A new study co-led by the University of Maryland and the University of Innsbruck has unveiled sobering insights into the future of grassland ecosystems under climate change. The study, published in the journal Science, reveals that increasing temperatures and heightened CO2 levels could profoundly change water dynamics in grasslands, which cover nearly 40% of the Earth's land area and play a critical role in the water cycle.
"If we want to predict the effects of climate change on Earth's water resources, we need data showing how the hydrologic cycle will respond at a small scale where we can define mechanisms, but that just hasn't been available," study corresponding author Jesse Radolinski, a post-doctoral research associate in the UMD Department of Environmental Science & Technology who started the research while at the University of Innsbruck, said in a news release.
"Our experiments found that under summer drought conditions, and higher air temperatures that are expected under a future with elevated CO2, two things change fundamentally: One, the structural properties of the soil in the root zone change so that water flows differently than we expected, and two, these altered climate conditions and soil properties cause the plants to access water differently," he added.
The research team conducted their experiments in open plots within an Austrian grassland at the University of Innsbruck, employing large shelters to simulate six different climate conditions by manipulating air temperature, CO2 levels and drought intensity.
They used water marked with deuterium, a heavy isotope of hydrogen, to trace its movement through the soil and plants.
Their findings indicate that, under future climate scenarios, rainfall might bypass existing soil water stored in the root zone, rapidly heading to local streams and rivers. This rapid movement of water could reduce the interaction with stored soil water, influencing nutrient and pollutant dynamics.
Moreover, plants experiencing these conditions conserved more water, which could lead to reduced atmospheric cooling and potentially trigger a feedback loop of increased drought and warming.
The study also highlights significant changes in soil structure post-drought. With elevated CO2 and warming, the pores within the soil altered, causing older water to be trapped while newer rainfall drained rapidly.
Furthermore, plants adapted by accessing the most available soil moisture and conserving water by limiting transpiration.
These insights into how soil and plant water interactions may shift due to climate change provide a critical understanding of potential future ecosystem dynamics. This knowledge will be vital for formulating effective conservation strategies and managing grassland ecosystems in a rapidly evolving climate landscape.