Composition and structure of tugai communities in indication of ecological conditions in Lower Amu Darya
A. Yu. KOROLYUK1, Kh. F. SHOMURODOV2, B. Sh. KHABIBULLAEV2, Zh. S. SADINOV2
1Central Siberian Botanical Garden of SB RAS, Novosibirsk, Russia
2Institute of Botany, Academy of Sciences of the Republic of Uzbekistan, Tashkent, Republic of Uzbekistan
Keywords: tugai vegetation, phytoindication, desertification, Central Asia
Abstract
Tugai ecosystems of desert river valleys are one of the most affected and endangered landscape types. The largest areas of tugai vegetation in Uzbekistan are preserved in the lower basin of the Amudarya River. Here are the main massifs of poplar forests. To assess their current state the analysis of 284 relevés representing tugai plant communities in the lower basin of the Amudarya river was carried out. For each of them the position on ecological gradients was determined by species indicator values. It is shown that the greatest scatter of relevés is observed on moisture gradient - from 17 to 97 grades, it is noticeably smaller for pasture digression (2.5-6.5) and soil salinity (16.1-19.5). To reveal the relationships between the species composition and environmental factors, CCA ordination was done. Groups of relevés were identified, representing the native tugai vegetation and three ecological series which are connected with salinity, soil moisture, and anthropogenic pressure. Accordingly, 4 generalized plant communities were distinguished, differing in species composition, floristic diversity, and structure. Indicator plants were identified on the base of formalized assessment of species constancy and importance values. The changes in species composition and structure of communities (life form spectra) are shown. It has been established that the most active process followed the progressive desertification is the halophytization of vegetation. This process is reflected in the replasement of poplar forests to shrub communities dominated by Halostachys belangeriana and Tamarix hispida. As a result of intensive anthropogenic impact, the vegetation is transformed and the importance value of ruderal annual plants become higher.
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