Transient landscapes, changing ecosystems
2024
Ranheim Sveen, Tord
Land-use changes lie at the heart of ongoing ecological crises and pose a criticial threat to biodiversity and the functioning of ecosystems. However, the responses of communities and ecosystems to land-use changes are not uniform and vary across space and time. In this thesis I investigate the effects ongoing and historical land-use changes have on soil microbial communities, including plant-soil interactions and potential consequences for carbon cycling. I employ a large-scale successional gradient comprising paired grasslands and forest sites to examine the impacts of land abandonment and afforestation. In addition, I build on historical land-use maps to explore the lingering legacy effects of historical land use on present-day microbial communities. I find that soil microbes are generally resilient to succession in grasslands but undergo marked changes in diversity and functioning when compared to adjacent forest sites. Specifically, microbial communities shift from being more functionally redundant to become more functionally specialized and diverse with land-use change, with shifts in functional diversity and metabolic efficiency potentially posing constraints on soil carbon accumulation during afforestation. I also find that legacy effects of historical land use continue to shape present-day microbial communities. Still, these effects are transient and mostly relate to free-living microbes and fungal pathogens. Overall, the results highlight that the repercussions of land-use changes extend spatially and temporally and affect structural and functional components of microbial communities, which may have significant implications for carbon cycling and ecosystem functioning.
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