Community stability plays a crucial role in ensuring the consistent provision of ecosystem services despite environmental changes, including alterations in precipitation patterns. Over the past decades, significant progress has been made in understanding the responses of the stability of grassland plant communities and underlying mechanisms, defined as the ratio of the temporal mean biomass to the standard deviation. However, a crucial knowledge gap remains regarding whether the impacts of precipitation on the stability of grassland biomass are contingent upon specific contextual factors.

Here, we examined the stability of above- and below-ground biomass in adjacent grass- and shrub-dominated communities through a 7-year manipulation experiment involving seven precipitation levels: 20%, 40%, and 60% decreases, as well as 20%, 40%, and 60% increases in natural rainfall, in addition to ambient precipitation.

We found that the stability of community biomass was influenced by three contextual factors including the magnitude and directionality of precipitation, above- and below-ground biomass, and the type of vegetation. In particular, higher and more intense precipitation resulted in higher stability of above-ground biomass in both grass- and shrub-dominated communities. Conversely, higher precipitation intensity led to decreased below-ground biomass stability in grass-dominated communities but increased below-ground biomass stability in shrub-dominated communities. Species stability and species asynchrony consistently played a positive role in explaining the stability of above-ground biomass in both grass- and shrub-dominated communities. However, species asynchrony negatively influenced below-ground biomass stability in grass-dominated communities without a comparable effect in shrub-dominated communities. The preeminent contribution to the total community biomass was identified in the stability of below-ground biomass, evident in both grass-dominated and shrub-dominated communities.

Synthesis. This study highlights that while the specific effects of changes in precipitation may vary depending on the context, the fundamental processes governing biomass stability are consistent. These findings elucidate the desert steppe ecosystems’ adaptive response to precipitation variations and emphasize their pivotal role in maintaining ecosystem functions under climatic perturbations.