Enhanced net primary productivity across Inner Mongolian grasslands despite diverging stability under climate...

Understanding ecosystems functioning under frequent climatic perturbations is central to predicting ecosystem stability. While studies suggest that stable ecosystems can buffer against climate extremes, there is no agreement on whether this stability arises from their resistance (ability to absorb shock) to perturbations, resilience (capacity to recover) towards disturbances, or a combination of both. Using annual net primary productivity (NPP) and Standardized Precipitation Evapotranspiration Index (SPEI) and aridity index (AI), we investigated the (i) spatiotemporal changes of NPP, (ii) correlation between NPP, SPEI and AI, and (iii) resistance and resilience of meadow steppe, typical steppe, steppe desert, and desert steppe in Inner Mongolia from 2000-2019.

Despite substantial interannual variability, all grassland types showed an upward trend in NPP, ranging from 1.21 g C m^-2 yr^-1 in desert steppe to 4.54 g C m^-2 yr^-1 in meadow steppe. The highest NPP (g C m^-2 yr^-1) was observed in meadow steppe (251), followed by typical steppe (160), steppe desert (95), and desert steppe (83). NPP increased significantly with increasing SPEI values across all grassland types, and with rising AI in steppe desert and desert steppe. Partial correlation analysis controlling for CO₂ confirmed that NPP remained significantly and positively correlated with precipitation across all grassland types. Species richness ranged between 9 and 14 in meadow steppe, 7 and 17 in typical steppe and 5-10 in steppe desert. The measured NPP showed an increasing trend with rising species richness across these three grassland types, demonstrating a positive diversity-productivity relationship. Vegetation exhibited lower (higher) resistance against dry (wet) climatic conditions and higher (lower) resilience towards dry (wet) climatic conditions for all grasslands except for desert steppe. Typical steppe, meadow steppe and steppe desert are susceptible to extreme dry climate as these grasslands showed lower resistance against extreme dry climate. However, the higher resilience of these grasslands after extreme dry climate highlights that they recover faster after dry conditions compared to the recovery after wet conditions.

The observed increase in vegetation productivity and differing stability has practical implications for pastoralists, landscape managers, and conservationists for grassland management. The demonstrated positive diversity-productivity relationship suggests maintaining greater species richness could buffer productivity losses during climate extremes, while the NPP-AI correlations in steppe desert and desert steppe offer early warning indicators for drought preparedness.