PARENT SESSION
Oral Session 15: Soil Ecology I: Mycorrhizal Communities.
Presiding: V Borowicz and X He
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room D 137.
Impacts of atmospheric deposition on New Jersey pine barrens forest soils and ectomycorrhizal communities.
Dighton, John*,1, Tuininga, Amy2, Dennis, Gray1, Huskins, Rebecca2, Belton, Thomas3, 1 Rutgers Pinelands Field Sation, New Lisbon, NJ, USA2 Fordham University Cader Center, Armonk, NY, USA3 NJ DEP, Trenton, NJ, USA
ABSTRACT- A gradient of increasing N deposition was identified in a southwestern to northeastern transect through the New Jersey pine barrens from 0.04 to 0.09 kg N / ha. The effect of this change in N deposition rate on soil chemistry and ectomycorrhizal community of pitch pine was studied by sampling from the field under mature pine trees and in a greenhouse study where differential rates of N applications (0, 35, 140 kg / ha equivalent) were made on intact soil cores in which pitch pine seedlings were grown. Along the transect, ectomycorrhizal abundance and species richness declined significantly under pitch pine. The decline in richness was significantly correlated with the N deposition rate. In the greenhouse, pine seedling biomass was inversely related to N addition, where N content of plants increased, but P content decreased, suggesting that P is limiting in this ecosystem. Extractable N increased in cores to which tree seedlings had been added as N addition increased, indicating an approach to a critical loading of N for these oligotrophic soils. In treeless cores N supply appears to exceed microbial immobilization potential even when no exogenous N is applied. As N supply to greenhouse seedlings increased, ectomycorrhizal richness declined. Specific ectomycorrhizal morphotype groups were identified by their response to added N. Cortinarius and Lactarius - like morphotypes are restricted to low levels of N availability. Suilloid, Russula and Ascomycete - like are more abundant as soil N availability increases. We discuss the results from these oligotrophic sandy soils in comparison with European data derived from richer soils, where mycorrhizal responses appear to occur only at much higher levels of exogenous N. We attribute these differences to the evolved adaptations of pitch pine to growth in highly oligotrophic environments.
Key words: ectomycorrhizae, N deposition, oligotrophy