UBC Theses and Dissertations
Forest stand type and ectomycorrhizal fungal communities of western hemlock on northern Vancouver Island, Canada Lim, Sea Ra
This thesis explores the diversity and phylogenetic structure of the ectomycorrhizal fungal community of western hemlock from five forest types on northern Vancouver Island. Chapter One reviews methods and provides background for studies of ectomycorrhizal fungal communities. In Chapter Two, I describe the results of a new correlative study using recently developed measures of phylogenetic diversity as well as standard measures of diversity and of fungal species composition to relate ectomycorrhizal fungal species to productivity of hemlock trees. I sampled ectomycorrhizal root tips of western hemlock from northern Vancouver Island and amplified, cloned and sequenced the fungal DNA from root extracts. In my analyses, I combined new data from plots of mature western hemlock-amabilis fir stands on Hemlock-Amabilis fir (HA) sites, and from plots of old-growth western red cedar-western hemlock stands on Cedar-Hemlock (CH) sites, with data previously gathered from plots of 24-year-old regenerating hemlock on CH sites. I detected 147 operational taxonomic units among 1435 fungal clone sequences. Phylogenetic diversity indices showed that mature hemlock stands on HA sites had significantly higher ectomycorrhizal fungal diversity than regenerating hemlock stands on CH sites. In an analysis of beta diversity, I found that the species composition of the 24-year-old stands was more similar to the composition of old-growth stands on CH sites than to the species composition of mature stands on HA sites. Fungal species composition was strongly correlated with foliar nitrogen concentration. My phylogenetic analyses of net relatedness of species from forests of different types provided some of the first insights into how ectomycorrhizal fungal communities are structured. I found phylogenetic clustering in the plots of 24-year-old regenerating hemlock stands that contrasted with a pattern of phylogenetic evenness in the plots of mature and old-growth stands. A possible explanation for the difference between the patterns is that the regenerating hemlock stands were selecting for related, r-adapted fungi with similar traits while the older stands had more complex environments and selected for divergent fungi with varied traits. Finally, in Chapter Three I discuss some limitations and strengths of my research study, incorporating ideas on future research and implications.
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