Effects of Disturbance On Ectomycorrhizal Mat Microbial Communities: Perspectives From a Long-Term Birth/Death Study.

Ectomycorrhizal fungi (EmF) form symbiotic associations with many tree species, trading soil nutrients and water for carbon.  Old-growth conifer forest soils of the Pacific Northwest support specialized profusions of EmF hyphae, known as fungal mats, which can cover 25% of the forest floor and account for up to 40% of soil microbial biomass.  Two dominant mat genera, Piloderma and Ramaria, stratify in the organic and mineral horizons, respectively, support unique microbial communities, and differentially alter soil biogeochemistry.  This study continues an EmF mat birth/death experiment established in 2006 at the H.J. Andrews Long-Term Ecological Research site.  At seven old-growth Douglas-fir sites Piloderma, Ramaria and non-mat areas underwent birth (non-mat into mat), death (mat into non-mat), and no manipulation.  Previously, the dynamics of these mats and their associated microbial communities has been assessed using TRFLP analysis at 10, 16, and 24 months.  This study assesses changes at 51 months and at a greater genetic depth.  The primary objectives are to determine the effect of EmF mat birth/death on (1) EmF community structure and abundance using PCR/RFLP/ITS sequencing and qPCR, and (2) mat microbial community structure and abundance using 454-pyrosequencing.