Peculiarities of growth and cultivation of plantations of QUERCUS ROBUR L. on the sands of the north-eastern Pre-caucasian region

Rational use and prevention of deflationary desertification of the sandy lands of the arid zone is impossible without their provision with protective forest plantations. On the pastures of the region, the stands of oak have a high protective effect and durability. The purpose of the study is to study the peculiarities of oak growth and water supply on different geomorphological types of sands, to improve their afforestation regimes and methods of growing oak forests in the region. The objects of the study were 68-85-year-old plantations on the Tersk and Bazhigansky sand massifs, growing at a precipitation rate of about 320 mm/year, with an evaporation rate of 800-1000 mm/year. The condition and growth of stands were studied in temporary test areas using generally accepted methods followed by mathematical processing of the data obtained. It has been established that the influence of atmospheric precipitation on the water supply of oak forests has a relatively low and extremely unstable effect. Only in 6-9% of the years it is provided by their number. In other years, the growth and viability of stands is determined by the availability of groundwater, which is replenished by the influx from neighboring non-forested areas. The best conditions for oak growth are formed on sandy loam soil of depressions with the occurrence of fresh or slightly mineralized groundwater at a depth of 2-4 m. On re-sown multi-layered sands, forest conditions worsen as the thickness of the soil layer previously moistened by precipitation decreases and with groundwater mineralization exceeding 8-9 g/l, as well as everywhere with the age of plantings, due to the depletion of the initial reserve of soil and soil moisture. Pasture digression of the herbage in adjacent pastures slows down this process and helps to increase the longevity of the stands. On all types of sands, fine-contoured plantings, their alternation with open areas of functioning pastures, moisture-accumulating tillage, the creation of clean crops, timely agrotechnical care and thinning of the stand are relevant.