Estimating Understory Stem Density From Overstory Structural Characteristics
Final rept. Oct 1999-Jul 2000
ARMY TOPOGRAPHIC ENGINEERING CENTER ALEXANDRIA VA
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Current airborne imagery provides a fairly good mechanism for the measurement of such forest elements as tree crown diameter and tree height. The nature of the understory, however, can only be subjectively estimated by the analyst. Understory density and species composition can have an impact of such military activities as cross country mobility, cover and concealment, line-of-sight, and bivouac locations. This work involves the development of preliminary models to estimate understory stem densities through the use of measured overstory structural characteristics that can be derived by an image analyst. Over 4300 overstory and understory stems were measured at 56 sites at seven forested locations in central Virginia. Measured parameters included overstory and understory tree height, average crown diameter, diameter at breast height d.b.b, and species. Overstory tree locations within the plot distance and azimuth were computed and plot characteristics were gathered slope, aspect, ground cover, drainage, soils, etc.. Preliminary equations were developed using simple and multiple regression to estimate understory stem density from these selected overstory stem characteristics.