Virginia, 2009 forest inventory and analysis factsheet
This science update is a brief look at some of the basic metrics that describe forest resources in Virginia. Estimates presented here are for the measurement year 2009. Information for the factsheet is updated by means of the Forest Inventory and Analysis (FIA) annualized sample design. Virginia has about 4,600 sample plots across the State, and each year 20 percent of these plots (one panel) are visited and measured by field crews, the data compiled, and new estimates produced. Users should keep in mind that in each year of new estimates, only 20 percent of the data are new, with the older data making up the remaining 80 percent of the sample. This may result in some spikes in estimates when comparing successive survey years but in most instances the annualized design should give a reasonable indication of directional trends in the resource, such as increasing, decreasing, or no change. After 5 years of measurements, the full sample complement (a cycle) is complete and a new survey cycle begins. The strongest and most reliable trend information (especially that concerning magnitude of change) comes from comparing two full cycles of data.