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Title: A new conceptual model on the fate and controls of fresh and pyrolized plant litter decomposition

Author
item SOONG, JENNIFER - Colorado State University
item PARTON, WILLIAM - Colorado State University
item Calderon, Francisco
item CAMPBELL, NELL - Colorado State University
item COTRUFO, M - Colorado State University

Submitted to: Biogeochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2015
Publication Date: 2/25/2015
Citation: Soong, J.L., Parton, W., Calderon, F.J., Campbell, N., Cotrufo, M.F. 2015. A new conceptual model on the fate and controls of fresh and pyrolized plant litter decomposition. Biogeochemistry. DOI 10.1007/s10533-015-0079-2.

Interpretive Summary: As plant residues lay on the soil surface, rainfall leaches soluble organic substances from the residues into the soil. These leachates can contribute to the buildup of soil organic matter. In this experiment, we carried out a laboratory incubation to measure how much of the litter leachate became part of the soil organic matter, how much of the leachate was lost from the soil as CO2, and what litter properties determine these fates of litter carbon. Our results show that the amount of lignin and the total soluble material in litter play important roles on whether the litter C is lost as CO2, or remains in soil.

Technical Abstract: The leaching of dissolved organic matter (DOM) from fresh and pyrolyzed aboveground plant inputs to the soil is a major pathway by which decomposing aboveground plant material contributes to soil organic matter formation. Understanding how aboveground plant input chemical traits control the partitioning of mass loss to dissolved organic carbon (DOC) leaching versus respiration to CO2 would help to inform predictions of plant input-soil-atmosphere carbon (C) cycling. To test these controls, we incubated five fresh and one pyrolyzed leaf litters with differing chemistry and measured DOC and CO2 fluxes as well as changes in substrate and DOM chemistry over time using Fourier transformed infrared spectroscopy (FTIR). We found that the amount of hot water extractable C was a strong predictor of initial DOC leaching, while the lignocellulose index was a strong predictor of later stage DOC versus CO2 partitioning. Changes in substrate and DOM chemistry indicated a progression of substrate availability for leaching: from soluble plant components, to partially decomposed cellulose and lignin, to microbial products. We propose that these chemical traits of fresh and pyrolyzed aboveground plant inputs to soil can be used to predict aboveground organic matter decomposition dynamics and form a better linkage between aboveground decomposition and terrestrial ecosystem C cycling.