Water metabolism of leaves of Quercus robur in antierosion stands in the south of its range

Abstract

We have investigated the main parameters of water exchange in leaves of Quercus robur L. which grow on the south-facing slope of the Viyskoviy ravine in a variety of water supply conditions. We established that the greatest intensity of transpiration of leaves of Q. robur occurred in the forest vegetation conditions of SG2, the smallest in SG1–0. In all study periods the largest amplitude of daily fluctuations in intensity of transpiration occurred in leaves of plants along the talweg, at other test sites the limits were much lower. The highest rates of transpiration were in September, which is connected with the high temperatures and lower relative air humidity compared with the days of measurement in July and May. We established that at the beginning of the growing season there was no difference in the total amount of water in the leaves of the trees that grow on the middle and upper parts of the slope, but that it was greater in plants along the talweg. In the following months the difference between the water content in the leaves of trees along the talweg and upper third of the slope increased. The leaves of trees that grow in the poorest conditions of water supply were characterized by the highest water-holding capacity, which is coordinated with their containing the highest content of hydrophilic colloids. The values for water deficit in May and in July fell within the maximum fluctuations for the species studied, but in early September they exceeded the maximum value in the leaves of trees on the upper third of the slope.