B. Papp szerk.: Studia Botanica Hungarica 38. 2007 (Budapest, 2007)

Szollát, György, Seregélyes, Tibor, S. Csomós, Ágnes; Standovár, Tibor: The flora and vegetation of Gödi Láprét near Göd, Pest county, Hungary

species of the purple moorgrass meadows, like Carex panicea, Serratula tinctoria and Valeriana dioica are abundant, however, Orchis laxiflora subsp. palustris, Sanguisorba officinalis, at some sites Selinum carvifolia and Succisa pratensis are also not rare, but less abundant. Of the common species of mesophilous habitats Potentilla erecta, Centaurea pannonica, Carex flacca, Mentha aquatica, Lysimachia vulgaris, Lythrum salicaria and Tetragonolobus maritimus subsp. siliquosus are frequent. Occurrence of Carex buekii, a Ponto-Pannonian rarity of the country, and Carex appropinquata (a few shoots, not forming tussock), having a boreal distribution character, are worth mentioning. Carex elata is also represented by a few shoots as remnants of some decayed tussocks. The dense moss layer is typical for these rich fen beds. Rich fens in general are severely threatened by a number of factors. In our area one is the decreasing water supply caused by the drainage effects of the extensive housing developments, resulting in successive changes in species composition eventually shifting towards the purple moorgrass meadows. The range of the rich fen beds phytosociologically belonging to this vegetation unit has suffered sincere reduction since 1992. The other reason is the expansion of certain species for the lack of any conservation management in the area. In 1992 we found only one relatively small population of Cladium mariscus, which has been expanding greatly from the bank of the thermal water ditch. It is easy to recognise the direction of expansion as the youngest shoots, forming the advancing frontline of the population, are the shortest and surely of vegetative character, while the older parts of the stand are composed of fertile shoots of almost a man's height. The monodominant Cladium mariscus beds are so closed that practically all other plant populations are excluded from the invaded area, and this can be fatal for the future of the species-rich fen if not dealt with the problem properly. The expansion of Cladium mariscus may be correlated with increasing amounts of nutrients or the accumulation of minerals in the soil probably originating from the thermal water ditch. Phragmites australis is also invading the area from the thermal water ditch, though not threatening the most waterlogged parts of the site yet. The relatively small areas of rich fens are surrounded by purple moorgrass meadows, so the representation ofMolinia coerulea in the rich fen sites is significant: it can be abundant, even codominant mainly in the transitional zone of the two vegetation units. However, Molinia coerulea in this zone form short and vegetative or poorly flowering shoots, while in the adjacent beds of purple moorgrass meadows they are 1.5 metres tall and flourishing. The same can be recognised in respect of two other characteristic species of purple moorgrass meadows, Sanguisorba officinalis and Succisa pratensis, as their individuals are getting shorter and shorter, gradually growing closer and closer to the rich fen beds, finally dwindling away, and making a visual outline at the border of the two associations in the autumn. As in other similar habitats, this border is not particularly sharp, but still has a considerable extension at the Gödi Láprét. Similar transitional association types have been analysed in KOVÁCS (1962) as Juncetum moliniosum and Schoenetum molinietosum.