THE PHYTOCOENOSES OF ANTHROPOGENICALLY TRANSFORMED AREAS WITH A GREAT IMPORTANCE FOR APOIDEA

The paper indicates the phytocenoses most rich in bee taxons and occurring in habitats located along railway lines crossing Lublin Upland. To date, in the study area 124 basic phytocoenoses have been discovered, described and classifi ed into 12 different synecological groups. Among 52 phytocoenoses, the participation of bee fl ora was considerable. Most voluble phytocoenoses represent ruderal and segetal associations (Artemisietea vulgaris, Stellarietea mediae classes – 87 species), meadow and pasture associations (Mollinio-Arrhenatheretea – 56 species), psammophilous and xerothermic grasslands (FestucoBrometea, Koelerio glauce-Corynophoretea canescensis – 38 species), thermophilous forest edge communities and thickets (Trifolio-Geranietea and Rhamno-Prunetea – 33 species). Signifi cantly fewer melliferous and polleniferous taxons were noticed in mesophilous deciduous forests or thermophilous oak forests – 29 species. Most simple in structure and species richness are associations with Rumex acetosa, Reseda lutea, Linaria vulgaris, Papaver rhoeas, Cirsium arvense, Oenothera biennis, Viola arvensis and Potentilletum anserine or Sisymbrietum altissimi. The communities form patches (15-20 m2) with 80-100% cover of the diagnostic taxon and are of low or medium stability. The most persistent and fl oristically stable are Tanaceto Artemisietum, Rudbeckio-Solidaginetum, Echio-Melilotetum, Sambucetum nigrae, Rubo fruticosi-Prunetum spinosae and communities with Rosa rugosa, Rubus caesius, Geranium robertianum, Pastinaca sativa, Trifolium medium or Euphorbia cyparissias. The maintenance of the mosaic of phytocoenoses in anthropogenically transformed habitats, including those along railway lines, is of decisive importance for the protection of fl oristic diversity and adaptation processes of Apoidea.


INTRODUCTION
There is a general understanding of the fact that due to human activities biodiversity is threatened on a global scale, and it concerns species, populations and also the ecosystem level.The negative changes in different environmental components cause the shrinkage of natural habitats and infl uence particularly organisms of high sensitivity, such as insects (K o r n e r , 2005).Populations decrease among them or even extinctions of pollinator species have been documented widely across Europe, including Poland (B a n a s z a k , 1992; C a rr e c k and W i l l i a m s , 1998).The lack of pollinators affect entomophilous crops causing great economical loses on a big scale (Z y c h and J a k u b i e c , 2006).The shrinkage of available forage reserves is considered to be a main factor limiting bee populations.Thus, basic fl ora records perform an important part in the estimation of natural resources for bees.Nectariferous and polleniferous species are fundamental for apiaries and essential as food resources for different wild Apoidea (J a b ł o ń s k i and K o ł t o w s k i , 1995).Studies on the distribution of bee fl ora proved that many of these species occur in highly transformed anthropogenic habitats, such as road sides, sandpits, railway tracts, quarries, ruderal sites in urban areas (W r z e s i e ń and D e n i s o w , 2006 a,b).
The present paper deals with the analysis of railway fl ora which constitutes a permanent anthropogenic element in natural landscape of most regions in Poland.Railway lines are characterized by an exceptional mosaic of habitats since they run across open areas, meadows, agrocoenoses, compact forest complexes and urban areas.The areas under consideration make excellent migration routes for diasporas of various species; among them are taxons of potential value as a food source for Apoidea.Thus phytocoenoses located along railway tracks are important as the main or supplementary source of food for pollinators nesting there or just penetrating the area.Phytosociological analyses can document how communities are structured and can show what may be consequences of biodiversity losses for entire ecosystems.
The main reason of the investigations was to indicate phytocoenoses in railway areas of the greatest importance as the sources for nectariferous and polleniferous taxons.Special attention was paid to the abundance of insect visitors in the analyzed phytocoenoses.

MATERIALS AND METHODS
The data concern both fl oristic and phytosociological richness of railways areas.The paper is based on own, published or unpublished, studies, which were conducted since 1998, including the Lublin Upland, Roztocze, Polesie and Volhynia Upland (Fig. 1).The studied area was divided into 883 incomplete squares of ATPOL units which belong to 83 squares with 10 km long sides (Z a j ą c , 1978).The analyses of fl ora covers all types of habitats related to railway lines, with the total length of about 900 km, and it includes railway tracks, cargo yards, ridges and embankment slopes, trenches and drainage ditches as well as edges of the nearby semi-natural communities.
The phytocoenoses found in the areas under consideration were classifi ed into synecological groups according to C e l k a (2004) and J a c k o w i a k (1990,1993) and linked to syntaxons of higher units (classes, orders and alliances).The syntaxon determination was based on M a t u s z k i e w i c z (2001) and Z a r z y c k i et al. (2002).The synecological units represented by typical associations with diagnostic species (characteristic or differential) of high density and preferred by Apoidea are shown in Table 1.The average patch area, stability, location of stations and frequency are given for each phytocoenosis.The phenology of phytocoenoses based on the intensity of pollinator visits, which is in close relation with abundance of most valuable forage taxons, is presented in Table 2.The blooming stages were established according to an assumption that the beginning of blooming was the moment when 10% of fl owers bloomed, the full bloom stage being 70-80% of fl owers in bloom, and the end with over 75% of fl owers came out of bloom.

RESULTS
The spontaneous fl ora of railway areas in the middle-eastern part of Poland consists of 950 angiosperms taxons.In the landscape under consideration, 124 basic phytocoenoses were discovered and described (Wrzesień and Świę s , 2006).Among 52 chosen phytocoenoses, as many as 324 fl ow species were noticed.The phytocoenoses under consideration belong to different synecological groups and mainly represent ruderal and segetal associations (Artemisietea vulgaris, Stellarietea mediae classes -87 species), meadow and pasture associations (Mollinio-Arrhenatheretea -56 species), psammophilous and xerothermic grasslands (Festuco-Brome-tea, Koelerio glauce-Corynophoretea canescensis -38 species), thermophilous forest edge communities and thickets (Trifolio-Geranietea and Rhamno-Prunetea -33 species), rarely mesophilous deciduous forests or thermophilous oak forests -29 species (Tab. 1, Fig. 2).Plants species occur as single individuals, create loose patches or are dominants in the analyzed phytocoenoses.Among the recorded phytocoenoses, in which polleniferous or nectarifeous taxons are of great participation, most simple in structure and species richness are communities with Rumex acetosa, Reseda lutea, Linaria vulgaris, Papaver rhoeas, Cirsium arvense, Oenothera biennis, Viola arvensis and Potentilletum anserine or Sisymbrietum altissimi associations.The communities form patches (15-20 m 2 ) with 80-100% cover of the diagnostic taxon and are of low or medium stability.The fl oristic composition of the phytocoenoses does not provide the possibility of survival for insects for a long time.At different seasonal stages, bees penetrate there, migrating from trophically poorer ecosystems.The density of pollinators in the phytocoenoses increases signifi cantly at full bloom stage (Figs 3, 4).Mosaics of phytocoenoses in landscape form a rich source of food supply for meliophages and create an uninterrupted chain of nectar and pollen from early spring to late summer.
The phytocoenoses with a high share of fl ow species most often prefer railway embankments and slopes where the habitat is similar to natural and almost not converted by humans (com.with Thymus serpyllum, with Astragalus cicer, with Euphorbia cyparissias or with Galium verum).The railway edges are usually covered by phytocenoses with kenophytes as diagnostic species (Bunietum orientalis (Fig. 7), Helianthemum tuberosi, com.with Galinsoga parvifl ora and G. ciliata).
Most of the remaining phytocoenoses which developed in the study area were connected with different habitats.That proves the existence of different strategies as high potential mobility or rapid adaptation possibilities of plant species to overcome the enormous pressure of man.The pressure usually relates to different changes of environmental habitat conditions, mainly physical Table 1 The synecological units of chosen phytocoenoses with frequent occurance of nectariferous and polleniferous taxons.Table 2 The phenology of blooming of chosen phytocoenoses abundant in bee taxons.elements.Also, the phytocoenoses are not linked with open or urban areas.The exception is segetal communities which are in a high degree connected with agricultural areas and were located along railways crossing agrocenoses.Generally, modifi ed agricultural landscape creates specifi c conditions for pollinators.The simplifi ed structure of plant associations decreases bee diversity and is characterized by the diminishing density of bees.The unusual density of plants in monocultures per unit square ensures the food fl ow in abundance, if any, only in the short period of blooming.Thus, the fact of increasing fl oristic diversity and the mosaic structure of plants associations, even weeds at a controlled level, will affect signifi cantly plant restoration and conservation, the differentiation of pollinators.Generally, the wide range of fl owering of the most important nectariferous and polleniferous plants in antropogenicaly transformed phytocoenoses located along the railways areas creates the unbroken food chain for Apoidea from early spring till autumn (Tab.2).However, the main food fl ow is provided in summer time.That is particularly important as it creates conditions for proper, balanced nutrition and food storage for nesting during winter.Thus, it infl uences the condition of pollinators in the next vegetation season and indirectly determines fl ora restoration in the environment.

CONCLUSIONS
1. Anthropogenically modifi ed habitats along railways tracks are of high importance in the conservation of fl oristic variability in all environments they run across.
2. The communities with Reseda lutea, Linaria vulgaris, Papaver rhoeas, Cirsium arvense, Oenothera biennis, Viola arvensis and Potentilletum anserine or Sisymbrietum altissimi association are of low or medium stability.The mosaic of the phytocenoses in the landscape forms a rich source of nectar and pollen for Apoidea in different seasonal aspects of blooming.
4. The phytocoenoses formed along railways crossing agrocenoses are often the only areas in the landscape which increase fl oristic diversity and the mosaic structure of plant associations, thus they positively affect the differentiation of pollinators or even enable the survival of wild Apoidea in agricultural landscape.Utrzymanie mozaiki fi tocenoz na siedliskach antropogenicznie przekształconych, w tym w obrębie linii kolejowych, ma decydujące znaczenie w ochronie różnorodności fl orystycznej i procesach adaptacyjnych pszczołowatych.

Fig. 4 .
Fig. 4. A community with Rorippa austriaca at the edge of railway track.