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

"climate-zonal, extrazonal, azonal-extrazonal" (see later) types of climax. The production levels

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' of the association types as fixed gradients of the succession within the flora determined by the vegetation history, as ODUM (1969) also holds are strictly linked to the "water-heat" and "heat" factor of the climate and the movement within the association is essentially not succession but a permanent movement and dynamism, a constant renewal within the production level, the autogenesis — succession — of the individual within the biosystem, which is the climax of the individual plants and not of the association.

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) In order to clarify all these, particularly in the case of the theories tracing cyclical succession processes, it is important to know whether, in the case of forest associations, the ageing of a given tree, the appearance of a pioneer or of a tree species that is temporarily less productive, indicate succession (NUMATA 1979), whether a case of cataclimax is involved in the North American forests observed by Numata. The "perpetuated stage" in the process of the spread of woodland at the "excessively dry lower woodland limit" in the Balaton Upland. The vegetation of the area studied (see later) developed on a south-facing slope with soils of poor water retention on a hard basic stratum — similarly to the squares of an arrested film strip — we see the survival of the praeglacial, former common Alpine-Balkan Alpine, today, predominantly Balkan subalpine-Alpine elements in the photophil-xerotolerant moss and rupicolous associations and the xerophil woody elements forced into a lower zone in the glacial-postglacial period (BÍRÓ & DEBRECZY 1985) as perpetuated gradients of the spread of woodland in a xero-series. We can actually observe the beginning of a CONNEL & SLATYER (1977) type inhibitional succession model and its equilibrium through periodical denudation as regards the moss and rupicolous associations and the rupicolous associations and scrub wood too. The perpetuated sub-climax associations maintained by the local- and microclimate as more or less stabilized stages of a vegetation historical successional xero-series are compared with the climate-zonal climax vegetation of the present. They are gradients of the extraclimate-zonal climax, that is, the "extraclimax" series that has been perpetuated by the extrazonal climates caused by exposition. In this row all members and gradients of the xero-series survive until there is a decisive change of climate, essentially forming a row of negative extraclimax'*' with production level less than climax. When studying the south-facing areas with a water loss and heat gain in the oak zone of the Transdanubian Central Mountains, JAKUCS (1961, 1972) outlined what is essentially a cyclical succession model to explain the survival and equilibrium of grassland and scrub woodland (JAKUCS 1972, p. 210-212; see also Fig. 2). The essence of this process is that with the constant spatial movement of the photophilous-xerothermotolerant grasslands and dwarfed scrub woods (Cotino-Quercetum) of the pubescent oak forests (Orno-Quercetum

) at the limits of their existence — the movement that takes place with the frontal advance of the woodland and the dynamism of the grassy areas taking over the place of the forests — there is constant alternating spread of woodland and rupicolous communities. JAKUCS drew the conclusion that the woodland is spreading on the basis of two major factors : on the one hand he measured the extent of the scrub wood, especially the Cotinus ring (

Saum) and on the other, by making precise analyses he showed the gradation in soil from the black rendzina soil of the scrub wood to the deteriorating rendzina of the edge and the skeletal soil of the rupicolous associations (JAKUCS 1972, p. 65, Fig. 9; for a microclimatic diagram supplemented with Jakucs' data, see also Fig. 21). However, he needed to account for denudation in the woodland succession to explain the survival of rupicolous associations over a period of vegetation history. His concept of denudation was that while the woodland spreads at the expands of the rupicolous associations, with the death of ageing trees and the collapse of the scrub woods, the climate in the interior of the wood*) For this reason the author can interpret Clement's "climax" expression in the case of natural plant associations in the sense identified with the (zonal or extrazonal) "climate maximum" that is the vegetation unit with maximum production for the given ecological enviroment mainly limited by the actual (local- and micro-) climate and flora, and rejects the notion that with unchanged ecological (climatic) conditions and even without exogenous factors, an associa tion can reach the phase "climax" as a highest developmental phase before decline (as CLEMENTS ( 1916. p. 3) stated : "As an organismthe formation arises, grows, matures and dies.

.. But the most stable association is never in complete equilibrium, nor is free from disturbed areas in which secondary succession is evident." 3> The author proposes the introduction of the concept of "negative (-) extrazonality" for associations with a production of less than that of climate-zonal climax (reaching the greatest production within the given climate and vegetation zone) and "positive (+) extrazonality" in areas with water gain for associations with greater than climate-zonal production (DEBRECZY 1981, 1987). Another term in context is the "azonal type extraclimax" which qualifies a type of vegetation having developed on territories with extra water supply being independent from the water factor of the local climate. The "azonal-extrazonal" expression is used to distinguish between a theoretical azonality, entirely independent of the climate zone, and a genuine azonality. Fekete (ex verb.) questions this combination of climax, zonality and production; however, in the author's experience, it is very well suited for concisely indicating interrelated phenomena and facts.