A COMPARISON OF THE VEGETATION AND SOILS OF NATURAL, RESTORED, AND CREATED COASTAL LOWLAND WETLANDS IN HAWAI'I

The loss of coastal wetlands throughout the Hawaiian Islands has increased the numbers of created (CW) and restored (RW) wetlands. An assessment of these wetlands has yet to occur, and it has not been determined whether CWs and RWs provide the same functions as natural wetlands (NWs). To address these concerns, vegetation and soil characteristics of 35 wetlands were compared within sites along hydrologic gradients and among sites with different surface water salinity and status (i.e., CW, RW, NW). Only 16 of 85 plant species identified were native and three of the four most abundant species were exotic. Vegetative characteristics differed primarily across salinity classes, then along hydrologic zones, and to a lesser extent among CWs, RWs, and NWs. Soil properties exhibited fewer differences across salinity classes and along hydrologic zones and greater differences among CWs, RWs, and NWs. The dominant presence of invasive species in coastal Hawaiian wetlands suggests that it will be difficult to locate reference sites that can be used as restoration targets. Differences in edaphic characteristics suggested that RWs/CWs do not exhibit the same functions as NWs. Future restoration and creation should include planting of native vegetation, controlling invasive vegetation, and alleviating inadequate soil conditions.