PARENT SESSION
Poster Session 23: Soil Ecology
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Soil fungal communities in successional and mature deciduous forests in Maryland: heterogeneity and implications for an ecological understanding of mycorrhizal interactions.

McCormick, Melissa^*,1, van den Heuvel, Ronald¹, Whigham, Dennis¹, Filley, Timothy², Edwards, Chris², ¹ Smithsonian Environmental Research Center, Edgewater, Maryland, USA² Department of Earth and Atmospheric Sciences, West Lafayette, Indiana, USA

ABSTRACT- Fungi play important roles in soils as mycorrhizae, pathogens, and saprotrophs, but we know little of the variation in fungal communities or the distribution of fungal taxa. While molecular techniques are now available to study soil microbial communities, these techniques have primarily been applied to bacterial communities. The overall objective of this research is to characterize the response of fungi to wood and leaf litter additions, focussing on Tulasnella spp. that form mycorrhizal associations with terrestrial orchids that occur in forests. We used a combination of length heterogeneity polymerase chain reaction (LH-PCR) and terminal restriction fragment length polymorphisms (T-RFLP) to analyze the soil fungal community in old (>100 years) and young (50-70 years) forests in response to amendment with leaves and wood. In May 2004, plots in three forests of each type were amended with locally collected Liriodendron tulipifera wood and leaves. Soil cores, collected prior to treatment and after five months, were analyzed from amended and control plots to characterize the fungal community. Composition of the fungal community was assessed by the presence of LH-PCR or T-RFLP fragments of different lengths. Major differences in the fungal communities occurred between the young and old forests and the pattern mirrored differences in -glucosidase and phenol oxidase activity (enzymes involved in cellulose and lignin degradation, respectively), with young forest sites having greater activity in both enzymes. Differences among treatments were not significant after five months. We found that there was substantial spatial and temporal heterogeneity in the fungal community, even at small scales, and most fungi (different fragment sizes) were rare and were found in only one or two samples. The distribution and diversity of Tulasnella spp. followed a similar pattern, supporting other findings that orchid mycorrhizal fungi are distributed in small discrete colonies.

Key words: Tulasnella, soil microbial community, fungal ecology, RFLP