Beyond species richness: grazing and fertilization shape temperate grassland stability through distinct stabilizing effects

1. Alterations in land use, particularly grazing and fertilization, pose significant threats to the stability of grassland ecosystems. While biodiversity is often associated with ecosystem stability, the precise processes through which various disturbances impact diversity's effects remain incompletely understood.
2. This investigation delves into the individual and combined impacts of grazing and fertilization on the temporal stability of community productivity within a temperate meadow steppe. Additionally, the study examines the relationships between these practices, species diversity, and specific stabilizing effects, including the dominance, asynchrony, averaging, and interaction stability effects.
3. Through nine years of field experimentation, it was discovered that grazing decreased community stability by reducing aboveground biomass, while fertilization partially offset this destabilizing effect. Notably, changes in land use predominantly affected stability via their influence on stabilizing effects, regardless of species diversity itself. Specifically, stability modifications induced by grazing were primarily related to the dominance effect, whereas those resulting from fertilization were associated with the asynchrony effect. Moreover, the averaging effect and interaction stability together played a crucial role in driving stability shifts within various land-use change scenarios. Bayesian structural equation modeling (SEM) revealed that these stabilizing effects exerted a substantial and positive influence on temporal stability.
4. Synthesis. Our findings emphasize that grazing and fertilization differentially regulate grassland stability via dominance and asynchrony pathways, respectively. More broadly, our work reveals that land use fundamentally reshapes the architecture of stability, demonstrating that stability is not maintained through a universal mechanism but through context-dependent pathways shaped by specific environmental pressures. This research enhances the mechanistic understanding of diversity-stability relationships and offers valuable insights for tailored grassland management strategies, such as the integration of moderate nitrogen supplementation with grazing practices to optimize the productivity-stability trade-offs.