Abstract

Viability Assessment of Ecological Communities Based on Species Area Requirements and Disturbance Scale In the Northern Appalachian Ecoregion

Mark G. Anderson
The Nature Conservancy
Boston, Massachusetts

The objective of this research was to design a conservation reserve system that included multiple viable examples of all ecological community types within one specific ecoregion - the Northern Appalachians. Toward this goal, we developed and defined a comprehensive list of the ecological communities in the ecoregion that, if appropriately protected, should serve as "coarse filters" for the conservation of associated species, ecological processes and evolutionary environments. Actual examples of each community were identified and each occurrence was required to meet specific viability criteria to qualify for inclusion in the reserve system. The viability criteria were designed relative to the natural size of the community in the ecoregion and were scaled to insure that each occurrence would be large enough to 1) contain at least 25 female territories of all associated species that breed in this community and 2) meet the minimum area requirements identified for any associated area-sensitive species. Additionally the occurrence had to be large enough to recover from characteristic disturbances. Adequate size was determined relative to the size of severe disturbances patches from catastrophic disturbance occurring over the last century. Lastly each occurrence had to meet an internal condition standard and a measure of landscape context. We assessed 1500 community occurrences in the region compiled from state Natural Heritage databases and an analysis of roadless areas. In total, 510 community occurrences (34%) met the viability criteria. These were distributed across 120 community types with 38 occurrences being large matrix-forming forest types and 482 being patch communities. Replicate viable occurrences were identified across biophysical subregions to increase the overall chances of each community persisting over time.