The influence of warming, site characterestics [sic], and host plant on root-associated fungal communities from Alexandra Fiord in the Canadian high arctic

Arctic systems are expected to be impacted earlier and more severely by global warming than temperate ecosystems. However, much of the research on the impact of warming on arctic ecosystems has centered on plant communities. One objective of this thesis was to examine how passive warming would impact the root-associated fungal community at Alexandra Fiord, Nunavut. The root-associated fungal community consists mostly of mycorrhizal, dark-septate and hyaline-septate fungi, which are considered important mutualists in arctic ecosystems. The objective was to compare the fungal community from plots warmed by open-top chambers to ambient plots, using two methodologies: 1) fungal DNA extracted directly from root tips with terminal restriction fragment length polymorphisms (T-RFLPs) used to estimate variation, and 2) fungal cultures isolated from root tips to which PCR-RFLP techniques were applied to assess variation. T-RFLPs were used to examine the root-associated fungal community on Salix arctica. Differences between the communities were analyzed using canonical correspondence analysis (CCA). Genotype diversity was tested using a 2-way, 2-stage, nested ANOVA. Warming did not significantly change genotype cumulative frequency or diversity of the root-associated fungal community, but cumulative frequency tended to increase on the warmed plots. Genotype richness was significantly different according to site, which was correlated with differences in soil chemistry. Again site, not warming, was the main factor that distinguished the root-associated fungal community of Salix arctica, Saxifraga oppositifolia, Cassiope tetragona, and Dryas integrifolia based on fungal cultures. Warming did not have a detectable impact on cumulative frequency and diversity, based on CCA and a nested, 3-way ANOVA. Fungal cultures were identified based on sequence analysis and morphology. Phialocephala fortinii was the most frequently identified taxon, but almost half of the fungal isolates remained unknown. The root-associated fungal community was examined along a glacier forefront characterized by a directional, non-replacement primary plant succession pattern. CCA was used to examine genotype frequency; linear regressions were used to test for changes of cumulative frequency and diversity as succession advanced. The fungal community on only one of the host plants increased in frequency and richness as succession advanced. The dark- and hyaline-septate endophyte communities were distinct on different host plants, providing evidence for host specificity and higher diversity than previously reported.