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The paper uses statistical methods to examine whether origination from different Pleistocene centers influences the present-day variation of Carpinus betulus in Poland. Twenty-nine populations of the species were sampled in communities of the Carpinion betuli alliance in most of the country. Samples of 100 involucres for each population were analyzed for 26 morphological characters. Despite the rather accidental similarities among the sampled populations, their geographic variation confirmed their origin from at least two different refugia, southeast and west.
117 nests of Red-breasted Flycatchers in Białowieża primeval forest (NE Poland) were characterised. Most nests (79%) were built in Hornbeam Carpinus betulus and lime Tilia cordata. Three types of nest sites were distinguished: chimney shaped (26.4%), half cavities (46.4%) or shelves — the nest was wedged under a piece of bark against the main trunk (27.3%). Most cavity entrances were exposed to the south. Compared to other species of secondary cavity nesters in Białowieża National Park, Red-breasted Flycatchers used cavities of a different shape, with a smaller bottom area and at a relatively low height above the ground (x̅= 4.9 ± 3.13 m). Nesting trees had a smaller diameter (x̅= 31.2 ± 21.4 cm) and were more often dead (29.8%) than trees used by the other secondary cavity nesters. Only four nest sites were used in consecutive seasons.
The resting site choice of 14 pine martens Marten martes (Linnaeus, 1758) (6 males and 8 females) in Białowieża National Park (BNP), north-eastern Poland, was analysed. The radio-collared martens were located 1,790 times in 877 different resting sites. For both males and females, arboreal resting sites (cavity and nest) constituted over 95% of the resting events. Cavities were used more frequently than nests. Resting site use differed significantly between sexes and seasons. Females rested in nests less often than males (especially in spring), but selected cavities more frequently than did males. Females with young chose only cavities, whereas non-breeding females often rested in nests. Weather conditions influenced the choice of resting sites in various months. For males, temperature was a significant factor from October to May, for females from December to March and in June-July. Martens rested in nests when mean ambient temperatures were higher, in cavities or on the ground when tempera­tures were lower. In summer and winter, when average humidity was high males often rested in cavities or places on the ground. When winds were strong or snow cover was deep, martens chose ground sites. In years of high squirrel density, frequency of nest use by marten increased. During severe winters, frequency of use of ground sites increased. Oak, lime, and spruce trees were frequently used by martens (males - 85.7% and female - 70.6% of all resting sites). Males rested in spruce more often than females, while females used oak and lime more often than males. Martens selected lime and oak, and avoided hornbeam trees. Literature on winter resting sites of pine martens in Europe was reviewed. It was shown that in northern Europe martens rested primarily on the ground. In the temperate zone, martens used cavities in trees (eastern Europe) on nests (western Europe).
The purpose of this study was to determine the trends and rates of spontaneous changes in the structure and species composition of natural forests which are composed mostly of tree species growing at the limits of their natural range of distribution. We analyzed the demographic processes in populations of woody species in the years 1968‒2005. The investigations were conducted in strictly protected areas in the Roztoczański National Park (The Roztocze Highlands, Eastern Poland) on four 0.5-ha sample plots, established in the 1960s. These plots represented three forest communities: upland fir mixed forest Abietetum polonicum (Ap), Carpathian beech forest Dentario glandulosae–Fagetum (DgF), and pine-oaks mixed forest Querco roboris– Pinetum (QrP)). Measurements were conducted in 1968, 1978 (two sample plots only) and in two study periods (1993‒1995 and 2003‒2005). Measurements in the last two periods included canopy trees (DBH and height) forest regeneration (saplings, seedlings and germinants) as well as dead wood (snags and coarse woody debris). The results revealed significant and dynamic changes in the studied forests. The directions and rates of changes were different among forest communities. Silver fir (Abies alba Mill.) showed continuous decrease in all the forest associations. The highest rates of change were found in the DgF forest association. Data from the last measurement showed, that the rate of fir decline has slowed down, and in some cases even a slight increase of its share was recorded. However, the continuous decrease in abundance of the fir regeneration in all study plots suggests, that fir in the near future can be partly replaced by the broadleaved species. Among them, European beech (Fagus sylvatica L.) revealed the most dynamic species. It showed a systematic increase of it’s share in stand composition, according to the number of trees and basal area in all investigated plots. The largest increase of this species was recorded in the QrP forest association. Untill 1993 hornbeam (Carpinus betulus L.) developed well in the DgF association, and it also increased in abundance in the Ap association. The last measurements confirmed large increase the number of hornbeams in the DgF association, whereas it’s share in stand basal area revealed a weak downward tendency in both associations. After 1993 Norway spruce (Picea abies (L.) H. Karst.) grow only in the Ap forest communities, where its development is rather weak. The share of Norway spruce in forest composition has diminished systematically since 1968. The measurements from 2003 revealed a slight increase of the basal area of spruce and substantial decrease of its regeneration. Other tree species: Scots pine (Pinus sylvestris L.) and pedunculate oak (Quercus robur L.) in the successive measurements showed a systematic decrease of their number, basal area and share in the stand composition. There was also no natural regeneration of these species. Observed changes could be mainly attributed to natural rocesses of forests development (including natural disturbances) in general and to specific mechanisms of competition in forests composed of tree species growing close to the limits of their natural distribution ranges. In some cases the dynamics of researched species (hornbeam, pine and oak) can be explained as the regeneration processes of ecosystems affected previously by human activities.
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