Carbon Dynamics in Tallgrass Prairie and Wheat Ecosystems


Abstract: Soil carbon (C) dynamics is an important aspect of the global C cycle. Soils can be a sink or source for atmospheric CO_2 depending upon management. Tallgrass prairie and wheat (Triticum aestivum L.) are 2 dominant ecosystems in the Great Plains. This study determined the distribution of C in these 2 ecosystems. Soil C pools, plant root biomass, and aboveground plant biomass were determined at a wheat (winter wheat) and a tallgrass prairie site in northern Oklahoma from 1998 through 2001. The objectives of this study were to determine C storage and changes in soil organic matter in tallgrass prairie and wheat ecosystems under similar environmental conditions and soil characteristics. Soil C was assessed by measuring soil C pools (active, slow and recalcitrant). Mineralizable C and N (C_o and N_o) were determined by long-term laboratory incubation, 314 days at 35 °C. Soil C and N content was 2 times greater in the prairie than under wheat. The greater level of C_o and N_o occurred in prairie. Wheat had proportionally greater mineralizable C and N than did prairie, but microbial biomass was the opposite, being greater in prairie. Wheat had more dynamic C pools with a faster turnover rate than did prairie. The more dynamic C pools with a faster turnover rate in wheat was the result of the greater disturbance effects of intensive tillage practices on soil structure.

Keywords: Soil carbon, carbon pools, mineralizable carbon, microbial biomass carbon, recalcitrant carbon

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