Herbaceous and woody vegetative assessment in a newly restored mixed tidal regime freshwater wetland

Background/Question/Methods

The ecological restoration of a prior converted wetland was characterized within a recently drained impoundment along the James River in Charles City County, Virginia. We quantified the recruitment and colonization of native and non-native wetland vegetation within a former impoundment using GPS/GIS technology. Colonizing vegetation was assessed over two growing seasons in both tidal and non-tidal environments. Standing herbaceous cover was assessed with GPS community delineations and line intercept transects. Ocular reconnaissance was used in combination with GPS/GIS methods to locate and map bald cypress (Taxodium distichum L.) within the wetland. Potential colonizing species were examined by assessing soil seed banks across the following four habitats: forested tidal wetland, non-vegetated tidal mudflat, vegetated non-tidal marsh, and vegetated tidal marsh. 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 invasive species, (3) quantify species composition in the extant seed bank and (4) assess geospatial patterns in recruitment of bald cypress in order to identify areas where cypress restoration efforts may be most effective. 

Results/Conclusions

The two most common native colonizing species during the study were narrow-leaf cattail (Typha angustifolia L.) which decreased from 93,917 m² in 2010 to 86,973 m² in 2011 and rice cutgrass (Leersia oryzoides L.) which increased from 54,804 m² in 2010 to 56,446 m² in 2011.  The two most common exotic invasive species were Asian spiderwort (Murdannia keisak Hassk.) which increased from 27,827 m² in 2010 to 36,286 m² in 2011 and Japanese stilt grass (Microstegium vimineum Trin.) which increased from 1,400 m² in 2010 to 3,735 m² in 2011. We determined that narrow-leaf cattail and Asian spiderwort were the most dominant species in tidal portions of the basin. In non-tidal portions of the basin rice cutgrass tended to dominate vegetative communities and there were fewer invasive species present. Differences in extant species at the site and seed bank composition were observed across all habitats. Two hundred and eighty-one bald cypress individuals were located and mapped within the restored wetland. Over 75% of the cypress individuals found were seedlings or saplings. Based on geospatial relations of these recruits we have identified potential areas within the restored wetland for natural and facilitated recruitment.