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Paper presents an analysis of phenotypical variation and an evaluation of silvicultural quality of progeny from 27 beech stands around Poland that grow on the provenance plot in the Brzeziny Forest District (51.791997°N, 19.813841°E). The trial commenced in spring 1996, on the basis of 2−year−old saplings with covered root systems. A randomised block method with 3 replications was applied, with subsequent measurements and analyses carried out in 2015, following 20 years of growth. The considered features included height, breast−height diameter, crown habit, trunk curvature and height of branching. Single−factor analysis of variance and Tukey’s HSD test were applied to determine the significance of differences among provenances. The largest mean height was attained by beeches originating from Gdańsk, Szczecinek and Bierzwnik. The least−tall beeches were in turn those whose origins were in Tomaszów, Łagów and Grodzisk. The greatest intra−population variation in height characterised the beeches from Gryfino and Krucz, while the most limited variation was noted for Gdańsk population. The beeches of greatest girth were again those deriving from Gdańsk, Bierzwnik and Szczecinek populations, as well as the one from Kwidzyn 15. The lowest values for diameter at breast height were again noted for the Grodzisk, Tomaszów and Łagów provenances. Marked intra−population variation in this feature characterised trees from the Gryfino, Bieszczady National Park (42), Zdrojów and Krucz provenances. The populations also differered in relation to analysed more−qualitative features. The group of populations prized most in terms of their overall silvicultural quality included Gryfino, Grodzisk, Zdrojów, Bieszczady National Park, Bierzwnik and Szczecinek provenances. In contrast, only low quality was manifested by beeches from Tomaszów, Rymanów, Wejherowo, Młynary, Golub−Dobrzyń and Kwidzyn provenances. In general, populations originating from the north (especially Pomerania) achieved better growth and a more favourable quality evaluation than those from the south, and sites located near the range limits of the species (fig. 7). The obtained results show that northern Poland boasts the most plastic populations of beech. Equally, it was not possible to establish that populations of local origin were superior in terms of growth to those originating in more far−flung parts of Poland. Furthermore, assessments of different populations in terms of their growth and quality features often proved highly disparate.
Currently observed climate change creates favourable conditions for the development of not only deciduous species (oak and beech), but also some coniferous (e.g. fir). In the Scots pine stands growing on fertile forest site types one can observe the dynamic development of the under−canopy layers composed of those species. Oak or beech saplings are often characterized by good silvicultural value. Also silver fir creates a well−developed cover under Scots pine trees. Beech and fir as the most shade−tolerant tree species are able to handle the conditions under Scots pine. They can grow for a long time under the cover without damage to their height or diameter growth. Especially, a dynamic growth of oaks can often be observed on fresh mixed coniferous and fresh mixed broadleaved habitats. Oak layers in Scots pine stands are generally created in the way of natural regeneration with remarkable contribution of the jays, which spread the seeds even at considerable distances from the old trees. The corresponding intensity of thinnings supports to shape the proper silvicultural value of such under−canopy storeys. Observations on growth of such stand layers in the Scots pine stands in eastern and central Poland consider the desirability of including them in the next generation of stands. Their presence contributes to improvement of the biological stability of the stands, and also leads to increased productivity. By implementing to the forest practice the model of semi−natural silviculture, one wants to consider the possibility of using the saplings currently existing under the Scots pine as a component of the future stand. Knowledge about the silvicultural value and the impact on growth of lower layers will enable to develop the principles of proper cultivation of the multi−storey stands.
The paper describes a case study of thinning experiment established in 1976 with a use of random block design in 21−year−old Scots pine stand in Janów Lubelski Forest District (south−eastern Poland). The stand was subjected to no thinning (control variant K), weak thinning with removal of 10% of basal area (variant S1), strong thinning with removal of 30% of basal area (variant S3) and extreme thinning, where only future crop trees and some reserve trees were left (variant TE). S1 and S3 treatments were repeated each 5 years, while in TE treatment the 20−year interval was applied. During the period of 40 years all trees were measured each 5 years and current basal area increment was calculated for the whole stand and for future crop trees population. The relative increment of future crop trees population calculated as a percentage of stand total increment was taken into account too. Data were subjected to ANOVA and differences were compared with Tukey test. The results showed that total stand increment was not influenced by thinning intensity. The future crop trees increment was significantly higher in a case of extreme thinning in comparison to weak thinning and to the control treatment during the first 20 years of experiment (age 21−41). During the second 20 years (age 41−61) only relative basal area increment of future crop trees population was significantly higher on the plots with extreme thinning in comparison to other treatments. The results suggest that a weak thinning brings no silvicultural effect meant as increased growth of previously selected future crop Scots pines. Strong or very strong thinnings give a long−term growth effect and they can be acceptable, but in healthy and well−tended young pine stands only.
The paper was aimed at determination of the effect of different tree density in the naturally regenerated monotypic and even aged young Scots pine stands growing in the fresh coniferous or mixed fresh coniferous forest sites on their further development. Research was carried out in Nowa Dęba Forest District (south−eastern Poland). A total of 12 research plots (160×40 m) were established in the selected stands. Plots were divided into 4 equal square pieces (40×40 m), where different methods of tending were applied (variant A – control, variant B – thinned, leaving 16 thousand trees/ha, variant C – thinned, leaving 10 thousand trees/ha, variant D – thinned, leaving 6 thousand trees/ha). The thinning was carried out in April 2007. In subsequent years (2007−2010), selected elements of stand structure like: height, height increment, density and damage resulting from abiotic and biotic factors were determined. Tree density significantly influenced both height increment and qualitative (tree shape) characteristics of naturally regenerated young pine trees. In the course of early thinnings, the number of trees needs to be reduced approximately down to the 10−16 th. stems/ha in the first stage of growth (seedlings), and further down to about 6 th./ha in the coppice stage. Such density enhances the chance of good growth and silvicultural quality of the stand. Noteworthy, even the heavy thinning does not significantly impact the actual proportion of both biotic (e.g. ungulate browsing) and abiotic (e.g. heavy snow) damage in the young naturally regenerated Scots pine forest stands.
European beech is one of the most important broadleaved tree species in Poland and will play probably even more significant role in the future due to the predicted climate change. The main objectives of this study was to analyse and compare the growth parameters and morphological traits between 23 European beech provenances from south−eastern Poland (fig. 1). The research was conducted on the experimental plot established in Łosie Forest District in 2006. The experiment employed a randomized complete block design consisting of 92 plots (23 provenances×4 blocks). On each plot 100 trees representing given provenance were planted in 1.5×1.5 m spacing. In the spring and autumn 2015 we measured and determined the following parameters for the subsample of 36 trees on each plot: survival rate, tree height, diameter at breast height, diameter of the branch at the middle height of the crown length, stem straightness, crown shape, tendency to create forks, mean angle between stem and branches and spring phenology. We also included different eco−physiographical characteristics for each provenances (tab. 1). We performed basic statistics to describe mean values and standard errors (fig. 2, tab. 2) and finally we quantified the interaction between traits and eco−physiographical characteristics by Principal Component Analysis (PCA) (fig 3, tab. 3). The obtained results indicates that under growth conditions on experimental trial in Łosie Forest District, the provenances from lower elevated regions with lower precipitation and higher mean temperature (i.e. more arid conditions; Kielce and Narol provenances) were characterized by thicker dbh and branch dimeters in contrast to regions from southern Poland (Łosie, Bricza 1, Stary Sącz and Nawojowa). European beech provenances from regions with more humid conditions and lower mean annual temperature, as well as shorter vegetation season are characterized by higher survival rate. They are also higher than other provenances, but reveal the lower ratio dbh to branch diameter.
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