Mechanisms of resistance and resilience in the plant-soil system of Mountain grassland communities
Overall, the findings of this thesis highlight the importance of land use and plant-microbial interactions for the resilience of terrestrial ecosystems to extreme climatic events. The results from stable isotope (13C and 15N) labelling experiments on mountain grasslands extend the existing knowledge about the link between plant and soil processes during drought and subsequent recovery. There is indication that the continuous release of carbon substrates from plants into the rhizosphere during drought plays a relevant role in the priming of soil microbial activity after rewetting. Furthermore, this thesis demonstrates that the mechanisms underlying ecosystem resistance and resilience can be altered by land use, in particular by management-related changes in plant functional composition. More conservative plant communities with low nutrient demands, as found in abandoned grassland, are more resistant and can profit from stronger interactions with mycorrhizal fungi during drought. On the contrary, more exploitative plant communities with high nutrient uptake, as found in managed grassland, are able to quickly recover and can benefit from stronger interactions with fast-growing bacteria after rewetting. In consequence the results of this work suggest a general trade-off between resistance and recovery, i.e. high resistance is followed by a slow recovery and vice versa. On the one hand, this is important for biogeochemical models dealing with the global carbon cycle and climate change feedbacks. On the other hand, this allows to control ecosystem resilience by adapting land use according to local risk scenarios, through promoting either the resistance to or the recovery from extreme climatic events.
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