Description
The research was aimed at analyzing the peculiarities of water exchange in Pinus pallasiana D. Don needles from the anti-erosion plantation on the slope and in the thalweg of the Viyskovyi ravine under different forest growth conditions. The ravine is located in the Dnipropetrovsk region and belongs to the southern geographical variant of ravine forests. The studied plants grew at three experimental sites of man-made plantation: in the thalweg (forest growth conditions – mesophilic, fresh, CL2), in the middle part of the slope of the southern exposure (mesoxerophilic, somewhat dry, or semi-arid, CL1), and on the upper part of this slope (xerophilic, arid, CL0–1). The course of the daily intensity of transpiration, the average daily amount of midday transpiration, the humidity of the needles, its water deficit, and the water-holding capacity of the needles were studied. The research was conducted from May to September. The curve of the daily intensity of transpiration had differences in different versions, but it had the most smoothed character in May. The maximum values of the intensity of transpiration and the amplitude of their changes were observed in July and August. During the study, the plants of the thalweg evaporated water most intensively and the plants of the upper part of the slope evaporated it least intensively. In the morning and evening, the values of this physiological process differed little in plants growing under different forest growth conditions. A significant difference was recorded at noon. The moisture content in needles in all areas was maximum in May and minimum in August, which is caused by the increase in soil dryness. During the experiment, the difference was the largest in mesophilic plant areas and smallest in xerophilic plant areas. The midday water deficit in the needles of thalweg plants was the lowest in May, but slightly increased during the summer months. In more arid conditions, compared to plants normally supplied with water, the water deficit was more pronounced, despite the decrease in the intensity of transpiration. Its maximum values in all variants were noted in August. In all variants of the experiment, a high water-holding capacity of needles was found, especially in July and August. Water loss was the highest for thalweg plants and the lowest in dry areas. The plants of xerophilic habitats have adaptations such as a decrease in the intensity of transpiration in hot hours, a shift of the maxima in their daytime course to the morning and later periods compared to plants of normally watered areas, and an increase in the water-holding capacity of the needles.
