Researcher, Laboratory of Dynamics of Terrestrial Ecosystems

Under the Influence of Water Factor, Water Problems Institute

of Russian Academy of Sciences

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Abstract. The vigorous water economic activities carried out from the middle of 1950 in the basin of Amu Darya river have led to sharp reduction of river flow in its delta. The environment of Southern Priaralje has essentially changed. In the 1980s, the southern basin of Aral Sea was declared to be the zone of ecological disaster. The analysis of hydrological data (1944–2000) at different locations of the Amu Darya delta made it possible to detect and characterize a succession of periods with different mean values of the river flow. Each period was studied as the zone of normal vital activity (the optimum zone) for a finite subset of plant species from the set of all species found in the Amu Darya delta in 1947–2000. Dynamics of ecosystem components of the Amu Darya delta has been investigated. Hydromorphic soil formation process had replaced the automorphic process (1971–1977). The relations between the elements of the rich structure of plant species in the Amu Darya delta (1947–1981) have been described by equation. Irreversible changes had occurred in the composition and structure of the flora of the Amu Darya’s ecosystem (1977–1981). Bifurcation period (1982–1989) has been established. A new state of Amu Darya’s delta ecosystem (1990–2000) has been established on the basis of dynamics of the structural components of flora. The richness of plant species in the ecosystem of the Amu Darya delta in this period increased by 46 % compared to the conventionally natural period before the year 1960. The relations between the elements of the plant species richness structure in the Amu Darya delta have been changed.

Key words: ecosystem of the Amu Darya delta, river flow, species richness, structural invariant, bifurcation period.