Ectomycorrhizal (EM) fungi play key functional roles in forest ecosystems; they are fundamental to the health and nutrition of their plant partners and they cycle vast amounts of photosynthetically fixed carbon (C) through the soil. They also form diverse belowground communities, yet to date only a few studies have tested the effects of EM diversity on host plant responses, with belowground C flux effects remaining ignored. This thesis investigated how increasing species and genotypic richness affected the productivity and CO2 efflux of EM fungal mycelium grown in pure culture, and examined whether similar patterns between diversity and respiration were found in the field. Furthermore, the response of soil respiration to additions of increasingly diverse EM necromass was tested. Results from in vitro studies revealed that not only did productivity and respiration change significantly, but genotype richness also had strong effects on these processes. Biodiversity effects were driven by a combination of selection effects (dominance by a species) and complementarity effects (niche partitioning/complementary resource use). Furthermore, variation in productivity and CO2 efflux between individuals was large, and in some cases differences between genotypes was as great, if not greater, than between species. Strikingly, not only did the addition of EM fungal necromass to soil rapidly enhance respiration above that produced by unamended controls, but CO2 efflux also increased dramatically with increasing necromass richness. The relationship between species richness and soil CO2 efflux in the field was not as pronounced, although further work is needed to distinguish between sources of soil CO2 efflux variation in the field and to address confounding factors. This PhD thesis stresses the importance of diversity for soil C cycling in both living and decomposing EM fungi, and it supports calls to consider fine scale phylogenetic information about microbial communities when testing the effects of diversity on ecosystem processes.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:600050 |
| Date | January 2011 |
| Creators | Wilkinson, Anna |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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