A new study has revealed that extreme drought conditions are altering the stability of grassland productivity by shifting underlying ecological mechanisms. Research from a team at the Institute of Applied Ecology of the Chinese Academy of Sciences, published in Ecology Letters, indicates 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 research led by Dr. LUO Wentao conducted a long-term drought experiment using rain shelters that reduced growing season precipitation by 66%. Figure 1 illustrates the infrastructure for controlled grassland drought conditions. The team 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.

The findings indicate that under normal conditions, the functional traits and population dynamics of dominant grass species largely determine the temporal patterns of grassland productivity. These species typically contribute most to biomass production, and their consistent growth stabilizes ecosystem output over time. However, the study revealed that prolonged extreme drought weakens the regulatory influence of these dominant grasses. Instead, the asynchronous responses of different plant species become the critical factor in maintaining overall ecosystem stability. This discovery challenges the traditional understanding of grassland ecosystem resilience.

Furthermore, the research provides the first evidence that a specific combination of functional traits—high specific leaf area (SLA), indicating faster growth, and compact tissue structure, potentially enhancing water retention—can significantly enhance the drought resistance stability of plant communities. This finding offers theoretical guidance and technical indicators for selecting drought-resistant grass species and for the restoration of degraded grasslands.

The research team intends to expand this research to a wider range of global grassland types to develop a more comprehensive theoretical framework for understanding how grassland ecosystems respond to drought.