Wednesday, November 4, 2009
Convention Center, Exhibit Hall BC, Second Floor
Earthworms create distinct habitats in soil that support active microbial communities. Surprisingly, we know very little about the composition and diversity of non-culturable microbial communities in these “hot spots”, which include burrow linings, or the drilosphere. A plot-level study was conducted to examine microbial community structure and C assimilation activity within and outside Lumbricus terrerstris drilosphere soil in plots that did or did not receive mustard residues on the surface (2 Mg ha-1 rate). Five weeks after residue addition, L. terrestris were extracted from residue-amended and non-amended plots, counted, and their biomass recorded. Lumbricus terrerstris-occupied burrows were excavated from plots to collect soil for targeted sampling of drilosphere soil (within 2 mm of burrow wall, 5-15 cm depth) or non-drilosphere soil (2 cm away from burrow wall; 0-5 and 5-15 cm depths). In all plots, delta 13C values of drilosphere soil (5-15 cm depth) were intermediate between the 0-5 cm and 5-15 cm nondrilosphere soil, demonstrating the mixing of SOC pools at depth by L. terrestris. Microbial phospholipid fatty acids (PLFAs) were extracted from drilosphere and non-drilosphere soils and analyzed for fatty acid composition and delta 13C values. Results from this study will provide novel information on the functional significance of L. terrestris for supplying carbon substrate to soil microorganisms residing at depth and in distinct spatial habitats in soil.