Individual study: Microtopographic re-establishment in a restored wetland in Beaufort County, North Carolina, USA
Bruland G. & Richardson C. (2005) Hydrologic, edaphic, and vegetative responses to microtopographic reestablishment in a restored wetland. Restoration Ecology, 13, 515-523
Variations in microtopography (e.g. hummocks and hollows), a characteristic feature of natural wet meadows, are frequently absent at newly restored sites. Such subtle variations promote a mosaic of soil patches of varying characteristics which in turn, contribute to a more diverse vegetation structure and more diverse plant communities. This study examined the responses of soil and vegetation to microtopographic re-establishment at a restored wetland.
Study area: The 3-year-old restoration site is located in Beaufort County, North Carolina (35º36'52N, 76º51'17W), eastern USA. The area was a former agricultural field (37 ha) restored to wetland status as compensatory wetland mitigation.
Experimental design: The restoration was undertaken from September 2000 to January 2001. The topsoil was removed followed by the creation of : 48 hummocks (each 1 m in height and 1.5 m in diameter); 15 hollows (depth 0.3 m; surface area 20-40 m²); and numerous flat tops, created to mimic such features in nearby natural wet meadows. The topsoil was then spread over the surface and hydrology restored by infilling of drainage ditches etc.
To determine edaphic responses, soil samples were collected (May-October 2003) from 18 randomly selected plots, six from each of the three microtopographic zones, for analysis. Aboveground plant biomass was measured by sampling these plots and plant species richness was determined.
Edaphic responses: Differences between the three microtopographic zones were not consistent throughout the growing season for soil moisture and temperature. However overall, hollows had lower moisture loss and less temperature variation than flats or hummocks. Slightly higher nitrate and ammonium levels were found in hummocks than in flats and hollows for most of the growing season.
Vegetation responses: Microtopographic re-establishment had significant effects on vegetation diversity and productivity. On average, flats had higher species richness (5 species/m²), than hollows (3.3) and hummocks (1.9). Hollows had significantly higher biomass than flats or hummocks due to the rapid growth of emergent marsh herbs.
Overall, the creation of these microtopographical features was considered beneficial to the restoration in terms of achieving plant communities resembling those of nearby natural wetlands.
Note: If using or referring to this published study, please read and quote the original paper, which can be viewed at: http://www3.interscience.wiley.com/cgi-bin/fulltext/118708075/PDFSTART