Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 79. (Budapest 1987)

Debreczy, Zs.: Fluctuating-dynamic equilibrium of photophil, xerophil rupicolous plant communities and scrub woods at the lower arid woodland limit

ANNALES HISTORICO-NATURALES MUSEI NATIONALIS HUNGARICI Tomus 79. Budapest, 1987 p. 89-112. Fluctuating-dynamic equilibrium of photophil, xerophil rupicolous plant communities and scrub woods at the lower arid woodland limit by Zs. DEBRECZY, Budapest Zs. DEBRECZY : Fluctuating-dynamic equilibrium of photophil, xerophil rupicolous plant communities and scrub woods at the lower arid woodland limit. — Annls hist.-nat. Mus. natn. hung. 1987 79: 89-112. Abstract — The investigations, conducted on the lower arid woodland limit, confirmed a fluctuating static grassland-woodland equilibrium rather than a dynamic balance according to the cyclical successional model. Thus over a longer term, the edge of the scrub wood is maintained by the median-line equilibrium between expansion and regression. The investigations did not produce evidence of such a degree of denudation ("auto-denudation") of the scrub wood patches and the soil, built up over a period of many centuries, that even an association with the lowest production level can arise within its area. With 21 figures. Introduction — The main plant communities that have developed as a result of the competition of the open plant communities in the geobotanical unit of the Carpathian Basin can be summed up from the viewpoint of successional processes as the process of the gradual spreading of grass communities and then wood in the areas that are "too wet", "too dry" and "too cold", that is, by tracing the fixed gradients of a hygro-, a xero- and a frigido-series measured on a vegetation historical scale (Fig. 1). A "meso-series" may appear as a secondary process after the destruction of the most favourable final state of any series. The hygro-series (essentially the "spread of woodland in the open stretches of water" ) on the areas of "too wet" soil is poor in oxygen, rich in toxic gases with an inhibited vegetation and soil succession. The xero-series (Fig. 1) range through the spread of grassy rupicolous and woody vegetation on the raw basic stratum mainly according to an inhibitional type successional model (see later) and of a cataclimax (WHITTAKER 1974) showing succession end-points, from associations of lichen and moss (e. g. Mannio-fGrimaldio- JTortelletum inclinatae, RhacomitrioPolytrichetum piliferae, etc.), open and closed rupicolous associations ( Festucetalia, Festuco-Brometea

) and scrub woods (e.g. Cotino-, Mahalebo-Quercetum

) to the closed forest associations, like the Balkan type manna ash-pubescent oak, Turkey oak woods (Orno-, Corno-Quercetum, Quercetum petraeae-cerris, Quercetum frainetto-cerris

) or the West European type "acidophil" sessile oak woods (like Genisto-Quercetum). To the southwest direction, in the more humid West Balkan (lllyrian) territories the tomentose lime-oak woods (Tilio argenteae-Quercetum

) and the Balkan type sessile oak-peduncle oak woods (Genisto-Quercetum petraeae-roboris

) utilize best the climate-zonal ecological conditions. Near the mountains they give way to the most highly developed gradients of the hygro- and frigido-series like Balkan type oak-hornbeam associations (e. g. Asperulo taurinaeCarpinetum) and beech wood (e.g. Melitti-, Vicio oroboidi-Fagetum). Finally, the frigido-series (Fig. 1) begins with the spread of grass- and woodland to the upper flora and the forest limit, with the associations of Alpine moss-lichen (e.g. Epipetraea) associations on higher elevation and mixed firbeach (Abieto-Fagetum

), and mountain peduncle oak-sessile oak forests (Quercion robori-petraeae

) in lower elevation, where the end steps of the theoretical (vegetation historical) frigido-series join to the different stages of the other two series started at the two lower woodland limits. With regard to the attainment of the "macroclimatic climax" related to the climatic zone, the only acceptable view is to regard the succession processes as a long-term climatic period on the scale of climatic and vegetation history and on a territory sufficiently large enough to allow the ehmination of the secondary (internal-dynamical), autogenic processes. The allogenic succession processes directed by external circumstances of nonclimatic origin — where the formation really "arises ... and dies" as CLEMENTS (1916) stated — should be completely separated from the real concept of the true U The term "production level" is used to mean the approximately similar production "production scale" value domain of the more important units within the succession processes. In this way it is possible to bridge over the differences that do not essentially influence production, characterized by certain species present or absent regionally and expressed in the phytocenological nomenclature.