Water Exchange in Coniferous Phytocenoses under the Influence of Climate Change

Woody vegetation and the atmosphere are closely related, which determines the relevance of studying this interaction within the framework of the problem of global climate change and the resilience of terrestrial ecosystems to external influences. For the research region, the Komi Republic, climate warming has been revealed, expressed in increased air temperature in the summer. The warmest year over the years of observation was 2013, when the average air temperature in the summer was 17.2 °C, while the longterm annual average norm was 14.6 °C. The growth and productivity of woody plants in a forest community depend on the amount of moisture in the soil. In the middle subzone of the taiga, moisture reserves are 60–200 mm, so woody plants do not lack it. In this regard, transpiration rates of Scots pine and Siberian spruce needles in different types of forest under fluctuating weather conditions has been studied. The results of the research have shown that at elevated air temperatures, low amounts of precipitation and favourable soil water supply, the transpiration rate in pine increases by 1.5 times, and in spruce by 3 times. This is probably due to the fact that the spruce stomata react especially quickly to changes in external conditions, which is determined by the increased sensitivity of the needles to moisture conditions. It has been established that during the same period there is the closest relationship between the transpiration rate and the air temperature (r = 0.7–0.9). In different types of forest, the transpiration rate in pine varies from 4 to 16 %, in spruce within 5 %. An assessment of changes in the pine and spruce needles transpiration rates in response to changing weather conditions has shown that this process is largely determined by the species membership. Pine is a light-demanding species with a taproot system. Spruce is a shade-tolerant species with a shallow root system.