Intensive management of Scots pine stands in southern Finland:: First empirical results and simulated further development

The growth and yield responses to management practices of different intensities were studied in five Scots pine (Pinus sylvestris L.) thinning experiments 8-10 years after the treatment. In the first commercial thinning, the plots were thinned to densities of 400, 600 and 1200 stems ha(-1) with or without nitrogen fertilisation and pruning. In order to assess the long-term growth responses, the development of the plots was simulated with growth and yield models up until the end of rotation. During the 8-10-year growth period after the treatment, intensive thinning (600 stems ha(-1)) decreased the annual volume increment per unit area by 34%, but the fertilisation treatment compensated for a considerable part of this reduction. The intensive thinning combined with fertilisation increased the diameter increment of the remaining stems, and the volume of log-sized trees increased by 28% compared with the unfertilised plots with the density of 1200 stems ha(-1). This corresponds to a development benefit of 4-5 years. The proportion of damaged trees was not affected by the treatments. Thinning increased stem taper and decreased slenderness, but fertilisation had no effect on stem form. According to the simulation results, intensive management can shorten the rotation by ca. 15 years, without notable losses in mean annual increment. Intensive management enables a shorter rotation period, but the final advantages and disadvantages cannot be assessed until the final felling. (c) 2005 Elsevier B.V. All rights reserved.