Spatial analysis and delineation of ecological landtype phases for the Hoosier National Forest, Indiana, USA

The US Forest Service adopted the National Hierarchical Framework of Ecological Units in 1993 with the ecological landtype (ELT) and ecological landtype phase (ELTP) forming the lowest levels of the hierarchy. This study examines the potential of computer mapping ELTPs for the Hoosier National Forest (HNF) located in southern Indiana. ELTPs were sampled in 2001–2003 within four units of the HNF that are situated within the Brown County Hills and Crawford Upland subsections. A 10-m resolution USGS DEM and a soil survey map were used as source data layers. GIS layers were produced with ArcGIS tools using elevation, slope, aspect, curvature, and soil type. Statistical analysis was performed for those ELTPs that occupy sites similar in physiography but differing in vegetation and soils. A Kruskal–Wallis test of landform variable means indicated a statistically significant variation (p<0.05) among all ELTPs in elevation, aspect, slope, and profile curvature within both subsections. A pairwise Mann–Whitney test showed a significant difference (p<0.05) in elevation, general, and plane curvature among selected ELTPs. A χ2 test of soil types derived from soil survey map units revealed a significant difference (p⩽0.05) in soil type constancy among selected ELTPs. An ELTP map was developed using physiographic characteristics defined in the classification and information from statistical testing. The resulting map provides the basis for management decisions and development of landtype associations (LTAs) using a “bottom-up” approach.