On 3 December at 12:15 Eveli Otsing will defend her doctoral thesis “Tree species effects on fungal richness and community structure” for obtaining the degree of Doctor of Philosophy.
Dr. Leho Tedersoo, University of Tartu
Prof. Tarja Lehto, University of Eastern Finland (Finland)
Fungi play key roles in forest ecosystems. Various groups of fungi drive organic matter decomposition and soil nutrient cycling, act as tree root symbionts or cause diseases. Trees are influential components of forest habitats that modify their surroundings via shedding litter and root exudates, but little is known about the functional importance of tree species diversity on soil organisms and soil biological processes. Mixtures of tree species can create fine-scale environmental heterogeneity that supports higher biodiversity in forest stands.
Biodiversity enhances productivity and stability, buffering ecosystems against changing environmental conditions. In this thesis, I examined fungal diversity in relation to plant litter, host plant diversity and tree neighbourhood effects. Leaf litter mixtures with higher plant species richness harboured higher fungal diversity, indicating that heterogeneity of resources in litter mixtures provides more habitats and allows a larger number of fungal species to co-exist. Conversely, the root litter richness effect on fungal diversity was weak. Furthermore, leaf litter composition had a strong effect on composition of saprotrophic and plant pathogenic fungi. Richness of ectomycorrhizal fungi was positively related to host plant richness at global scale.
At regional scale, fungal richness correlated with plant richness, but this effect was related to improved soil conditions in mixed forests. Communities of ectomycorrhizal fungi on spruce roots differed in spruce monocultures and mixed stands of birch and spruce, which points to the influence of birch on soil quality. To conclude, tree species richness and fungal diversity are usually positively correlated, but the direct impact of plant richness depends on the context, including the influence of particular plant species and analysis of other factors.