Disturbance alters transience but nutrients determine equilibria during
grassland succession with multiple global change drivers
Abstract
Disturbance and environmental change may cause communities to converge
on a steady state, diverge towards multiple alternative states, or
remain in long-term transience. Yet, empirical investigations of
successional trajectories are rare, especially in systems experiencing
multiple concurrent anthropogenic drivers of change. We examined
succession in old field grassland communities subjected to disturbance
and nitrogen fertilization using data from a long-term (22-year)
experiment. Regardless of initial disturbance, after a decade
communities converged on steady states largely determined by resource
availability, where species turnover declined 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 under low nutrients,
revealing an important interaction effect between nutrients and
disturbance as drivers of community change. Our results underscore the
dynamical nature of grassland and old field succession, demonstrating
how community properties such as beta-diversity change through transient
and equilibrium states.