Ecosystem stability and productivity dynamics of Inner Mongolian grasslands under climate extremes

Understanding how ecosystems function under frequent climatic disturbances is crucial for predicting their long-term stability. Although previous research indicates that stable ecosystems can mitigate the impacts of climate extremes, there remains debate over whether this stability is primarily driven by resistance, resilience, or a combination of both. In this study, we analyzed annual net primary productivity (NPP) in relation to the Standardized Precipitation Evapotranspiration Index (SPEI) and the aridity index (AI) to examine: (i) the spatiotemporal variations in NPP, (ii) the correlations between NPP, SPEI, and AI, and (iii) the resistance and resilience of four grassland types—meadow steppe, typical steppe, desert steppe, and steppe desert—across Inner Mongolia during the period 2000–2019. Despite noticeable interannual fluctuations, all grassland types exhibited an overall increase in NPP, with rates 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. Meadow steppe recorded the highest average NPP (251 g C m⁻²), followed by typical steppe (160 g C m⁻²), steppe desert (95 g C m⁻²), and desert steppe (83 g C m⁻²). NPP was significantly correlated with increasing SPEI values across all grasslands, and with higher AI values in steppe desert and desert steppe. Species richness varied from 9–14 in meadow steppe, 7–17 in typical steppe, and 5–10 in steppe desert, with NPP rising with greater species diversity—indicating a positive biodiversity–productivity relationship. Vegetation showed lower resistance but higher resilience under dry conditions, and the opposite under wet conditions, across most grasslands except desert steppe. Although typical steppe, meadow steppe, and steppe desert were more vulnerable to extreme droughts due to low resistance, their strong resilience suggests a quicker recovery following dry periods compared to wet conditions. The identified positive relationship between biodiversity and productivity suggests that preserving higher species richness may help mitigate productivity declines during climatic extremes.