HR: 1340h
AN: B13C-0236    [Abstracts]
TI: Detrital Controls on Dissolved Organic Matter in Soils: A Field Experiment
AU: * Lajtha, K
EM: lajthak@science.oregonstate.edu
AF: Department of Botany and Plant Pathology Oregon State University, 2082 Cordley , Corvallis, OR 97331 United States
AU: * Lajtha, K
EM: lajthak@science.oregonstate.edu
AF: Department of Crop and Soil Sciences Oregon State University, Ag Life Sciences Building, Corvallis, OR 97331 United States
AU: Crow, S
EM: crows@science.oregonstate.edu
AF: Department of Botany and Plant Pathology Oregon State University, 2082 Cordley , Corvallis, OR 97331 United States
AU: Yano, Y
EM: yyano@mbl.edu
AF: Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543 United States
AU: Kaushal, S
EM: kaushals@ecostudies.org
AF: Institute of Ecosystem Studies, Box AB, Millbrook, NY 12545 United States
AU: Sulzman, E
EM: elizabeth.sulzman@oregonstate.edu
AF: Department of Crop and Soil Sciences Oregon State University, Ag Life Sciences Building, Corvallis, OR 97331 United States
AU: Sollins, P
EM: phil.solins@oregonstate.edu
AF: Department of Forest Sciences Oregon State University, Peavy Hall, Corvallis, OR 97331 United States
AB: We established a long-term field study in an old growth coniferous forest at the H.J. Andrews Experimental Forest, OR, to address how detrital quality and quantity control soil organic matter accumulation and stabilization. The Detritus Input and Removal Treatments (DIRT) plots consist of treatments that double leaf litter, double woody debris inputs, exclude litter inputs, or remove root inputs via trenching. We measured changes in soil solution chemistry with depth, and conducted long-term incubations of bulk soils and soil density fractions from different treatments in order to elucidate effects of detrital inputs on the relative amounts and lability of different soil C pools. In the field, the effect of adding woody debris was to increase dissolved organic carbon (DOC) concentrations in O-horizon leachate and at 30 cm, but not at 100 cm, compared to control plots, suggesting increased rates of DOC retention with added woody debris. DOC concentrations decreased through the soil profile in all plots to a greater degree than did dissolved organic nitrogen (DON), most likely due to preferential sorption of high C:N hydrophobic dissolved organic matter (DOM) in upper horizons; %hydrophobic DOM decreased significantly with depth, and hydrophilic DOM had a much lower and narrower C:N ratio. Although laboratory extracts of different litter types showed differences in DOM chemistry, percent hydrophobic DOM did not differ among detrital treatments in the field, suggesting microbial equalization of DOM leachate in the field. In long-term laboratory incubations, light fraction material did not have higher rates of respiration than heavy fraction or bulk soils, suggesting that physical protection or N availability controls different turnover times of heavy fraction material, rather than differences in chemical lability. Soils from plots that had both above- and below-ground litter inputs excluded had significantly lower DOC loss rates, and a non-significant trend for lower respiration rates . Soils from plots with added wood had similar respiration and DOC loss rates as control soils, suggesting that the additional DOC sorption observed in the field in these soils was stabilized in the soil and not readily lost upon incubation.
DE: 1860 Runoff and streamflow
DE: 1615 Biogeochemical processes (4805)
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting