Influence of soil management onbacterial morphotype diversity in soil aggregates

Dopp, H.A., E.J. Park, and A.J.M. Smucker

Presented at the ASM in Seattle (2003-09-18 to 2017-12-05 )

Soil aggregation processes and wetting-drying cycles modify microhabitats by changing pore networks and sequestering carbon © within interiors of aggregates.  Morphotype analysis of bacterial communities within concentric layers of soil aggregates can be used to estimate bacterial populations associated with the microhabitats located on surfaces and within the central regions of macroaggregates.  Bacterial morphotypes were identified by computer image processing software developed by the Center for Microbial Ecology Image Analysis System (CMEIAS) at Michigan State University.  Bacteria and soil were extracted from exterior and interior regions of soil aggregates by mechanical soil aggregation erosion (SAE) chambers, separated and stained with DTAF (5-(4,6-dichlorotriazin-2-yl)aminofluorescein).  The diversity and the number of bacteria were compared with C and nitrogen (N) concentrations, soil texture, and mean weight diameters (MWD) of aggregates by the wet sieving method.  Soil C contents on aggregate exteriors were 5% and 12% greater than interior regions of macro-aggregates sampled from native forest (NF) and conventionally tilled (CT) agroecological soils at the KBS LTER site and the Upper Peninsula research sites, respectively.  Increased numbers of bacteria per gram of soil were observed in the exterior regions of soil aggregates from the KBS LTER site (1.8E9 in exterior, 1.2E9 in interior).  It is expected that a greater range of bacterial morphotypes will be identified on exterior regions of soil aggregates that have greater intra-aggregate porosities and higher C and N concentrations.  External more robust bacterial communities contribute to the function and strength of soil aggregates through carbon mineralization. 

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