Supervisors: Professor Urmas Kõljalg (University of Tartu), Researcher Leho Tedersoo (University of Tartu, Natural History museum), Doctor Shahin Zarre (University of Teheran, Iran)
Opponent: Doctor Andy Taylor (James Hutton Institute, UK)
This thesis examines the species richness and community structure of ectomycorrhizal (EcM) fungi across different spatial scales. These fungi are one of the key microbial groups in many forest ecosystems, supplying nutrients to their host plants and contributing to nutrient cycling. The following alternative hypotheses were postulated: 1) EcM fungal diversity decreases towards the poles and higher altitude; 2) climate is the main determinant of fungal diversity at both the regional and global scales; 3) spatial structure of EcM fungal communities is more pronounced in tropical forests, mainly due to patchy distribution of host plants; and 4) an individual host tree may support a highly diverse community of EcM fungi. The main results and conclusions are the following: 1) spatial processes are important in structuring EcM fungal communities at both local, regional and global scales; 2) the range of spatial autocorrelation in fungal communities is greater than reported previously; 3) contrary to macroorganisms, EcM fungi do not follow latitudinal pattern of diversity, which could be ascribed to the poor habitat conditions and more recent evolution of host trees in tropical ecosystems; 4) both average temperature and precipitation affect EcM fungal diversity at the regional and global scales, with extreme values causing abiotic stress and thus leading to the exclusion of rarer species; and 5) a single tree individual may potentially host hundreds of EcM fungal species that is comparable to the discovered diversity across the whole forest sites, indicating that mycorrhizal networks are highly complex on the plant perspective.
These studies were supported by European Social Fund's Doctoral Studies and Internationalisation Programme DoRa. Programme DoRa is carried out by Archimedes Foundation.