Abstract
Pesticides are important to combat pests and diseases. However, they also influence non-target organisms and may negatively affect soil biodiversity. So far it is still poorly understood whether pesticides influence soil fungi and the ecosystem functions provided by fungi. This master’s thesis aimed to understand the impact of pesticides on soil fungi. It is specifically tested whether rare and abundant fungal species that possess different functional traits are differently affected by pesticide exposure. Abundant species are known to play a crucial role in many ecosystem functions and processes. However, rare species, despite their potential significance for certain processes, have often been neglected by research. Therefore, this study provides valuable information on the impact of pesticides on both abundant and rare fungal communities in the fulfilment of various ecosystem functions (i.e., litter decomposition and plant biomass). It was hypothesised that fungal inoculation might improve both parameters, while increased pesticide concentration might negatively affect both abundant and rare fungal taxa, resulting in a reduction of litter decomposition and plant biomass. Finally, a combination of both fungal taxa is hypothesised to potentially decrease the impact of the pesticide. To test this, a microcosm experiment was conducted using different abundant, rare and combined fungal communities with treatments of increasing pesticide concentrations. An additional microplate assay with 95 different carbon sources was performed to gain insights into the metabolic properties of the fungal taxa. Litter decomposition rate and total dry plant biomass were measured to assess differences among pesticide treatments and whether pesticides influence the impact of fungi on plant biomass and litter decomposition. The addition of fungi significantly reduced plant biomass and enhanced litter decomposition. Pesticide treatments did not significantly influence the different fungal communities and their effects upon plant biomass and litter decomposition. Only with the overdosed treatment, plant biomass was reduced, whereas litter decomposition rates were less sensitive. In contrast to abundant communities, which show higher total plant biomass compared to rare communities, decomposition rates were higher for rare species. The combination of abundant and rare communities resulted in the highest total plant biomass and decomposition rates across all pesticide treatments indicating that mixed communities of rare and abundant fungal taxa stabilised ecosystem performance. We did not find significant evidence that rare fungal taxa are stronger affected by pesticides than abundant fungal taxa. However, the findings of this study provide significant insights into the relationship of various fungal communities under pesticide exposure. Future research could increase their focus by testing an even greater diversity of fungal taxa. An additional emphasis should be placed on different types of pesticides to gain a better understanding of the impacts of pesticide application on soil organisms.
Summermatter, Jenny