The research aims at identifying the effect of nitrogen on daily growth and intensity of physiological processes in pine trees. The research was carried out in 2017–2018 in the north taiga zone of the Arkhangelsk region. A 33-year-old shrub-sphagnum pine forest (64° 45ʹ N), formed of pine undergrowth after felling of a parent stand, served as an experimental object. It was found that in the North in the sphagnum forest site conditions, pine growth in height has a maximum rate in the evening

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... ky) and night hours. The highest intensity of physiological processes in pine trees is observed in the daylight hours. As a result of increased photosynthesis, the tree receives the macronutrients necessary for normal growth. Unlike lichen pine forests, in which the roots are not affected by waterlogging, in excessively moistened shrub-sphagnum pine forests pine trees grow much slower and during the day have a less evident intensity of physiological processes than in lichen pine forests. The low growth rate and slow physiological processes of pine in shrub-sphagnum pine forest are due to the disturbance of its root system as a result of root anaerobiosis caused by flooding. Constant excessive soil humidity and, as a consequence, its reduced aeration, reduce the effective action of nitrogen on the growth of pine trees in these conditions, and at the same time inhibit the absorptive activity and synthetic processes of the roots. Nitrogen fertilizers applied to shrub-sphagnum pine forests have a generally positive effect on the growth and physiological processes of pine trees, but act much weaker than in dry lichen pine forests. Under the influence of the nitrogen dose N180 pine trees have a 30 % increase in daily growth in height, the intensity of photosynthesis increases significantly, and as a result of reduced water consumption for transpiration, the water regime is normalized and transpiration productivity increases. These positive changes in growth and metabolic processes, occurring under the influence of nitrogen fertilizers introduced into the stands, improve the functional activity of pine and increase (in the case of additional drainage) the productivity of excessively moistened shrub-sphagnum pine forests.