effect of water level variation on the growth of Melaleuca seedlings from the Lake Okeechobee littoral zone

The invasive exotic wetland tree, Melaleuca quinquenervia, continues to rapidly expand throughout seasonally wet areas of southern Florida. Water managers are concerned that lowering the water levels of Lake Okeechobee, part of the Everglades ecosystem, while benefitting various natural resources, would stimulate the Melaleuca population. Saplings and seven-week old seedlings were subjected to various hydroperiod treatments, based on a simulation of historical water level variations. Saplings grew taller, increased shoot number, and increased root biomass under longer hydroperiods with fluctuating water levels, including short periods of submersion. Age affected seedling response--those submersed at seven weeks grew slower and had less biomass than submersed 12-week old seedlings, yet mortality was low at both ages. While Melaleuca's plasticity allows it to adapt to hypoxic, aquatic conditions by means of aquatic heterophylly and adventitious roots, like other wetland trees, Melaleuca has limited flood tolerance. Algae and drought also increase mortality.