From plant communities to landscapes in conservation inventories: A look at the nature conservancy (USA)

Abstract

The Nature Conservancy (TNC—USA) has developed an efficient system for inventory and evaluation of ‘elements-of-diversity’. The major components of this system are a ‘fine filter’ for species inventory and a ‘coarse filter’ for community-type inventory. As in traditional vegetation science, community sampling and classification are restricted to relatively homogeneous stands and avoid edges, ecotones, and disturbed areas. TNC employs a habitat-based system of natural communities to complement plant community classification. This system is used to identify stands that cumulatively encompass the full range of variation within each defined natural community type. Ecological relationships among community-types in real landscapes, however, are not accounted for. This paper reviews some important ecological functions of heterogeneous landscapes, which are not necessarily protected by conservation strategies that focus on separate, homogeneous community-types. Recommendations to expand TNC's coarse filter to landscapes include: (1) Disturbance regime and regeneration patterns should be evaluated for each major community-type, and for each site representing a type or group of types; (2) Functional combinations of community-types and developmental stages (landscape mosaics) should be addressed in the TNC system; (3) Landscape context (e.g., surrounding habitat types and connectivity) for a site is as important as the habitat content (e.g., the rarity or quality of community-types present). Attention to landscape-level patterns and processes will be helful for evaluating large sites that are composed of many community-types, and in setting selection and stewardship priorities for sites for any size that are surrounded by dissimilar habitat.