HR: 0800h
AN: B51A-0190    [Abstracts]
TI: Dissolved Organic Carbon and Nitrogen Leaching From Soil Formed in Grass, Oak and Pine Ecosystems of California
AU: * Pittiglio, S L
EM: spitt@ucdavis.edu
AF: University of California, Davis, 3149 Plant & Env. Science Bldg. , Davis, CA 95616
AU: Zasoski, R J
EM: rjzasoski@ucdavis.edu
AF: University of California, Davis, 3149 Plant & Env. Science Bldg. , Davis, CA 95616
AB: Dissolved organic matter (DOM) leaching from decomposing detritus accumulated above mineral soils is an important carbon (C) and nitrogen (N) flux that influences biogeochemical processes, C sequestration and the health of individual ecosystems. This study compared the retention and transformation of DOM leached through soils formed under three contrasting vegetation types. In a laboratory study, columns of surface soil (10 cm diameter, 10 cm height) from either a grass, oak or pine site were leached with DOM derived from either grass, oak or pine litter. In the field, the laboratory study was replicated by burying columns of soil from the grass, oak and pine sites under the organic horizon at each sites. Leachates from in-situ field columns were collected biweekly beginning in January 2005. Samples were analyzed for volume, pH, total N, NO3-, NH4+, DON and DOC. In the laboratory leaching studies soils retained DOC derived from its native ecosystem to a greater extent. These results suggest that the microbial community from each ecosystem is adapted to consume the native DOC. No clear trends were found with DOC in the field study. Leachates from the field columns did show significantly lower levels of DON from pine soil columns at all sampling dates and sites. Similar results were found in the laboratory study with pine soil decreasing initial total N inputs from 32.9 to 3.6 mg kg-1. While all three sites contain kaolinite, vermiculite and chlorite, soil from the pine site also has high levels of iron oxides and gibbsite. The greater iron content likely contributes to higher DON retention since these minerals are know to have high affinities for the retention of DOM. The results from the field and laboratory experiments show that both soil minerals and the soil microbial communities play an important role in DOM retention in the subsoil.
DE: 0428 Carbon cycling (4806)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0469 Nitrogen cycling
DE: 0486 Soils/pedology (1865)
SC: Biogeosciences [B]
MN: Fall Meeting 2005