Effect of Gas Extraction on the State of Euphorbia sclerocyathium Korov.et M.Pop. Population Habibullo F. SHOMURODOV* 1) and Shakhnoza SARIBAEVA 1) Abstract: This article cites the results of a three-year study of the modern state of a rare Central Asian species, Euphorbia sclerocyathium Korovin et Popov, the population of which is affected by gas extraction. The age composition and biometrical values of individuals were revealed to assess the state of populations of this species. The analysis of the obtained data shows that the ontogenic structure of the species in Shahbahta is not complete as senile individuals are absent. However, in most cases biometric values are positive. Based on the aggregation of ontogenetic structures and biometric values, the vitality of the species in this cenopopulation is evaluated as moderate. It is noteworthy that the prevalence of a pre-generative age state and young generative individuals in a population is connected with plants supporting their population through vegetative breeding ( i.e. the availability of rhizome). Key Words: Cenopopulation, Ontogenetic structures, Species vitality, Ustyurt Plateau 1. Introduction The Uzbek part of Ustyurt occupies the area of more than 7.2 million ha and is an elevated plateau occupying the northern part of the Aral-Caspian watershed. The Ustyurt escarpment in the east is formed by a former western coast of the Aral Sea. The extreme conditions resulting from the drying up of the Aral Sea have brought about the deterioration of the ecological complex of the Ustyurt, which significantly affected the natural vegetation. Plant landscapes in Ustyurt have been forming owing to plants of a primary stony desert and heterogeneous flora (Popov, 1923), the fragments of which have been preserved in a modern plant cover in the form of rare species. Korovin (1943) assigned Salsola chiwensis , Sisymbrium subspinescens, Cleome noeana, Seseli tenuifolium, S. cuneifolium, Zygophyllum macropterum, Z. brachypterum, Z. eichwaldii and Z. turcomanicum to this group. According to this author, 402 plant species grow there, of which 19.7% belong to the family Chenopodiaceae. The most authentic data on the flora of the studied region are available in the work of Allaniyazov (Saribaev, 1983). In this work, the author cites 406 plant species of 208 genera belonging to 46 families. While analyzing the flora of the entire Ustyurt, Saribaev (1987) established that the flora of this region is comprised 724 species of 295 genera and 60 families. According to Allaniyazov (1995), the families Chenopodiaceae, Asteraceae, Brassicaceae, Poaceae and Fabaceae prevail by their specific diversity in Ustyurt. In the plant cover perennial herbs prevail, followed by annual herbs, semi-shrubs, biennial herbs, trees and shrubs. The numbers of rare and endemic species in the plant cover of the Ustyurt Plateau is low. These include Climacoptera ptiloptera U.P.Pratov, Euphorbia sclerocyathium Korovin et Popov, Malacocarpus crithmifolius (Retz.) C.F.May., Atriplex pratovii Sukhor., Crambe edentula Fish. et Mey. and Salsola chiwensis Popov, growing in grey-brown gypsum bearing and saline soils of Ustyurt. The eastern border of the range of the latter two species to some extent overlaps the Kyzylkum desert. Besides, not far from the eastern escarpment of the plateau in 2010 we found and described Allium ravenii F.O.Khass., Shomuradov and Kadyrov from the subgenus Allium L. (Khassanov et al ., 2010). Four species of vascular plants from this region were included into the last edition of the Red Data Book of the Republic of Uzbekistan, namely, Malacocarpus crithmifolius (Retz.) C.F.May., Climacoptera ptiloptera U.P.Pratov, Salsola chiwensis Popov and Euphorbia sclerocyathium Korovin et Popov, to which the present article is devoted. 2. Materials and Methods Euphorbia sclerocyathium Korovin et Popov belongs to the Euphorbiaceae family. It grows on stony and sandy soils, as well as on solonetz soils, saline grey-brown, stony and sandy soils. Outside Uzbekistan it also grows in Turkmenistan. To assess the cenopopulation of Euphorbia * Corresponding Author: h.shomurodov@mail.ru 232 gishamol streer, Tashkent, Uzbekistan 1) Institute of Gene pool of Plants and Animals, Uzbek Academy of Sciences Received, September 14th, 2013; Accepted, December 10th, 2013 － DT11 Refereed Paper － 沙漠研究 24-1, 265-268 (2014) Journal of Arid Land Studies