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

Impact of nematode fungivory on mycorrhizal/seedling (Pinus strobus) microcosms.

Wilson, Melanie^*,1, Adl, Sina^*,1, ¹ Dalhousie University, Halifax, Nova Scotia, canada

ABSTRACT- The most essential process governing the flow of nutrients throughout the soil food web is decomposition. Primary decomposers, capable of assimilating decomposing matter are mostly the bacteria and fungi microflora, where fungi are the main driving force in forests. Fungal mycelium can exploit large volumes of the environment while forming mutualistic associations with surrounding plants and animals, therefore the impact of fungi can be seen on a much larger scale. Since, mycorrhization of Eastern White Pine (Pinus strobes) is crucial during early stages of seedling development it would be of value to determine the impact of fungivory on mycorrhization. Through the use of microcosm techniques, nematode grazing rates were evaluated non-destructively. Measurements of daily consumption were quantified by calculating the ratio of nuclei to length of hyphae. Grazing rates accumulated from an incremental series of grazing pressure on fungal hyphae were used to obtain a functional response curve. Greenhouse pot experiments with a combination of seedling, ectomycorrhizae, nematodes and micro-arthropods were used to determine the impact of fungivory on early mycorrhization of Pinus strobus. Seedlings incubated for 16 weeks under natural conditions were stressed at week 8, where half of each treatment received limited water supply to ensure a mycorrhizal advantage. Preliminary results show nematode grazing to have a negative impact on hyphal density as grazing removes fungal cell contents. Therefore, we expect to find a negative association between increased grazing pressure and seedling biomass, as grazers will take away from the resources otherwise supplied to the plant through its fungal partner. Findings from this study will contribute valuable data towards the role of grazing on fungi in soil food webs. Information on grazing rates will provide a functional response model which can be applied to natural populations of nematodes and ectomycorrhizae to quantify the ecosystem effect of nematode grazing.

Key words: ectomycorrhizae, nematodes, Pinus strobus, mutualism