Limits...
Mediating Water Temperature Increases Due to Livestock and Global Change in High Elevation Meadow Streams of the Golden Trout Wilderness.

Nusslé S, Matthews KR, Carlson SM - PLoS ONE (2015)

Bottom Line: Inside the livestock exclosure in Mulkey, we found that riverbank vegetation was both larger and denser than outside the exclosure where cattle were present, resulting in more shaded waters and cooler maximal temperatures inside the exclosure.In addition, between meadows comparisons showed that water temperatures were cooler in the ungrazed meadows compared to the grazed area in the partially grazed meadow.Our results highlight that land use can interact with climate change to worsen the local thermal conditions for taxa on the edge and that protecting riparian vegetation is likely to increase the resiliency of these ecosystems to climate change.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Science, Policy & Management, University of California, Berkeley, California, United States of America.

ABSTRACT
Rising temperatures due to climate change are pushing the thermal limits of many species, but how climate warming interacts with other anthropogenic disturbances such as land use remains poorly understood. To understand the interactive effects of climate warming and livestock grazing on water temperature in three high elevation meadow streams in the Golden Trout Wilderness, California, we measured riparian vegetation and monitored water temperature in three meadow streams between 2008 and 2013, including two "resting" meadows and one meadow that is partially grazed. All three meadows have been subject to grazing by cattle and sheep since the 1800s and their streams are home to the imperiled California golden trout (Oncorhynchus mykiss aguabonita). In 1991, a livestock exclosure was constructed in one of the meadows (Mulkey), leaving a portion of stream ungrazed to minimize the negative effects of cattle. In 2001, cattle were removed completely from two other meadows (Big Whitney and Ramshaw), which have been in a "resting" state since that time. Inside the livestock exclosure in Mulkey, we found that riverbank vegetation was both larger and denser than outside the exclosure where cattle were present, resulting in more shaded waters and cooler maximal temperatures inside the exclosure. In addition, between meadows comparisons showed that water temperatures were cooler in the ungrazed meadows compared to the grazed area in the partially grazed meadow. Finally, we found that predicted temperatures under different global warming scenarios were likely to be higher in presence of livestock grazing. Our results highlight that land use can interact with climate change to worsen the local thermal conditions for taxa on the edge and that protecting riparian vegetation is likely to increase the resiliency of these ecosystems to climate change.

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Related in: MedlinePlus

Willow height and concentration.(A) Willow location along the riverbank, with increased definition inside the inset box. (B) Individual willow heights [cm] and concentration along the riverbank with a view from the side. (C) Kernel density estimation for the willow height distribution [cm]. For each panel, green coloration represents the ungrazed area inside the cattle exclosure, and red coloration represents the area outside the exclosure in the grazed area.
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pone.0142426.g003: Willow height and concentration.(A) Willow location along the riverbank, with increased definition inside the inset box. (B) Individual willow heights [cm] and concentration along the riverbank with a view from the side. (C) Kernel density estimation for the willow height distribution [cm]. For each panel, green coloration represents the ungrazed area inside the cattle exclosure, and red coloration represents the area outside the exclosure in the grazed area.

Mentions: In Mulkey Meadows, we found that the vegetation was not spatially structured (i.e., no spatial autocorrelation, Morans’ I = -0.034 ± 0.025, p = 0.47), but differed inside and outside the cattle exclosure. In the presence of livestock, the riparian vegetation was dominated by sedge (Carex spp.) while in the absence of livestock, significantly more willow (Salix spp.) were present (Fig 2A, chi-squared test: = 10.9, p < 0.05). Additionally, we found important differences in vegetation cover (Fig 3). In the area where cattle were excluded, we found 13 times more willows (980 trees, for a river length of 1200 m) compared to the area where cattle were present (75 trees, for a river length of 900 m). This difference can be tested with the average distance between two consecutive willows along the transect, which is 5.9 meters inside the exclosure and 12.4 meters outside (Autoregressive model: F1,1049 = 74.8, p < 0.001, Moran’s I on residuals = -0.0001 + 0.0007, p = 0.86). In addition, the willows in the exclosure were on average twice as tall (0.92 ± 0.56 meters) compared to the willows outside of the exclosure (0.43 ± 0.29 meters) (Fig 3C, Autoregressive model: F1,1049 = 65.3, p < 0.001, Moran’s I on residuals = -0.0012 + 0.0007, p = 0.10). Accordingly, the solar exposure was not spatially structured (Morans’ I = -0.039 ± 0.025, p = 0.11) and the river was shadier when cattle were excluded (84.1% sunny inside exclosure, 95.4% outside, logistic regression: z28 = 3.3, p < 0.05, Fig 2B). In both the grazed and the ungrazed area, we found no association between any of the water temperature metrics and the solar exposure at a given point, using both a continuous metric (percentage) and a binary metric (shade / no shade) for solar exposure (all p > 0.05). We found no association between cattle exclosures and river depth, water velocity, or habitat type (pool, riffle, or under bank) (all p-values > 0.05).


Mediating Water Temperature Increases Due to Livestock and Global Change in High Elevation Meadow Streams of the Golden Trout Wilderness.

Nusslé S, Matthews KR, Carlson SM - PLoS ONE (2015)

Willow height and concentration.(A) Willow location along the riverbank, with increased definition inside the inset box. (B) Individual willow heights [cm] and concentration along the riverbank with a view from the side. (C) Kernel density estimation for the willow height distribution [cm]. For each panel, green coloration represents the ungrazed area inside the cattle exclosure, and red coloration represents the area outside the exclosure in the grazed area.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4643935&req=5

pone.0142426.g003: Willow height and concentration.(A) Willow location along the riverbank, with increased definition inside the inset box. (B) Individual willow heights [cm] and concentration along the riverbank with a view from the side. (C) Kernel density estimation for the willow height distribution [cm]. For each panel, green coloration represents the ungrazed area inside the cattle exclosure, and red coloration represents the area outside the exclosure in the grazed area.
Mentions: In Mulkey Meadows, we found that the vegetation was not spatially structured (i.e., no spatial autocorrelation, Morans’ I = -0.034 ± 0.025, p = 0.47), but differed inside and outside the cattle exclosure. In the presence of livestock, the riparian vegetation was dominated by sedge (Carex spp.) while in the absence of livestock, significantly more willow (Salix spp.) were present (Fig 2A, chi-squared test: = 10.9, p < 0.05). Additionally, we found important differences in vegetation cover (Fig 3). In the area where cattle were excluded, we found 13 times more willows (980 trees, for a river length of 1200 m) compared to the area where cattle were present (75 trees, for a river length of 900 m). This difference can be tested with the average distance between two consecutive willows along the transect, which is 5.9 meters inside the exclosure and 12.4 meters outside (Autoregressive model: F1,1049 = 74.8, p < 0.001, Moran’s I on residuals = -0.0001 + 0.0007, p = 0.86). In addition, the willows in the exclosure were on average twice as tall (0.92 ± 0.56 meters) compared to the willows outside of the exclosure (0.43 ± 0.29 meters) (Fig 3C, Autoregressive model: F1,1049 = 65.3, p < 0.001, Moran’s I on residuals = -0.0012 + 0.0007, p = 0.10). Accordingly, the solar exposure was not spatially structured (Morans’ I = -0.039 ± 0.025, p = 0.11) and the river was shadier when cattle were excluded (84.1% sunny inside exclosure, 95.4% outside, logistic regression: z28 = 3.3, p < 0.05, Fig 2B). In both the grazed and the ungrazed area, we found no association between any of the water temperature metrics and the solar exposure at a given point, using both a continuous metric (percentage) and a binary metric (shade / no shade) for solar exposure (all p > 0.05). We found no association between cattle exclosures and river depth, water velocity, or habitat type (pool, riffle, or under bank) (all p-values > 0.05).

Bottom Line: Inside the livestock exclosure in Mulkey, we found that riverbank vegetation was both larger and denser than outside the exclosure where cattle were present, resulting in more shaded waters and cooler maximal temperatures inside the exclosure.In addition, between meadows comparisons showed that water temperatures were cooler in the ungrazed meadows compared to the grazed area in the partially grazed meadow.Our results highlight that land use can interact with climate change to worsen the local thermal conditions for taxa on the edge and that protecting riparian vegetation is likely to increase the resiliency of these ecosystems to climate change.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Science, Policy & Management, University of California, Berkeley, California, United States of America.

ABSTRACT
Rising temperatures due to climate change are pushing the thermal limits of many species, but how climate warming interacts with other anthropogenic disturbances such as land use remains poorly understood. To understand the interactive effects of climate warming and livestock grazing on water temperature in three high elevation meadow streams in the Golden Trout Wilderness, California, we measured riparian vegetation and monitored water temperature in three meadow streams between 2008 and 2013, including two "resting" meadows and one meadow that is partially grazed. All three meadows have been subject to grazing by cattle and sheep since the 1800s and their streams are home to the imperiled California golden trout (Oncorhynchus mykiss aguabonita). In 1991, a livestock exclosure was constructed in one of the meadows (Mulkey), leaving a portion of stream ungrazed to minimize the negative effects of cattle. In 2001, cattle were removed completely from two other meadows (Big Whitney and Ramshaw), which have been in a "resting" state since that time. Inside the livestock exclosure in Mulkey, we found that riverbank vegetation was both larger and denser than outside the exclosure where cattle were present, resulting in more shaded waters and cooler maximal temperatures inside the exclosure. In addition, between meadows comparisons showed that water temperatures were cooler in the ungrazed meadows compared to the grazed area in the partially grazed meadow. Finally, we found that predicted temperatures under different global warming scenarios were likely to be higher in presence of livestock grazing. Our results highlight that land use can interact with climate change to worsen the local thermal conditions for taxa on the edge and that protecting riparian vegetation is likely to increase the resiliency of these ecosystems to climate change.

Show MeSH
Related in: MedlinePlus