FLORA OF FALLOW LANDS OF THE PODLASKI PRZEŁOM BUGU MESOREGION

Studies on flora of fallow lands of the Podlaski Przełom Bugu mesoregion were carried out between 2001 and 2003 in the area of 77 localities, situated in 20 communes. A systematic list of fallow land flora was made and its variation with respect to occurrence frequency, biological spectrum, persistence and be longing to geographic historical and sociological ecological gro ups was analyzed. Flora of fallow lands of the Podlaski Przełom Bugu mesoregion includes 442 species included in 60 families and 241 botanical genera. The most numerous group comprises very rare, rare and quite frequent species. In the floristic com position of the analysed flora, apophytes (72.2%) predominate over anthropophytes (2.8%) as well as perennials (61%) over ephemerals (39%). Considering the biological spectrum of flo ra, hemicryptophytes (49%) and terophytes (32%) predominate over other life forms. Forest and shrub species (18.5%) as well as meadow (17%) and xerothermic sward plants (17.4%) have the largest share in the flora. The abundant occurrence of sege tal (15.8%) and long lived ruderal communities (8.1%) was also noted. Moreover, the occurrence of 25 species endangered with extinction in fallow land communities of the Południowopodla ska Lowland was noted. They are as follows: Nigella arvensis, Potentilla recta, Platanthera chlorantha, Agrostemma githago, Prunella grandiflora, Populus alba, Silene tatarica, Papaver argemone, Papaver rhoeas, Veronica polita, Hieracium floribundum, Bromus secalinus, Polygonum bistorta, Geum alleppicu, Astragalus arenarius, Centaurium erythraea, Veronica agrestis, Veronica verna, Cirsium rivulare, Allium oleraceum, Hierochloë odorata, Chenopodium polyspermum, Vinca minor, Dipsacus silvestris and Campanula latifolia.


INTRODUCTION
The socio-economic transformation observed in Poland for the last several years has resulted in the increase of the area of cultivated fields excluded from purposeful farming.The estimated area of fallow land in the studied communes is about 10 000 ha.The increase in the area of soil lying fallow in the investigated mesoregion is mostly an effect of the economic conditions (low agricultural productivity as a result of the dominance of poor soils) as well as the ageing of farmers settled down in this area.Thus, it is assumed that this area will still be excluded from farming in future.
In other regions of Poland, floristic studies on fallow lands were usually focused on state-run farms, which were abandoned due to constitutional transformations ( B a r a b a s z -K r a s n y, 2002; K u t y n a , 1997), on soils which were recently excluded from farming (Ł a b z a et al. 1997 a, b; K u t y n a , 1994; M a l i ck i et al. 2002) and were concentrated on little experimental areas (D z i e n i a et al. 1998; J a b ł o ń s k i and Wi d e r a , 1996).Very few studies were undertaken on long-term fallow land covering large areas.The results of similar investigations were published by F a l i ń s k i (1986) and D u b i e l (1984).
The aim of the floristic investigations, the results of which are presented in this paper, was to make an inventory of fallow land flora of the Podlaski Przełom Bugu mesoregion (including the accurate location of species in the network of ATPOL squares) and its multiaspect analysis.

THE STUDY AREA
The examined area is situated in eastern Poland.In the physical-geographic division of Poland (K o nd r a c k i , 2000), the study area is situated in the Podlaski Przełom Bugu mesoregion, belonging to the Południowopodlaska Lowland macroregion.The investigations were carried out in the 155 km long section of the Bug river valley, between the localities of Terespol and Małkinia Górna.
The list of the studied localities: 1 -Grzymki, 2 -Wszebory, 3 -Zgleczewo Pańskie, 4 -Zgleczewo Szlacheckie, 5 -Zuzela, 6 -Ołtarze Gołacze, 7 -Rytele Święckie, 8 -Rytele Olechny, 9 -Adolfów, 10 -Białobrzegi, 11 -Kiełpiniec, 12 -Kolonia Nur, 13 -Kossaki, 14 -Natolin, 15 -Przewóz Nurski, 16 -Kamieńczyk, 17 -Kobyla, 18 -Wojtkowice, 19 -Głęboczek, 20 -Granne, 21 -Kruzy, 22 -Krzemień Zagacie, 23 -Leśniki, 24 -Osnówka, 25 The systematic order of species follows Rutkowski (1998), nomenclature of species Mirek et al. (2002).The classification of species into geographic-historical groups was made according to Kornaś (1968), Z a j ą c and Z a j ą c (1975,1979), J a c k o w ia k (1990) and R u t k o w s k i (1998).The origin of apophytes was determined based on the studies by K o r n a ś (1957), A n i o ł -K w i a t k o w s k a (1974) and Z a j ą c and Zając (1992).A group of plants which temporarily escaped from cultivation (ergasiophytes) was also analyzed.The biological type of species and their persistence followed K o r n a ś (1957), A n i o ł -K w ia t k o w s k a (1974), J a c k o w i a k (1990), C h m i e l (1993) and R u t k o w s k i (1998).The classification of species to socio-ecological groups was adopted based on a slightly modified system of J a c k o w i a k (1990).In total, 17 socio-ecological groups were distinguished and marked by numbers 1-16 and "n" (species of uncertain phytosociologial status).The species were included in particular groups on the basis of research by J a c ko w i a k (1990) and M a t u s z k i e w i c z (2001).The following groups of species were identified: 1. Deciduous forest and shrub communities; 2. Coniferous forests, mixed forests and their substitute communities; 3. Shrub and forest edge nitrophilous communities; 4 The occurrence frequency of species was estimated on the basis of the modified scale of J a s i e w i c z (1965), assuming one stand = locality.
son for the great floristic diversity of fallow lands of the Podlaski Przełom Bugu mesoregion is its openness for newcomers from various habitats.The studied fallow lands neighbour different types of habitats, including cultivated fields, forest complexes, forest edge communities, meadow, shrub, ruderal and roadside vegetation.Hemicryptophytes (218 species -49%) are the most frequent life form in the flora of the studied fallow lands.Terophytes reaching a 32% share in the flora (140 species) are also numerous.The occurrence of 43 species of phanerophytes was also noted (6%).Other life forms do not exceed 5% of the fallow land flora.The dominance of apophytes ( 2. The dominance of very rare, rare, and quite frequent species, accounting for 80.5% of the total flora, was observed in the vegetation of fallow lands in the studied area.The share of very common and common species was only 4.7%. 3. In the flora of fallow lands of the Podlaski Przełom Bugu mesoregion, a distinct dominance of apophytes (72.2%) over anthropophytes (27.8%) is noted.Among apophytes, forest, shrub and meadow species dominate, while among anthropophytes archaeophytes are predominant.4. The biological spectrum of flora indicates the dominance of hemicryptophytes (49%) and terophytes (32%) over other life forms.5. Perennials (61%) predominate over short-lived species (39%) in the flora of the Podlaski Przelom Bugu mesoregion.
6.The occurrence of 25 species endangered with extinction in the Południowopodlaska Lowland was noted in the fallow land communities of the Podlaski Przełom Bugu mesoregion.

other regions of Poland. The cli- mate of the studied area is colder than in central Poland. According to the Meteorological Station in Siedlce, an- nual precipitation total in the studies period ranged from 500 to 600 mm.
The valley reaches 5 km in width in this region.The study area includes 20 communes, belonging to Mazovia, Lublin and Podlasie Provinces.In the National Ecological Network ECONET-Poland (L i r o 1995), the region is an important part of the nodal area of international significance, namely "The Area of the Lower Bug River Valley".