Abstract
A digitized aerial panchromatic photo of a thinning experiment in pure even-aged Norway spruce (Piceaabies (L.) Karst.) is smoothed by a two-dimensional isotropic Gaussian kernel. The number of stems per hectare is estimated from the number of maxima above a certain level of the smoothed image. For the crucial kernel bandwidth estimation problem we suggest a two-step procedure where the first step consists of computing (for each homogeneous stand (or subplot)) an "internal curve" corresponding to the number of maxima at a series of bandwidths. The estimated stem number and the optimal bandwidth is then obtained as the crossing of the internal curve with an "external curve," here assumed to be of a simple parametric form. If a series of stands (or subplots) with different known stem numbers is available, the external curve can be estimated by use of a nonlinear regression method. An experiment with 48-year-old trees and six subplots with varying thinning treatments is analyzed. The stem number estimation method, checked by cross validation, performs satisfactorily for all thinning grades except the unthinned control.
Publisher
Canadian Science Publishing
Subject
Ecology,Forestry,Global and Planetary Change
Cited by
108 articles.
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