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.

Interspecific competition changes composition and reduces abundance of pinyon pine ectomycorrhizal fungal communities.

Haskins, Kristin^{*,1, 2}, Gehring, Catherine^{1, 2}, ¹ Northern Arizona University, Flagstaff, AZ, USA² Merriam-Powell Center for Environmental Research, Flagstaff, AZ, USA

ABSTRACT- The increased frequency of drought predicted for much of the United States will likely intensify competition among plants for limited resources. Belowground competition can affect plants either directly or indirectly via their associated mycorrhizal fungi. However, no study has experimentally examined the consequences of root competition for these important mutualists in the field. We used a trenching experiment to examine how belowground competition between pinyon pine and one-seed juniper affected the ectomycorrhizal (EM) fungal communities of pinyon pine. Three major findings emerged: 1) pinyons responded to the reduction of juniper roots with a near doubling of fine root biomass in just two years, 2) this increase in pinyon roots translated into a potential four fold increase in EM abundance, 3) the EM fungal communities of trenched trees differed significantly from controls largely due to a decrease in ascomycete fungi. Because species of EM fungi vary in the benefits they provide, changes in EM communities could have long-term consequences for host plant establishment, growth and survival. Belowground competition with juniper may also contribute to the high mortality of pinyons and the reduced diversity of EM fungi associated with recent droughts.

Key words: juniper, drought, RFLP