Legacy effects of temperature alterations on microbial resistance and resilience to drying and rewetting

Sammanfattning: With warming in soils due to climate change, a series of secondary factors arise, which have multifaceted effects on soil microbial communities. Of these, alterations to soil moisture are among the most crucial to understanding how microbial functions will change in the face of climate change. As living organisms, microbes must adapt to their environment, and their adaptations are reflected in their response to contemporary events. How they respond can determine the fate of soil organic matter and have relevant feedback to climate systems. In this thesis, I address how the legacy effects of a soil microbial community affect its response to a drying and rewetting event in terms of resilience and resistance, as well as how these strategies can affect carbon dynamics in subarctic ecosystems. I achieved this by taking soil samples from study sites that have undergone two-year warming in Abisko, Sweden. I then subjected them to a drying and rewetting cycle, assessing the samples as they dried down and subsequently responded to being rewet. During this time, I measured bacterial and fungal growth via stable isotope probing as well as respiration via gas chromatography. I found that while moisture was affected, microbial resistance was unaffected by warming treatments. However, resilience was affected by warming treatments. Responses also differed primarily based on NDVI, possibly indicating the importance of plant inputs of carbon to the microbial response. Possible conceptual frameworks are then used to explain the observations, notably the YAS framework. Implications for carbon budgeting and models are inferred from these findings. I conclude that interactions between microbes and moisture and plant inputs impact microbial response to moisture stress in warming experiments and that future experiments may want to examine the vegetation relationship with more focus.