THINNING AND CLIMATE EFFECTS ON GROWTH OF BEECH (FAGUS-SYLVATICA L) IN EXPERIMENTAL STANDS

The most recent thinning in a beech trial provided a sample of trees that were analysed for past basal area growth, using ring measurements. The study covered 24 years in which there were four between-thinning periods of 6 years, and concerned two thinning intensities. Thinning and climate effects on yearly basal area increment of trees were considered. The only influential climatic factor appeared to be precipitation in the current growing season. The analysis of the data resulted in a differential equation, including climatic terms, that could be used to predict tree basal area growth. The integration of this equation, for fixed climatic conditions, gave the evolution of tree basal area growth over the observation period of 24 years for the thinning treatments considered, without most of the erratic effects caused by climate. The thinning effects were then investigated with this simulated basal area trajectory, and could be related to stand and thinning characteristics.