HR: 0800h
AN: B41C-0646    [Abstracts]
TI: Decomposition of Soil Organic Matter From Physically Derived Decay Rates
AU: * Forney, D C
EM: dforney@mit.edu
AF: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139,
AU: * Forney, D C
EM: dforney@mit.edu
AF: Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139,
AU: Rothman, D H
EM: dhr@mit.edu
AF: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139,
AB: The decomposition of organic matter in soils and marine sediments exhibits both marked similarities and unmistakable differences [1]. Despite obvious chemical and biological complexity, a surprisingly simple physical model captures the dynamics of decay in a wide variety of sediments [2]. This physical model consists of a porous reaction-diffusion system where a wide distribution of reaction rates derives purely from microbial accessibility and diffusion-limited enzymatic hydrolysis. Here we consider whether such a model can be similarly applied to the late stages of organic matter decay in soils where microbes degrade recalcitrant substrates. We consider the presence of both bacteria and fungal hyphae. Predictions from the model are found to fit over 30 litter and soil carbon data sets. The similarity between the temporal decay of natural organic matter with the evolution of this simple physical system indicates that diffusion-limitation may be a common characteristic of detrital decay in both soils and sediments. It also reiterates the importance of the substrate structure in the microbial decomposition of organic matter. [1] J.~I Hedges, J.~M. Oades, Org. Geochem. 27, 319 (1997).
[2] D.~H. Rothman, D.~C. Forney, Science 316, 1325 (2007).
DE: 0412 Biogeochemical kinetics and reaction modeling (0414, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0486 Soils/pedology (1865)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting