UBC Theses and Dissertations
Rhizopogon mycorrhizal networks with interior douglas-fir in selectively harvested and non-harvested forests Van Dorp, Carrie
Rhizopogon vesiculosus and Rhizopogon vinicolor are sister species of ectomycorrhizal fungi that associate exclusively with Douglas-fir (DF). My first objective was to determine whether a change in the number or relative abundance of R. vesiculosus and R. vinicolor tubercules and genotypes was related to a change in the percent of DF in a regenerating phase (<50 years-old). The number of R. vesiculosus tubercules correlated positively with an increasing proportion of DF in a regenerating phase, while the number of R. vinicolor tubercules was similar across all age structures. The number of R. vesiculosus genotypes did not correlate with age structure, whereas the number of R. vinicolor genotypes showed a negative relationship with an increasing proportion of DF in a regenerating phase. When numbers of R. vesiculosus tubercules and genotypes were expressed as a relative abundance of the two species, there was a positive correlation with an increasing proportion of DF in a regenerating phase for both genotypes and tubercules. Results suggest that the degree of DF regeneration or ecosystem factors related to DF regeneration affect the population dynamics of R. vesiculosus and R. vinicolor differently. My second objective was to quantify and compare the extent of Rhizopogon mycorrhizal networks in selectively logged (25 years-old) and non-logged plots. The networks of the harvested plots, when including both Rhizopogon species, were as highly connected as the undisturbed plots. However, they differed in that they had two Rhizopogon species rather than one and had a higher node density. R. vinicolor networks of harvested and unharvested forests had very different link densities. When I accounted for density differences, networks of both treatments were not significantly different, apart from a greater vulnerability to fragmentation in harvested forests than in undisturbed forest. When R. vesiculosus was included in the analysis, both treatments had similar connectivity and limited vulnerability to fragmentation. Results suggest that when a forest transitions from a regenerating to a non-regenerating one, the Rhizopogon network will lose R. vesiculosus and will have increased link density. Nevertheless, both the selectively harvested and non-harvested forests will have well connected and potentially functional Rhizopogon networks.
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