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nr 09
31-45
EN
The dynamics of decline of Norway spruce forests in the Beskid Śląski Mts. (S Poland) in a 2007−2016 period was analysed based on data from the State Forests Information System. For that purpose we used modified growth model and wind damage risk model. The harvested timber volume (salvage cuts) exceeded the allowable harvest modeled with the stand growth model by 270% in years 2007−2010 (earlier period) and by 89% in the 2011−2016 (later period) period. The highest volume exceed (503 and 307% for earlier and later period respectively) was recorded for the Wisła Forest District. For the deadwood, the harvested volume exceeded the modeled one by 45% (162 in earlier, and 59% in later period). In the Węgierska Górka Forest District the harvested volume amounted to 287% of the modeled one (438 in earlier, and 70% in later period). The largest amount of wind−broken and wind−fallen trees was found in Wisła. Their volume amounted to 48% of the modeled volume (59 in earlier, and 40% in later period). The highest exceed occurred in Węgierska Górka (89 and 70% in the later period respectively). The species composition in the analysed region changed significantly as the share of spruce decreased and share of beech and fir increased (tab. 1). Changes in the aeral fraction of stands in age classes in the Bielsko and Ustroń forest districts were insignificant (tab. 2). For Węgierska Górka, share of stands in age class <20 years increased from 11 to 40%, while the older stands fraction decreased. Major changes occurred in Węgierska Górka and Wisła as far as structure of the stands in the risk damage factor classes is concerned. Fraction for the risk factor classes I and II increased, while for class VI decreased (tab. 3, fig. 4). The highest dynamics of the wind threat measure was recorded especially in Węgierska Górka, where its value decreased from 42 in 2009 to 19 in 2016 (fig. 5). The biggest changes are likely to occur in Wisła in the next years due to the very high fraction of spruce. A significant damage caused by wind may also be expected in Ustroń, where the threat measure is high.
EN
On the basis of the wind damage risk model for forests using the data of the State Forests Information System, the stand damage risk factor Wr for each of the 430 forest districts in Poland and the threat measure Ms for a given forest district were determined. The measure of threat to forest Ms for a forest district is a methodical basis for assessing the potential damage to forests in Poland. Its value ranges from 8.1% for the Brzózka Forest District to 48.9% for the Ujsoły Forest District (fig. 1), giving the average value of 24.6% and standard deviation of 7.03%. The measure Ms was the basis for differentiating the levels of threat of wind damage to forest for forest districts. Level 1 (Ms 10%) indicates low threat, level 2 (10%Ms 20%) – elevated threat, level 3 (20%Ms 30%) – moderate threat, level 4 (30%Ms 40%) – high threat, level 5 (Ms 40%) – very high threat. Low threat to forests was found only in two forest districts located in the western part of the country. 113 forest districts, which form large concentrations particularly in western and central Poland, are exposed to an elevated threat. Most forest districts (233) are classified to a group of moderate threat. They are located across the country and are mostly concentrated in the northern and southern regions of Poland. 71 forest districts exposed to high threat are concentrated in the south of Poland in the Carpathians and the Sudetes, with scattered presence in the north of the country. Most of the 11 forest districts with a very high threat to forests are located in the mountains (tab., fig. 1). For the forest districts with a particularly high and very high threat, new silvicultural procedures and the basis for decision making in the field of forest management should be developed to reduce the risk of damage to forest.
EN
In Polish forest management planning, the species composition of stands in a forest district is established by adding up the volumes of tree species from individual forest stands. These volumes are calculated according to the estimated share of species cover and the estimated volume of the entire forest stand. The species structure of stands in a forest district, established on the basis of such a method, may be different than that obtained from sample plots. The aim of the study was to compare three ways of determining the tree species structure of stands in a forest district. In Method 1, the species composition was estimated on the basis of the volume of trees measured on sample plots as part of a periodic forest inventory based on stratified sampling. The same data were used in Method 2, but the share of species was calculated on the basis of the basal area. In Method 3, the species structure was estimated according to the volume of trees estimated in each forest stand based on the cover of a given species. The empirical material was collected in 53 forest districts. In method 1 and 2, data from an average of 740 sample plots within the forest district were used. In Method 3, data from the forest stand descriptions contained in the database of the State Forests Information System were used. For each forest district, species composition was calculated, including 6 tree species and 8 groups of tree species. For all forest districts, the average shares of individual species and groups of species differed, depending on the applied method (tab. 1). In case of methods 1 and 2, the biggest difference was found for pine – the most numerous species – but it was also big for less numerous ones: birch and oak (tab. 2). In case of methods 1 and 3, the biggest difference in share was also found for pine (tab. 3). The greater the species diversity of a forest district (determined according to Simpson’s index of diversity), the greater was the average difference in the estimated share of an individual species (figs. 1 and 2). The method of determining the species structure in a forest district used in forest management practice nowadays was considered insufficient. It was proposed to establish it in larger units (subclass, age class, forest district) only according to the volume of trees measured on the sample plots (without rounding and ‘switching’ of species), using the stratified sampling method.
EN
The paper presents the dendrochronological analysis of silver firs (Abies alba Mill.) growing in the canopy layer of the forest stands. We searched for the similarities in the rhythm of radial growth of studied trees and we analysed the response of these stands to the increment disturbances related to the occurrence of adverse climatic factors and the pressure from industrial pollution. The research material was collected in 30 pure and uneven−aged silver fir stands located in the Świetokrzyskie Mountains (central Poland). We investigated the effect of age of the stands and the conditions for their growth (location, forest habitat type) on an average tree−ring width. In order to detect similarities in the rhythm of radial growth of the surveyed stands, we grouped the raw chronologies by the means of the cluster analysis, using Ward's agglomeration procedure with 1−r distance (r – Pearson correlation coefficient). We assessed the incremental response of the investigated stands to the disturbances (situations of significantly reduced radial growth) using indicators of resistance, recovery and resilience proposed by Lloret et al. [2011]. We also studied the influence of the stand age and the forest habitat type on the response of analysed for stands to the detected disturbances. The shortest chronology consisted of 94 tree−rings, while the longest one of 137. Average length of the obtained silver fir chronologies was 119 years. Older fir stands characterised with narrower rings (r=–0.451, p=0.012). Neither the location, nor the forest habitat type are the factors determining the similarity of the rhythm of radial growth of silver firs from the Świętokrzyskie Mountains (p=0.243 and p=0.967 respectively). The extreme climatic conditions responsible for the majority of the short−term (one−year−long) incremental depressions are the factor of regional importance, which affects the growth of investigated trees. Older stands characterized with better possibilities of increment recovery after the disturbance than younger stands (p<0.001), which may be a result of the production of secondary crowns. No consistent differences in the indices of resistance and resilience were found among analysed stands.
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