Existence of alternative stable states in the producer communities of temporary wetlands

Discontinuous variation in community structure over space and time is present in many natural systems. One theory attributes this variation to the existence of alternative stable states, suggesting that two or more possible community structures are equally likely in certain environmental conditions. I conducted an observational study and a pilot experiment to explore the potential role of alternative stable states in the producer communities of temporary and semipermanent fishless ponds. In the observational study, I surveyed producer community composition of ponds in 2005 and 2006. These data suggested alternative producer states in these communities, with bimodally distributed abundances of floating plants, submerged plants, and phytoplankton. In addition, I began a field experiment in 2006 to test the resilience of one community state in a pond dominated by floating plants (watermeal). I removed watermeal from experimental enclosures but not from control enclosures. Strong differences in phytoplankton abundance were observed in the first season, although watermeal responses were more variable. Monitoring of this experiment will continue in 2007 and 2008. Combined with other studies, this work will improve our understanding of the existence, controls, and consequences of alternative vegetation states in temporary wetlands.