We established several large-scale field experiments to study different aspects of plant responses to changing climate and competitive interactions. Using a whole-community transplant experiment across an elevation gradient combined with demographic modelling (WP1), we showed that novel competitors accelerate rates of local extinction of alpine plants under climate change, which can be decisive under low amounts of warming, helping to explain why we see “extinction debt” in alpine ecosystems up to now (Nomoto & Alexander, 2021). Using this experiment, we performed selection analyses and estimated trait heritability to explore evolutionary implications of changing competition and climate. We found that warming can impose selection on alpine plant traits, but that competitors generally constrain selection, and in some cases reduce evolvability, suggesting that evolutionary rescue is unlikely to occur in our study species (Nomoto et al., two articles in prep.). We also expanded WP1 to study novel plant-soil interactions under climate change (Cardinaux et al. 2018, Hagedorn et al. 2019, Walker et al. 2021).
We established a separate field experiment (WP2) at three elevations to investigate whether species’ traits predict the population-level outcome of pairwise competitive interactions measured on 14 lowland and alpine species. We found that competition shapes upper as well as lower elevation range limits in this system (Lyu & Alexander 2022), and that this is mainly due to impacts of competitors on plant growth. Nonetheless, functional traits were in general not strong predictors of interactions between either current or novel competitors. We therefore developed alternative modeling approaches to study species’ ranges and their dynamics (WP3), including occupancy models, evolutionary functional-structural plant models, Bayesian non-linear distribution models (Bramon Mora et al., in revision), metacommunity models (Alexander et al. 2018) and evolutionary trade-off models (Alexander et al. 2022). We also reviewed how positive biotic interactions shape range limits (Stephan et al. 2021) and outlined challenges and opportunities to link community ecology and marcoecology (Alexander et al. 2016; Wüest et al. 2019, Guisan et al. 2019).
So far, the project has led to 15 publications, with several others currently in prep. or review, involved 13 student projects from bachelor to PhD levels, and been represented in over 30 seminars or presentations and numerous public events.
