Correction for slope in point and transect relascope sampling of downed coarse woody debris.
In this article, the effect of sloping terrain on estimates in point and transect relascope sampling (PRS and TRS, respectively) is studied. With these inventory methods, a wide angle relascope is used either from sample points (PRS) or along survey lines (TRS). Characteristics associated with line-shaped objects on the ground are assessed, e.g., the length or volume of downed logs. In their basic forms, the methods only work in flat terrain, and thus bias is incurred under sloping conditions. Two different possibilities to correct for bias due to slope are presented. The first one involves using a slightly modified relascope device and making a measurement of the angle of inclination of each sampled object. The second involves applying correction factors based on the steepness of the terrain in the area surveyed. However, it is shown that moderate slopes cause only limited bias and in such cases there is little need to adjust the measurement procedures or apply correction factors.
Society of American Foresters
Ståhl, G., Ringvall, A., Gove, J.H., Ducey, M.J. Correction for slope in point and transect relascope sampling of downed coarse woody debris. (2002) Forest Science, 48 (1), pp. 85-92.