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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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Temperature summaries.Temperature was recorded every 20–30 minutes at each probe. To limit the amount of data from each probe (and to remove temporal autocorrelation), we calculated three metrics that resulted in only one value/probe/day for analyses (See S1 Fig): daily minimum (DminT), daily average (DavgT), and daily maximum (DmaxT). To remove exceptional or erroneous data, we then computed the median value over seven day windows for each of these three metrics. Each boxplot represents the overall variation for the median daily value over seven day moving windows (WminT, WavgT, and WmaxT) in the three different meadows, with the two different areas (grazed/ungrazed) in Mulkey. The plots are arranged in order from (left to right) the lowest elevation meadow (Ramshaw) to the highest elevation meadow (Big Whitney).
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pone.0142426.g005: Temperature summaries.Temperature was recorded every 20–30 minutes at each probe. To limit the amount of data from each probe (and to remove temporal autocorrelation), we calculated three metrics that resulted in only one value/probe/day for analyses (See S1 Fig): daily minimum (DminT), daily average (DavgT), and daily maximum (DmaxT). To remove exceptional or erroneous data, we then computed the median value over seven day windows for each of these three metrics. Each boxplot represents the overall variation for the median daily value over seven day moving windows (WminT, WavgT, and WmaxT) in the three different meadows, with the two different areas (grazed/ungrazed) in Mulkey. The plots are arranged in order from (left to right) the lowest elevation meadow (Ramshaw) to the highest elevation meadow (Big Whitney).

Mentions: The three study meadows differed in elevation with Ramshaw Meadows at 2636 m, Mulkey Meadows at 2837 m, and Big Whitney Meadow at 2943 m. Despite Mulkey’s intermediate elevation, all three weekly temperature metrics (WminT, WavgT, and WmaxT) were higher in Mulkey, which is the only meadow partially grazed by livestock in recent years (Fig 5, Table 2). Across the study duration (2010–2012), the average water temperature during the eight warmest weeks of Mulkey Meadows was 13.2°C in the grazed area and 13.0°C in the ungrazed area. In contrast, it was cooler in Ramshaw (11.8°C) and in Big Whitney (10.7°C). The monthly average median minimal temperature over 7 days (WminT) was 1.79 ± 0.24 degrees higher in the grazed area of Mulkey compared to Big Whitney (mixed model multiple regression: t23 = 7.36, p < 0.001), but was not significantly different from Ramshaw (mixed model multiple regression: t22.9 = 0.01, p > 0.05), and also not significantly different from the ungrazed part of Mulkey Meadows (mixed model multiple regression: t22.9 = 1.35, p > 0.05). The median average temperature over 7 days (WavgT) was on average 2.65 ± 0.27 degrees higher in the grazed area of Mulkey compared to Big Whitney (mixed model multiple regression: t23.1 = 9.65, p < 0.001), 1.65 ± 0.26 degrees higher in Mulkey compared to Ramshaw (mixed model multiple regression: t22.9 = 6.24, p < 0.001), and not significantly different from the ungrazed part of Mulkey (mixed model multiple regression: t22.9 = 1.17, p > 0.05). The median maximal temperature over 7 days (WmaxT) was on average 2.63 ± 0.63 degrees higher in Mulkey compared to Big Whitney (mixed model multiple regression: t31 = 4.17, p < 0.01), 3.53 ± 0.61 degrees higher in Mulkey compared to Ramshaw (mixed model multiple regression: t31 = 5.77, p < 0.001), and not significantly different from the ungrazed part of Mulkey (mixed model multiple regression: t31 = 1.17, p > 0.47). These results were robust with regards to the scale at which we averaged the temperatures, that is, the results were similar when we instead used yearly or weekly averages instead of monthly averages (Table 3).


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)

Temperature summaries.Temperature was recorded every 20–30 minutes at each probe. To limit the amount of data from each probe (and to remove temporal autocorrelation), we calculated three metrics that resulted in only one value/probe/day for analyses (See S1 Fig): daily minimum (DminT), daily average (DavgT), and daily maximum (DmaxT). To remove exceptional or erroneous data, we then computed the median value over seven day windows for each of these three metrics. Each boxplot represents the overall variation for the median daily value over seven day moving windows (WminT, WavgT, and WmaxT) in the three different meadows, with the two different areas (grazed/ungrazed) in Mulkey. The plots are arranged in order from (left to right) the lowest elevation meadow (Ramshaw) to the highest elevation meadow (Big Whitney).
© Copyright Policy
Related In: Results  -  Collection

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

pone.0142426.g005: Temperature summaries.Temperature was recorded every 20–30 minutes at each probe. To limit the amount of data from each probe (and to remove temporal autocorrelation), we calculated three metrics that resulted in only one value/probe/day for analyses (See S1 Fig): daily minimum (DminT), daily average (DavgT), and daily maximum (DmaxT). To remove exceptional or erroneous data, we then computed the median value over seven day windows for each of these three metrics. Each boxplot represents the overall variation for the median daily value over seven day moving windows (WminT, WavgT, and WmaxT) in the three different meadows, with the two different areas (grazed/ungrazed) in Mulkey. The plots are arranged in order from (left to right) the lowest elevation meadow (Ramshaw) to the highest elevation meadow (Big Whitney).
Mentions: The three study meadows differed in elevation with Ramshaw Meadows at 2636 m, Mulkey Meadows at 2837 m, and Big Whitney Meadow at 2943 m. Despite Mulkey’s intermediate elevation, all three weekly temperature metrics (WminT, WavgT, and WmaxT) were higher in Mulkey, which is the only meadow partially grazed by livestock in recent years (Fig 5, Table 2). Across the study duration (2010–2012), the average water temperature during the eight warmest weeks of Mulkey Meadows was 13.2°C in the grazed area and 13.0°C in the ungrazed area. In contrast, it was cooler in Ramshaw (11.8°C) and in Big Whitney (10.7°C). The monthly average median minimal temperature over 7 days (WminT) was 1.79 ± 0.24 degrees higher in the grazed area of Mulkey compared to Big Whitney (mixed model multiple regression: t23 = 7.36, p < 0.001), but was not significantly different from Ramshaw (mixed model multiple regression: t22.9 = 0.01, p > 0.05), and also not significantly different from the ungrazed part of Mulkey Meadows (mixed model multiple regression: t22.9 = 1.35, p > 0.05). The median average temperature over 7 days (WavgT) was on average 2.65 ± 0.27 degrees higher in the grazed area of Mulkey compared to Big Whitney (mixed model multiple regression: t23.1 = 9.65, p < 0.001), 1.65 ± 0.26 degrees higher in Mulkey compared to Ramshaw (mixed model multiple regression: t22.9 = 6.24, p < 0.001), and not significantly different from the ungrazed part of Mulkey (mixed model multiple regression: t22.9 = 1.17, p > 0.05). The median maximal temperature over 7 days (WmaxT) was on average 2.63 ± 0.63 degrees higher in Mulkey compared to Big Whitney (mixed model multiple regression: t31 = 4.17, p < 0.01), 3.53 ± 0.61 degrees higher in Mulkey compared to Ramshaw (mixed model multiple regression: t31 = 5.77, p < 0.001), and not significantly different from the ungrazed part of Mulkey (mixed model multiple regression: t31 = 1.17, p > 0.47). These results were robust with regards to the scale at which we averaged the temperatures, that is, the results were similar when we instead used yearly or weekly averages instead of monthly averages (Table 3).

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