HR: 16:40h
AN: B44A-03    [Abstracts]
TI: A Simple Three Pool Model Accurately Describes Patterns of Long-term Litter Decomposition in Diverse Climates Across Two Continents
AU: * Adair, E
EM: adair016@umn.edu
AF: Departments of Ecology, Evolution, and Behavior and Forest Resources, University of Minnesota, 1987 Upper Buford Circle, Saint Paul, MN 55108, United States
AU: Parton, W J
EM: billp@warnercnr.colostate.edu
AF: Natural Resource Ecology Laboratory, and Graduate Degree Program in Ecology, Colorado State University, 2nd Floor, 1231 East Drive, Fort Collins, CO 80523, United States
AU: Del Grosso, S J
EM: delgro@warnercnr.colostate.edu
AF: Natural Resource Ecology Laboratory, and Graduate Degree Program in Ecology, Colorado State University, 2nd Floor, 1231 East Drive, Fort Collins, CO 80523, United States
AU: Silver, W L
EM: wsilver@nature.berkeley.edu
AF: Ecosystem Sciences Division, Department of Environmental Science, Policy, and Management, University of California, 137 Mulford Hall #3114, Berkeley, CA 94720, United States
AU: Harmon, M E
EM: mark.harmon@oregonstate.edu
AF: Department of Forest Sciences, Oregon State University, 321 Richardson Hall, Corvallis, OR 97331, United States
AU: Hall, S A
EM: shall@tnc.org
AF: The Nature Conservancy, North Central Washington Field Office, Wenatchee, WA 98801, United States
AU: Burke, I C
EM: indy@warnercnr.colostate.edu
AF: Department of Forest, Rangeland, and Watershed Stewardship, and Graduate Degree Program in Ecology, Colorado State University, 1401 Campus Delivery, Fort Collins, CO 80523, United States
AU: Hart, S C
EM: steve.hart@NAU.EDU
AF: School of Forestry and Merriam-Powell Center for Environmental Research, Northern Arizona University, POB 15018, Flagstaff, AZ 86011, United States
AB: As atmospheric CO₂ increases, ecosystem carbon sequestration will largely depend on how global changes in climate will alter the balance between net primary production and decomposition. The response of primary production to climatic change has been examined using well-validated mechanistic models, but the same is not true for decomposition, a primary source of atmospheric CO₂. We used the Long-term Intersite Decomposition Experiment Team (LIDET) data set and model selection techniques to choose and parameterize a model that describes global patterns of litter decomposition. Mass loss was best represented by a three pool negative exponential model, with a rapidly decomposing labile pool, an intermediate pool representing cellulose, and a recalcitrant pool. The initial litter lignin/nitrogen ratio defined the size of labile and intermediate pools. Lignin content determined the size of the recalcitrant pool. The decomposition rate of all pools was modified by climate, but the intermediate pool's decomposition rate was also controlled by relative amounts of litter cellulose and lignin (indicative of lignin-encrusted cellulose). The effect of climate on decomposition was best represented by a composite variable that multiplied a water stress function by the Lloyd and Taylor (1994) variable Q10 temperature function. Although our model explained nearly 70% of the variation in the LIDET data, we observed systematic deviations from model predictions. Below- and aboveground material decomposed at notably different rates, depending on the decomposition stage. Decomposition in certain ecosystem-specific environmental conditions was not well represented by our model; this included roots in very wet and cold soils, and aboveground litter in N-rich and arid sites. Despite these limitations, our model may still be extremely useful for global modeling efforts, because it accurately (R² = 0.6804) described general patterns of long-term global decomposition for a wide array of litter types, using relatively minimal climatic and litter quality data.
DE: 0400 BIOGEOSCIENCES
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0469 Nitrogen cycling
SC: Biogeosciences [B]
MN: 2007 Fall Meeting