The Intimate Life of Soil Carbon.

There is not doubt that differences in soil carbon dynamics can have macroscopic impacts on soil function and the global C cycle.  However, to understand the mechanistic details of C cycling these processes must be investigated at the micro-scale, the scale at which soil microbiota and soil mineral components are of comparable size and interact directly. It is this intimate life of soil carbon that we seek to understand using a combination of micro-analytical techniques and isotopic labeling.  Specifically, we have recently applied this approach to studying the micro-scale dynamics of ¹³C- and ¹⁵N-labeled chitin during a 3-week incubation into fungi-dominated microenvironments in O/A-horizons of old-growth forest soils adapted to rapid cycling of amino sugars. Our results show that microbial transformation and the subsequent association of amide N with Fe (oxyhydr)oxides occurs within weeks, emphasizing the potential importance of hydroxylated Fe oxide surfaces in microbially-mediated cycling of C and N in organic soil horizons.