ENDANGERED SPECIES OF VASCULAR FLORA IN FISHPOND COMPLEXES OF THE CENTRAL-EASTERN POLAND

Michał Falkowski, Krystyna Nowicka-Falkowska, Janusz Krechowski
Department of Botany, Institute of Biology, University of Podlasie, Siedlce, Poland

ABSTRACT

The group of 81 endangered species (79 of them are mentioned at regional Red Book of Plants) have been recorded in the 44 selected fishpond complexes of the central-eastern Poland (Południowopodlaska lowland). The studies demonstrated the importance of these elements in the agricultural landscape of the Polish lowlands as refugees for endangered plant species, especially those ecologically associated with hydrogenic sites.

Key words: fishponds, endangered species, Południowopodlaska lowland, central-eastern.

INTRODUCTION

Both transformation and decline of aquatic habitats have contributed to the increase of significance of objects of anthropogenic origin, e.g., peat holes, excavations and fishponds. The latter ones, apart from productive values, play the key role in conservation of wetland biodiversity [24,9]. Many endangered species continue to be found there. The fishpond complexes are in fact a substitute for natural habitats, especially in environment destroyed or deformed by human activity. A group of plants mentioned in the Polish red data list of plants, e.g., Lindernia procumbens, Lythrum hyssopifolia, Nymphoides peltata, Trapa natans and species from genus Elatine were found exclusively in that water reservoirs [22]. The floristic regional studies strongly support that suggestion [5]. The abundance of sites is often remarkable. For example the population of Rhynchospora fusca in Stawy Wilczowskie fishpond complex occupies the area of over 1 ha [16]. Fishponds also play an important role of refugees for rare and endangered aquatic and alluvial plant communities [33]. Nevertheless, fishponds, contrary to old river-beds and lakes, were not thoroughly investigated by botanists in Poland.

During comprehensive investigations on vegetation of fishponds in central-eastern Poland, carried out between 1995 and 2002, both floristic and phytosociological studies were made [11,13,14,15]. The dependences between vegetation diversity and intensity and manner of fish-farming were presented [12]. A degree of naturalness and anthropophytization indices for the fishpond flora as well as its relations with close surrounding were also examined [15].

AIM OF STUDIES

The aim of the studies carried out in central-eastern Poland was the indication of the group of threatened vascular plant species occurring in substitute habitats of fishpond complexes. Due to observed decline of natural stands, these objects can be a refugee for them. Moreover an attempt of determination of environment factors, resulting from presence of fishpond complexes and affecting occurrence of particular groups of species endangered extinction was made.

CHARACTERISTICS OF THE FISHPOND COMPLEXES

The studies were carried out in the area of 44 fishpond complexes (total area – 4133 ha) of the central-eastern Poland (Fig. 1). The fishpond complex is called object, consisting of all ponds (also these completely overgrown, abandoned many years ago), dikes, system of surrounding ditches and the zone 15 m wide adjoining to them. The minimum area of the investigated fishponds was 10 ha.

The history of the fishpond complexes in this region of Poland dates back to the 18th and 19th century. Since that time they have become an integral element of regional, natural-cultural landscape. Primarily fishponds were a part of estates. After the Second World War the fishpond complexes were transformed into National Fishing Farms. Afterwards, some of them were privatized or taken into lease, however in the whole region regression of fishery is observed. Fish-farming intensification was observed only in few objects (complexes Kotuń, Gójszcz, Gołębiówka, Przekop, Ryczyca and Szczeglacin). The area of complexes was differentiated. The fishponds in Ryki (325.06 ha), Wólka Sobieszyńska (311.55 ha), Jagodne (305.55 ha), Klimonty (270 ha), Radoryż Kościelny (201.72 ha), Rybakówka (190 ha) and Stawy Broszkowskie nature reserve (156 ha) belong to the largest ones. Complexes in, Bartków, Gójszcz and Rudnik (10 ha each) are the smallest. The average area of studied objects was  93.93 ha. The fishpond complexes consist of 619 separate water basins. As many as 310 of them are filled with water and vegetation cover not exceed 40%. Plant cover in another 139 ponds exceeds 40%. The remaining 170 ponds are totally overgrown, waterless and have no fish-farming function. They were transformed into moist meadows (complexes Cieleśnica, Rudnik and Sinołęka) or undergo spontaneous processes of succession. They are covered by mosaic of rush communities from class Phragmitetea, moist meadows from Filipendulion ulmariae, Calthion palustris and Molinion caeruleae alliance, peatbogs from Caricetalia nigrae alliance, shrubs of association Salicetum pentandro-cinereae and plots of alder forests. Well developed alder forests Ribeso nigri-Alnetum and alluvial forests Fraxino-Alnetum (typical species composition and structure) occur e.g., in ponds Byczek, Karczonek, Olszynka, Dębinka and Jeziorek (Klimonty complex) and Piekło, Wielki Dolny, Staw Mały, Staw Nowy, Staw Czysty and Odrost II (Stawy Broszkowskie nature reserve). Some of them are cultivated according to forest economy rules. More accurate data on the studied complexes are provided by Falkowski and Nowicka-Falkowska [12,13].

METHODS

The area of studied objects was calculated using a millimeter carbon paper of a side of 10mm (calculation of mm²) and topographic maps in scale 1:10 000. The measurements were made twice, horizontally and vertically. If the difference between obtained result was not larger than 5% arithmetical mean was calculated. Additional measurements, using polar planimeter were made twice, changing the polar location. After all measurements a arithmetical mean was calculated . The obtained results was used for calculation of a real area of the studied object.

The total of 92 phytosociological relevés (7121 floristic data) were made during field studies. Each relevé was composed of three parts: ordinal, information-descriptive and the list of recorded species. The phytosociological relevés were made in the optimal period of the vegetative season and were repeated in the other phases of the phenological plant development. Moreover data from the Scientific Herbarium of Department of Botany, University of Podlasie in Siedlce (WSRP) and literature sites were provided.

Each species was classified according to the regional [20] and state [22, 35] category of threat. Phytosociological [26] and socio-ecological attachment of species [1], slightly differaet on the basis of own field observations was also determined. Nomenclature of species was accepted after Mirek et al. [27]. Species of Taraxacum section Palustria [23] were also identified. Location of the studied complexes in the ATPOL network of squares [34] was presented in Table 1.

The collected herbarium specimens were gathered in the Scientific Herbarium of Department of Botany, University of Podlasie in Siedlce (WSRP).

ANALYSIS AND  ELABORATION OF THE OBTAINED RESULTS

The list of vascular plants of the  Nizina Południowopodlaska lowland (central-eastern Poland) includes about 1300 species, of which 411 are mentioned in the regional Red List [20]. As a result of studies carried out in the area of 44 fishpond complexes, 79 endangered plant species were recorded (Table 1), that is 19.22% of species listed there. Considering categories of threat, the studied objects are the refugees for 9 critically endangered species (category CR), 20 endangered species (EN), 26 vulnerable species (VU), 15 lower risk species (LR) and 9 data deficiency taxa (DD). The group of endangered species includes representatives of aquatic, alluvial, rush, forest and seminatural communities. They represent 11 classes of vegetation (Table 1), including Molinio-Arrhenatheretea – 20 species, Scheuchzerio-Caricetea nigrae – 13, Potametea – 11, Isoëto-Nanojuncetea – 7, Alnetea glutinosae – 3, Bidentetea tripartiti, Lemnetea minoris and Querco-Fagetea – 2 species each. The classes Epilobietea angustifolii, Littorelletea uniflorae, Phragmitetea and Thlaspietea rotundifolii are represented by one species. According to socio-ecological division, the endangered species belong to the following groups of vegetation: meadows – 21 species (24.7% of species from that group mentioned in the regional Red List), alluvial – 14 (70%), peatland – 14 (41.2%), aquatic – 14 (58.3%), swampy alder forests – 3 (75%), mesophilous deciduous forests – 3 (6.2%) and rushes – 1 species (14.2%). The remaining endangered species occupy various biotopes in the borders of fishpond complexes, that makes their classification impossible.

The studied fishpond complexes are the refugee for 24 vascular plant species mentioned in the state Red List [35], including critically endangered species – Pedicularis sceptrum-carolinum (category E) and 23 vulnerable species (category V). Two species threatened in Poland Ranunculus lingua and Illecebrum verticillatum are not endangered in the area of Nizina Południowopodlaska lowland.

Occurrence of 5 species listed in the Polish red data book of plants – Betula humilis, Cyperus flavescens, Lythrum hyssopifolia, Ostericum palustre and Polemonium coeruleum [22] is also noteworthy.

Taking into consideration both Red Lists and the Polish red data book of plants we can ascertain that the fishpond complexes of the central-eastern Poland are or were (non existing stand of  Dactylorhiza maculata and Trollius europaeus in the fishpond complex in Golice) the refugees for 81 endangered species.

The group of species directly attached to water reservoirs as well as plants characteristic for communities developing as the subsequent stages of their succession (34 species) prevail in the studied area. Among them there are aquatic, rush and alluvial species, representatives of swampy alder forest communities as well as waterside terophytes (Table 1).

DISCUSSION

The studied fishpond complexes belong to the most important refugees of endangered species in the central-eastern Poland. From among 20 plant species ecologically attached to alluvial habitats, mentioned in the regional Red List [20], 14 species (70%) were recorded in the studied objects. Similarly 58% endangered aquatic plants and 75% alder forest representatives were noted in the examined fishponds. Stands of such species, as, Alisma lanceolatum, Cyperus flavescens, Eleocharis mamillata, E. ovata, Illecebrum verticillatum, Leersia oryzoides, Potamogeton friesii, P. nodosus, P. obtusifolius and Salvinia natans in the studied macroregion were noted exclusively in area of fishpond complexes. Population constancy of some species is also noteworthy. For instance, the stand of Gentiana pneumonanthe recorded for the first time 40 years ago by Podbielkowski [31] in abandoned pond in Rybakówka complex was confirmed in 70’s [21], at the turn of 20th and 21st century [7,8] and at present. Abundant occurrence of species of Orchidaceae family in the area of fishpond complex is also noteworthy [28].

All the investigated fishpond complexes were built within peat-covered, usually deforested river valleys. Nowadays, they usually border on the areas of reclaimed meadows. The penetration of water through the dikes strongly enlarge the reserves of ground water retention in the area of fishpond complexes and adjacent areas. Therefore the increase of soil humidity and inhibition of the drop of ground water table in these objects is observed. Numerously the retention is much higher that it would be under natural conditions [25]. Such advantageous moisture conditions are favourable for many endangered species, as, Carex flacca, C. hartmanii, Cnidium dubium, Cirsium rivulare, Dactylorhiza incarnata, D. majalis, Dianthus superbus, Epipactis palustris, Gratiola officinalis, Lathyrus palustris, Menyanthes trifoliata, Ophioglossum vulgatum, Ostericum palustre and Parnassia palustris.

Fishpond complexes abandoned a long time ago undergo spontaneous natural processes of succession.  Swampy alder forests Ribeso nigri-Alnetum are usually the terminal stages of water basins succession. The narrow zones of alluvial forests Fraxino-Alnetum characterized by the surface or underground water flow are also observed, especially along ditches surrounding the fishpond complexes. A group of species rare in these objects, e.g, Corydalis solida and Dactylorhiza fuchsii are found there.

The intensity of fish-farming is also very important for maintenance of endangered species. The extensive fishery, irrespective of fishpond area, seems to be the most favourable because it enables development of diverse plant communities. Various types of habitats found there make possible development of endangered vascular species of different ecological  requirements. Complexes excluded from farming in late stages of succession are characterized by lack of aquatic, alluvial, meadow and peat-bog species. Intensively exploited fishponds are the species-poorest ones, that is a result of regular vegetation cutting, significant water fertilization, dike reinforcement with stone and concrete material and cleaning-up of the bottom of water basins [12].

CONCLUSIONS

The studies carried out in fishpond complexes demonstrated their significance as  refugees for endangered vascular plant species in the area of central-eastern Poland. That objects are areas of special importance for plants ecologically attached to hydrogenic habitats. Location of fishpond complexes in river valleys make them one of the most important elements of ecological corridors. Populations of species occurring in catchment areas and rapidly loosing their primeval habitats due to human activity survived there. Many species will probably start the secondary colonization of river valleys from fishpond areas, as soon as human impact declines. That process is supported by economic-social changes in rural areas, observed currently in Poland, e.g. regression of fish-farming in the region. The occurrence of endangered species and remarkable abundance of stands, apart from other scientific values, would affect the decisions concerning the future of fishpond complexes. Wetland protection, e.g. fishpond maintenance in the rural landscape is one of the main elements for the conservation strategy of biological diversity of freshwater ecosystems in Poland. Moreover, our knowledge of biological and functional diversity of fishponds and their relations with landscape is still insufficient.

Acknowledgements. The authors are very grateful for verification and determination of numerous specimens to dr Joanna Zalewska-Gałosz (Potamogeton), prof. dr hab Zygmunt Głowacki (Batrachium, Carex, Eleocharis, Juncus) and dr Leszek Bernacki (Epipactis, Dactylorhiza, Platanthera). Additionally, we would like to thank the anonymous reviewer for helpful suggestions, from which the paper benefited significantly.

This studies has been supported by funds from the research project 6 P04G 003 21.

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Accepted for print: 10.12.2009

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