Cross-site comparison of soil microbial biomass, soil nutrient status, andnematode trophic groups

Soil microbial biomass, soil nutrient status, and nematode trophic groups w ere examined at the Coweeta, Harvard Forest, and Hubbard Brook Long Term Ec ological Research (LTER) sites. Soils were divided into standardized depths (0-5 cm and 5-10 cm) for all analyses. Microbial biomass, nematode abundan ce and labile soil phosphorus levels were significantly higher in the 0-5 c m soil than in the 5-10 cm soil. Overall, both Harvard Forest and Hubbard B rook had greater nematode abundance and soil phosphorus than Coweeta, while Harvard Forest had the highest levels of microbial biomass. Bacterial feed ers, followed by fungal feeders and Tylenchidae were the dominant nematode trophic groups at all three sites. Soil factors such as organic matter, roo t biomass and total soil C and N contributed to increased levels of microbi al biomass, nematode abundance and soil phosphorus levels. In contrast, lit ter quality and climatic factors such as temperature and moisture apparentl y had little effect upon the parameters measured. This study illustrates th e complex interrelationships between decomposer communities, climate, litte r quantity, litter quality, soil nutrients, and site specific ecosystem pro cesses. Continued long-term, cross-site ecosystem studies remain necessary to better understand the complex and dynamic processes causing variability both within and between ecosystems.