Document: JEN-3-58-34

Ectomycorrhizal fungal communities in four North American ecosystems: Biodiversity, spatial distribution, and effects of nitrogen fertilization.

LANSING, J.L* ¹ and M.FALLEN ²

San Diego State University, San Diego, CA 92182 USA ¹
University of California Riverside, Riverside, CA USA ²

Abstract:
Ectomycorrhizal fungal (ECM) communities were evaluated in four North American ecosystems under ambient and elevated nitrogen (100 kgN/ha/yr fertilization). This study compared the ECM communities associated with 3 gymnosperm (Picea glauca, Pinus edulis , Pinus resinosa ) and 2 angiosperm ( Quercus spp. , Populus balsamifera) plant symbionts. The ECM abundance, richness, and species composition were evaluated using morphological characterization and molecular analysis. The internal transcribed spacer (ITS) region (rDNA) of single root tips was digested and the restriction fragment length polymorphism (RFLP) patterns generated were used to differentiate between species. Environmental factors known to influence ECM distribution were measured for each community ((NH₄, NO₃, soil organic matter, pH, and soil moisture). Canonical correspondence analysis (CCA) was used to investigate the effects of these environmental variables on ECM species spatial distribution. Sites did not differ significantly in the percentage of ECM root tips and there were no differences between ambient and nitrogen fertilized plots. Soil respiration at the soil surface above each ECM community differed significantly between sites. The Alaskan sites had the greatest respiration rates (22 and 18 mol CO₂m^-2s^-1 for balsam poplar and white spruce, respectively) while red pine and pinyon pine had the least (0.93 and 0.17 mol CO₂m^-2s^-1, respectively). Soil nutrients also differed significantly between sites. Balsam poplar and oak had the most NH₄ (64 ppm and 58 ppm, respectively) while red pine and pinyon pine had the least (13 ppm and 5 ppm, respectively). Balsam poplar and white spruce had the most NO₃ (66 ppm and 57 ppm, respectively) while red pine and pinyon pine had the least (3 ppm and 1 ppm, respectively). Using morphological characterization we found that for each ECM community one or two species are dominant in abundance. The greatest diversity of ECM species is evident when evaluating at a regional scale. Cenococcum geophilum is present at all sites. It is present in over 80% of the communities and often comprises 25-50% of the ECM infected tips.

Keywords: ectomycorrhizal fungi, nitrogen fertilization, biodiversity

This abstract is being presented at: 10:45 AM in session:
Oral Session #8: Mycorrhizal Fungi.