Monday, November 13, 2006

Linking Microbial Community Structure and Function Related to Greenhouse Gas Emissions from Planted and Mulched Soils.

Matthew T. McCoy, Dept. of Crop & Soil Sciences, The Pennsylvania State University, 116 Ag. Sci. & Ind., University Park, PA 16802, Loren B. Byrne, The College of Wooster, Dept. of Biology, 931 College Mall, Wooster, OH 44691, and Mary Ann Bruns, 116 AG Sciences and Industry Bldg., Pennsylvania State Univ., Penn State University, Dept of Crop and Soil Sciences, University Park, PA 16802-3504.

Land management can drastically affect biogeochemical processes and greenhouse gas emissions from soils by physically and chemically altering microbial habitats. We investigated C and N transformations and soil microorganisms in planted and mulched plots of a complete randomized block design experiment (n = 4) established in 2003 at Penn State’s Agronomy Research Farm in Rock Springs in central Pennsylvania. Planted soils consisted of unmowed oldfield vegetation and mowed lawns containing mostly Poa pratensis. Mulched soils were covered with shredded hardwood bark mulch or limestone gravel. Within one year of plot establishment, gravel-covered soils contained significantly less microbial biomass carbon, and they exhibited higher nitrification rates and nitrous oxide fluxes than bark-mulched or planted plots. Bark-mulched soils showed net immobilization of nitrogen, highest denitrification rates in incubated soil cores, and highest ergosterol contents indicating higher fungal biomass. Although highest numbers of culturable denitrifiers were observed initially under lawns and bark mulch, N2O fluxes in the field were greatest for gravel-mulched plots. No statistically significant differences in culturable ammonia-oxidizing bacteria were observed within one year after plot establishment. Soils with and without plants were shown to provide different microbial habitats associated with significantly different microbial communities, C and N pools, and greenhouse gas emissions.