An evaluation of GIS-derived landscape diversity units to guide landscape-level mapping of natural communities

As conservation planning increases in scale from specific sites to entire regions, organisations like The Nature Conservancy face a critical need for GIS-based tools to evaluate landscapes on a regional scale. An existing, field-based approach to analyse the diversity of a landscape is by delineating natural community types, which is a time-intensive process. This study evaluated the utility of using an existing, GIS-derived landscape diversity model as a predictive tool for mapping natural communities on a large (8369 ha) upland forest site in the northern Taconic region of Vermont. The GIS model incorporates four geophysical factors: elevation, bedrock type, surficial deposits, and landform. A significant level (α=0.05) of association between eight pairs of landscape diversity unit (LDU) types and natural community types was found. However, the strength of these associations is low (Cramer's V values 0.172), suggesting a poor predictive efficiency of landscape diversity units for natural community types. The results suggest that variables in the LDU model are relevant to natural community distribution, but the LDU model alone is not an effective tool to aid in mapping of natural community types of upland forests in Vermont. Until better landscape-level techniques are developed, the role of this type of model is limited to screening the landscape for areas with a particular set of geophysical characteristics, which can help an ecologist interpret the patterns on the landscape, but cannot substitute for a field-based approach to natural community mapping.