Effects of heavy thinnings on the increment and selection of trees for tending in Norway spruce monoculture in natural hazard conditions

Martin Bobinac,Sinisa Andrasev,Nikola Susic,Andrijana Bauer-Zivkovic

doi:10.2298/gsf1715031b

Abstract

The paper studies the effects of two heavy selection thinnings on the increment of Norway spruce trees exposed to ice and snow breaks in eastern Serbia. In a thinning that was carried out at 32 years of age, 556 candidates per hectare were selected for tending, and at the age of 40, of the initial candidates, 311 trees per hectare (55.9%) were selected as future trees. In all trees at 41-50 age period, diameter increment was higher by 31%, basal area increment by 64% and volume increment by 67% compared to 32-40 age period. The collective of indifferent trees is significantly falling behind compared to future trees in terms of increment values in both observed periods. However, the value of diameter, basal area and volume increments, of the collective of "comparable" indifferent trees are lower in comparison to the values of increments of future trees by 10-15% in the 32-40 age period, and by 15-21% in the 41-50 age period and there are no significant differences. The results show that heavy selective thinnings, initially directed at a larger number of candidates for tending at stand age that does not differ much from the period of carrying out first "commercial" thinnings, improve the growth potential of future and indifferent trees, where it is rational to do the tree replacement for the final crop in "susceptible" growth stage to snow and ice breaks.

Highlights

In Serbia excluding Kosovo, Norway spruce cultures have been established on an area of 32,400 ha, i.e. 26.0% of the total area covered by conifer cultures (Banković et al, 2009)
The results show that heavy selective thinnings, initially directed at a larger number of candidates for tending at stand age that does not differ much from the period of carrying out first ‘’commercial’’ thinnings, improve the growth potential of future and indifferent trees, where it is rational to do the tree replacement for the final crop in,susceptible’’ growth stage to snow and ice breaks

Summary

Introduction

In Serbia excluding Kosovo, Norway spruce cultures have been established on an area of 32,400 ha, i.e. 26.0% of the total area covered by conifer cultures (Banković et al, 2009). The first thinnings were usually carried out at the age when economically viable assortments were most likely to be obtained. Such a trend has been a characteristic of other conifer cultures in Serbia and throughout Europe because late crown thinnings provide higher and more valuable cutting yields in the observed growth stage (Slodičák et al, 2005). Thinning approaches to spruce cultures in Serbia have been studied by a number of authors These studies were mostly based on the analysis of the structure of untended stands or on the research results of initial state in experimental plots (Marković, Petrović, 1960; Vučković et al, 1990; Dražić, 1994; Bjelanović, Vukin, 2010). The effects of two heavy thinnings on the increment and stability of Norway spruce trees and stand have been treated on one permanent experimental plot in eastern Serbia (Bobinac, 2004)

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