Water depletion drives plant succession in farm ponds and overrides a legacy of continuous anthropogenic disturbance

QuestionsAbandonment of anthropogenic ecosystems threatens biodiversity in rural areas globally. Successional responses in anthropogenic ecosystems have been shown to differ from those in natural ecosystems because of the legacy of continuous management activities. However, few studies have focused on successional changes in anthropogenic freshwater ecosystems following abandonment. Focusing on two drivers (water depletion and cessation of anthropogenic disturbance), we tested whether water depletion plays a larger role than years since abandonment in determining the both plant functional diversity and composition in farm ponds. LocationAwaji Island, western Japan. MethodsWe investigated flora at 200 farm ponds, which had experienced long-term continuous anthropogenic disturbance. We interviewed 100 managers of the surveyed ponds and local farmers to identify the ponds' management status. To capture community processes during succession, we focused on functional richness and functional trait composition. We assessed the relative contribution of the two successional drivers in determining functional richness by adopting a linear model. We classified the survey ponds into five groups based on the two successional drivers and performed PERMANOVA to test differences in functional composition among the groups. ResultsWater depletion played a larger role than elapsed time since cessation of anthropogenic disturbance in determining functional richness. Functional composition of water-depleted ponds significantly differed from that of managed ponds, regardless of years since abandonment. ConclusionsOur results indicate that water depletion has a larger effect on successional changes in ponds than cessation of anthropogenic disturbance; that is, water depletion drives succession and overrides the legacy of continuous anthropogenic disturbance. The results suggest that, in freshwater ecosystems, the functional change in a community is greater in the transition from macrophytes to terrestrial plants than it is in the transition from stress-tolerant species to competitive species.