Delineation and spatial analysis of ecological classification units for the Hoosier National Forest

Abstract

The objective of this study was to delineate ecological land type phases (ELTP) as well as define and delineate Land Type Associations (LTA) that will complete the USDA Forest Service ecological classification hierarchical system for the Hoosier National Forest (HNF) area. ELTPs were sampled in 2001 and 2002 within the four units of HNF that are situated within the Brown County Hills (BCH) and the Crawford Upland (CUP) subsections of the eastern United States classification. A 10 meter resolution USGS DEM and a soil survey map were used as source data layers with an addition of other GIS layers (slope, aspect, and curvatures). Statistical analysis was done for those ELTPs that occupy sites similar in physiography but different in vegetation and soils. Elevation, slope, general and planform curvature were physiographic characteristics that indicated differences between selected ELTP pairs. An association between ELTPs and landforms as well as ELTP clustering on the landscape was observed. ELTP maps were developed using physiographic characteristics defined in the classification and data from sample points as well as information from statistical testing (characterizing differences in vegetation and soils). For LTA delineation, two approaches were tested: automated (moving window with area 4–12 km2) and semi-automated (visual detection of areas of different ELT/ELTP patterns followed by multivariate statistical analysis and clustering). An expert based approach (semi-automated) was selected and used in further delineation of LTAs for all the HNF area. Four LTAs for the BCH subsection (Pleasant Run unit of the HNF) and six LTAs for the CUP subsection (Lost River, Patoka River and Tell City units of the HNF) were mapped. Differentiating criteria used in LTA development include, in the general order of most frequent use, patterning of ELTPs and soil survey units, landforms, bedrock type, dominant tree species occurrence, and disturbance processes. The LTA boundary identification was based on physiographic boundaries such as stream channels or watershed boundaries (ridges). All units are nested within boundaries of subsequent upper and lower hierarchical units (LTA ↔ ELT ↔ ELTP). Spatial statistics on ELT, ELTP, soils, erosion, and elevation are reported to highlight differences between LTAs