Uncertainty of Forested Wetland Maps Derived from Aerial Photography

Forested wetlands (FWs) are economically and environmentally important, so monitoring of change is done using remote sensing by several U.S. federal programs. To better understand classification and delineation uncertainties in FW maps, we assessed agreement between National Wetlands Inventory maps based on aerial photography and field determinations at over 16 000 Forest Inventory and Analysis plots. Analyses included evaluation of temporal differences and spatial uncertainty in plot locations and wetland boundaries. User's accuracy for the wetlands map was 90% for FW and 68% for nonforested wetlands. High levels of false negatives were observed, with less than 40% of field-identified wetland plots mapped as such. Epsilon band analysis indicated that if delineation of FW boundaries in the southeastern U.S. met the data quality standards (5 meters), then the area within uncertainty bounds accounts for 15% to 30% of estimated FW area.

Visualizing Plant Community Change Using Historical Records

Ecological data from land surveys from 1811 for the 100,000-acre Connecticut Tract in western New York were transcribed and then analyzed using ArcGIS and IDRISI GIS software. The surveys contained both witness tree data and line descriptions, which were analyzed for species composition and community type. Results illustrate that many changes have occurred in species composition. Possible causes of these changes to the mature forests may include introduced pests and diseases or anthropogenic land-use change. Comparisons to the National Wetlands Inventory Database reveal that while some of the wetlands that were present in 1811 still exist today, particularly in the Byron-Bergen Swamp and in the wetlands along the Lake Ontario shoreline, other original wetlands have been lost while new wetlands have replaced some upland forests. This study helps elucidate past causes of temporal and spatial variability, and it provides a reference point for land managers who need to understand the effects of land-use history for ongoing restoration efforts.