Park, E.-J. and A.J.M. Smucker
Presented at the All Scientist Poster Reception (2006-05-09 )
We investigated the spatial distribution and dynamics of labile DOC (13C-glucose) supplied to individual soil aggregates and its contribution to aggregate stabilization and microbial communities during multiple DW cycles. Moist macroaggregates were treated with no DW cycles and no glucose (Control), 5 DW cycles and no glucose (DW0G), and 5 DW cycles with additions of 250mg glucose-13C g-1 soil during each cycle (DW+G). Aggregate stability decreased significantly following 2 DW cycles when C was not added. Additions of glucose-13C with each DW cycle maintained soil aggregate stability throughout the 35-day incubation and increased C flux into aggregate interiors. Spatial gradients in glucose-derived C within aggregates developed by repeated glucose additions with DW cycles controlled spatial distributions of microbial communities within aggregates. Rapid reductions in mineralization rates of glucose C indicated either physical protection or chemical stabilization of new C within aggregates. Constant supplies of glucose C at aggregate surfaces established C concentration gradients that promote C flux into microfissures of interior regions within stable aggregates during repeated DW cycles. These results identify additional C-enhancing mechanisms which increase soil sequestration of C generated by decomposing plant residues of no tillage agriculture.
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