Anthropogenic disturbances are currently affecting temperate deciduous forests by increasing concentrations of atmospheric carbon dioxide and rates of nitrogen deposition. These disturbances are creating global climate changes that may alter carbon and nutrient cycles, resulting in unknown feedback processes and other ecological consequences. This project examines the effects of three years of nutrient additions that mimic possible biogeochemical changes resulting from global climate changes (increased carbon in detrital pools and greater soil nitrogen bioavailability) on the belowground processes of a temperate hardwood forest through the use of full-factorial field and mesocosm experiments. Specifically, this research involves measuring the effects of carbon, nitrogen and phosphorus additions on soil CO2 efflux, fine root biomass, C, N and P concentrations of both fine roots and bulk soil, and arbuscular and ectomycorrhizal colonization on white oak (Quercus alba) and sugar maple (Acer saccharinum). These two species exhibit different carbon and nutrient characteristics that may affect ecosystem scale processes.
Results/Conclusions
Results from the field experiment show distinct species-specific responses to resource alterations. Sugar maple fine root biomass was more responsive to nitrogen and phosphorus additions than white oak. Soil CO2 efflux was increased by carbon additions in white oak, but unaffected in sugar maple. Soil carbon for both species was increased by phosphorus fertilization. Arbuscular mycorrhizal colonization was increased by nitrogen and phosphorus fertilization while ectomycorrhizal diversity was reduced by the addition of nitrogen and phosphorus. The mesocosm experiment showed that the fine root biomass of sugar maple was decreased by carbon and phosphorus fertilization. Additionally, soil nitrogen concentrations were increased by the addition of carbon to the soil. The addition of labile carbon to the soil most likely increased competition between the soil microbial biomass and the plant roots. Both the field and mesocosm experiments highlight the importance of the soil microbial community in driving ecosystem scale biogeochemical cycles.
