Effects of Crown Expansion into Gaps on Evaluation of Disturbance Intensity in Northern Hardwood Forests

Crown encroachment by trees surrounding newly formed gaps reduces their size, a fact that may cause error in area-based analyses of rate of gap formation and disturbance intensity. Generally, an estimate of proportional area occupied by age classes within a stand of trees can be obtained by determining the age of a selected canopy tree nearby each of randomly or uniformly located sample points. Possible methods of selecting nearby canopy trees include: (1) the nearest-tree selection method, in which the canopy tree with its stem closest O the sample point is chosen; and (2) the overhead-crown selection method, in which the canopy tree whose crown is directly above the sample point is chosen. These two methods of selecting sample trees differ greatly in their sensitivity to crown encroachment. In sugar maple stands, the nearesttree selection method leads to better estimates of the area originally occupied by a cohort of trees. The overhead-crown selection method leads to an unbiased estimate of area currently occupied by a cohort. FOR. ScI. 34:(2):530-536. ADDITIONAL