Powell, Katherine M听1听;听Blanken, Peter D听2听;听Anderson, Dean E听3听;听Stannard, David I听4听;听Thienelt, Thomas听5
1听University of Colorado
2听University of Colorado
3听U.S. Geological Survey
4听U.S. Geological Survey
5听Martin-Luther-Universitaet Halle-Wittenberg听
Near surface soil-water content is crucial to the sustainability of an ecosystem. Additionally, the feedbacks between soil water and soil carbon improve the ability to predict carbon sequestration rates. Organic-carbon content in surface soils influences soil texture and, subsequently, water holding capacity. Preliminary research for two growing seasons (2010 and 2011) compares soil water, temperature, heat flux, and evapotranspiration (ET) with soil organic carbon content at several sites in the Colorado Front Range. Continuous measurements of precipitation, soil moisture and temperature, and energy fluxes were conducted from eddy covariance flux towers at three sites around metropolitan Denver: one urban site and two adjacent sites, a montane forest (Flying J Ranch Open Space), and a native tallgrass prairie (Rocky Flats National Wildlife Refuge (NWR)). Irrigation data were obtained for the Denver urban site and added to its precipitation to obtain total water inputs. Soil samples (0-5cm) were collected at each tower site and analyzed for bulk density, volumetric water content, and organic carbon content. Soil water inputs and losses (as ET) were analyzed for each site and compared to soil organic carbon content. The tallgrass prairie soils contained the highest organic carbon content, with a mean value of over 13 percent (N=18, 蟽=2.44), the montane site had a mean of 7.5 percent (N=24, 蟽=3.56), and the urban contained a mean organic carbon content of 5.9 percent (N=29, 蟽=1.18). Comparing grassland sites, the urban soil received much more water than the soil at the tallgrass prairie, 5 times higher water input (600mm, more than half from irrigation) in 2010, and approximately 3 times higher water input (840mm, 3 quarters from irrigation) in 2011. Despite less water input, the tallgrass prairie site developed more soil organic carbon. Research is focusing on the soil moisture conditions through the season that are more favorable to organic carbon accumulation and what conditions may be limiting soil carbon formation in irrigated urban soils. Plans include expanding the use of ecosystem process models to increase predictability under different land management and climate scenarios.
Amundson, R., 2001, The carbon budget in soils, Annual Review of Earth and Planetary Sciences, v. 29, p. 535-562.
Craine, J. M. and T. M. Gelderman, 2011, Soil moisture controls on temperature sensitivity of soil organic carbon decomposition for a mesic grassland, Soil Biology and Biochemistry, v. 43, no.2, p. 455-457.
Pouyat et al., 2008, A comparison of soil organic carbon stocks between residential turf grass and native soil, Urban Ecosystems, v. 12, p. 45-62.