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Analyzing the impacts of off-road vehicle (ORV) trails on watershed processes in Wrangell-St. Elias National Park and Preserve, Alaska.

Arp CD, Simmons T - Environ Manage (2012)

Bottom Line: These observations of trail evolution relative to stream and wetland crossings together with process studies suggest that ORV trails are altering watershed processes.These changes in watershed processes appear to result in increasing drainage density and may also alter downstream flow regimes, water quality, and aquatic habitat.Addressing local land-use disturbances in boreal and arctic parklands with permafrost soils, such as WRST, where responses to climate change may be causing concurrent shifts in watershed processes, represents an important challenge facing resource managers.

View Article: PubMed Central - PubMed

Affiliation: Alaska Science Center, U.S. Geological Survey, Anchorage, AK 99508, USA. cdarp@alaska.edu

ABSTRACT
Trails created by off-road vehicles (ORV) in boreal lowlands are known to cause local impacts, such as denuded vegetation, soil erosion, and permafrost thaw, but impacts on stream and watershed processes are less certain. In Wrangell-St. Elias National Park and Preserve (WRST), Alaska, ORV trails have caused local resource damage in intermountain lowlands with permafrost soils and abundant wetlands and there is a need to know whether these impacts are more extensive. Comparison of aerial photography from 1957, 1981, and 2004 coupled with ground surveys in 2009 reveal an increase in trail length and number and show an upslope expansion of a trail system around points of stream channel initiation. We hypothesized that these impacts could also cause premature initiation and headward expansion of channels because of lowered soil resistance and greater runoff accumulation as trails migrate upslope. Soil monitoring showed earlier and deeper thaw of the active layer in and adjacent to trails compared to reference sites. Several rainfall-runoff events during the summer of 2009 showed increased and sustained flow accumulation below trail crossings and channel shear forces sufficient to cause headward erosion of silt and peat soils. These observations of trail evolution relative to stream and wetland crossings together with process studies suggest that ORV trails are altering watershed processes. These changes in watershed processes appear to result in increasing drainage density and may also alter downstream flow regimes, water quality, and aquatic habitat. Addressing local land-use disturbances in boreal and arctic parklands with permafrost soils, such as WRST, where responses to climate change may be causing concurrent shifts in watershed processes, represents an important challenge facing resource managers.

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Mean active-layer depths from 121 point, 1 ha grids measured on 10-Sept-2009 and 16-Sept-2010 at a reference site with no ORV trails and at a site with substantial ORV trails and braiding. Error bars are standard deviations and letter indicate a significant difference at P < 0.01 using a student’s T test between sites for both years
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Fig6: Mean active-layer depths from 121 point, 1 ha grids measured on 10-Sept-2009 and 16-Sept-2010 at a reference site with no ORV trails and at a site with substantial ORV trails and braiding. Error bars are standard deviations and letter indicate a significant difference at P < 0.01 using a student’s T test between sites for both years

Mentions: A more spatially comprehensive assessment of ALD was made using CALM grids (100 × 100 m, 121 points) at the reference site (Mentasta Fen) and at a highly disturbed trail site (Tanada Lake Muskeg) that is bisected by a swath of trail braids. Both sites are moderately sloping (1–2%) with organic soils supporting tussock peatland interspersed with black spruce muskeg. Comparison of these CALM grids showed a significantly deeper mean ALD of 59.5 cm (±18.7 cm SD) at the trail site compared to a mean ALD of 50.5 cm (±11.1 cm SD) at the reference site (P < 0.01) (Fig. 6). At the reference site, variation in ALD was relatively moderate, ranging from 30 to 85 cm, whereas at the trail site there was a zone of deep thaw >100 cm that corresponded to a set of trails with deep thaw subsidence (Fig. 7). In September 2010, the mean ALD was deeper at both CALM sites, 58.5 cm (±11.9 cm SD) at the Mentasta Fen reference site and 69.6 cm (±19.1 cm SD) at the Tanada Lake Muskeg disturbed site, likely due to a slightly warmer and wetter summer than in 2009 (Fig. 6).Fig. 6


Analyzing the impacts of off-road vehicle (ORV) trails on watershed processes in Wrangell-St. Elias National Park and Preserve, Alaska.

Arp CD, Simmons T - Environ Manage (2012)

Mean active-layer depths from 121 point, 1 ha grids measured on 10-Sept-2009 and 16-Sept-2010 at a reference site with no ORV trails and at a site with substantial ORV trails and braiding. Error bars are standard deviations and letter indicate a significant difference at P < 0.01 using a student’s T test between sites for both years
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3298735&req=5

Fig6: Mean active-layer depths from 121 point, 1 ha grids measured on 10-Sept-2009 and 16-Sept-2010 at a reference site with no ORV trails and at a site with substantial ORV trails and braiding. Error bars are standard deviations and letter indicate a significant difference at P < 0.01 using a student’s T test between sites for both years
Mentions: A more spatially comprehensive assessment of ALD was made using CALM grids (100 × 100 m, 121 points) at the reference site (Mentasta Fen) and at a highly disturbed trail site (Tanada Lake Muskeg) that is bisected by a swath of trail braids. Both sites are moderately sloping (1–2%) with organic soils supporting tussock peatland interspersed with black spruce muskeg. Comparison of these CALM grids showed a significantly deeper mean ALD of 59.5 cm (±18.7 cm SD) at the trail site compared to a mean ALD of 50.5 cm (±11.1 cm SD) at the reference site (P < 0.01) (Fig. 6). At the reference site, variation in ALD was relatively moderate, ranging from 30 to 85 cm, whereas at the trail site there was a zone of deep thaw >100 cm that corresponded to a set of trails with deep thaw subsidence (Fig. 7). In September 2010, the mean ALD was deeper at both CALM sites, 58.5 cm (±11.9 cm SD) at the Mentasta Fen reference site and 69.6 cm (±19.1 cm SD) at the Tanada Lake Muskeg disturbed site, likely due to a slightly warmer and wetter summer than in 2009 (Fig. 6).Fig. 6

Bottom Line: These observations of trail evolution relative to stream and wetland crossings together with process studies suggest that ORV trails are altering watershed processes.These changes in watershed processes appear to result in increasing drainage density and may also alter downstream flow regimes, water quality, and aquatic habitat.Addressing local land-use disturbances in boreal and arctic parklands with permafrost soils, such as WRST, where responses to climate change may be causing concurrent shifts in watershed processes, represents an important challenge facing resource managers.

View Article: PubMed Central - PubMed

Affiliation: Alaska Science Center, U.S. Geological Survey, Anchorage, AK 99508, USA. cdarp@alaska.edu

ABSTRACT
Trails created by off-road vehicles (ORV) in boreal lowlands are known to cause local impacts, such as denuded vegetation, soil erosion, and permafrost thaw, but impacts on stream and watershed processes are less certain. In Wrangell-St. Elias National Park and Preserve (WRST), Alaska, ORV trails have caused local resource damage in intermountain lowlands with permafrost soils and abundant wetlands and there is a need to know whether these impacts are more extensive. Comparison of aerial photography from 1957, 1981, and 2004 coupled with ground surveys in 2009 reveal an increase in trail length and number and show an upslope expansion of a trail system around points of stream channel initiation. We hypothesized that these impacts could also cause premature initiation and headward expansion of channels because of lowered soil resistance and greater runoff accumulation as trails migrate upslope. Soil monitoring showed earlier and deeper thaw of the active layer in and adjacent to trails compared to reference sites. Several rainfall-runoff events during the summer of 2009 showed increased and sustained flow accumulation below trail crossings and channel shear forces sufficient to cause headward erosion of silt and peat soils. These observations of trail evolution relative to stream and wetland crossings together with process studies suggest that ORV trails are altering watershed processes. These changes in watershed processes appear to result in increasing drainage density and may also alter downstream flow regimes, water quality, and aquatic habitat. Addressing local land-use disturbances in boreal and arctic parklands with permafrost soils, such as WRST, where responses to climate change may be causing concurrent shifts in watershed processes, represents an important challenge facing resource managers.

Show MeSH
Related in: MedlinePlus