Abstract:

Aims: Ecosystem stability is crucial for maintaining ecosystem functioning and services. Nutrient enrichment and precipitation change are two major drivers affecting the stability of grassland ecosystems under global change. However, previous studies have primarily focused on the effects of individual drivers, while the impacts of their interactive effects and the underlying mechanisms remain poorly understood. 

Methods: We conducted a field experiment in the Hulunbuir meadow steppe with six treatments: ambient, nutrient addition (NPK), increased precipitation (50% increase in annual precipitation, +50% W), drought (50% reduction in annual precipitation,–50%W), nutrient addition plus increased precipitation (NPK + 50%W), and nutrient addition plus drought (NPK – 50%W). Using a 7-year dataset (2018–2024), we systematically evaluated the effects of eutrophication, precipitation change, and their interactions on the temporal stability of aboveground net primary productivity (ANPP). We further explored the underlying mechanisms by examining species diversity, species asynchrony, dominant species stability, and subordinate species stability. 

Results: The results showed that, compared with the ambient, all treatments significantly reduced the temporal stability of ANPP, with no significant differences among treatments. Significant positive interactions were detected between nutrient addition and both increased precipitation and drought, indicating that their combined effects on the temporal stability of ANPP were non-additive, and the magnitude of reduction was comparable to that under single-factor treatments. Mechanistically, nutrient addition significantly reduced average species richness, species asynchrony, and subordinate species stability; increased precipitation reduced only species asynchrony, whereas drought reduced only average species richness. Significant interactions between nutrient addition and precipitation change were reflected in positive effects on average species richness and species asynchrony. In addition, the temporal stability of ANPP was significantly positively correlated with average species richness, species asynchrony, and subordinate species stability, but was not significantly related to dominant species stability. 

Conclusion: In summary, average species richness, species asynchrony, and subordinate species stability jointly regulated ecosystem stability under the combined effects of nutrient enrichment and precipitation change, whereas the interactions between nutrient addition and precipitation change were primarily mediated by average species richness and species asynchrony. This study improves our understanding of ecosystem stability responses and underlying mechanisms under multiple global change drivers and provides a scientific basis for the conservation and management of meadow steppe ecosystems.

Key words: eutrophication, drought, increased precipitation, ecosystem function, temporal stability, biodiversity