Оцінка посухостійкості Ailanthus Altissima (Mill.) в умовах Правобережного Лісостепу і Степу України

Abstract

The drought resistance of\xa0A. altissima during the growing season on the five-point scale of\xa0S.\xa0S.\xa0Pyatnytsky in the conditions of the Right-bank Forest Steppe and Steppe of Ukraine was investigated. Plants of the genus Ailanthus are found to be well tolerated by drought and often grow in places with limited water access. Increased air temperatures cause a change in the distribution of biomass from the aboveground part of the plants to the root system, as well as an increase in stem volume. This indicates increased water absorption from the soil and vascular movement due to the large cross-sectional area. The annular-porous structure of\xa0A. altissima tap water promotes the rapid transfer of water from the roots to the leaves. Due to the droughts, Ailanthus can quickly mobilize its reserves and then intensify the cambial growth and, as a result of prolonged stress, redistribute its reserves to the lateral roots from which new ramets may emerge after the loss of the primary shoot. Plants of the genus Ailanthus are well tolerated by drought and often grow in places with limited water access. According to the need for moisture and the degree of resistance to arid conditions, A. altissima is one of the most drought resistant wood species of xerophytes. According to the analysis of the monthly and average long-term data of the weather station in Uman during may\xa0– august, a comparative characteristic of the hydrothermal regime of the years of researches is given. The water and thermal regimes of tree and shrub species in the Steppe have been determined to be a major physiological aspect of the success of the steppe afforestation, which is why the relevance of the study of the resistance and adaptation of the introduced\xa0A.\xa0altissima species to the unfavorable conditions of the steppe zone is obvious. It has been proved that\xa0A.\xa0altissima plants growing in the conditions of the Right-bank Forest Steppe and Steppe of Ukraine responded to the drought without significant damage, maintaining a high turgor of leaves and young shoots. Trees of the studied species had close to the highest and highest drought tolerance scores (4.8-5.0\xa0points). It was found that during the 2014-2017\xa0period no significant signs of leaf foliage in adult\xa0A.\xa0altissima trees were detected in the Right-Bank Forest Steppe and Steppe of Ukraine. All the A.\xa0altissima trees under study were well-tolerated\xa0to high summer temperatures (up to +38 °C) and long sleepless periods (55-60\xa0days). The results of the study of the water regime of the leaves of\xa0A.\xa0altissima by the indicators of the total water content, water deficit and the intensity of moisture loss, which indicates a high level of adaptation of the studied plants to arid periods in the Right-bank Forest-Steppe and Steppe of Ukraine are presented.