Descriptive statistics of tree crown condition in the North Central United States
The U.S. Forest Service Forest Inventory and Analysis (FIA) Program uses visual assessments of tree crown condition to monitor changes and trends in forest health. This report describes four crown condition indicators (crown dieback, crown density, foliage transparency, and sapling crown vigor) measured in Illinois, Indiana, Michigan, Minnesota, Missouri, and Wisconsin between 1996 and 1999. Descriptive statistics are presented by species and FIA species group. Inter- and intra-species variation, crown condition stressors, and statistical issues that should be considered when analyzing and interpreting the crown condition data are discussed.