Doctoral defence: Siqiao Liu “The effect of anthropogenic disturbance on soil fungal communities”

On September 9 at 9:15 Siqiao Liu will defend her doctoral thesis “The effect of anthropogenic disturbance on soil fungal communities” for obtaining the degree of Doctor of Philosophy (in Plant Ecology and Ecophysiology).

Supervisors:
Associate Professor Kadri Koorem, University of Tartu
Professor Maarja Öpik, University of Tartu

Opponent:
Professor David Johnson, University Manchester (United Kingdom)

Summary
This doctoral thesis extends our understanding of how soil fungal communities respond to disturbances caused by human activities, which have led to the degradation of local biodiversity and disruption of ecosystem services. Soil fungi play a crucial role in sustaining ecosystem functions, so understanding the impact of anthropogenic disturbances on soil fungal communities is essential for fully grasping the consequences of human activities for ecosystems. This thesis found that non-native plant invasion, the most common biotic disturbance resulting from international trade, had little impact on the soil fungal community. Minor variation in soil fungal communities could be detected in relation to morphological dissimilarity between native and non-native plants, but not in relation to non-native plant abundance. In addition, common chemical abiotic disturbances, such as mineral and organic fertilizer application, have effects ranging from negative to positive on soil fungal diversity. However, mechanical disturbances such as tillage, showed no strong influence on soil fungal diversity. Interestingly, the results suggest that the combination of two chemical disturbances, such as mineral fertilizer and pesticide application, can amplify their negative effects on soil fungi, while mechanical disturbance can alleviate the negative effect of herbicide addition. This indicates that the combined effects of multiple disturbances is not simply the addition of single-factor effects, and further studies are needed as anthropogenic disturbances commonly occur simultaneously in real life. Moreover, with the intensification of human activities, small-scale disturbances in natural or semi-natural habitats have increased significantly but have received very little attention. This thesis shows that suppression of soil fungi decreases the diversity and biomass of re-established vegetation after small-scale disturbance, highlighting the importance of soil fungi in the self-recovery of plant communities following disturbance. In conclusion, soil fungi exhibit complex responses to multiple disturbances and play a crucial role in vegetation recovery. Further studies should investigate the effects of multiple disturbances on soil fungi, while considering their key role in vegetation recovery.