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Numerous studies show that in the pedunculate and sessile oaks there are two forms that differ in terms of the spring development of leaves – one can distinguish early and late variants. Acceleration of leaves development gives the particular tree a chance to gain advantage over others, as well as enables to avoid herbivory caused by insects. However, it is fraught with the risk of damage caused by the late frosts. In turn, trees that develop leaves later can avoid losses, but they have to face the shortened growing season. The article presents the results of repeated observations of the spring development of sessile oak trees in about 90−year old stand in central Poland (19.920365° E, 51.837381° N). The trees were observed every week and classified into one of six classes of leaves development – from the absence of bud burst symptoms to the fully−developed leaf. It was found that over time, the share of trees was gradually increasing at higher and higher stages of development, while at the end of the observation period the rate of development of trees was very high. Importantly, at each stage of development, the trees emerged, which proceeded to much faster development than previously, and their share was increasing over time, as shown in the elaborated model of stand development.
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Debowe drzewostany nasienne w Nadlesnictwie Runowo

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The aim of the study was to investigate the structure of forest site types and of soil types of oak seed stands in Poland. The study was comparatively conducted with reference to sessile (Quercus petraea) and common (Q. robur) oaks. As in Poland the seed stands are established only in stands characterized by favourable both growth parameters and timber quality, it was suspected that the results of the study would enable to indicate optimal sites and soil units for oak breeding in Poland. The study was conducted on the basis of data obtained from the SEMEN database (www.bnl.gov.pl) which were broadened by descriptions of the investigated seed stands found in the Forest Data Bank (www.bdl.lasy.gov.pl). For both oak species, the research was conducted with reference to the two types of seed stands: permanent (WDN) and temporary (GDN). In total, 531 stands of Quercus petraea and 2043 of Q. robur located across whole Poland were investigated in the study. It was found that optimal soils as well as forest site types overlap for both investigated oak species only for fresh broadleaved forest (Lśw). For other forest type sites distinct differences for the oak species were found. The optimum for common oak were expanded towards the wet sites (moist broadleaved forest – Lw, and riparian forest – Lł), while for sessile oak towards semi−fertile mixed broadleaved forest (LMśw). It is interesting that seed stands of both oak species overgrow not only fine−textured soils, but significant share of them (ca. 50% area of Q. petraea and 15% of Q. robur seed stands) occurs on sandy soils (Brunic Arenosols mainly). It proves that Brunic Arenosols constitute forest sites enabling production of broadleaved forests characterized by favourable growth parameters and high timber quality. However, it is possible unless the soil have been podzolized by conifers due to podzolized Brunic Arenosols were rarely represented in the oak seed stands and, if so, the stands were characterized by relatively low site index. It was also stated that on podzolized Brunic Arenosols of fresh mixed coniferous forest (BMśw) admixture of oak should enable reducing negatively impact of conifers on a soil.
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