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.

Thesis (M.S.)--Southern Oregon University, 2005. / Includes bibliographical references (leaves 31-36). Also available via Internet as PDF file through Southern Oregon Digital Archives: http://soda.sou.edu. Search Bioregion Collection.

Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 85-98). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 55-60). Also available on the World Wide Web.

Ericoid mycorrhizal fungi form mycorrhizal associations with Ericaceae plants and are regarded as essential to the ecological fitness of the plants in extremely nutrition-poor soils world-wide. The culturable fungible assemblages associated with hair roots of Epacris pulchella and Rhododendron lochiae (Ericaceae) from different forest habitats in eastern Australia were investigated using rDNA internal transcribed spacer (ITS) restriction fragment length polymorphisms (RFLPs) and sequence analysis, and the abilities of the fungi to form ericoid mycorrhizas were tested. The functional significance of members of the H. ericae complex, Sebacinaceae and the ectomycorrhizal basidiomycetes are discussed particularly in regard to the possibility of symbiont sharing between Ericaceae and ectomycorrhizal hosts. / Doctor of Philosophy (PhD)

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 107-124).

I examined the effect of Frankia spp. and ectomycorrhizal fungi on green alder (Alnus viridis ssp. crispa), growing in nutrient-poor soil and saline conditions. The first experiment involved inoculating green alder growing in low fertility soil with three species of ectomycorrhizal fungi (Lactarius torminosus, Lactarius theiogalus, Hebeloma crustuliniforme) alone or in combination, with and without Frankia spp. on. Frankia spp. inoculation significantly increased plant performance compared to non-Frankia treatments. However, nodulated plant total biomass decreased with an increasing number of fungi. The second experiment examined the effect of Hebeloma crustuliniforme and Frankia spp. on green alder exposed to 0, 50 and 100 mM NaCl. Frankia spp. inoculation showed significant increase on plant performance but Hebeloma crustuliniforme did not. Plant mass, root:shoot ratio, nodule allocation and total nitrogen fixation decreased with NaCl exposure. A decrease in root:shoot ratio caused by salt was more moderate in nodulated plants compared to non-nodulated plants. / October 2016

Pisolithus is an ectomycorrhizal (ECM) fungal genus that exists in native and plantation forests worldwide. Despite many aspects of the genus having been studied over the years, there is limited knowledge of the genetic population structure of Pisolithus spp. The major aim of this study was to begin to elucidate the genetic structure of populations of Pisolithus native to the eastern states of Australia. Initially, the number of species represented in the University of Western Sydney Pisolithus culture collection was investigated using ITS-RFLP and previously developed simple sequence repeat (SSR) markers. From these analyses, two clear groupings emerged with the RFLP groups corresponding to the SSR groups identified. To study genetic population structure, appropriate markers were required and SSR markers were considered to be most suited to this end. The developed SSR markers were successfully used to amplify P. microcarpus and P. albus DNA from ECM root tips and soil samples. Therefore, these markers will be a useful tool for future investigations into the population structure of above and below-ground structures of P. microcarpus and P. albus populations. / Doctor of Philosophy (PhD)

Thesis (M.S.)--Southern Oregon University, 2002. / Includes bibliographical references (leaves 37-43). Also available via Internet as PDF file through Southern Oregon Digital Archives: http://soda.sou.edu. Search Bioregion Collection.

In boreal and northern temperate forests, the moss layer and ectomycorrhizal (ECM) fungi play important roles in carbon and nutrient cycling. ECM mycelium is present in the lower parts of the moss layer, but little is currently known about the interaction between these two key components of northern forest ecosystems. This thesis aims to address this knowledge gap and to improve our understanding of the mechanisms through which the moss layer and ECM fungi influence carbon and nutrient cycling. Nutrient transfer between litter and Scots pine seedlings in symbiosis with the ECM fungus Paxillus involutus (Batsch) Fr. was investigated in highly controlled microcosm experiments using, for the first time, intact moss and pine litter. In addition, moss removal plots were established in a Scots pine forest which allowed measurement of processes involved in carbon (C) and nutrient turnover and related variables. There was a close, reciprocal exchange of carbon and nutrients between the host plant and ECM mycelium colonising moss and pine litter (Chapter 2). This was greatly enhanced by intensive colonisation of moss litter, suggesting that mosses provide a key source of nutrients for ECM fungi and may facilitate transfer of photosynthetic C belowground. During almost 2 years of decomposition, moss tissue released more nitrogen (N) but retained more C than pine litter (Chapter 3), further highlighting the importance of the moss layer in providing nutrients for overstorey trees, and in the accumulation of recalcitrant C in soil. In addition to contributing directly to C cycling through inputs of recalcitrant C in litter, the moss layer can influence C cycling indirectly, by increasing soil microbial activity; CO2 efflux was on average 1.4 times greater from soil under the moss layer than from soil covered only in pine litter (Chapter 3). The results suggest that an indirect influence can occur via two pathways: through an insulating effect of the moss layer on soil temperature, and through inputs of dissolved organic carbon (DOC) leached from moss (Chapter 4), both of which may stimulate activity of soil microbes. These findings demonstrate the importance of both the moss layer and ECM fungi in carbon and nutrient cycling in boreal and northern temperate forests, and indicate that mosses provide a key pathway through which nutrients may bypass sequestration in saprotrophic microbial biomass and be transferred directly from plant tissue to ECM fungi and overstorey trees.