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Scots pine is the most common tree species in Poland with the share in the species structure of Polish forests exceeding 58%. The most dangerous pathogen of this species is Phellinus pini (Brot.) Pilát), which causes the white pocket rot (also called red ring rot) of pine heartwood. It is estimated that as a result of the fungus’s activity, about 8% of annually harvested pine stems is damaged and worthless. As the Ph. pini damages only heartwood, it is often recognized that its occurrence has no influence on the tree’s physiology. As it is still unknown whether the presence of this fungus also does not affect the cambium responsible for the radial growth. We carried out studies in Scots pine stands located in the Radziwiłłów Forest District (central Poland). We investigated trees from 5th and 7th age classes (Biała Góra and Budy Stare forests, respectively). A total of 60 trees were sampled (30 per site). Half of them were specimens showing advanced symptoms of sickness, while the others were healthy specimens with no evidence of infection. From each tree we took one increment core and measured the tree−ring widths. Average tree−ring width was in case of healthy trees significantly higher than for sick trees. The research showed a significant, even of a dozen percent, reduction in the annual increment of infected trees in relation to healthy trees growing on the same site. Presumably, unidentified chemicals secreted to the cambium by the growing mycelium of Ph. pini may be responsible for this. It also seems that this relationship is progressing with the growing age of tree stands and is particularly visible in old stands, for example in reserves. Thus, Ph. pini could be one of the factors limiting the natural age of pine trees and accelerating their dieback. We also found that the growth of trees affected by the disease is influenced by a factor other than climatic, disturbing the natural rhythm of their radial increments. This factor is most likely the presence of mycelium of Ph. pini in the wood.
In homogeneous climate conditions Scots pine trees at different sites have similar short−term incremental rhythm. It was determined by the temperature of early spring and precipitation in June. Differences in the growth pattern are caused by various sensitivities of pines from different habitats to the temperature in May and precipitation in February and April of the current year.
The intermediate cuttings have an important impact on the stand structure and productivity. Choosing the right method of the treatment performance is the decision, which is fundamental in shaping tree stands stability. The radial increment, apart from the natural growth potential of particular species, is influenced by many abiotic, biotic and anthropogenic factors, among which one can distinguish those that influence it directly, e.g. thinning. The study objective was to determine the effect of silvicultural treatments on the increment reaction of oak (Quercus sp.) stands in the Międzyrzec Forest District (eastern Poland). The empirical material was collected in six forest stands located in the Witoroż forest range. In each stand we cored 10 dominant and co−dominant trees (representing 1st and 2(sup)nd Kraft’s biosocial classes). After the measurements of the tree−ring widths and the synchronization of incremental series, the raw and standard chronologies were elaborated for each stand. In total, we analysed 8 treatments: six early and one late selection thinnings, and one late salvage thinning (tab. 1). For each treatment, three− and five−years’ value of mean tree−ring width was calculated for the period before and after the cut. Additionally, we calculated the incremental response parameters: recovery (Rc), resilience (Rs) and resistance (Rt) indices. For the majority of the analysed treatments, the cuts resulted in an increase in average tree−ring width both in the 3−, and 5−years perspective. However, statistically significant changes in this parameter occurred only in a few cases (fig. 2). The average values of incremental response indicators show that the investigated oak stands are characterized by a significant adaptive capacity and a rapid recovery of incremental capacity in the analysed time spans. At the same time, the low values of Rt index suggest that their growth resistance to disturbance caused by the thinning is rather low. The age of the stand at the time of the treatment significantly affected the incremental response parameters of the examined oaks. The older the stand, the incremental response was less intense.
The aim of the study was to determine the effect of small forest water reservoirs on the radial increment of Scots pine and Norway spruce. We selected four small water reservoirs that were reconstructed in autumn 2006 in the Maskulińskie Forest District (northern Poland). Around each reservoir we placed transects according to the cardinal directions. At those transects we set up 10×10 m sample plots at different distances from the edge of the water reservoirs. On the each sample plot we made simplified phytosociological releve and set the type, subtype, and variety of soil. The impact of the water reservoirs on the radial increment was determined for Scots pine and Norway spruce growing on transects. Conducted research showed that the examined species stronger reacted to the water stored in the reservoirs by diameter increase in the initial two or three years after the reservoir reconstruction. The increment of Scots pine growing near to edge of the water reservoirs (up to 20 m) was reduced. In contrast, there was no significant impact of environmental features or weather conditions on radial increment of the analysed species.
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