Crown ConditionThis article is part of a larger document. View the larger document here.
Photosynthetic capacity is dependent upon the size and condition of the tree crown. Trees with full, vigorous crowns are generally associated with more vigorous growth rates (Zarnoch and others 2004). Therefore, the Forest Service Forest Inventory and Analysis (FIA) Program measures a suite of crown condition indicators to evaluate forest health. Among the crown condition indicators are crown dieback and two measures of foliage abundance, crown density and foliage transparency. Crown density is the amount of crown biomass, i.e., branches, foliage, and reproductive structures, that blocks light visibility through the projected crown outline. Foliage transparency is the amount of skylight visible through the live, normally foliated portion of the crown, and crown dieback is the recent mortality of branches with fine twigs, which begins at the terminal portion of a branch and proceeds inward toward the trunk. All three variables are determined by means of ocular estimates to the nearest 5 percent.1 High levels of crown dieback indicate potentially serious declines in tree health, while low levels of crown density and high levels of transparency may indicate greater amounts of defoliation and signal that a tree may have a reduced capacity for growth.