Improvement of biological stability of young spruce stands by tending felling
Journal Title: Лісівництво і агролісомеліорація - Year 2014, Vol 125, Issue
Abstract
Introduction In Novgorod-Siverskiy Polissya (Ukraine), Norway spruce growing on the southern edge of its range and has a high growth rate and a rapid accumulation of stem wood. However, due to the forestry and ecology properties of this breed spruce plantations have low biological resistance to summer heat, air and ground drought. An acute problem of mass die-back of spruce stands arose after abnormal drought in 2010. Due to the sudden changes of the hydrothermal regime, there was a decline of biological stability, worsening of sanitation conditions and weakening and dying of middle- and old-aged spruce stands. Young stands preserved biological stability. The aim of this work was to study the dynamics of the sanitation condition of young spruce stands as well as their re-formation into stable mixed deciduous-coniferous plantations through tending felling. Materials and Methods The research was conducted in artificial spruce stands, which grow in fresh and moist fairly fertile site types in Novgorod-Siverskiy Polissya. Permanent sample plots (PPP) were laid out using generally accepted techniques and in accordance with the regulatory documents. Normative reference materials were used for stands’ parameters calculating. Stand condition was determined by the sanitary condition of the trees and by indicators of mortality. The sanitary condition of each tree was determined according to “Sanitary rules in forests of Ukraine”. Features of trees mortality were characterized by levels of absolute mortality, relative mortality and mortality gradient. Results and Discussion Young stands of Norway spruce in Novgorod-Siverskiy Polissya (Ukraine) grow well, are biologically stable and have high resistant properties to counteract the unfavorable weather and climatic factors. Along with the phenomenon of mass dying of middle-aged and older spruce occurring in the region, young stands, constituting 47.9% of the total spruce Novgorod-Siverskiy Woodlands, preserved biological stability. Tending felling in spruce stands in moist conditions in fairly fertile site types in Novgorod-Siverskiy Polissya should be aimed to the re-formation of pure spruce stands into mixed ones, which are more effectively resistant to the negative environmental factors. During thinning, in mixed spruce stands the share of other species could be enhanced up to 6 units and Norway spruce could form the second storey. First cleaning and weeding are carried out only for viable pine and oak trees using biogroup method. Secondary wood species and Norway spruce trees exceeding the height of pine and oak trees are assigned to logging. Tending based on this principle reduces the growth of Norway spruce trees in height and promote the formation of mixed stands. Tending a Norway spruce begins after the age of 20. During thinning, tending to the pine and oak trees could be continued as well as to other viable broad-leaved trees of natural origin, which shading by spruce trees. Thinning is carried out in dense rows and biogroups of Norway spruce, leaving mostly larger Norway spruce trees with the best form of stem and well-developed symmetrical acute crowns. Stand density has reduced less than 0,8. Conclusions Young stands of Norway spruce in Novgorod-Siverskiy Polissya (Ukraine) grow well, are biologically stable and have high resistant properties to summer heat, air and ground drought. Weakened by extreme drought, young stands of class II in fresh and moist fairly fertile site types restore sanitation conditions after termination of negative factors of the environment. In young cultures of Norway spruce with economically valuable species (natural and artificial) contained in the structure, during tending felling it is necessary to form mixed deciduous-coniferous stands. Due to the risk of shrinkage caused by sudden fluctuations in climate indicators the share of Norway spruce in stand composition should not exceed 40–50 % of growing stock for each age class before maturity.
Authors and Affiliations
I. Porohnyach
Keywords
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