Key words: succession system, landscape, vegetation, sere, stage, indicator
A succession system of vegetation is a system of succession series of plant communities within a landscape province. The succession system includes the communities formed in the course of both spontaneous and directed (recultivation) succession dynamics. This system is a model which serves for ordering the time and space vegetation pattern along the axes of time and the main ecological factors. Each specific community (ecosystem) is ordered in the hyper- space of succession systems (axes - time or successional age, location in the relief, lithology of overlying deposits, initial disturbance level, etc.). Each landscape has its succession system which causes its resistance as ability to self-restoration.
The model succession system of the Polessye province of alluvial terraces, marshy and secondary water-glacial landscapes is suggested. The basic object of research is an alluvial terrace landscape. The ecological floristic method of Braun Blanquet was used for material treatment. To estimate the conditions of habitats indicator scales by Ellenberg, Landolt and Tsyganov were used. The vegetation dynamics was studied on permanent plots and the method of space for-time substitution was applied.
Only those series which started on bare ground where a succession is traced from the very beginning were considered. During the research a number of succession series occurring in localities disturbed to different degree by human activities was compared. Three basic series spontaneous successions were distinguished: 1) mesic sere (succession on a terrace with moderately damp and rich ground, the leader to a climatic climax); 2) wet sere (succession on strongly damp and boggy ground the leader to an edafic climax); 3) dry sere (succession on dunes and ridges with strongly dry and poor ground). Peculiar features of succession stages in each sere are described. In the course of succession some changes of the species composition, prevailing vital forms, phytocoenosis structure of vegetation and also ecological conditions are observed. The early successional and late successional communities typical for region are observed.
The initial stage of the mesic sere is represented by communities of the class Chenopodietea albi Br.-Bl. in Br. В I., Rouss. et Negre 1952 em Lohm., J. et R. Tx. ex Mat. 1962, that are replaced by communities of the class Artemisietea vulgaris Lohm., Prsg. et R. Tx. in R.Tx. 1950 em Kopecky in Hejny et al. 1979. The early stages lasted as long as 5 years. The succession end is the climax which is represented by communities of the class Querco Fagetea Br. Bl. et Vlieger in Vlieger 1937 (association - Tilio cordatae-Carpineturn betuli Tracz. 1962). The broad leaved forest is restored in 100-200 years.
The influence of anthropogenic factors (cattle breeding, mowing, fires, recreation) at the stage of the basic series causes rows of transformation (digression series). During a digression series it is possible to reveal the character, time, capacity and degree of influence. Examples of such series are presented.
The model of the succession system is the framework for phytoindication of the natural and anthropogenic dynamics of landscapes. The study of successional processes is important for restoration ecology and restoration programs. The use of the succession system permits the tentative prediction of the rate and directions of succession unless a detailed study is conducted usually due to the lack of time or money or both.
