Grössenvariabilität in einer Population von Pinus Silvestris

Abstract

Growth variation among individuals in a naturally established population of Pinus silvestris. — The aim of this study was to explain growth variation among individual trees in a population of Pinus silvestris near Zurich in terms of age, previous size, and local competition. This population developed when the drainage pattern in a bog was altered due to peat harvesting before the second world war. As part of a management plan to re-establish the natural bog vegetation, all the trees had been harvested and the original drainage patterns again been imposed. The locations of all trees were mapped. Individual growth in cross-sectional area was measured on disks from the base of each tree. Using a range of statistical methods, the following insights into the process of stand development in trees were gained. (1) Although the trees were randomly distributed over the area, a directional spatial pattern in biomass distribution related to the position of now invisible old drainage ditches was detected by two-dimensional spectral analysis. (2) In the absence of asymmetric competition (5 below) size variability decreased through the course of stand development. (3) Individual growth rates were significandy affected by age, size and local competition. Size was by far the most important factor. (4) Trees interacted with each other at least over distances of up to 5 m. (5) Competition was ‘symmetric’ in this population. Unlike other populations studied, larger trees did not have a disproportionate effect on smaller trees.