Abstract
Background and Objectives: The study aimed to determine the changes of the main stem and branch parameters of Norway spruce (Picea abies (L.) H. Karst) trees under different stand densities. More specifically, the objective was to develop the models for the determination of branch diameter in 0–6 m log from root collar, taken as one of the parameters directly influencing the stem quality. The study continues a piece of research on stem and branch parameters’ responses to different stand density (SD) in the plantations of coniferous tree species in Lithuania. Materials and Methods: The following key parameters were measured in this study: total tree height, diameter at breast height, height to the lowest live branch, height to the lowest dead branch, and diameter of all branches in 0–6 m log. The linear regression models to predict branch diameter in 0–6 m log were developed based on stand density (SD), tree characteristics (tree diameter at breast height, DBH; and tree height, H) and other related stem and branch parameters. Results and Conclusions: Directly measured tree DBH, branch diameters and number of branches in 0–6 m log decreased significantly with the increasing SD. In the 0–6 m log, the branch diameter and the diameter of the thickest branch were identified as the main parameters related to stem quality. The best fitted models, developed including SD, tree DBH, branch diameter, and diameter of the thickest branch in 0–3 m log, can be proposed as a predictor for stem-wood quality for Norway spruce in hemiboreal forest zone.
Highlights
The growth of trees with high-quality stemwood depends on tree genetics, environmental factors, and applied forest management methods [1,2,3,4]
The results of the present study showed that the basic branch parameters, including the number of branches in 0–6 m log (Nbr0-6 ), the mean branch diameters in the 0–6, 0–3, and 3–6 m log (Dbr3-6 ), differed significantly between the highest and lowest stand density (SD), and some similarities were only recorded in the adjacent SDs
The results of the present study showed moderate to strong correlations between tree diameter at breast height (DBH) and branch parameters; moderately strong correlations were obtained between SD and branch diameters (Dbr0-6, Dbr0-3 and Dbr3-6 ) but weak correlation was found between SD and Nbr0-6
Summary
The growth of trees with high-quality stemwood depends on tree genetics, environmental factors, and applied forest management methods [1,2,3,4]. The following measures are often preferred: improved regeneration material (seedlings), fertilization, selection of sitespecific regeneration methods, different intensities of intermediate cuttings, etc. The optimal environmental conditions, appropriate silvicultural techniques and harvesting regime provide the basis for the growth of good quality wood [2,9]. It is well known that intermediate cuttings improve the growth of the remaining trees. The development of the good quality stem-wood requires a complex knowledge on past management practices, soil fertility and moisture regimes, and climatic parameters, etc. Relatively large variations in stem-wood quality of Scots pine are found in the sites of medium soil fertility [10]. The codominant trees with narrow crowns and thin branches develop the stems of better quality
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