Tropical Storm Driven Hydrologic Regimes Support Spartina spartinae Dominated Prairies in Texas

We measured daily precipitation, duration of ponding and soil redox potential for 2 years in three coastal prairie sites near the mouth of the Rio Grande in south Texas. The area historically was dominated by gulf cordgrass, Spar- tina spartinae. Much of the area was plowed for agriculture and Spartina has not recolonized disturbed sites. Regulation of the Rio Grande has eliminated flooding and disconnected the study area from the river. The goal of this project was to use continuous measures of water levels and soil redox potential to determine whether the study areas have a wet- land hydrologic regime. Anoxic soils formed and persisted for at least 2 weeks only following hurricanes or large tropical storms that produced at least 15 cm of precipitation over 1-3 days and created ponding. Over the past century storms of this magnitude occurred only 1 out of 4 years. This study determined that the study sites do not support wetland hydrologic regimes due to river regulation, however reestablishment of the dominant wet prairie species is possi- ble through planting.