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The Viola epipsila-V. palustris complex is a highly taxonomically complicated group of species in its entire circumboreal range of distribution. Habitat loss, forest flooding, and hybridization could lead to the extinction of V. epipsila. A hybrid index and principal component analysis (PCA) were used to select qualitative and quantitative morphological features to distinguish parent species and hybrids, inter simple sequence repeat (ISSR) markers to determine the genetic diversity of the populations, flow cytometry to estimate the genome size (GS), and non-coding chloroplast DNA (cpDNA) regions to indicate the directions of crosses. All taxa are very morphologically variable, and their features can change within a season. The most stable feature is the distance of the bracts on the pedicel from the rhizome. The genetic diversity of all taxa populations is low and highly influenced by selfing and vegetative propagation. The population structure is differentiated: populations of V. epipsila or V. palustris, mixed populations with both parent species, F1 hybrids and populations with introgressive forms occur in different regions. The interspecific GS variation corresponds to the ploidy level (4x = 2.52 pg, 8x = 4.26 pg, 6x = 3.42 pg). Viola epipsila is the mother plant of the hybrids. Research has shown the risk of V. epipsila extinction in Central Europe and the importance of local populations in studying the role of hybridization in reducing/maintaining/increasing biodiversity.

The long−term changes of vegetation cover at the level of woodland community taking place between 1959 and 2016 on the permanent study plot located in the compartment 319 of Białowieża National Park are discussed. In 1959 two distinctive woodland community types occurring on sample plot were distinguished: subboreal mixed pine−oak forest (Serratulo−Pinetum) and hornbeam−lime forest (Tilio−Carpinetum). The phytosociological investigations, carried out almost 60 years later, revealed that in case of both communities, significant, directional changes of their floristic composition took place. Particularly high rate of change occurred in case of the phytocoenosis representing the Serratulo−Pinetum community. In 1959 it contained a full set of characteristic plant species. During the study period, this community type representing the Vaccinio−Piceetea class, was replaced by the initial form of lime−hornbeam forest belonging to the Querco−Fagetea class. Also, in case of the previous Tilio−Carpinetum association, the significant changes in the floristic composition occurred, although not as large as in case of Serratulo−Pinetum community. 60 years ago this community type contained several plant species typical for thermophilous oak forests. Nowadays, it represents a typical form of lime−hornbeam association. The changes in both community types were mainly related to the strong expansion of lime and hornbeam, which took place during the study period and involved the whole study plot. As a result, the vegetation occurring on the study plot is much more homogenous now than it was ca. 60 years ago. The maintenance of Serratulo−Pinetum phytocoenoses distinguished by a high floristic diversity calls for active protective measures in all cases where such measures are allowed and where this community type can potentially develop., Sylwan 162 (11): 907-914

Changes in the herbaceous layer (vascular plants), taking place between 1959 and 2016 on the permanent study plot in the compartment 319 of the Strict Reserve in the Białowieża National Park are presented. Zaręba [1972] presented phytosociological research carried out in 1959 on the 1.2 ha plot. The author established 10 relevés (size between 100 and 400 m), in which in total 91 different species of vascular plants were noted. In 2016, the similar study was conducted, using slightly modified methods (the inventory of plants involved the total area of the study plot). The comparison of data recorded during both investigations revealed that the total number of plant species declined from the initial 91 to current 83. During the ca. 60−year long period, 43 plant species disappeared completely and were replaced by 35 new species. In the declining group, almost the half (20) were species important from the point of view of nature conservation, including four Red List species (emArnica montana/em, emGoodyera repens/em, emLathyrus laevigatus/em, emTrolius europaeus/em), 10 plant species protected by law, and several other precious species related to rare and declining woodland community types. The obtained results confirm the findings of other authors describing unfavourable changes in the flora of the Białowieża Forest during the past several tens of years. The floristic richness is an important part of the overall biodiversity of Białowieża Forest. It appears that strict protection does not secure the maintenance of this key component. Thus, an attempt to preserve diverse values of Białowieża Forest on a sustainable basis should, first of all, look for a proper balance between strict and active protection. The later can (and should) be integrated within the multifunctional forest management, conducted on the prevailing area of the Białowieża Forest., Sylwan 162 (12): 980-988

The paper presents the main results of the comprehensive inventory of monumental trees in the Strict Reserve of the Białowieża National Park, which was conducted in years 2002−2017 on an area of ca. 4700 ha and included all live trees with diameter at breast height (dbh) exceeding a minimum threshold value ranging from 60 cm for hornbeam to 120 cm for oak. For every tree fulfilling this condition, species identity, circumference at 1.3 m (measured with tape), geographical coordinates (GPS record) and health status (five classes) were determined. In total, 9190 trees from eleven different species were inventoried. Hornbeam, oak, maple, lime, ash and aspen were the most abundant with their total share in the amount of monumental trees equal to ca. 96%. The average density of monumental trees in the Strict Reserve was approximately 2 ind./ha. The majority (88%) of monumental trees were found in different subassociations of Tilio−Carpinetum community: T−C. calamagrostietosum, T.−C. typicum, T.−C. circaeaetosum alpine, T.−C. caricetosum remotae and T.−C. stachyetosum. As a rule, the fraction of particular species in the amount of monumental trees did not correspond to their fraction in the total pool of trees with dbh 5 cm. Particularly high over−representation characterized oak, maple, ash and aspen. On the other hand, such species like spruce and, to a lesser degree, hornbeam, lime, alder and birch played much smaller role in the group of monumental trees than among all trees with dbh 5 cm. The monumental trees of particular species were distinguished by a high diameter differentiation. In this respect, oak clearly prevailed over the other ones. In contrast, the smallest dimensions were typical for hornbeam. The results obtained suggested the need of revision of minimum threshold values of circumference (and of corresponding dbh), used to classify a given individual as a monumental tree. This problem was particularly acute in case of pine, spruce, alder and birch. We suggest that the current minimum values of dbh for these species should be reduced by 10−20 cm. Further, the comparison of the recorded values of dbh for some species with maximum values of dbh provided in the literature indicated the necessity of correction of the last values, both ‘in plus’ as well as ‘in minus’. For alder, aspen and maple, the current values should be increased by ca. 20−30 cm. On the other hand, for pine, the recent value should be reduced by at least 30 cm. We point out that the definition of large (monumental) tree is, to a large extent, an arbitrary issue. The various growth potential of particular tree species, occurring within a given area, implies that this definition should be used flexibly. It means a necessity of using different thresholds for different species and varied environmental conditions. Also, because of the relative rarity of large trees, the reliable estimation of their density can only be obtained on the basis of sufficiently large sample size. Some high values of density of large trees, which can be found in the existing literature (10−20 trees per hectare and more), may be the result of too small sample sizes., Sylwan 162 (11): 915-926

Pollen productivity estimates of individual plant taxa are necessary when determining changes of vegetation cover during the Holocene. To date, studies describing this parameter in lowland temperate Europe have been carried out in cultural landscapes showing low forest cover and dominated by human activities. However, these may be of limited use when applied to reconstruct past land cover, for instance, from pre-agricultural landscapes. The aim of this paper is to ascertain whether pollen productivity from the closed-canopy old-growth forest in the Białowieża National Park, Poland, where human impact has been minimal for nearly a century, is different from that calculated in much more open landscapes. We ask: how much does forest antiquity and structure influence the amount of pollen released from particular taxa? We implemented maximum likelihood estimation of relative pollen productivity for seven tree species and for Poaceae using 18 modern pollen assemblages and distance-weighted plant abundances. Our results demonstrate that the ratio of pollen productivity between high producers ( Pinus sylvestris and Quercus robur) and low producers ( Poaceae, Corylus avellana) is on an average six times greater in Białowieża than across other European cultural landscapes. Pollen from forest Poaceae and C. avellana is six times more under-represented in old-growth forest than hitherto estimated from cultural landscapes. This finding reinforces the idea that pollen productivity can vary in response to changes in the prevailing environmental settings and we present for the first time a quantification of this variability, likely induced by differences in light availability.

International audience; Global biodiversity is affected by numerous environmental drivers. Yet, the extent to which global environmental changes contribute to changes in local diversity is poorly understood. We investigated biodiversity changes in a meta-analysis of 39 resurvey studies in European temperate forests (3988 vegetation records in total, 17-75 years between the two surveys) by assessing the importance of (i) coarse-resolution (i.e., among sites) vs. fine-resolution (i.e., within sites) environmental differences and (ii) changing environmental conditions between surveys. Our results clarify the mechanisms underlying the direction and magnitude of local-scale biodiversity changes. While not detecting any net local diversity loss, we observed considerable among-site variation, partly explained by temporal changes in light availability (a local driver) and density of large herbivores (a regional driver). Furthermore, strong evidence was found that presurvey levels of nitrogen deposition determined subsequent diversity changes. We conclude that models forecasting future biodiversity changes should consider coarse-resolution environmental changes, account for differences in baseline environmental conditions and for local changes in fine-resolution environmental conditions.

Sylwan 151 (1): 58-65