Assessing wetland mitigation efforts using standing vegetation and seed bank community structure in neighboring natural and compensatory wetlands in north-central Texas

Abstract

It is often presumed plant recruitment from the soil seed bank and nearby wetlands will be sufficient to establish a wetland plant community following the restoration or creation of wetland hydrology. This approach to wetland restoration was examined in four compensatory wetlands and a natural oxbow wetland (Oxbow) in a floodplain of the West Fork Trinity River in north-central Texas. We assessed: (1) similarities in vegetation and seed bank composition among natural and compensatory wetlands, (2) within site similarity of vegetation relative to its seed bank community, and (3) the effects of hydrology (Wet vs. Drained soil) on the germination of seeds from the seed bank. Species richness of the standing vegetation was variable across sites and years, however when pooled across years (2008–2009) vegetation and seed banks showed similar species richness (66 vs. 70 species). Fewer wetland species (i.e., species occurring in wetlands >50 % of the time) were observed in the vegetation relative to the seed bank (25 vs. 41 species), and seed banks of compensatory wetlands were more similar to the natural wetland than was the standing vegetation. In the seed bank study, location (i.e., site) significantly affected total species richness, wetland species richness, diversity, and germinated seeds m−2, however no significant effect of hydrology was detected. These results suggest hydrology alone is not sufficient to establish a desired wetland plant community in a created wetland and the inclusion of seed bank surveys with field vegetation surveys provides a more complete assessment of wetland creation and restoration.