatic macroinvertebrates caught at each stream site: White Trail (121),
Bike Moto-Cross Area (30), Red Trail (2), Roadside (3), and CatDogSnake (9), Picnic (122), and Culvert
(29) (Table 5). We found no significant difference among Hike, Bike, and Control treatments (KruskalWallis, p > 0.05) (Figure 8). Mean sediment load did not influence aquatic macroinvertebrate abundance
(R2 = 0.184, p > 0.05) (Figure 9).
We measured stream parameters (Table 6 and 7). Conductivity at Roadside was noticeably
higher than all other streams (Table 6). White Trail had lowest mean pH at 6.01. Culvert had the highest
mean pH at 7.06 (Table 6). Stream temperatures ranged from 22.23°C to 25.03°C (Table 6), though we
forgot to measure temperature at White Trail. Stream velocity was also highly variable among streams,
though this is most likely due to some of our streams drying up as our study progressed into July (Table
6).
DISCUSSION
Though most of our regressions were not significant, we noticed many patterns along our data.
One trend implied that as sediment loads increased, fewer salamanders were caught. This pattern
seems to follow Smith and Grossman’s (2003) findings where fewer salamander larvae were caught in
streams mostly comprised of silt. We may not have gotten a significant trend because we caught many
salamanders at our Control streams but also at one of our Hike streams, relative to the other Hike and
Bike streams. Another trend seemed to be that as trail-users increased, salamander abundance
decreased. When comparing salamander abundance with total number of trail-users, the data point for
Red Trail was removed because it was odd. Even if the number of trail-users was increased to make up
for the camera underestimation, the point would still be an outlier. These trends seem to also suggest
that as trail-users increase, sediment loads in streams will increase and cause decreases in salamander
abundance. Before new bike trails are constructed, park managers should decide what minimum buffer
zone length they must create to ensure healthy stream habitat for salamanders A barrier of at least 15m
has been deemed necessary to protect streams and other wetlands (Castelle et al., 1994).
There was a general trend among streams that seemed to indicate streams designated Bike had
lower numbers of aquatic macroinvertebrates collected, lower percent EPT, and decreased aquatic
macroinvertebrate species richness compared to streams designated Hike and Control. This may mean
lower food availability for salamanders, potentially decreasing survival. Lemly (1981) found that while
increased sediment may not affect total numbers of aquatic macroinvertebrates, species richness and
diversity may be significantly reduced. Lower percent EPT may suggest poorer water quality. However
more data is needed to make more definitive conclusions. Though the total number of aquatic
macroinvertebrates was the same for Hike and Control treatments, the trend showed Control treatment
streams as having greater percent EPT. This may imply that streams where no recreational trails are
present have healthier water quality relative to those streams where trails are present.
There were several limitations to our study. There was not enough time during our study,
conducted over the course of a month, to complete sediment analysis on tiles from our second and third
collection days. Given more time, we may have had more significant data.
A water treatment plant located in the park was observed leaking aluminum chloride, used for
treating wastewater, and Admiral Liquid, an algaecide, into one of our Bike streams. We believe the
aluminum chloride is responsible for the high conductivity levels we measured as well as the strikingly
vibrant blue color of the water at our stream labeled Roadside.
As time progressed, some of our streams began to dry up. All of our 50m plots for CatDogSnake
became completely dry with the exception of scattered puddles remaining in the stream bed. Likewise,
the uppermost 50m plot of White Trail became mostly dry. Picnic too had lower water levels over time
relative to those observed at the beginning of our study. Many of our tiles were unsubmerged as a
result. This may have impacted the ability of our tiles to collect sediment.
While we did not have many significant correlations, we did observe many trends and patterns
in our data that were consistent with our hypotheses. Based on these trends, we have concluded that
ten meters does not seem to be a sufficient distance or buffer zone between trails and streams to
negate erosional effects. Future studies conducted for a longer duration may shed more light on the
matter. With the objective of maintaining good water quality, salamander abundance, and aquatic
macroinvertebrate densities, it is our recommendation that future trails be placed more than 10m away
from streams in Oak Mountain State Park.
ACKNOWLEDGEMENTS
We would like to thank the National Science Foundation for funding this research project,
Samford University for providing equipment and lab rooms used in the study, all the professors who
gave advice on the project, and all the people who donated their time to help us set up our tiles, leaf
litter bags, salamander checks and IDs, and those who reviewed this paper.
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Table 1: Starting and ending points for each of the designated treatments for each stream. Stream
abbreviations are WT (White Trail), BMX (Bike Moto-Cross Area), RT (Red Trail), RS (Roadside), CDS
(CatDogSnake), PN (Picnic Area 1), and CV (Culvert). GPS coordinates are included, though their accuracy
is suspect due to difficulty in acquiring satellites in the forest. The start coordinates for BMX and PN
were mistakenly not recorded.
Treatment
Stream
GPS Start
GPS End
Hike
WT
N33°17'46"
W86°47'20"
N33°18'17"
W86°46'17"
Hike
BMX
n/a
N33°25'5"
W86°46'51"
Bike
RT
N33°18'48.8"
W86°46'10.9"
N33°18'47.7"
W86°46'12.4"
Bike
RS
N33°20'5.2"
W86°44'50.7"
N33°20'8.7"
W86°44'54.3"
Bike
CDS
N33°22'52"
W86°41'41"
N33°22'48"
W86°41'7"
Control
PN
n/a
N33°20'28.9"
W86°44'36.5"
Control
CV
N33°21'35"
W86°41'56"
N33°22'30"
W86°42'30"
Table 2: Measures of abundance to correct for unequal sampling effort. LLB stands for Leaf Litter Bag.
VIS stands for visual survey sampling. Sal is an abbreviation for salamander. Stream abbreviations are
the same as those used in Table 1.
Total
Area
Sampled
(m2)
Total
Catch
(sal/m2)
Stream
Area
(m2)
Salamander
Density
(sal/m2)
Stream
CPUE_LLB
(sal/m2)
CPUE_VIS (sal/m
WT
0.27
0.43
36.48
1.21
582.17
0.08
BMX
0.21
0.00
36.48
0.27
604
0.02
RT
0.47
0.00
12.15
0.66
156.75
0.04
RS
0.11
0.02
24.27
0.12
113.45
0.04
CDS
0.08
0.08
24.26
0.25
159
0.04
PN
0.27
0.08
36.51
0.55
1071.5
0.02
CV
0.18
0.28
36.49
0.79
220.5
0.13
2)
Table 3: Captured salamanders at seven stream sites in Oak Mountain State Park showing species, age
class, and count (n).
Species
Eurycea spp.
Eurycea cirrigera
Eurycea guttolineata
Desmognathus spp.
Desmognathus conanti
Desmognathus monticola
Pseudotriton r. ruber
Gyrinophilus porphyriticus
Unknown spp.
Age class
n
Larva
75
Adult
0
Larva
14
Adult
15
Larva
1
Adult
0
Larva
1
Adult
0
Larva
3
Adult
1
Larva
0
Adult
5
Larva
1
Adult
1
Larva
1
Adult
0
Larva
2
Adult
0
Table 4: Total amount of sediment collected from each stream site. Mean sediment load per tile and tile
count (n) are included. Stream abbreviations are the same as those used in Table 1.
Stream
n
Total sediment (g)
Mean sediment load
(g)
WT
9
25.75
2.86
BMX
4
24.48
6.12
RT
3
4.61
1.54
RS
6
110.03
18.34
CDS
6
30.30
5.05
PN
8
10.08
1.26
CV
6
12.73
2.12
Table 5: Total number of macroinvertebrates collected from each stream site. Species richness is
included. MI stands for macroinvertebrates. Stream abbreviations are the same as those used in Table 1.
Stream
Total MI
Species richness
WT
121
18
BMX
30
6
RT
2
2
RS
3
3
CDS
9
6
PN
122
19
CV
29
9
Table 6: Stream parameters; one measurement was taken at the top, middle, and end of each stream
reach. These measurements were averaged. Stream abbreviations are the same as those used in Table
1.
Mean
Width
Mean
Thalweg
Mean
Velocity
Mean
Conductivity
Mean
Temperature
(m)
(cm)
(sec)
(µS/cm)
(°C)
WT
3.94
19.8
0
22.6
n/a
6.01
BMX
4.03
19.39
16.24
53.52
22.23
6.76
RT
3.14
47
4.53
64.91
23
6.83
RS
1.42
9.01
27.8
417.8
25.03
6.83
CDS
1.59
20
0
36.94
22.45
6.14
PN
7.14
24.08
0
54.57
24.06
6.84
CV
1.47
9.33
90
51.11
22.88
7.06
Stream
Mean
pH
Table 7: Stream parameters, continued. Bank slope is in degrees. Stream abbreviations are the same as
those used in Table 1.
Mean Left
Stream Bankfull height
(cm)
Mean Right
Bankfull height
(cm)
Mean Left
Bankfull
elevation (cm)
Mean Right
Mean Left
Bankfull elevation
Bank
(cm)
slope
Mean
Right
Bank
slope
WT
22.8
37.8
34.4
32.6
>90
90<
BMX
26.9
41.8
15.2
31.3
50
75.8
RT
20.25
15
31.5
55
<90
90
RS
24.2
15.2
31.4
16.4
>90
<90
CDS
77.4
102
68.5
92.5
90
122.5
PN
72.1
64.5
87.6
75.2
90
>90
CV
51.7
54.4
40.3
40.3
43.3
36.6
Figure 1: Map of Alabama with Shelby County, where Oak Mountain State Park is located, highlighted
(inset map from Wikipedia.org), overlaying a map of Oak Mountain State Park. Our study sites are
labeled on the map WT (White Trail), BMX (Bike Moto-Cross Area), RT (Red Trail), RS (Roadside), CDS
(CatDogSnake), PN (Picnic Area 1), and CV (Culvert).
Figure 2: The large arrow represents a stream, illustrating direction of flow. The three large rectangles
within the arrow represent 50m plots.  represent leaf litter bags (spread 10m apart).  within 50m
plots represent quadrat surveys taken on both sides of the stream.  above the 50m plots represent
tiles. The long rectangle beside the stream represents a trail (for Hiking and Biking treatments) within
10m of the stream.
Mean CPUE_LLB (salamander/m2)
0.40
0.30
0.20
0.10
0.00
HIKE
BIKE
Treatment
CONTROL
Figure 3: Mean catch per unit effort, noted as CPUE_LLB, ± standard error per treatment.
0.30
PN
Salamander Density
WT
y = -0.0002x + 0.2367
R² = 0.783
0.20
BMX
CV
0.10
CDS
RS
0.00
0
300
600
900
Total Trail-users
Figure 4: Salamander densities plotted against total trail-users per stream site. R2 = 0.783. Stream
abbreviations are the same as those used in Table 1. The data point for Red Trail has been removed.
Total number of Trail-users
1200
900
Hiker
Biker
600
300
0
HIKE
BIKE
Treatment
Figure 5: Total number of trail-users per stream site. Stream abbreviations are the same as those used in
Table 1.
.
Mean Sediment (g)
16
12
8
4
0
HIKE
BIKE
Treatment
Figure 6: Mean sediment per treatment. Mean ± SE
CONTROL
20
RS
Mean Sediment (g)
16
y = 0.0103x + 3.3545
R² = 0.2807
12
8
BMX
4
CV
CDS
WT
RT
PN
0
0
300
600
900
Total Trail-users
Figure 7: Mean sediment plotted against total trail-users per stream site. Stream abbreviations are the
same as those used in Table 1.
160
Total MI Caught
80%
Percent EPT
Percent EPT
120
60%
80
40%
40
20%
0%
Total number of MI captured
100%
0
Control
Hike
Treatment
Bike
Figure
8: Percent EPT vs. total aquatic macroinvertebrates (MI) caught at each treatment.
160.00
Total Number of MI
120.00
y = -3.8126x + 65.168
R² = 0.184
WT
PN
80.00
40.00
CV
0.00
0.00
RT
BMX
RS
CDS
5.00
10.00
Mean Sediment (g)
15.00
20.00
Figure 9: Total number of aquatic macroinvertebrates plotted against mean sediment per stream. MI
stands for macroinvertebrates. Stream abbreviations are the same as those used in Table 1.