Natureserve Ecological Systems - California and Nevada

NatureServe and its natural heritage program members, have completed a working classification of terrestrial ecological systems in the conterminous United States, southern Alaska, and adjacent portions of Mexico and Canada. NatureServe has developed two, inter-related terrestrial classifications, the International Vegetation Classification (IVC), which provides a hierarchical ordering of vegetation around the globe, from broad formations or biomes to fine scale alliances and associations, and the International Terrestrial Ecological Systems Classification, which provides a single, mid-scale level unit suitable for classification and mapping of ecosystems at a scale relevant to many conservation and resource management applications. The IVC and Systems are linked at mid-scales based on the shared vegetation patterns, but Systems integrate associated abiotic factors and ecological processes that allow for alternative ecological arrangements of ecosystem patterns, and facilitates mapping. Together they provide valuable tools for inventory, monitoring and assessment.
Approximately 600 terrestrial ecological system units are described in a comprehensive classification for the lower 48 United States and adjacent Canada (Comer et al 2003). This number compares with some 1,800 alliances and over 6,000 associations in the same area.Download the complete publication, Ecological Systems of the United States.