Forest Inventory and Analysis Database of the United States of America (FIA)
Extensive vegetation inventories established with a probabilistic design are an indispensable tool in describing distributions of species and community types and detecting changes in composition in response to climate or other drivers. The Forest Inventory and Analysis Program measures vegetation in permanent plots on forested lands across the United States of America (GIVD ID NA-US-001). Plot sizes and protocols for measuring tree species are standardized across the country. Additional standardized protocols have been implemented to measure the abundance of non-tree vascular plant and epiphytic lichen species. Research using this and re-lated regional datasets have provided new insights into the key biophysical drivers of community composition and their importance at different spatial scales. Studies have also explored regional differences in species diversity patterns, documented the importance of non-native species, and described the importance of environment and management on the distribution of selected species. Although representation of locally rare community types may be low, the probabilistic sample ensures that ecological drivers are regionally sig-nificant and that results are representative of a region as a whole. Remeasurement of permanent plots provides direct evidence of vege-tation change and enables detection of impacts due to climate, natural disturbance, and forest management.