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11DEGRADATION OF VEGETABLE COVER ON A DRY BOTTOM OF
THE WESTERN ARAL SEA
S. A. Kochkarova F. V. Sapozhnikov P. O. Zavyalov
Karakalpak state university Moscow, P.P. Shirshov Institute of Oceanology RAS named after Berdakh
ABSTRACT
This article presents the results of an international research expedition conducted in May 2019 on the territory of the dried bottom of the Aral Sea in the region of the western chink. The types of vegetation are described in detail along 2 routes of 31 sites. It is shown that the processes of overgrowing of the soil cover of a drained sea day depend on the spatio-temporal dynamics and have a peculiar pattern.
Keywords: vegetation cover, desertification, ecosystem, anthropogenic impact, plant communities, western chink of the Aral Sea.
Introduction
As you know, the drying up of the Aral Sea gives rise to the process of desertification, which is actively developing in conditions of salinization of soils and insufficient moisture in areas exposed to intense anthropogenic impact [5]. In turn, this led to a rapid restructuring of the ecosystems of the coasts and the dried seabed. In recent decades, both the water mass of the Aral Sea and its dried bottom have attracted great attention of domestic and foreign researchers [3]. Of particular interest is one of the main components of the ecosystem - the vegetation cover and its dynamics.
Fundamental principles of vegetation dynamics were developed by the founders of geobotanical science G.N. Vysotsky [4], V.N. Sukachev [13], L.G. Ramensky [12], B.A. Bykov [2], E.M. Lavrenko [6], A.P. Shennikov [14], T.A. Rabotnov [11] and others. The dynamics of vegetation is understood as gradual directional changes that can be caused by both internal and external factors and have a reversible or irreversible character [11; 7].
The aim of this work is to study the characteristics of the vegetation cover and identify its species composition on the dried bottom of the Aral Sea in the area of the western chink, as well as determine the area occupied by vegetation.
Materials and methods
The basis of the factual material is the data of field studies, which were carried out in May 2019 on the territory of the dried bottom of the Aral Sea in the area of the western chink [1]. The expedition was carried out along two routes characterized by a high diversity of vegetation. The peculiarities of the terrain and the rather steep slope of the relief towards the sea make it possible, along the entire 2-3 kilometers of the route,
to follow the picture of the change of vegetation during the transition from the water edge of the indigenous coast in 1960-1961 to modern dry terraces. On the routes, vegetation descriptions were made on 31 control plots measuring 10x10 meters each. These areas were drained in different years and, accordingly, were characterized by periods of vegetation development of different duration (Table 1).
Site number Latitude degrees, minutes, seconds Longitude degrees, minutes, seconds Height above sea level (m) Dry year Since drying Saliniti of water (g/kg) Number of vegetation species Vegetation area (%)
1 45 6 2,7 58 20 0,4 53 1961 58 10 16 98
2 45 6 0,6 58 20 3,3 52 1966 53 11 13 100
3 45 5 52,1 58 20 4,9 49 1975 44 15 9 98
4 45 5 56,1 58 20 6,9 48 1977 42 16 13 94
5 45 5 52,4 58 20 8,1 47 1979 40 17 11 98
6 45 5 48,9 58 20 7,8 44 1983 36 22 9 96
7 45 5 46 58 20 10,4 41 1986 33 25 11 94
8 45 5 44,5 58 20 11,7 40 1988 31 30 6 97
9 45 5 44,1 58 20 12,7 38 1991 28 34 4 99
10 45 5 43 58 20 12,8 37 1993 26 38 9 97
11 45 5 41,4 58 20 12,9 35 1996 23 44 3 45
12 45 5 39,4 58 20 13 34 1998 21 54 6 79
13 45 5 38,3 58 20 13,6 32 2001 18 68 6 71
14 45 5 34 58 20 17,4 29 2004 15 92 3 100
15 45 5 32,8 58 20 19 28 2006 13 101 4 100
16 45 5 31 58 20 22 25 2012 7 117 3 50
17 45 5 44,1 58 19 18 47 1979 40 17 6 88
18 45 5 40,6 58 19 18 45 1981 38 19 13 98
19 45 5 28,8 58 19 19,6 46 1980 39 17 11 97
20 45 5 37,4 58 19 23,3 45 1981 38 19 8 97
21 45 5 36,3 58 19 25,8 43 1984 35 23 9 96
22 45 5 33 58 19 30,1 42 1985 34 25 9 97
23 45 5 30,2 58 19 33,2 40 1988 31 30 9 97
24 45 5 27,4 58 19 38,5 38 1991 28 34 5 99
25 45 5 24,6 58 19 43,3 35 1996 23 44 7 66
26 45 5 21,7 58 19 46,9 31 2002 17 82 0 0
27 45 5 19,3 58 19 55,8 27 2008 11 104 1 50
28 45 5 18 58 19 58,3 25 2012 7 117 1 50
29 45 5 17,5 58 19 59,7 24 2016 3 121 1 30
30 45 5 16 58 20 2,5 23 2018 1 125 1 20
31 45 5 26 58 20 14,8 23 2018 1 125 2 10
Table 1. Periods of vegetation development.
The description of vegetation was carried out for each stage separately, since each of them has its own period of life (Tables 2,3,4).
Geobotanical descriptions were made in all communities, where the population structure of species was studied, according to the generally accepted method "Field geobotany" [10]. When identifying the species of plants, we used the "Keys to Plants of Central Asia" [9]. Results and discussion.
An analysis of the results of the expedition at the sites under study revealed the current state of the prevailing plant communities:
1. Communities of barbed curl (Atraphaxis spinosa) with Segier's milkweed (Euphorbia seguieriana) - area 1, 2
2. Communities of leafless saxaul (Haloxylon aphyllum) with the participation of the Turkmen green leaf (Zygophyllum turcomanicum), sandy-woody astragalus (Astragalus ammodendron), leafless beetle (Calligonum aphyllum), comb beetles (Tamolimon taxonium), T. , tartar swan (Atriplex tatarica), small-toothed rosewort (Senecio subdentatus), etc. - area 3-10, 17-22, 24, 25.
3. Communities of the climacopter Aral (Climacoptera aralensis) - area 11, 12, 16, 23, 29, 31
4. Small-species communities with a low projective cover of the Aral climacopter (Climacoptera aralensis), salt marshes (Suaeda salsa), swan species (Atriplex sp.) And crossworts (Senecio sp.) - area 13-15, 27, 28, 30
5. Bare earth, sometimes with remnants of dry plants, shells - area 26.
Analysis of geobotanical descriptions and collected herbarium materials shows that the species diversity is relatively poor, but after 20-25 years in a drained state, the soil is covered with vegetation on almost 100% of the area. Comparative analysis of plant communities shows some similar features of them with the vegetation of Ustyurt. [15]. These are, first of all, wormwood (Artemisia terrae-albae), common on slightly gravelly, takyr-like and sandy loam soils. Less commonly, the dominants and subdominants of plant communities are (Salsola dendroides), (Stip hohenackeriana), (Atraphaxis spinosa) [8].
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Conclusions
Due to the distribution of the study route by sites, the state of plant communities in different drying zones, which occurred in different periods of shallowing and salinization of the sea, were noted. Changes in the plant community were recorded, the formation of saxaul forests, smoothly turning into semi-deserts and deserts on the modern bank of the Aral Sea. Quantitative geobotanical methods have revealed patterns of changes that have occurred over the past 60 years. The above data on the age spectrum of coenotic populations will serve for further monitoring of rare species of vegetation cover.
Participation of P.O.Z. and F.V.S. this work was partially funded by the Russian Foundation for Basic Research (grant 20-55-12007).
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