Plant community change and 20th century land-use history in a suburban wetland

Every landscape has a history which impacts current and future landscape and ecosystem properties. Understanding a landscape's history provides vital information for management, conservation and restoration decisions. We investigated the response of wetland vegetation communities to different land-use histories in the Great Swamp located in northern New Jersey. Great Swamp, a 4500-ha wetland, has a long and varied land-use history. The western portion of Great Swamp was intensively farmed through the 1930s while the eastern portion remained relatively undisturbed. In 1964, both portions of the swamp joined to become the a National Wildlife Refuge; however, the division in land-use continued, as the western portion was managed to protect a broad variety of animal and plant populations, while the eastern portion was designated a Wilderness Area. Aerial photographs spanning 70 years were analyzed to determine the relative extent of change in vegetation community structure associated with the different land-use histories of these two areas. We analyzed three time periods: the earliest available images (1932), 1964 imagery and the most recently available aerial photos (2002). Land-cover differed significantly between the eastern and western portions of the swamp. The western area transitioned through orchards in 1932, a decline in agriculture by 1962, and a predominant land-cover of scrub/shrub wetlands and pin-oak forests by 2002. In contrast, red maple swamps dominated the eastern portion of the swamp throughout the entire survey period. Over time, plant community diversity increased in both areas of Great Swamp; however, diversity was consistently higher in the western portion of the swamp, perhaps as a result of succession and current management practices. Great Swamp land managers have applied these results to tailor restoration and conservation goals to each portion of the swamp. This study underscores the necessity of historical studies in understanding landscape patterns and in making land management decisions.