Patterns of change in tree islands in Arthur R. Marshall Loxahatchee National Wildlife Refuge from 1950 to 1991

Size, shape, orientation, and distribution of tree islands in a remnant of northern Everglades wetland were examined from 1950 and 1991 aerial photogr aphy. The objectives were to quantify the patterns of tree islands in Loxah atchee National Wildlife Refuge, to determine if the patterns of toe island s had changed between the two dates, and to relate the tree island patterns to modeled pre- and post-drainage hydrologic patterns. There was considera ble variation in the patterns of tree islands spatially and temporally. Cha nges in the size and shape of tree islands from 1950 to 1991 are consistent with changes in the modeled pre- and post-drainage hydrologic patterns. Ph oto plots along the edges of the refuge, when hydroperiods are longer and d epths deeper than they were historically, show a decrease in tree island si ze and in overall area of tree islands in the plots. Photo plots in the int erior, where hydroperiods are shorter than they were pre-drainage, show an increase in tree island area. Overall, there is a tendency for more tree is lands to be irregularly shaped in the 1991 photo plots than in the 1950 plo ts, a reflection of the loss of water Row, reduction of pulse magnitude, an d the pending of water along the perimeter dikes. This study illustrates th e importance of considering long-term changes in hydroperiod, depths, and w ater hows in the restoration of this area.