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| ŠUMARSKI LIST 13/2005 str. 154 <-- 154 --> PDF |
S. Kucbel: TI Ili STRUCTURE AND NATURAL REGENERATION OF A SUBALP1NF. SPRUCE FOREST ... Šumarski list- SUPLEMFNT (2005). 144-153 The analyses of natural regeneration was conducted cies and height classes (up to 20 cm, 21-50 cm, 51-80 on the transect. All individuals according to tree spe- cm, 81-130 cm, from 131 cm to dbh 1 cm) were noted. RESULTS Stand structure The values of basic dendrometric traits on particular research plots are summarized in Table 1. On the basis of the obtained diameter frequencies and regarding other stand characteristics it is possible to consider the stem number of 1,000-1,500 ha"1 as sufficient (all living individuals with dbh over 1 cm). If only the large timber is taken into consideration (individuals with dbh over 7 cm), the stem number should range from 500 to 1,000 ha"´. The stem numbers with less than 500 ha"1 can be one of the indicators of an unstable homogenous structure or of the presence of wider parts without continuous forest stand. Diameter distribution curves are one of the basic characteristics of a stand structure (Fig. 1). On every observed research plot the distribution curve has more or less distinctly decreasing shape, which is typical for a differentiated structure (very close to a selection forest structure). Some visible differences between particular research plots follow from the figures. Although the distribution on the PRP 1 has a decreasing shape, there is a quite high stem number in higher diameter classes (trees of the upper layer). The regulation of the structure should head to the reduction of the upper layer individuals in favour of the trees from middle and lower layer. The diameter distribution on the PRP 2 is approximating the required model at most. The individuals from the lower layer (diameter classes 2 and 4 cm) arc moderately deficient. The PRP 3 is covered with the youngest stand. A part of the plot is in the growth phase of thicket and small pole-stage stand. This homogenous part represents an unstable element which requires a silvicultural measure. The intervention should reduce the stem number and differentiate the stand. According to obtained data the basal area should range from 35 to 40 m2 ha 1 by the given structure. The growing stock has quite different values on particular research plots (from 268.43 m3 ha 1 to 444.22 m ha 1). Considering the stand structure as well as the influence of outliers (e.g. one stem with dbh of 88 cm on PRP 1 increases the total growing stock for more than 80 m3 ha"1) it is possible to propose the optimum growing stock on the level from 300 to 400 m3 ha"´, according to the production conditions of the site. The defoliation grade ranges under 10 % on all plots and on the basis of this characteristic the stands can be evaluated as vital and healthy. The analysis of tree frequencies according to the layers shows that approximately 3/4 of all individuals are concentrated in the lower layer, whilst other 25 % are divided by different ratio into middle and upper layer. After the evaluation of stand structure on particular plots the most appropriate ratio of the layers seems to be the model: 75 % lower layer, 15 % middle layer and 10 % upper layer. The model concerns the ratio according to the stem number, in the case of area ratio each layer should take roughly the same area (i.e. 1/3 of the stand area). Coarse woody debris (CWD) is an important component of a high-elevation forest especially from the viewpoint of its regeneration processes. Table 2 sums up the results of the stand volume divided according to vital, standing and lying dead trees. The volume of lying deadwood ranges from 43.56 m3 ha"´ on PRP 2 to 71.67 m3 ha"1 on PRP 1 in absolute values. Besides the total amount of CWD the ratio between particular grades of decomposition is important, above all the volume of CWD in the 2nd and 3rd grade of decomposition, because only the logs in this state provide appropriate conditions for the development of natural regeneration. From this point of view the best conditions are on the PRP 1 where almost all CWD is at least partly rotted and creates a convenient seedbed for spruce seedlings. From given data it is difficult to quantify the sufficient amount of CWD but it is possible to say the worse are the conditions for the natural regeneration in the stand, the higher should be the amount of CWD. The distribution of the whole biomass on the observed plots is following: approximately 80-85 % fall on vital trees, the rest is divided in ratio 1:2 between standing and lying deadwood. Different situation is only on PRP 3, where a quite high number of standing deadwood has been observed. REGENERATION PROCESSES Two tree species are present in the natural regeneration on all research plots - Norway spruce {Picea abies IL.I Karst.) and rowan (Sorbus aucuparia L.). Although the tables 3 and 4 show also the total number of individuals (spruce + rowan), this values as well as the comparison of the numbers according to the tree species have only an orientation meaning. The first reason is, that although rowan is an important and permanent |