Searching for Eastern Old Growth: Modeling Primary Forest in Western North Carolina Using Terrain Attributes and Multispectral Satellite Imagery

Abstract

After centuries of timber harvest and conversion of forest to farmland and development, only small pockets of old growth forest remain in the eastern United States. These remnant portions of older forest have intrinsic value as a rare forest type and they play an important ecological function on the landscape. However, old growth forests in the eastern U.S. are less well-studied and documented than their counterparts in the Pacific Northwest. This study was undertaken to predict the geographic location, ecological and spectral characteristics of existing old growth, specifically in the southern Appalachian forests of western North Carolina. Stands of old growth previously field validated by the Southern Appalachian Forest Coalition were used as the response variable. Predictor variables included a range of landscape, topographic, and satellite indices derived from Landsat TM 7 satellite imagery and terrain analysis. Predictions were made using Classification and Regression Tree (CART) and Maximum Entropy (MaxEnt) modeling techniques. Model results were successful based on validation with existing field data. However, the MaxEnt model produced the most realistic estimate of potential old growth area given the inherent rarity of this forest type and suitability of the MaxEnt modeling technique for predicting the distribution of rare species. Results highlight over 54,000 hectares of potential old growth to be investigated by researchers on the ground. This analysis will contribute to the relatively limited body of knowledge about old growth in the eastern U.S. and is unique in terms of its broad geographic extent. Continued research on these remnant eastern old growth stands must be done to increase our understanding of this rare forest stage and to better inform related management decisions on both public and private land in the eastern U.S.