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ACTA AGROBOTANICA Vol. 64 (3): 39–46 2011 THE PROSPECTS FOR THE SURVIVAL OF THE POPULATION OF A BOREAL RELICT SPECIES, Betula humilis Schrk., IN A SMALL ISOLATED PEAT BOG IN THE ŁĘCZNA – WŁODAWA LAKELAND Magdalena Pogorzelec, Joanna Wojciechowska Department of General Ecology, University of Life Sciences in Lublin, Akademicka 13, 20-950 Lublin, Poland e-mail: [email protected] Received: 02.12.2010 Abstract lake, fed and drained by the Piwonia river. Currently, it An attempt was made to identify the major risks to the is surrounded by a drainage ditch and an embankment population of Betula humilis Schrk. existing in a small isolated on its western side and functions as a storage reservoir transitional peat bog near Lake Bikcze, in the Łęczna-Włodawa (Wojciechowski, 1979). The space between the Lakeland. The biometric features of 40 Betula humilis individu- reservoir water-table and the embankment is covered als were measured as well as the growth of shoots, flowering and by a transitional peat bog. fruiting were observed. Habitat conditions were characterized by A part of this peat bog, especially from the we- making measurements of selected abiotic and biocenotic envi- stern and northern sides, undergoes succession by the ronmental factors. The obtained results allowed us to identify intensive development of plant communities with Sa- two main threats to the proper functioning of the study popu- lix cinerea and the encroachment of species such as lation. The first one is the possible loss of genetic identity of Betula pendula and Phragmites australis, which has the species as a result of probable ongoing introgression by the a significant influence on the change in habitat con- potential crossing of Betula humilis with other species of the ge- ditions in this area (primarily water and light condi- nus Betula, which are numerous in the flora of the studied area. tions). It determines the withdrawal of species specific Another threat is a change in habitat conditions (mainly light and water conditions), which is due to the accelerated secondary suc- to bog flora, including the so-called “special concern” cession manifested by the expansion of common species such as species (Lorens et al. 1998; Pogorzelec and Salix cinerea, Betula pendula, and Phragmites australis. Banach, 2008). One of the relict plant species is the rare and Key words: Betula humilis, biometric features, threats, habitat protected Betula humilis, a highly branched shrub conditions that reaches a height of 0.5 to 2.0 m. Betula humilis is an anemophilous, monoecious plant with dioecio- us flowers (B i o ń ska, 1974; Staszkiewicz INTRODUCTION et al. 1991). Betula humilis can create hybrids with other birch species: Betula pendula, B pubescens, and Transitional and raised peat bogs are among the B. nana (P i ę koś -Mirkowa and Mirek, 2003). most valuable natural sites of the Łęczna-Włodawa La- Betula humilis is a late-glacial relict which keland. They are characterized by the presence of plant came to Central Europe from the north in the Pleisto- species with the so-called narrow ecological spectrum cene. The geographical range of Betula humilis inc- (Fijał kowski, 1991). These species, which are ludes Eastern Europe and the central part of Europe. often relict, rare and protected species, are also found In isolated stands, it also grows in the foothills of the in the flora of the transitional peat bog adjacent to the Alps, in south-western Germany, northern Switzerland western shore of Lake Bikcze (Pogorzelec and as well as in the eastern and southern Carpathians. Banach, 2008). Outside Europe, Betula humilis extends its range to Lake Bikcze is located in the south eastern part the Altai Mountains, beyond Baikal, northern China, of the Łęczna-Włodawa Lakeland, 51o22’ N longitude reaching as far as the Sea of Okhotsk. A narrow strip 23o03’ E latitude. In the past, it was a flow-through along the Yenisei River reaches into the Arctic Circle 40 Magdalena Pogorzelec, Joanna Wojciechowska (Bioń ska 1974; Z a ł uski et al. 2001; Pię koś - measurements of the same shoot were repeated each -Mirkowa and Mirek, 2003). year; the examined specimens were marked with tags In Poland Betula humilis reaches the south-we- (leaf measurements were made in 2008-2009). stern border of the compact range. Its stands are gro- Observations were conducted of flowering and uped in the northern and eastern parts of the country in fruiting individuals of Betula humilis at the study sites. Western Pomerania, Masurian Lakeland, Podlasie, and Selected abiotic environmental factors were the northern Lublin region. Small numbers can be fo- measured repeatedly: ground water level (cm; with und in dispersion in the western and eastern Great Po- a ruler), acidity (pH, using a field battery-operated land, Lubusz Land, in Mazovia, and northern Galicia. pH-meter), electrolytic conductivity (μS×cm-3, using Betula humilis is a species that is withdrawing a field battery-operated conductometer), in the upper from its stands. In Poland there were more than 350 layer of groundwater and the degree of shading of the sites recorded in the past, while only about 70 were re- bog surface (%) by the trees in each plot. cently confirmed. The current number of natural stands Detailed lists of vascular flora species in the confirmed in the Lublin Region is 20 (Jasnowski, plots were also prepared in 2008. The species occurring 1955; Soczewska, 2000; Z a ł uski et al. 2001). in the investigated phytocoenoses were identified using Betula humilis is one of three species of the ge- the key of Rutkowski (1998), species nomencla- nus Betula that are legally protected in Poland. ture, Polish and Latin, followed Mirek et al. (2002), The progressive disappearance of Betula humi- the assignment of particular species to syntaxonomic lis stands is the result of large-scale drainage of we- units followed Matuszkiewicz (2005). During tlands, their too intensive use as hay meadows and office investigations, Ecological indicator values of pastures, the conversion of grassland to farmland and vascular plants of Poland (Zarzycki et al. 2002) its reforestation, as well as peat extraction (Z a ł uski was also used to determine specific habitat conditions, et al. 2001; Jasnowski, 1955; P i ę koś -Mir- based on the affinity of plant species of particular phy- kowa and Mirek 2003; P i ę koś -Mirkowa, tocoenoses with characteristic ecological groups. 2006). This work aims to characterize the populations RESULTS of Betula humilis against the background of their ha- bitat conditions in one of the stands in a small isolated The Betula humilis population around the peat peat bog in the Łęczna-Włodawa Lakeland, and it is an bog numbered about 100 individuals (bushes). Alto- attempt to identify threats that may have a significant gether, 40 Betula humilis individuals grew within the impact on the further functioning of the study popula- study area (study plot no. 1-10 individuals, no. 2-6 tion in that area. individuals, no. 3-1 individuals, no. 4-5 individuals, no. 5-8 individuals). Measurements taken on the Be- MATERIALS AND METHODS tula humilis individuals located within the study area confirmed the high diversity of biometric features of A field study was conducted in the period 2007- plants (Table 1.) The height and diameter of the shrub 2009 in a transitional peat bog adjacent to the western determined the number of leaves of the examined in- shore of Lake Bikcze, in the Łęczna-Włodawa Lake- dividuals. Shrubs over 100 cm in height had a greater land (Fig. 1). number of leaves. The examined shoots grew from 0 to The first stage of the study was to explore this 80 cm per year. All specimens bloomed and bore fruit. area on foot; this was aimed to initially identify the During the analysis of floristic inventories in the study location and number of Betula humilis specimens in area, 54 species of vascular plants belonging to 27 bo- the peat bog. tanical families (the family Cyperaceae was the most 5 study plots of 100 m2 in area were selected. The numerous – 8 species) and 11 syntaxonomic classes selection of the plots was dependent on the abundance were recorded altogether (the most abundant class was and distribution of Betula humilis individuals, but also Alnetea glutinosae – 21 species). on the diversity of phytoceonoses and habitat condi- Betula humilis co-occurred with vascular plant tions. The number of Betula humilis individuals was species such as Betula pendula, Calamagrostis cane- identified for each plot. Biometric measurements were scens, Equisetum fluviatile, Oxycoccus palustris, The- made on 40 shrubs that grew within the plots, including lypteris palustris (Table 2) in the studied area. During the following: plant height (cm), two diameters of each the years of the study, the species composition of the shrub, number of properly developed shoots, number of flora did not change. leaves of a shoot with medium length, length and width The vast majority in the phytocoenosis of the of the largest of the first three leaves that were located peat bog were species characteristic of moderate- in the upper part of the representative shoot. Biometric ly warm and moderately cool climatic conditions. The prospects for the survival of the population of a boreal relict species, Betula humilis Schrk., in a small isolated... 41 The flora was dominated by plant species that prefer or a slightly acidic pH (5-6). The largest group consi- moderate light at their sites (including Betula humilis). sted of species that prefer humid habitats (Table 3). Both the field observations and flora analysis indicated In the peat bog near Lake Bikcze, a significant a predominant proportion of wet soil plants, but also increase was observed in the level of groundwater in moist and fresh soil plants.

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