Abstract
The functional composition of plant communities is a critical modulator of climate change impacts on ecosystems, but it is not a simple function of regional climate. In the Arctic tundra, where climate change is proceeding the most rapidly, communities have not shifted their trait composition as predicted by spatial temperature–trait relationships. Important causal pathways are thus missing from models of trait composition change. Here, we study causes of plant community functional variation in an oroarctic tundra landscape in Kilpisjärvi, Finland. We consider the community-weighted means of plant vegetative height, as well as two traits related to the leaf economic spectrum. Specifically, we model their responses to locally measured summer air temperature, snow conditions, and soil resource levels. For each of the traits, we also quantify the importance of intraspecific trait variation (ITV) for between-community functional differences and trait–environment matching. Our study shows that in a tundra landscape (1) snow is the most influential abiotic variable affecting functional composition, (2) vegetation height is under weak local environmental control, whereas leaf economics is under strong local environmental control, (3) the relative magnitude of ITV differs between traits, and (4) ITV is not very consequential for community-level trait–environment relationships. Our analyses highlight the importance of winter conditions for community functional composition in seasonal areas. We show that winter climate change can either amplify or counter the effects summer warming, depending on the trait.
Highlights
Contemporary climate change in the Arctic is so rapid that the ecosystem changes it causes can be observed over ecological timescales (Post et al 2009)
Our study focuses on the community-weighted means [the functional markers in Garnier et al (2004)] of three traits that represent the two above-ground trait axes: vegetative height, specific leaf area (SLA), and leaf dry matter content (LDMC)
Most of the variation (62%) in community mean height was due to intraspecific variation, while variation in leaf traits was more due to species turnover (83% and 47% of total variation for SLA and LDMC, respectively)
Summary
Contemporary climate change in the Arctic is so rapid that the ecosystem changes it causes can be observed over ecological timescales (Post et al 2009). The trait variation among species pools and communities can cover most of the global trait spectrum, especially for traits related to leaf economics (Wright et al 2004; Bruelheide et al 2018). This suggests that environmental factors with large variation at local to landscape scales, such as soil resources and disturbance, may be more important determinants of plant community trait composition compared to macroclimatic gradients (e.g., mean air temperature and/or precipitation) This suggests that environmental factors with large variation at local to landscape scales, such as soil resources and disturbance, may be more important determinants of plant community trait composition compared to macroclimatic gradients (e.g., mean air temperature and/or precipitation) (Bruelheide et al. Vol.:(0123456789)
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