Furthermore the selected 9 trees were taken as representatives of the 3 trees of their respective “dbh-LAI-class” (see Section 2.2). For example, the specific leaf area of the branch in the lowest crown section of sampled Tree 1 was taken for the entire lowest crown section of Tree 1, 2 and 3, since all these trees were in the same dbh-LAI-class. The leaf area of the kth sampled tree (LAk) was finally calculated by multiplying its specific leaf areas of the jth crown selleck inhibitor sections (SLAjk) and the according dry needle masses (dMNjk) and summing these products. equation(10)
LAk=∑j=13SLAjk⋅dMNjkIt is this estimate, to which we later on refer as “individual tree leaf area”. In the course of 3P-sampling, for three trees in one third of the crown no branch ZVADFMK fell into the 3P sample. Hence, for these trees the leaf area could not be calculated correctly in one crown third. For one pre-selected sample tree no sample of needles was collected. Therefore, for all three trees of the respective “dbh-LAI-class” no needle mass and leaf area could be calculated. Thus, finally there were 156 sample trees left for further analyses (Table 1). The dbh was measured with a diameter tape and the height with a Vertex IV (Haglöf, Sweden AB). The exact assessment of crown base, total height and crown length was performed on the felled trees with a measuring tape. To be able to calculate the crown projection area
(CPA) we used Field-Map® Version 8 (IFER, 2008) – a laser based tool for computer aided field data collection – to get coordinates of the tree positions and coordinates of 6–8 points (depending on the crown shape) of the crown
border of each tree. While Field-Map® also requires Beta adrenergic receptor kinase a person to visually determine the crown border, and therefore cannot help to increase the accuracy for the position of crown border points, it improves the overall accuracy for calculating the crown projection area. It allows recording more border points in the same time than conventional methods and therefore increasing the number of crown radii per tree which is much more essential for a precise calculation of the crown projection area than measuring a few radii with a high precision (Röhle and Huber, 1985). After collecting the data in the field we calculated the crown projection area using the quadratic mean of the recorded crown radii. For the crown surface area (CSA) we used the crown model described by Pretzsch (2001). This model assumes that the crown of Norway spruce consist of a cone above the maximum crown width, and a truncated cone between this maximum crown width and the base of the crown. The maximum crown width is assumed to occur at 33% of the crown length from below, and the crown width at the base of the crown is assumed to be half of the maximum crown width. From each of the felled sample trees, three disks were taken: one at breast height, one at three tenth of the tree height, and one at the base of the crown.
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