Resource–Disturbance Trade-Offs Regulate Grassland Plant Diversity Across Experimental and Model Systems

Disentangling the joint effects of resource availability and disturbance on plant diversity is fundamental to understanding community assembly. We developed a stochastic extension of the Lotka–Volterra model that explicitly incorporates resource facilitation and disturbance-induced mortality, both mediated by species-specific trait responses. Combining simulations with a long-term field experiment manipulating nitrogen addition and mowing, we show that mowing consistently increased species diversity, whereas nitrogen addition reduced it, with no significant interaction between the two factors. Notably, mowing increased evenness, suggesting that higher diversity can coincide with more even abundance distributions. Simulations reproduced these patterns and revealed a non-linear resource–disturbance relationship: diversity declined under high-resource, low-disturbance conditions but was maintained at intermediate disturbance and moderate-to-low resource levels. This pattern was further supported by shifts in evenness and dominance across environmental gradients. Our results demonstrate that plant diversity emerges from a balance between resource-driven competitive exclusion and disturbance-mediated coexistence, modulated by species-specific traits.