Merian Skouw Haugwitz:
Soil fungal community responses to global changes

Global change will affect the functioning and structure of terrestrial ecosystems and since soil fungi are key players in organic matter decomposition and nutrient turnover, shifts in fungal community composition might have a strong impact on soil functioning. The main focus of this thesis was therefore to investigate the impact of global environmental changes on soil fungal communities in a temperate and subartic heath ecosystem. The objective was further to determine global change effects on major functional groups of fungi and analyze the influence of fungal community changes on soil carbon and nutrient availability and storage.

By combining molecular methods such as 454 pyrosequencing and quantitative PCR of fungal ITS amplicons with analyses of soil enzymes, nutrient pools of carbon, nitrogen and phosphorus we were able to characterize soil fungal communities as well as their impact on nutrient storage in both a shorter and longer term global change experiment.

Extended drought at the dry, temperate heath showed that soil fungi were well adapted to dry conditions. Furthermore, soil fungal communities responded significantly to seasonal fluctuations at the temperate heath, but despite large fluctuations in community structure and relative abundance of the major functional groups induced by season, increased temperature, drought, and elevated CO₂ altered the functionality of the fungal community. Finally, long-term manipulations of nutrient availability and warming altered the functional composition of fungi, but the effects were generally limited to the litter layer and the uppermost humus layer (0-5 cm), which was unexpected considering the ecosystem had been manipulated for 18 years.

Taken together the global change experiments altered the soil fungal communities and thereby highlight the importance of these investigations for predicting the effects of climate change and elevated CO₂ on terrestrial ecosystems.