Grasslands in Asia and North America respond differently to drought, as revealed by a recent study. This research indicates that the variations in the dominant types of grasses and the lower diversity of species in the Eurasian Steppe grasslands could make them more susceptible to drought than the North American Great Plains.
A recent article in the journal Nature, led by faculty from Colorado State University, discusses how grasslands in Asia and North America react differently to drought conditions. The research suggests that the dominant grasses and reduced species diversity found in the Eurasian Steppe may render it more vulnerable to drought compared to the North American Great Plains.
The implications of these findings are significant for land management practices across both continents and offer a crucial comparative perspective for addressing climate change, which was lacking before now.
The study was headed by Professors Melinda Smith and Alan Knapp, both from the Department of Biology at CSU. According to Smith, this extensive project stemmed from ongoing collaboration with researchers in China, including first author Qiang Yu, Smith’s former postdoctoral fellow at CSU. Together, the team set up six experimental sites on each continent and subjected them to extreme drought conditions over four years. They discovered that the productivity of the Eurasian grasslands dropped by 43%, while in North America, the reduction was only 25% under the same drought conditions.
Smith noted that the detrimental effects of drought in Eurasia intensified over time, unlike in North America, where the system managed to stabilize after the second year of the experiment. The paper discusses this disparity, particularly how plant diversity influences the resilience of each region to prolonged extreme droughts.
Smith pointed out that the difference might be related to the higher number of uncommon, minor plant species in each area. These subordinate species account for much of the plant diversity and help maintain overall productivity, even when dominant species struggle to thrive during drought. The research indicates that these vital subordinate species decreased in Eurasian grasslands during dry spells but increased in North America, thereby stabilizing production losses over time.
“In North America, subordinate species appear to mitigate losses and support overall productivity, which is not observed in Eurasia due to its lower species richness,” she explained. “The ability of these species to adapt – likely due to drought tolerance developed over time – offers a unique insight into how these two vast grassland regions operate under such conditions.”
Furthermore, the two regions are home to contrasting types of dominant grass species. The Eurasian grasslands predominantly support C3 grasses, like wheat, which thrive in cooler, wetter climates, while C4 grasses, such as corn, thrive in the warmer climates of the American Midwest. This creates noteworthy comparisons regarding agricultural practices and management strategies in drought-affected regions, as mentioned by Knapp.
“Generally, C4 plants utilize photosynthesis more efficiently and can produce greater yields with less water compared to C3 plants. Understanding these differences is vital for predicting how productivity may shift in response to increasingly severe droughts,” Knapp stated.
Plant productivity is crucial for the global carbon cycle since photosynthesis is the primary mechanism by which atmospheric carbon dioxide enters ecosystems, making it available for animal consumption and biomass storage. Given that grasslands cover 40% of Earth’s surface, they are integral to global carbon uptake and sequestration.
Smith noted that grasping the contributions of these similar yet distinct biomes to the carbon cycle has been challenging. This is largely due to researchers’ difficulties in standardizing experiments for clearer comparisons. This study addresses that by implementing a large-scale, coordinated, multi-year experiment across multiple sites. Collectively known as the Extreme Drought Grasslands Experiment (EDGE), the 12 test sites were selected to represent various grasslands along precipitation gradients.
Smith emphasized that the research underscores the vulnerability of regions with lower species diversity to extended droughts. It also highlights the necessity for management strategies that enhance and sustain plant diversity, thus improving resilience to extreme droughts anticipated under future climate change scenarios.
“Drier grassland areas often coincide with regions where cattle grazing is prevalent, and where many people reside globally. Additionally, they are important in the context of carbon storage related to climate change,” she remarked. “Therefore, it is crucial to formulate management strategies for these regions, especially as climate change is expected to intensify the risks of extreme prolonged droughts.”