Epsilon Open Archive

Abstract

Dead wood constitutes an important substrate for biodiversity in boreal forests. As the wood decays, fungal communities develop and species associations are formed. Species interactions are thought to affect community development, but the mycelial dynamics within fungal communities are poorly understood.

In this thesis the diversity and temporal dynamics within fungal communities
in Norway spruce logs are studied. In particular, patterns of diversity and mechanisms during community assembly are investigated. 454 sequencing is applied to study the less well-known fungal diversity and fine-scale mycelial distribution patterns in decaying logs. The influence of priority effects during community assembly is studied using time-series data from re-inventoried logs. The importance of wood-modification by a primary species and competition is examined in species interaction laboratory experiments.

454 sequencing revealed species-rich fungal communities with diverse ecological roles. Wood-decaying basidiomycetes was found to be the most abundant ecological group, and saprotrophic, mycorrhizal and parasitic fungi were regularly detected. Mycobiont partners of lichens were isolated from interior parts of logs. Fine-scale distribution within logs revealed that resource utilization reflects the life histories of fungal taxa. More decayed samples hosted a higher number of taxa, particularly ascomycetes, whereas wood-decaying basidiomycetes were found in less decayed wood. Priority effects in terms of different mortality factors of trees and the presence of primary decay species were found to affect the subsequent community composition. A species-specific response to primary decay and antagonistic
interactions significantly affected decay rate and growth. It is concluded that priority effects are more important in early stages of community development while species more frequent in middle stages of decomposition relies more upon competitive abilities.