HR: 09:30h
AN: B11G-07    [Abstracts]
TI: Do Variations in Detrital Inputs Influence Stable Soil Organic Matter? – An Experimental Approach
AU: * Lajtha, K
EM: lajthak@science.oregonstate.edu
AF: Oregon State University, Dept. Botany and Plant Pathology, Corvallis, OR 97331, United States
AU: Townsend, K
EM: townsenk@onid.oregonstate.edu
AF: Oregon State University, Dept. Botany and Plant Pathology, Corvallis, OR 97331, United States
AU: Brewer, E
EM: elizabeth.brewer@oregonstate.edu
AF: Oregon State University, Dept. Crop and Soil Science, Corvallis, OR 97331, United States
AU: Caldwell, B
EM: bruce.caldwell@oregonstate.edu
AF: Oregon State University, Dept. Botany and Plant Pathology, Corvallis, OR 97331, United States
AU: Kalbitz, K
EM: karsten.kalbitz@uni-bayreuth.de
AF: University of Bayreuth, Dept. Soil Science, Bayreuth, D 95440, Germany
AU: Plante, A
EM: aplante@sas.upenn.edu
AF: University of Pennsylvania, Department of Earth and Environmental Science, Philadelphia, PA 19104, United States
AB: Recognition of the importance of feedbacks from plants in determining soil nutrient dynamics and C storage led to a large number of litter decomposition studies. Despite growing knowledge of short-term litter dynamics, we know relatively little about the fate of plant litter and its role in determining SOM content and nutrient cycling over time scales ranging from decades and centuries. To address this gap, we established long-term studies of controls on soil organic matter formation in an old-growth forest at the H.J. Andrews Experimental Forest, OR. This study complements a network of recently established similar experiments that pan climatic and soil gradients, as well as the original DIRT experiment established in the Wisconsin Arboretum in 1956 in both grassland and forested sites. The central goal of the DIRT project is to assess how rates and sources of plant litter inputs control the accumulation and dynamics of organic matter and nutrients in forest soils over decadal time scales. Treatment plots include doubled litter (needle) inputs , doubled wood, no above ground litter (screened) inputs, no root inputs (trenched), and no inputs (screened and trenched). For the 50th anniversary of the Wisconsin sites and the 10th anniversary of the H.J. Andrews site, we used sequential density fractionation of soils from all treatments to determine if adding or removing either below- or above-ground litter inputs influenced carbon stabilization as soil organic matter. After 50 years, double litter plots in both prairie and forested soils had higher %C in the 0-10 cm horizon. In the forested site, plots showed increased C content of the lightest fraction, which represents relatively young SOM with a short turnover time. However, the first two heavy fractions also showed increases in C with added aboveground litter, suggesting the importance of aboveground litter inputs to SOM in the forest. No such pattern existed for the prairie soil, and we hypothesize that this is because aboveground, labile litter adds very little to stabilized SOM in grasslands, and that root-derived C is the dominant control on SOM stabilization in grasslands. These results were confirmed with analysis of labile C (short –term respiration measurements) and acid hydrolysis resistant C across treatments. The relative contribution of aboveground vs. belowground litter was analyzed through the analysis of cutin and suberin acids, and we found that the detrital source of litter was retained in soils and could be fingerprinted through this analysis. Thermal analysis, including thermogravimetry (TG) and differential scanning calorimetry (DSC) performed simultaneously is currently being applied to explore both SOM quality and stability.
DE: 0428 Carbon cycling (4806)
DE: 0439 Ecosystems, structure and dynamics (4815)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting