PARENT SESSION
Poster Session # 10: Soil Ecology.

Tuesday, August 5 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Resource availability and co-existence of mycorrhizal fungi in an oak savanna.

Egerton-Warburton, Louise^{1, 2}, Querejeta, Jose Ignacio², Lindahl, Amy², Allen, Michael², ¹ Chicago Botanic Garden, Glencoe, IL² University of California, Riverside, CA

ABSTRACT- Resource partitioning is an important determinant of species diversity in many plant and animal communities, but its importance in structuring mycorrhizal fungal communities has been difficult to resolve. This is due mainly to the difficulties in studying in situ the distribution of fungal hyphae, and how certain species might proliferate in response to resource availability. We used molecular approaches to study the distribution and abundance of arbuscular (AM) and ectomycorrhizal (EM) fungal root tips and hyphae, the structures involved in the uptake of water and nutrients, in coast live oak woodlands during a severe drought. Comparing the distribution of mycorrhizal types and species with the pattern of available water across the site (mesic valley to xeric hill top) and with vertical depth suggested that mycorrhizal diversity was related to a fungal species' ability to exploit a scarce resource (soil water) and tolerate drought or moist conditions. That is, species diversity and dominance, and community composition closely matched soil water potentials. High levels of soil moisture corresponded with greater EM species diversity, whereas dry soils contained an abundance of AM and certain EM species (e.g., Cenococcum). These findings are consistent with the idea that shifts in mycorrhizal community composition and species dominance with resource availability might facilitate the co-existence of mycorrhizal fungi.

Key words: arbuscular mycorrhizae, coast live oak, ectomycorrhizae, drought