Defining Landscape Ecological Function with the use of Hydrodynamic Vectors

Abstract. The development of Ecological Site Descriptions (ESD) is a multi-agency effort conducted jointly by the Natural Resources Conservation Service, the U.S. Forest Service, and the Bureau of Land Management. This effort seeks to define all landscapes in terms of distinct ecological functions. The ESD community within NRCS generally accepts the use of the Hydrogeomorphic (HGM) landscape classification system for the development of site concepts on landscapes where a surplus of water drives the ecological functions. However, there is need for a method to define an individual site as a hydrologic element, which is part of a watershed complex. This method should conceptually link landscapes using the hydrologic processes that drive the import and export of water, sediment, nutrients, and other elements and compounds from headwaters to watershed outlets. Furthermore, this method should recognize the unique hydrodynamics that exist at the interface between uplands, wetlands, and floodplains. This method extrapolates these processes to the landscape level using hydrodynamic vectors, soil hydrodynamic and soil system concepts. The hydrodynamic vectors are determined with magnitude and direction in two dimensions using soil, landform, and land cover data at the pedon scale. The vectors are conceptualized in three dimensions at the landscape scale. Conceptual vectors are assigned using runoff, run-on, recharge, discharge, and storage.