Peculiar Influence of Nitrogen on the Daily Growth and Photosynthesis of Scots Pine in the Far North

Abstract

The study covered the Scots pine stands in the forest zone adjacent to tundra at the northern border of the coniferous forests range (66045‘N) and, in particular, the 33-year-old lichen pine forest which was analyzed for the dynamics of its physiological processes and the daily growth of longitudinal shoot. It has been found that both the physiological processes and daily growth can be intensified by using nitrogen fertilizer on the plantings. The research has further found that the daily growth of pine in the Far North is at its highest during twilight and night hours and that the greatest intensity of physiological processes occurs during daytime. It is during the indicated time periods that plants, due to intense photosynthesis, synthesize a significant amount of growth substances, which are then realized in the form of height increment during the twilight hours. Unlike the taiga zone (66045‘N), where the climate is more temperate, in severe climatic conditions of the Extreme North pine grows much slower and has a lower rate of physiological processes within 24 hours in comparison with the north taiga zone. The low rate of growth and physiological processes in the pine trees in the Far North are explained by low and fairly dynamic average daily temperatures. Nitrogen has a positive effect on the rate of growth and physiological processes in pine. Nitrogen exposure causes the daily longitudinal growth and its daily duration to increase in plants, the photosynthesis increasing significantly (1,4-fold) and the water regime normalizing the process. These positive changes lead to an improvement in the functional activity of pine and an increase in the productivity of pine stands.