Spatial patterns of herbaceous aquatic macrophyte recruitment in a naturally restored tidal and non-tidal freshwater wetland located within the Mid-Atlantic coastal plain

Background/Question/Methods

The natural ecological restoration of a prior converted wetland was characterized for a recently drained impoundment in the Mid-Atlantic coastal plain. We have defined the term “natural ecological restoration” as the re-establishment of ecosystem structure and function exclusive of anthropogenic inputs such as vegetative or hydrologic alterations. We quantified the recruitment and colonization of native and non-native wetland macrophyte species within a former impoundment using GPS/GIS technology. The presence of colonizing herbaceous vegetation was quantitatively assessed over two growing seasons in both tidal and non-tidal environments. Objectives for this study were (1) to examine geospatial relations of recruitment patterns among colonizing species over two growing seasons, (2) assess geospatial distribution of native and non-native invasive species, and (3) assess geospatial temporal dynamics of species coverage.

Results/Conclusions

Within the recently exposed lake basin aerial coverage of colonizing herbaceous vegetation increased over 9,000 m² from the 2009 to 2010 growing seasons. By the end of the 2010 growing season 20.3 hectares of the basin was covered by aquatic macrophytes.  The two most common native colonizing species in both 2009 and 2010 were Narrow-leaved Cattail Typha angustifolia L. (2009: 46.5%, 90,135 m2, 2010: 46.2 %, 93,917 m2) and Rice Cutgrass Leersia oryzoides L. (2009: 27.1%, 52,656 m2, 2010: 27%, 54,804 m2). The two most common exotic invasive species were Asian Spiderwort Murdannia keisak Hassk (2009: 9.8%, 19,070 m2, 2010: 13.7%, 27,827 m2) and Japanese Stiltgrass Microstegium vimineum Trin. (2009: 1.6%, 3,077 m2, 2010: 0.7%, 1401 m2). We determined that Typha angustifolia L., Murdannia keisak Hassk. were the most dominant species in tidal portions of the basin. Phragmites australis is becoming established in tidal portions of the basin.  In non-tidal portions of the basin cutgrass (Leersia oryzoides L.) tended to dominate vegetative communities and there were fewer invasive species. Baseline data collected during this study is critical to examining the effects of channel reestablishment and planned future woody vegetative restoration in the lake basin.