BCs Inland Rainforest Conservation and Community

Conference Proceedings

The fungal assemblages associated with visualized forest soil micro-sites

Denise Brooks 1, Melanie Jones 2, and Sue Grayston

Poster Abstract Tree growth is influenced by the ectomycorrhizal fungal community present on individual host trees. This growth effect may be influenced by the ability of ectomycorrhizal fungal species to acquire and transport nutrients to the host and by the carbon demand on the host to support these fungi. Though functional diversity in nutrient mobilization by ectomycorrhizal fungal hyphae has been demonstrated with fungal isolates in microcosms, it remains a challenge to demonstrate functional diversity in the field; not only due to the difficulty of identifying the fungal species present as hyphae in the soil, but also due to the fine scale patchiness of forest soil nutrient resources. Nutrient mobilizing enzymes such as phosphatase associated with these resource micro-sites have been visualized using an in-situ imprint technique, and a marked change in phosphatase activity has been observed between younger and older post-fire disturbance forest plots of interior Douglas-fir/paper birch (Betula papyrifera) located in the ICH of south central British Columbia. We collected small soil samples (0.25 g) from visualized phosphatase-active soil micro-sites at three replicate sites of the four age class forest stands. Enzyme micro-sites were sampled from one 20 cm x 20 cm plot in each stand using a root window to access the soil profile. Three phosphatase-active micro-sites were sampled from the organic and 3 from the mineral layer of each plot, and 3 samples were taken from each layer where no activity was visualized. Using terminal restriction fragment length polymorphism (TRFLP), we characterized the fungal assemblages associated with phosphatase-active soil micro-sites and compared these to the assemblages found in samples taken from areas where no phosphatase activity was visualized. Additionally, a TRFLP library was constructed from local ectomycorrhizal root-tip DNA and used to asses the spatial distribution ectomycorrhizal fungal hyphae in relation to phosphatase-active micro-sites. Multi-response permutation procedure (MRPP) was used to evaluate differences between the total fungal assemblages of micro-site samples and found that while micro-site sampling was able to identify broad differences between the total fungal assemblages present in the age classes of the forest chronosequence, the sampling effort was not sufficient to reveal the expected differences between soil layers, much less differentiate between phosphatase-active micro-sites and non-active soil areas. MRPP analysis of the ectomycorrhizal fungal species assemblages found on the younger stands produced similar results to those seen for the total fungal assemblages. However there were not enough ectomycorrhizal fungal species identified on the older stands to permit valid comparisons. While micro-site sampling has the potential to connect in-situ soil function to ectomycorrhizal fungal species, the minute scale of the sampling method needed to target in-situ enzyme activity and the sampling intensity necessary to determine fine scale differences between micro-sites needs further development and investigation.

Contact Information

1 University of British Columbia, Vancouver, BC. Email: denisebrooks3@hotmail.com

2 University of British Columbia Okanagan, Kelowna BC. Email: melanie.jones@ubc.ca

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"Treebeard" (above) is portrayed courtesy of McBride artist Sheilagh Foster.

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