Dependence of quality structure of Larix sibirica Led. trunks on plantation density in the Left-bank Forest-Steppe of Ukraine
Journal Title: Лісівництво і агролісомеліорація - Year 2014, Vol 125, Issue
Abstract
Introduction Larch is one of tree species introduced to Ukraine which is able to form stable, highly productive plantations due to its ecological and biological properties. The plantations accumulate phytomass quickly and produce wood of high quality. However, universally recognized single-tree assortment tables for larch have not been developed. The aim of the study is to analyze the merchantability of stands and assortment structure of Larix sibirica Led. sample trees in plantations of different growing conditions and to identify the factors having an influence upon the grade of forest products and main timber defects. Materials and methods We studied high-yielded uneven-aged cultures of larch grown in fresh oak and fairly fertile oak forest types in the Left-bank Forest-Steppe of Ukraine. The research methodology was based on comparative ecology methods, temporary sample plots establishment and analysis of sample trees trunks according to the generally recognized technique by M. P. Anuchin. Sample trees were selected on a proportional-gradual representation basis from average trees of largest and medium diameter classes (according to K. E. Nikitin’s technique) which were attributed to the Kraft classes I and II respectively. Assortment structure of samples’ trunks of each sample plot was determined by size-quality characteristics according to State Standard GOST 9463-88 "Softwood Round Timber". A grade of timber was evaluated based on the classification of wood defects (using State Standard GOST 2140-81). Results According to the studies, it was found that at the technical maturity age the larch stands are characterized by high merchantability classes. The cases of low merchantability of larch stands are the result of inconsistency between conditions of growing and biological and ecological characteristics of the breed. The results of investigations of length and merchantable part of trunk relative to its total volume indicate their increase with increasing age and site class and decreasing plantation density. The changes for assortment structure of the sample larch trees in log size and quality were examined by age, site class, and plantation density. It was found that medium-size log yield for 25-year-old plantations of site class I is 70.3–80.2 %; for 40 -year-old plantations it is 85.3 % at the density of 726 units on ha. The yield of large, medium and small logs was established for 60-year-old plantations. The yield of large diameter logs for the 100-year-old stands is 76.4 %; yield of medium ones is 21.4 %. Analysis of wood defects allowed the qualitative evaluation and sorting of timber. The most common defects were branch knots and crook. It was established that a diameter of knots has a critical impact on the grade of timber. Conclusions 1. Merchantability of Siberian larch stands in Left-bank Forest-Steppe of Ukraine ranges from 76 to 97 % in the number of merchantable trunks. The highest merchantability of larch plantations is achieved by taking into account the biological and ecological characteristics of the species and following appropriate conditions of forest growing. 2. When growing plantations, for 25-year-old trees of Kraft class II the optimal values of density and volume of the trunk are 1900 units on ha and 0,19 m3, respectively; for 40-year-old trees they are 1400 units on ha and 0.29 m3, respectively; for 60-year-old trees the optimal values are 860 units on ha and 0.68 m3, respectively. The determined dependence is repeated for trees of Kraft class I, and the trunk volumes are 30–40 % larger than for Kraft class II. 3. The share of timber in the trunk value of larch increases with age, site class, and Kraft class increasing, ranging from 77.4 % for the 40-year-old cultures to 86.6 % for the 60-year-old ones. 4. Round timber yield from merchantable trunks depends (in size) on age, site class and stand density. For 25-year-old sparse plantations, medium size log yield can be up to 80.2 %. For the 40-year-old plantations with a density of 726 and 1395 units on ha, medium size log yields are 85.3 and 81.7 %, respectively. The yield of large diameter logs for the 60-year-old stands having a density of 726 units on ha is 48.4 %; medium logs yield is 48.7 %. For the 100-year-old stands of I site class the large diameter logs yield is 76.1 %, medium logs yield is 21.4 %. The share of logs of large diameter increases with decreasing plantation density. 5. All the large diameter logs obtained from the butt fit the first grade; medium size timber corresponds to the first and second grades. A diameter of knots has a determinative impact on the grade of merchantable logs. 6. Identified relationship between plantation density and forest plantations growing conditions on one hand and qualitative indicators of merchantable wood in stands of different ages on the other should be used to create forest plantations of larch with specific parameters of the future stand.
Authors and Affiliations
V. Orlovsky
Keywords
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