Topographically-based Landscape-scale Ecological Mapping in Pennsylvania

Open Access
Kong, Ningning
Graduate Program:
Doctor of Philosophy
Document Type:
Date of Defense:
February 27, 2006
Committee Members:
  • Wayne Lawrence Myers, Committee Chair
  • Denice Heller Wardrop, Committee Member
  • Charles Andrew Cole, Committee Member
  • Rick Lane Day, Committee Member
  • landtype association
  • ecological landtype
  • topography
  • Pennsylvania
With emphasis on sustainable ecosystem management, ecological mapping at landscape scale provides basic information about the nature and distribution of ecosystems for natural resources management, planning, monitoring and assessment. Landtype association (LTA) and ecological landtype (ELT) are two landscape scales of ecological units in a hierarchical ecological classification system developed by the USDA-Forest Service for use in ecosystem management. LTA is a complex of complementary landscape components (ecological landtypes) that combine through spatial adjacency to create ecological contrasts across regions. ELT is a subdivision of LTA unit based on similarities in landform, soils, geomorphic processes, and plant associations. The goal of this study is to develop, describe and verify a scientifically based system of map units for Pennsylvania that incorporates ecological principles and processes across landtype association and ecological landtype scales. At the LTA level, the influences of topography and terrain topology on ecosystem distributions motivated an ecological mapping approach with the concern for ecological, hydrologic and environmental aspects of the area that separates LTA units into three major categories, as highland habitat (HH), transitional terrace (TT), and dual drainage (DD). Highland habitat is designated as being primarily headwater stream areas composed of mounding or arching to level upper land surfaces. Dual drainage is designated to be areas having both large streams and small tributary streams. Transitional terrace is intermediate level elevated terrain unit that is otherwise similar to highland habitat, but also receives some hydrologic influx from adjacent upland along partial margin. A GIS-assisted, top-down classification method was adopted in the mapping procedure, and produced 10,782 LTA units delineated across the state with size ranging from 100 to 5,000 acres. These units were classified into eighteen subtypes according to their topographic and hydrologic characteristics. At the ELT level, considered as unique combinations of topography and soil characteristics, the mapping units were generated by aggregating adjacent soil SSURGO polygons with same soil series, aspect and similar slopes. There were 699,336 ELT units mapped for sixty-four counties in the state where soil data are available with the size ranging from 10 to 100 acres. Relationships between the resulting ecological units and other spatial information were analyzed. The results indicate that physiographic characteristics, stream node and drainage densities, land cover patterns, and vertebrate species habitat distributions have substantial differences between different types of ecological units. In general, the highland habitats and transitional terraces have larger size, higher average elevation and relief, and steeper slope compared to the dual drainage units. The ELT units in highland habitats and transitional terraces also tend to have larger size and steeper slope. The hydrologic characteristics of LTA units indicate that in most of the physiographic subsections the first-order stream node density is much higher in the highland habitats and transitional terraces, whereas higher order stream node densities are higher in the dual drainages. Drainage densities are higher in dual drainages for all stream orders. In different LTA subtypes, the stream node and drainage density patterns also have definite differences. This establishes that the LTA mapping in this study can effectively separate headwater areas from downstream drainage areas, and also that the LTA subtype classification can separate different hydrologic characteristics in each subtype. Land cover has different patterns in different landtype associations. There are more intensive human land use areas located in the dual drainage units, whereas forests are more likely to be extensive in the highland habitats and transitional terraces. It is shown that the LTA unit types reflect the preference of human activities, thus determining the distribution patterns of forest and wildlife habitats. Most of the vertebrate species also have significantly different potential habitat distributions between the HH/TT and DD types of LTA units in each physiographic component. Some key species can be identified having strong affinity for certain kinds of LTA units. Highland habitats and transitional terraces are favorable for species associated with headwater streams, exposed environment and forest land cover types. Dual drainages are favorable for species associated with moist environments and large streams. The results confirm that LTA units can separate different habitats at the landscape level.