The Influence of Spatial Disposition of Neighbours on the Diameter Growth of Individual Trees

Wien

1980

S. 209-219

3 Abb., 14 Lit. Ang.

Unselbständiges Werk

200032112

The spatial disposition, of the immediate neighbours of a subject tree, is examined, for its influence on the diameter growth of the subject tree. The immediate neighbours, vis-a-vis any particular tree, are defined as those that form the "competitor polygon". The latter is assumed to be formed by the trees that contribute to the sides of a Theissen polygon defining Brown's APA (area potentially available) around the subject tree. The spatial orientation of the neighbours affects the shape of the "competitor polygon" as well as the point or focal density around the subject tree. The eccircularity and abcentricity of the "competitor polygon" are used as shape determinants. An unbiased estimator of focal density of any parameter is proposed. It is shown that focal density changes with the shape of the "competitor polygon", which is determined by the spatial orientation of individuals around the subject tree. Also for the same shape of the "competitor polygon" the actual disposition of tree sizes can substantially alter the estimates of focal density. As diameter growth is often influenced, inter alia, by focal or point basal area, it is seen that spatial disposition of individuals could have an important bearing on the diameter growth of the subject tree. Case studies are presented for plantation grown and natural stands. The indications are that shape determinants per se may not be so important as measures of focal density. The latter however is shape dependent. A Teletop coupled with a Karti plotter (both instruments - Carl Zeiss, Jena) was used to plot the spatial distribution of trees.