HR: 0800h
AN: B31B-04    [Abstracts]
TI: Coupled effects of soil heterogeneity and diffusion limitation on nitrogen availability
AU: * Manzoni, S
EM: sm86@duke.edu
AF: Duke University, Department of Civil and Environmental Engineering, 127 Hudson Hall, Durham, NC 27708-0287, United States
AU: Porporato, A
EM: amilcare@duke.edu
AF: Duke University, Department of Civil and Environmental Engineering, 127 Hudson Hall, Durham, NC 27708-0287, United States
AB: The heterogeneous distribution of nutrient-rich and nutrient-poor patches in soils strongly affects the rate of nitrogen cycling between organic and inorganic soil compartments. In particular, large differences in carbon-to- nitrogen ratios (C/N) among patches tend to increase cycling and the availability of inorganic nitrogen, which in turn affects plant nutritional status. We address the issue of substrate heterogeneous distribution by analyzing a two compartment model, where each fraction represents a class of micro-sites either mineralizing or immobilizing N from the inorganic forms, according to the C/N ratios of the substrate pools and the decomposer communities. Inorganic N is entirely or only partially shared by the two soil fractions depending on soil moisture and texture. We derive an equivalent lumped model for the macroscopic dynamics and show that the resulting structure embeds different schemes of commonly used biochemical models. We also assess the role of soil texture and soil moisture in limiting the diffusion of mineral N from N-rich to N-poor patches and show how microbial populations in dryer and finer-textured soils tends to experience stronger N-limitation than in more humid and coarser-textured soils. We close with a discussion of the effect of this interplay of micro-scale heterogeneity with soil moisture and textures on plant nutrient availability.
DE: 0412 Biogeochemical kinetics and reaction modeling (0414, 0793, 1615, 4805, 4912)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0469 Nitrogen cycling
DE: 1866 Soil moisture
SC: Biogeosciences [B]
MN: 2007 Joint Assembly