Prepared by Ryan T. Choi, Matteo Petit Bon, A. Joshua Leffler, Katharine C. Kelsey, Jeffrey M. Welker & Karen H. Beard
Tundra wetlands are experiencing rapid changes because of climate change. Two of the most important changes taking place in these ecosystems are warming and changes in the grazing activity of herbivores, both of which can affect the growth and composition of vegetation. Warming can make some vegetation species grow faster or larger, resulting in a change in the composition of different species. Grazing by herbivores, such as geese, rodents, or caribou, also influences the growth and composition of tundra plant communities both through vegetation removed by herbivores, and because some plants may increase their growth in response to grazing. Given the multiple means of vegetation change, warming and grazing may either have similar or opposing effects on tundra wetland ecosystems, and the response may differ among types of plants (e.g. grasses, sedges and forbs) and may play out differently across the varied wetland tundra landscape.
We conducted an experiment to determine how two summers of simulated goose grazing and summer warming affect tundra wetlands, and how the responses differ among three different tundra wetland plant communities that are different distances from the coast. Our results show that grazing had a greater effect than warming on vegetation species composition, but responses varied among communities and plant functional groups (e.g. grasses, sedges and forbs). Goose grazing decreased the abundance of grasses and sedges and increased the abundance of forbs, whereas warming only caused a decrease in forb abundance. By showing that tundra wetland plant communities can differ in their immediate sensitivity to goose grazing and, though to a lesser extent, warming, our findings have implications for ecosystem functioning of these rapidly changing high-latitude environments.
This is a plain language summary of the paper by Ryan T. Choi, Matteo Petit Bon and colleagues, published in the Journal of Vegetation Science (https://doi.org/10.1111/jvs.13139).