Identification of resistant climatypes of leafless saxaul (Haloxylon aphyllum (Minkw.) Iljin) in arid conditions

Leafless saxaul (Haloxylon aphyllum (Minkw.) Iljin) is a typical psammophyte that has begun to be widely introduced into the practice of protective afforestation in arid and semi–desert zones, as many years of growing experience have shown that plantings from other tree species of the xeromesophytic group in the semidesert zone cannot withstand harsh climatic conditions and die relatively quickly. The identification of stable saxaul populations was carried out in both natural and artificially created plantations, population variability was studied in permanent test areas, where each tree was described in detail. It turned out that shortage of water in the soil (40% of the total moisture capacity) activates the capacity of the cell membranes of the saxaul’s root, and excessive moisture saturation, on the contrary, slows down its growth and development. It has been found that with a decrease in solar radiation during plant growth, saxaul becomes less resistant to low temperatures in winter. The critical temperature for it changes from –19–20°C to –13–14°C. Based on the results of the experiment, negative temperatures were found, at which mass plant death begins (more than 50%). With the arrival of spring, when the temperature becomes positive, the saxaul begins to actively grow and develop. This usually happens within 610 days. By this time, its ability to withstand frosts is reduced to –1822°C. Two groups can be distinguished among the climatypes of the leafless saxaul in terms of resistance to the complex effects of factors: climatypes from Kazakhstan, which are highly resistant; climatypes from Uzbekistan and the Astrakhan region with moderate resistance.