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Provisional growth models for birch, alder, aspen and larch stands

100%

Bosiak P., Siekierski K., Zasada M.

Annals of Warsaw Agricultural University. Forestry and Wood Technology

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1996

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tom 47

13-20

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Zmiany zachodzące w drzewostanach Bieszczadów

84%

Dmyterko E., Bruchwald A.

Sylwan

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2018

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tom 162

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nr 05

The aim of the study was to analyse (on the basis of the data from the State Forests Information System) the changes occurring in the Bieszczady forests in the period of 2007−2016. One of the processes taking place in the study area is the withdrawal of grey alder stands and the appearance of natural regeneration of mainly beech and fir, and in a smaller proportion spruce (fig. 1). Another natural process is the encroachment of fir and beech under the canopy of pine stands, which is favoured by fertile habitats that meet the ecological requirements of these two tree species. As a result of economic activity supporting these processes, alder and pine stands are being rebuilt relatively quickly, turning into fir or beech stands, and sometimes into mixed stands with the participation of other tree species, including spruce (fig. 1). The decline of spruce stands occurs on the dominant area in Poland: in Beskid Śląski and Beskid Żywiecki, the Kaszuby Forest or the Białowieża Forest. The main causes of this process are abiotic and biotic factors, including frequent droughts causing the lowering of the groundwater level and insect outbreaks, especially of bark beetles. The proportion of spruce in the Bieszczady Mountains is relatively small (about 10%), and the high fertility of the habitats compensates, to some extent, the relatively high moisture requirements of this tree species and probably these factors determined the lack of decline of spruce stands in the analysed area. In the last 10 years, the average age of forests in the Bieszczady Mountains increased from 77 to 83 years (tab. 2), mainly as a result of too low volume of harvested timber (fig. 3). Comparing the total harvested volume with the volume of allowable cut determined by the stand growth model, the harvest of the wood raw material was understated by about 25%. The aging of forests is also confirmed by changes in stands in age classes (fig. 2). The aging of the Bieszczady forests is correlated with the process of increasing the threat to these forests by wind (figs. 4−5). The wind damage risk factor increased over the next 10 years in the two highest threat level, and thus the area of threatened stands increased. The forest threat measure in the Bieszczady forests increased in general as well as in individual forest districts (fig. 6). The forests in two of these districts are currently among the most threatened in Poland.

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Dynamika rozpadu drzewostanów świerkowych w Beskidzie Śląskim

59%

Dmyterko E., Bruchwald A.

Sylwan

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2018

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tom 162

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nr 03

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.

Ograniczanie wyników

2 Sylwan

1 Annals of Warsaw Agricultural University. Forestry and Wood Technology

2 Bruchwald A.

2 Dmyterko E.

1 Bosiak P.

1 Siekierski K.

1 Zasada M.

2 2018

1 1996

Provisional growth models for birch, alder, aspen and larch stands

Zmiany zachodzące w drzewostanach Bieszczadów

Dynamika rozpadu drzewostanów świerkowych w Beskidzie Śląskim