DIGITALNA ARHIVA ŠUMARSKOG LISTA
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relatively to developed boundary line (Fig.3). A total number of 124 growth pulses met the criterion "above the 20 % of the boundary line" and could be qualified as growth releases caused by canopy disturbance, 37 of these events were identified as a major release and 87 as a moderate intensity release. After the inspection of early growth rates we identified 22 sampled trees as the gap recruited (47 %). For the rest of individuals, we stated the canopy accession dates according to the occurrence and intensity of the first growth release. We paid special attention to the age when the tree entered the canopy. The analysis revealed that 34 % of trees reached the canopy position during the first 50 years of their live, almost 9 % entered the canopy in age from 50 to 100 years and 17 % of trees accessed the canopy after the 100 years of suppression (Fig.4).
The disturbance chronology is displayed in Figure 5. Disturbance events were recorded in every decade, however, we recognized three significant disturbance peaks during the inspected period. The first one occurred in 1860−1880, where the 18 % of trees showed major release and 21 % moderate release. Second period of disturbance activity occurs in 1920−1940 with the overall maximum in 1930. Major release was indicated for 10 % of trees, while 15 % of trees showed the moderate release. Third distinctive peak was recognized in 1980−2000 (Fig. 6).
The evaluation of age structure of cored trees revealed high age diversity of investigated forest. No remnants of understory trees were observed during the sample collection in studied area. Therefore it is very likely the diameter and height structure of stand was distinctively uniform. Similar character of stand structure in this locality was described by Kucbel (2000a). Author stated the homogenized structure for six of total number of eight permanent research plots. Moreover, approximately 90 years ago, the stand characteristic written in forest management plan (1920−1930) described this locality as the open canopy homogenous mature spruce stands with rather high number of snags. Nagel et al. (2007) found the examination of forest developmental stages by means of the biometric measures of diameter and height as a quite difficult, because of a weak relationship between the real tree age and its diameter. Our finding can only confirm this statement ("diameter – age" relationship R2=0.49).
High age variability points on the continuous tree regeneration. Evaluation of recruitment dates shows three distinctive waves of tree recruitment in 1800−1830, 1860 and 1910−1930.
Almost 50 % of inspected trees showed the early growth patterns referring to the open area growth. For the analysis we used the threshold value suggested by Svoboda et al. (2012). In our opinion, the number of trees that met the "gap recruited" criterion in the Veľký Bok site is