HR: 16:00h
AN: B44A-01    [Abstracts]
TI: Developing a General Understanding of the Decomposition Process: Results From a Network Experiment
AU: * Harmon, M E
EM: mark.harmon@oregonstate.edu
AF: Department of Forest Science, Oregon State University, 321 Richardson Hall, Corvallis, OR 97331-5752,
AB: Although leaf and fine root litter undergo many changes during the process of decomposition, there is relatively little long-term data to develop a general, global level understanding of this process. The LIDET (Long-term Intersite Decomposition Experiment Team) study, conducted at 27 sites in North and Central America using a wide range of litter types, created a database suitable for this purpose. Analysis of the long-term pattern of mass loss indicated that while a slower, later phase of decomposition occurred in most cases for a substantial fraction (30%) it did not. These results imply that average long-term decomposition rates may be overestimated by up to a factor of 2 if based on short-term (1 year) decomposition losses. The relationship between wooden dowel decomposition and climatic indices indicated limits on the ability to predict decomposition rates for sites more favorable for decomposition, with a maximum coefficient of determination of 70%. Regression analysis of the relationship between climatic and substrate quality indices and decomposition rates indicated controls on decomposition processes changed from the early to late stages, with early-stage processes controlled by climate and initial litter chemistry, but late-stage processes more likely controlled by other factors such as the soil environment. Development of a mechanistic model based on AIC analysis indicates at least 3 litter fractions need to be considered and that a climatic index that combines the effects of temperature and moisture explains the most variation (70%). Analysis of the relationship between nitrogen release and mass loss indicated a global relationship exists that is largely dependent on the initial nitrogen content with 77% of the variation explained by this simple model. Overall the LIDET study indicated that there are general global patterns to long- term decomposition dynamics, however, current models indicate limits to our ability to predict global patterns of this important process.
DE: 0330 Geochemical cycles (1030)
DE: 0428 Carbon cycling (4806)
DE: 0469 Nitrogen cycling
DE: 0486 Soils/pedology (1865)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting