HR: 0800h
AN: B51C-0973    [Abstracts]
TI: Carbon Cycling Dynamics in Mixed-Grass Prairie Following Coupled Changes in Winter Snow and Summer Precipitation
AU: * Chimner, R A
EM: rchimner@nrel.colostate.edu
AF: Natural Resource Ecology Laboratory, Colorado State University, 200 West Lake Street, Ft. Collins, CO 80523-1499 United States
AU: Welker, J M
EM: afjmw1@uaa.alaska.edu
AF: Natural Resource Ecology Laboratory, Colorado State University, 200 West Lake Street, Ft. Collins, CO 80523-1499 United States
AU: Welker, J M
EM: afjmw1@uaa.alaska.edu
AF: Environment & Natural Resources Institute, University of Alaska Anchorage, 3211 Providence Drive, Anchorage, AK 99508 United States
AU: Morgan, J
EM: morgan@lamar.colostate.edu
AF: USDA, ARS Rangeland Resources Research Unit, 1701 Centre Ave, Ft. Collins, CO 80526 United States
AU: LeCain, D
EM: lecain@lamar.colostate.edu
AF: USDA, ARS Rangeland Resources Research Unit, 1701 Centre Ave, Ft. Collins, CO 80526 United States
AU: Reeder, J D
EM: jdreeder@lamar.colostate.edu
AF: USDA, ARS Rangeland Resources Research Unit, 1701 Centre Ave, Ft. Collins, CO 80526 United States
AB: Changes in timing or amount of precipitation may be of great consequence for carbon cycling in the western U. S. Mixedgrass Prairie, partly due to the fact that both production and decomposition are tightly coupled to soil water properties. In addition, the Mixedgrass Prairie constitutes the largest grassland type in North America. The objective of our project is to quantify how net ecosystem C flux (NEE), ecosystem respiration (Re) and gross photosynthesis (GPP) respond to experimental changes in winter and summer precipitation in a Mixedgrass Prairie. Our study is conducted at the USDA-ARS High Plains Grasslands Research Station, west of Cheyenne, Wyoming. We installed three replicated 50 m snow fences to increase winter snow on the lee ward side of the snow fence and experimentally manipulated summer precipitation by either increasing or decreasing precipitation amounts. Snow additions showed no significant effects in the spring or early summer of 2003 due to the wet spring conditions. However, the snow treatments had greater fluxes of NEE, GPP and Re values in the late summer of 2003 compared to ambient conditions. Rates of ecosystem carbon flux in the snow addition plots were many times larger than ambient fluxes in the spring and summer of 2004. Additionally, snow addition plots in 2004 had almost twice the flux rates as snow addition plots in 2003, compared to lower fluxes in 2004 for ambient plots. The large fluxes in the 2004 snow plots were due to a combination of wet soils from snow packs melting and from hot and sunny spring and early summer. Summer precipitation treatments had much less of an effect on ecosystem carbon cycling than the winter precipitation treatment. Increasing summer precipitation generally had a slight increase in ecosystem carbon fluxes. This was most noticeable in the late summers. Decreasing summer precipitation tended to lower ecosystem carbon fluxes. Reductions in fluxes were most visible in GPP and Re measurements in the late summers. However, the reduction in GPP and Re were of similar magnitude so there were little changes in NEE. This research is important for predicting changes in soil carbon storage and plant production due to climate change in the largest grassland type in North America.
DE: 1655 Water cycles (1836)
DE: 1854 Precipitation (3354)
DE: 1615 Biogeochemical processes (4805)
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting