Bulgarian - Swiss Biodiversity Conservation Programme ECOLOGY AND CONSERVATION OF ATANASOVSKO LAKE Collection of Final Scientific Reports of Atanasovsko Lake, Sofia , 1997
grass populations, presented by Festuceta pratensis, Lolieta perennis, Agrostideta stoloniferae and others, on the place of the former forests of elm-trees (Ulmus campestris), pedunculated and robur oak-trees (Quercus robur and Quercus pedunculiflorae) and others. They have an indirect impact on the vegetation of the reserve. In connection with the above-mentioned specific ecological conditions, the cenoses of the reserve are presented by : xeromesophyte, mesophyte and hygrophylic microtherm vegetation, that can be divided into: 1. Hygrophyte vegetation - with the predomination of reed (Phragmites australis) and the insignificant participation of the narrow-leaf and broad-leaf rush (Typha latifolia and Typha angustifolia), the cene (Schoenoplectus lacustris) and others. The cenoses of reed are predominant, as somewhere they overgrow the whole dikes, that surround the by-pass channel on the inside and on the outside. Almost entirely overgrown are the outermost basins, that hadn’t been swept with water for a long time, on the northern part of the reserve territory and on the south-western side of the buffer zone. The reed there had occupied the slightly salty humid soils and retired only in the zones of infiltrated waters with the petrol wastes. Right next to the dikes of the next working basins, where the water is with comparatively higher saltiness, no reed overgrowings can be found. The same situation is in the other parts with high saltiness of the substrate. In these cenoses take part also Typha latifolia and a little, in the comparatively dry places Typha angustifolia. Separately, in small loose groups, in the reed massive can be found Salix alba and Salix eleagnus.. Also in these cenoses, in several parts of the channel and in the fresh-water lake, can be found considerable overgrowings of higher water plants with the predomination Lemna minor, Ceratophyllum demerum, Najas marina, Potamogeton crispus, P. Pectinatus, Spirodela polyrrhiza and several others. 2. Halophyte grass cenoses. They are presented mainly by the cenoses of Salicornia europaea and Sueda maritima, Limonium gmelinii, Salsola soda and others. These species occupy the areas with the soils of the greatest concentration of salt during the seasonal, incidential and continuous drying up of the basins, with higher concentration of salts in the water, as well as in the foot of the dikes, when there are considerable lowerings in the relief. The main part in these cenoses is of Salicornia europaea, as in some areas this species forms its own overgrowings and especially in the newly dug dikes, it is in the role of a pioneer element. (Velev, 1995). Mixed with the other species, mainly on the dikes can be found some other typical halophytes - Sueda maritima, Limonium gmelinii, Parapholis incurva, Aeropus litoralis and others. 3. Mesoxerotherm grass cenoses. These are populations, that had formed by the abrupt changes in the ecological conditions, after the development of the salt-works and their exploitation for industrial salt-mining. The embankment of the lake with dug dikes with imported soil, caused the ruderalization of the terrains, which was a prerequisite for the formation of derivative cenoses, on the basis of the pioneer vegetation, in abundance around the Atanasovsko Lake. At the moment they occupy the middle and the higher zones of the old dikes, parts of the peripheral areas of the reserve and the buffer zone and several basins, that had dried up continuously. They are represented by the cenoses of: Agopyreta intermediate, Festucaeta pseudovinae, Leymeta racemosae, Elimeta elongate, Poeata bulbosae, Lolieta perennae and others with the participation of Bermuda grass (Cynodon dactylon), on some places of Dichantium ischaemum and Chrysopogon grillus. Of second importance for the reserve and in connection with the ecological conditions of these habitats are the cenoses of the field and marine mugwort (Artemisia campestris and Artemisia maritim), as well as those, in which predominate Centaurea arenaria and Jurinea albicaulis. In the lower and more humid areas can be found the cenoses with the considerable participation of the Centaurea revenae and of the much abundant Juncus maritimus and Juncus atratus. Management Plan of Atanasovsko Lake
Appendix Three
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