PARENT SESSION
Poster Session #2: Carbon Storage.
Monday, August 5. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC
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Community and system-level constraints on NPP and C pool dynamics in a restored tallgrass prairie.
CAMILL, PHIL1, LIMMER, JACOB*,1, ELLIS, ERIN1, STURGES, SEAN1, MCKONE, MARK1, 1 Carleton College, Northfield, MN
ABSTRACT- In restored tallgrass prairie ecosystems, the development of plant communities and carbon and nitrogen pools and fluxes are poorly understood. During summers 2000 and 2001, we collected data on species richness, total C and N, potential net C and N mineralization, O horizon mass, and aboveground and belowground NPP (in experimentally fertilized, watered, and control plots) across a 7-year-old, restored prairie chronosequence in southern Minnesota. Aboveground productivity (AGNPP) in fertilized plots was 10-100% higher than in control plots and was relatively constant across prairie ages in control plots (~250 g-C m-2 yr-1). Belowground NPP (BGNPP) in the upper 20 cm rose after year 3, correlating with increases in C-4 grass cover but not nitrogen amendments. These results suggest both community and system-level constraints on NPP in restored prairies, indicating that the belowground C cycle may respond quickly following the establishment of warm-season grasses, whereas the aboveground carbon cycle may depend on the slow buildup of soil nitrogen pools. We developed a simple model of soil C dynamics in managed prairie ecosystems to examine processes controlling soil organic C (SOC) accumulation in the upper 40 cm. We parameterized this model using C fluxes from our prairie landscape and literature values. The model explained trends observed in many managed grassland ecosystems: little rise in SOC pools over the first 10 years, accumulation rates between 30-70 g-C m-2 yr-1 in subsequent decades, and SOC accumulation to levels of native prairies by 60-100 years. Sensitivity analysis of SOC accumulation indicated that 5 of the 7 most important processes occur below ground. BGNPP controlled almost two orders of magnitude more change in SOC than any other factor. Significant BGNPP control on SOC accumulation indicates that species diversity, especially the establishment of C-4 grasses after year 3, has a large impact on C sequestration in restored prairie soils.
KEY WORDS: carbon, restoration, prairie, NPP