Plant communities, populations and individuals have distinct responses to short-term warming and neighbour biomass removal in two montane grasslands

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By Travis Britton, Mark J. Hovenden, Meagan Porter, Rose Brinkhoff, Anna Flittner & Margaret M. Mayfield

Experimental warming chamber with a Ranunculus nanus flower in the foreground at Silver Plains field site, Tasmania, Australia (42.090254, 147.087945). Photo credit: Travis Britton.

Understanding how plant communities respond to environmental change is critical in the face of projected climate change. Plant communities can respond to environmental changes, such as warming, by altering community composition (the presence and abundance of different species) or by species’ populations adjusting individual plant physiology to suit new conditions. These community- and population-level responses can lead to “indirect” effects by altering the strength and direction of interactions among co-occurring plants. Altered plant-plant interactions influence the fitness of individual plants, species’ population growth rates and ultimately also the ability of many species to persist in a community. Therefore, these three organisation levels – community, populations and individuals – are interconnected and must be considered together to provide a complete view of the current and future effects of climate change.

To increase our understanding of how plant communities respond to climate change, we manipulated warming and community composition (random and dominant species biomass removal) in two montane grasslands in southern Tasmania, Australia. We measured individual plant fitness, population- and community-level functional traits (measurable characteristics of a plant linked to specific functions and processes), and species diversity.

After two years of experimental manipulations, we found simultaneous but distinct responses across all three organisational levels. Warming and dominant species removal both had a strong impact on the community- and population-level response, but these impacts were not always consistent across the two organisational levels. Neighbours had a stronger competitive effect on individual plant fitness in warmed compared to unwarmed conditions, and facilitation (positive effects of neighbours) was common in both communities.

A subset of the many species in the Silver Plains grassland community, Tasmania, Australia (42.090254, 147.087945). Photo credit: Margaret Mayfield.

Our study demonstrates that climate change associated factors do significantly influence montane communities at the community, population and individual plant levels. Our findings highlight that warming, as well as the indirect effects of altered community composition, can have a major impact on community structure and function. We support the emerging view that the direct effects of climate change will be heavily confounded by associated changes in plant-plant interactions and recommend their inclusion in future studies of climate change impacts on natural plant communities.

This is a plain language summary for the paper of Britton et al. published in Applied Vegetation Science (https://doi.org/10.1111/avsc.12557). The post was prepared by Travis Britton.