Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 77. (Budapest 1985)

P. Komáromy, Zs.: The role of algal synusia of grasslands in successional process in Hungary

ANNALES HISTORICO-NATURALES MUSEI NATIONALIS HUNGARICI Tomus 77. Budapest, 1985 p. 97-102. The role of algal synusia of grasslands in successional processes in Hungary by Zs. P. KOMÁROMY, Budapest Abstract

—The algal flora of the Hungarian grasslands was studied. The importance of cryptogamic crusts is well-known, but the studies of floristical patterns of algal communities are rare. Algological investigations on various soil types suggest that algal crusts have characteristic floristical composition and take a definite place in the biotic succession of grassy plant communities. With 4 figures. Grasslands are widespread in the Great Hungarian Plain in consequence of climatic and edaphic conditions. The soils of cultivated and uncultivated fields are exposed to erosive impacts because of the lack of woody vegetation. Owing to the low amount of precipitation (ranging between 500-600 mm per year) and the low relief energy, the importance of rainfall erosion is not considerable. On the other hand, winds devastate freely in the extensive open areas, mainly during the long dry periods. The grassy vegetation is characterized not only by the lack of woods but by extensive algal crusts as well. The visible algal coats are rich in species but sometimes they are the mass-production of one or two species only. The cryptogamic crusts are widespread throughout the world in arid zones (ALI & SANDHU 1972, BROTHERSON & RUSHFORTH 1983, CAMERON 1964, DEASON & BOLD 1960, DURRELL 1959, FLECHTER & MARTIN 1948). The algal crusts are also the primary components of grassy plant communities in Hungary and they play an important role in binding the soil particles and in decreasing the degree of soil erosion. Filamentous blue-green and green algae of mucilaginous sheaths produce a stable surface layer with soil particles. Having a characteristic microrelief, this layer deflects the micropattern of the wind and decreases the intensity of rain and hence the degree of soil erosion. The algal crusts promote occupation by mosses and lichens and so contribute to the progress of the successional processes. Therefore it is not without interest to have exact information about the species pattern, successional and other relations of the algal synusia of grassy plant communities under semiarid conditions. The salt-affected soils and calcareous sandy soils of the Great Hungarian Plain are characterized by filamentous green and blue-green algae : Chlorhormidium crenulatum, Phormidium, Lyngbya, Nostoc, Calothrix and other species. They have mucilaginous sheaths and form a compact network with soil particles. This rather firm thin layer offers resistence to mechanical effects in dry and wet conditions. Algological investigations on solonetz soils in the "Hortobágy" and on solonchak and solonchak-solonetz and calcareous sandy soils in the "Kiskunság" suggest that these algal crusts have characteristic floristical composition, they are synusia and take a definite place in the biotic succession of grassy plant communities. Biotic succession is the chronological succession of the plant communities under constant macroclimatic conditions, which happens as a result of either extrinsic ecological factors or by population dynamical processes. The successional processes themselves are realized through a series of coenostates. A coenostate can be considered as a species assemblage existing in a given place and at a given time under a given ecological circumstance. The various coenostates existing side by side in space may be considered as temporal successional stadia. In the case of salt-affected soils, the alternation of the particulate microrelief, the dry and wet biotopes eventuate the mosaic-like pattern of the small alkali flats, halophyte steppe patches and small astatic salt pools. All of the halophyte plant communities provide favourable conditions for the formation of algal crusts. These surface crusts may be rich in species or they are the massproduction of some species. 7 Természettudományi Múzeum Évkönyve 1985