A new study published in Ecology Letters has revealed that extreme drought conditions are altering the stability of grassland productivity by shifting underlying ecological mechanisms. Researchers from the Institute of Applied Ecology of the Chinese Academy of Sciences indicated that prolonged and intense dry periods can diminish the role of dominant grass species in maintaining consistent plant growth, potentially affecting the long-term health and functioning of grasslands globally.

Spanning roughly 40% of the planet's land, grasslands play a vital role in maintaining the global carbon equilibrium and sustaining livestock agriculture. Although prior investigations have documented that drought diminishes grassland productivity (the rate of biomass production), the processes influencing how this output changes over time have remained largely unclear.

To investigate this, the researchers led by Dr. LUO Wentao conducted a long-term drought experiment using rain shelters that reduced growing season precipitation by 66%. They analyzed community-weighted functional traits (the weighted average values of plant species characteristics like leaf area and tissue density) and species asynchrony (the degree to which different plant species' productivity fluctuates at different times) to assess drought's impact on both overall grassland productivity and its stability.

Under normal conditions, the study confirmed that dominant species, those contributing the most biomass, play a key role in stabilizing grassland productivity. Their steady growth patterns ensure consistent ecosystem output year to year. However, under prolonged drought, this dominance-driven stability weakens. Instead, it is the asynchronous responses among diverse species—some declining while others thrive—that emerge as the main buffer against ecosystem fluctuation.

This shift challenges traditional ecological theory that emphasizes the primacy of dominant species in sustaining ecosystem functions. 

Furthermore, the study provides the first evidence that specific trait combinations, particularly high specific leaf area (indicative of rapid growth) and dense tissue structure (suggesting enhanced water retention), can increase the drought-resistance stability of plant communities.

These insights offer a valuable scientific foundation for the restoration of degraded grasslands and for the strategic selection of drought-resilient species. The researchers plan to extend their investigations across diverse grassland ecosystems globally to build a more unified theoretical framework for understanding grassland responses to climate extremes.