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UBC Theses and Dissertations

The effect of decayed or downed wood on the structure and function of ectomycorrhizal fungal communities at a high elevation forest Walker, Jennifer Karen Marie


Shifts in ectomycorrhizal (ECM) fungal community composition occur after clearcut logging, resulting in the loss of forest-associated fungi and potential ecosystem function. Coarse woody debris (CWD) includes downed wood generated during logging; decayed downed wood is a remnant of the original forest, and important habitat for ECM fungi. Over the medium term, while logs remain hard, it is not known if they influence ECM fungal habitat. I tested for effects of downed wood on ECM fungal communities by examining ECM roots and fungal hyphae of 10-yr-old saplings in CWD retention and removal plots in a subalpine ecosystem. I then tested whether downed and decayed wood provided ECM fungal habitat by planting nonmycorrhizal spruce seedlings in decayed wood, downed wood, and mineral soil microsites in the clearcuts and adjacent forest plots, and harvested them 1 and 2 years later. I tested for differences in the community structure of ECM root tips (Sanger sequencing) among all plots and microsites, and of ECM fungal hyphae (pyrosequencing) in forest microsites. I assayed the activities of eight extracellular enzymes in order to compare community function related to nutrient acquisition. The retention of CWD caused a shift in ECM root tip fungal species composition on saplings at the plot scale within 12 years of clearcutting. Decayed wood and hard downed wood also provided habitat for some ECM fungal species. Abiotic conditions in decayed wood and near downed wood on clearcuts were most similar to forest soils, but I did not detect a shift in ECM root tip or ECM hyphae community composition or function among microsites. Instead, ECM fungus community structure and enzyme activity differed most between clearcut and forest plots, and among forest plots. I could not determine if ecosystem function, in terms of soil macromolecule breakdown by ECM fungi, was maintained in clearcuts. Amphinema byssoides, Thelephora terrestris, and Tylospora asterophora were consistently the most abundant ECM taxa at Sicamous Creek. With pyrosequencing of fungal DNA, I was able to identify more ECM fungal taxa than in my previous experiments at this site. I concluded that CWD on clearcut blocks provides habitat for ECM fungi.

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