Land-cover change and wetland plant zonation in Weeks Bay, AL

Changes in land-use/land-cover (LULC) and predicted changes in environmental conditions threaten the marginal occupancy of tidal marshes in Weeks Bay, Alabama. In a combined study, I investigated the implications of historic LULC and coastal wetland plant distributions on coastal wetland viability in the Weeks Bay area. The historically forested and agricultural landscape of Baldwin County is being rapidly converted by urban development, which puts increasing stress on downstream ecosystems. Further, simultaneous losses on the landward and seaward extent of the intertidal wetland transition may be contributing to coastal squeeze in this area. Within our study area, 17% of estuarine and marine emergent wetlands were lost to open water between 1956 and 2001, with over 30% converted to upland forested wetland (22.2%) and urban development (10.3%). There was also a near-complete loss (95.9%) of unconsolidated shore to open water. Within the coastal marsh transition of Weeks Bay, there was a heterogeneous micro-topography with a large overlap of plant distributions by elevation. However, salinity was found to be an indicator of plant zonation for the three dominant species: Spartina cynusuroides, Cladium jamaicense, and Juncus roemerianus. At intermediate salinity (3 – 9 psu), dominance alternated between Spartina cynosuroides in lower salinities and Juncus roemerianus in higher salinities. Because Cladium jamaicense is the least salt-tolerant of the three dominant wetland plants surveyed, changes in salinity due to altered upland hydrology and SLR may have the greatest effect on its distribution. Further, since the upland barrier of a wetland forest may prevent marsh transgression as sea levels rise, the ecotone between wetland forest and emergent marsh should be an area of specific interest for environmental managers. Factors that contribute to shoreline erosion or barriers to upslope migration will likely dictate the health and persistence of intertidal marsh habitat at Weeks Bay and will require special focus from local managers. (Published By University of Alabama Libraries