Development ofPinus sylvestrisMain Stems Following Three Different Precommercial Thinning Methods in a Mixed Stand

Abstract

Development of Pinus sylvestris main stems following three different precommercial thinning methods in a mixed stand. Reducing competition by point cleaning may be an attractive alternative to conventional precommercial thinning in forestry. In this study, survival and development of main stems of Scots pine (Pinus sylvestris L.) following point cleaning were examined in a mixed stand of mainly Scots pine and birch (Betula pendula Roth and Betula pubescens Ehrh.) in northern Sweden. Treatments studied were: no precommercial thinning, conventional precommercial thinning, point cleaning of all secondary stems, and point cleaning of only the secondary stems that were higher than the main stem, within a radius of 0.8 m from the main stem, respectively. A randomised complete block design with three replicates was used. Measurements taken 13 growing seasons after these treatments showed that conventional precommercial thinning was the best treatment for retaining Scots pines as main stems. However, conventional precommercial thinning resulted in the poorest timber quality of the remaining Scots pines in terms of stem taper, thickest branch diameter and relative live crown height. In conclusion, point cleaning has to be followed by a complementary cleaning operation if the objective is to retain Scots pines as main stems in such mixed stands.

Comparison of stem taper equations for eight major tree species in the Spanish Plateau

“…In terms of accuracy, the proposed models show that RMSE ranged from 0.75 to 2.72 depending on the species analyzed; a range that is similar to what has been reported in other softwood and hardwood studies. Taper functions for Scots pine have been widely studied in Spain (Diéguez-Aranda et al, 2006;Crecente-Campo et al, 2009) and Europe (Lappi, 1986;Petersson, 1999;Karlsson et al, 2002). All report small errors, similar to those obtained in this work Stem taper equations in the Spanish Plateau Table 4.…”

Cleaning methods in planted Scots pine stands in southern Finland: 4-year results on survival, growth and whipping damage of pines

“…The results are, however, preliminary and based on permanent plots that have been observed only during the first four years after their cleaning treatments. In the untreated plots the number of main pine stems decreased by 1-2% each year, while the mean height of the main pine stems increased from 1.5 to 5.0 m. According to Karlsson et al (2002), the average mortality of Scots pine main stems was even higher, i.e. 3-4% per year, when untreated plots were observed up to a mean height of 8 m. In addition to an increase in mortality, the proportion of serious whipping damage increased from 7% to 29% on the untreated plots observed in our experiments.…”

“…Räsänen et al 1985). There are, however, results that show that birch seedlings, when originated from seeds, can be used as supplementary trees in planted pine stands (Andersson 1993, Karlsson et al 2002, Valkonen and Ruuska 2003. On the contrary, birch sprouts growing faster than seed-origin ones (e.g.…”

“…According to the models developed by Valkonen and Ruuska (2003), the number of competing birch did not affect the height development of pine but, rather, the increased competition had a positive effect on the quality of pine stems in sapling stands at the height of 2-8 m. Stands with serious damage caused by birch were not included. Karlsson et al (2002) studied the development of Scots pine stands that were treated when the pines were about 2 m high. In the subsequent 13 years after total cleaning pines survived and maintained their dominant position better than after point-cleaning or topping.…”

“…On the other hand, the quality of the pine stems was poorer after total cleaning than after point-cleaning or topping. Karlsson et al (2002) also concluded that pointcleaning has to be followed by precommercial thinning.…”