Print PageAbrupt changes in community composition over space and time occur in many natural systems. Several explanations have been proposed for this discontinuous variation in community composition, making it challenging to determine which mechanisms operate in a given system. I characterized community composition and dynamics to sort among these hypotheses in one understudied system, the producer communities of temporary wetlands in southwest Michigan. I surveyed 26 temporary and semipermanent ponds for four years to explore variation in community composition over space and time.
Results/Conclusions
I identified four community states in these systems, characterized by dominance of different producer functional groups (floating, submerged, or emergent vegetation) or the absence of plants throughout a season. Similar communities were not clustered together in space, suggesting that dispersal limitation or patchiness of large-scale environmental drivers did not explain these patterns. Shifts between community states were rare within a season, but nearly half (46.2%) of the ponds shifted between two community states across years. The likelihood of these shifts was not associated with particular community states, eliminating succession as an explanation for these patterns. Notably, most of these shifts occurred with large changes in water levels, such as the occurrence of a floating plant outbreak during a high water year. This suggests water level fluctuations may drive some of these plant community changes, as previously documented in other wetland systems (such as Great Lakes coastal wetlands and prairie potholes). Further study of the dynamics and causal mechanisms of these patterns will improve our understanding of not only natural variation in wetland plant communities, but also potential responses to human-induced changes such as hydrological alterations and climate change.
