A three-year field experiment in Tasmania’s subalpine region, led by Melissa Gerwin, PDRA in Arctic Terrestrial Ecology in the School of GeoSciences, has found that warmer temperatures can quickly reshape plant communities in subalpine meadows, reducing diversity and changing which species dominate. The study found that the most dramatic shifts occurred in areas where soils were already dry, highlighting water availability as a critical factor in how climate change impacts ecosystems. Simulating climate change A rainout shelter with a warming chamber below. Image credit: Melissa Gerwin Researchers tested climate change scenarios by manipulating conditions in small plots of a specie-rich subalpine meadow. They used rainout shelters to reduce rainfall and open-top warming chambers to raise temperatures. These chambers were covered each summer to create a “mini-greenhouse” to simulate short, intense heatwaves. Plant cover was then tracked in detail to measure which species where thriving or declining. The warming chambers with a wild Echidna visitor. Image credit: Melissa Gerwin Within just three years, warmed plots showed marked declines in plant diversity across rare, common and dominant species. Grasses, mosses, and small rosette-forming wildflowers became less abundant, while sedges increased. By contrast, plots exposed to drought or short heatwaves showed no significant shifts in diversity or community composition. Dry soil increases the impact of diversity loss The strong impacts of warming were seen in the driest parts of the meadow, where higher temperatures amplified the effects of low soil moisture. This suggests that warming combined with reduced rainfall accelerates ecosystem change, driving declines in certain groups of plants, while allowing others to spread.For the southern hemisphere, the findings indicate that future shifts in rainfall patterns and cycles such as ENSO, which strongly influence soil water availability, will play a major role in shaping how subalpine meadows respond to climate change. The results show that multiple climate change drivers can interact to rapidly reshape plant communities, highlighting the vulnerability of high-altitude ecosystems to warming temperatures and altered rainfall patterns. A selection of wildflowers from Silver Plains. Image credits: Melissa Gerwin It was sobering to find that experimental climate change reduced diversity in the subalpine meadows at Silver Plains. The tiny, colourful flowers are a delight to see each summer, and the meadow supports so much wildlife. It would be a tragedy to lose such a beautiful place.But, there's still hope! Silver Plains is owned by the Tasmanian Land Conservancy (TLC), who now plan to fill in the old agricultural drainage lines to prevent the meadows from drying out as quickly over summer, thereby delaying the negative impacts of climate change here for a bit longer. It really goes to show, that conservation organisations can make an enormous difference if they use science-based evidence to inform management decisions, like the TLC are doing. Melissa Gerwin PDRA in Arctic Terrestrial Ecology, School of GeoSciences Read more Read the full study here: Dry Soils Increase the Impact of Experimental Warming on Plant Community Composition in an Australian Subalpine Meadow. Melissa R. Gerwin, Shane A. Richards, Elizabeth M. Wandrag, Mark J. Hovenden: https://doi.org/10.1111/jvs.70065 Publication date 23 Sep, 2025
