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We have implemented a long-term snow fence experiment at the Niwot Ridge Long-Term Ecological Research site in the Colorado Front Range to assess the effects of climate change on alpine ecology and biogeochemical cycles. During the first winter after construction, the 2.6 X 60 m fence resulted in a snowpack which was significantly deeper than adjacent areas. The average period of continuous snow cover in the main snow fence drift (1994) was approximately 115 days longer than at control sites outside the fence drift (1994), and 90 days longer than at the same sites the year before construction of the fence (1993). The deeper and earlier snowpack behind the fence insulated soils from extreme air temperatures resulting in a 9°C increase in minimum soil surface temperatures, and a 12°C increase in minimum soil temperatures at a depth of 15 cm, compared to preference (1993) conditions. Warmer soils allowed microbial activity, measured as carbon dioxide flux through the snowpack, to continue through much of the winter. Carbon dioxide production under the deeper, earlier snowpack after construction of the fence was 55% greater than produced before construction of the fence. The loss of CO₂ from snow-covered soils was approximately 20% of aboveground primary production before and 31% after construction of the fence. Areas with shallower snowpacks showed opposite trends with greatly reduced CO₂ production. These data suggest that small changes in the timing and depth of snowpack accumulation may have a large effect on carbon balance and associated biogeochemical cycles in alpine ecosystems.




Web Links Dept of EPOB Home CU Boulder Home Chinook Catalog Institute for Alpine and Arctic Research Mountain Research Station Tundra Cam Niwot Ridge Long-term Ecological Research Microbe Zoo Soil Ecology Society American Society for Microbiology The Microbial Genome Project NSF News Mycorriza Information Exchange	The Niwot Ridge snow fence experiment: biogeochemical responses to changes in the seasonal snowpack
	Paul D. Brooks, Mark W. Williams, Donald A. Walker, and Steven K. Schmidt

		We have implemented a long-term snow fence experiment at the Niwot Ridge Long-Term Ecological Research site in the Colorado Front Range to assess the effects of climate change on alpine ecology and biogeochemical cycles. During the first winter after construction, the 2.6 X 60 m fence resulted in a snowpack which was significantly deeper than adjacent areas. The average period of continuous snow cover in the main snow fence drift (1994) was approximately 115 days longer than at control sites outside the fence drift (1994), and 90 days longer than at the same sites the year before construction of the fence (1993). The deeper and earlier snowpack behind the fence insulated soils from extreme air temperatures resulting in a 9°C increase in minimum soil surface temperatures, and a 12°C increase in minimum soil temperatures at a depth of 15 cm, compared to preference (1993) conditions. Warmer soils allowed microbial activity, measured as carbon dioxide flux through the snowpack, to continue through much of the winter. Carbon dioxide production under the deeper, earlier snowpack after construction of the fence was 55% greater than produced before construction of the fence. The loss of CO₂ from snow-covered soils was approximately 20% of aboveground primary production before and 31% after construction of the fence. Areas with shallower snowpacks showed opposite trends with greatly reduced CO₂ production. These data suggest that small changes in the timing and depth of snowpack accumulation may have a large effect on carbon balance and associated biogeochemical cycles in alpine ecosystems.
		Biogeochemistry of Seasonally Snow-Covered Catchments (Proceedings of a Boulder Symposium, July 1995). IAHS Publ. no. 228, 1995.