Nutrient supply shifts successional paths but not speed of grassland recovery from disturbance

Disturbance and environmental change may cause communities to converge to a steady state, diverge towards multiple alternative states, or remain in long-term transience. Yet, empirical tests of these successional trajectories are rare, especially in systems experiencing multiple concurrent anthropogenic drivers of change. We compared competing models of succession in grassland communities subjected to disturbance and nitrogen fertilization using data from a long-term (22-year) experiment. Regardless of disturbance, after a decade communities settled on equilibrium states largely determined by resource availability, with species turnover declining as communities approached dynamic equilibria. Species favored by the disturbance were those that eventually came to dominate the highly fertilized plots. Furthermore, disturbance made successional pathways more direct, revealing an important interaction effect between nutrients and disturbance as drivers of community change. Our results underscore the dynamical nature of grassland succession, demonstrating how community properties such as beta-diversity change through transient and equilibrium states.