Dynamics of a Community of Dominant Woody Riparian Species Along a Coastal River of Texas

Little is known about the structure of riparian communities within the central Gulf coast of Texas. We present a phytosociological description of the riparian corridor within two contiguous sites along the Mission River in Refugio County, Texas, that differ in respect to tidal influence along the river, and compare this woody riparian community to others in Texas. In summer 2009 and 2010, we established 33 transects perpendicular to the river after reviewing digital data from ArcMap 9.3.1 on elevation, edaphic characteristics, uses of land, and cover of land and wetland. We included sites above and below the tidal zone to ensure that the diversity of the community was documented. Transects traversed the edge of the river, ridge and swale topography, and up to the transitional zone between the riparian zone and upland habitat. We sampled a total of 137 plots and documented all species of trees, shrubs, and vines with diameter at breast height ≥3 cm. The important species were Ulmus crassifolia, Celtis laevigata, Ehretia anacua, Vitis mustangensis, Acer negundo, Carya illinoinensis, Fraxinus berlandieriana, and Quercus virginiana. Riparian vegetation was restricted to particular zones within the Mission River floodplain. Elevation and river flow were identified as the environmental determinants that influenced the distributional pattern of colonizing species and species of middle or late stages of succession within riparian zones. Species with the greatest importance values in this study were compared to those in other studies of the riparian vegetation in Texas using Bray-Curtis similarity indices. In general, riparian vegetation from the sites grouped within ecoregions. The riparian vegetation in the Mission River was most similar to the nearby Aransas River, and both are in the Gulf Coast Prairies and Marshes ecoregion.