Accumulation Dynamics of Plastid Pigments in Spruce Undergrowth in Ontogenesis of the Bilberry Birch Forest

The paper presents the study of the seasonal and long-term dynamics of accumulation of photosynthetic pigments in spruce undergrowth in the ontogenesis of birch stands in the bilberry birch forests of the Northeast of Russia. The study was carried out by the spectrophotometric method. The minimum amount of chlorophyll and carotenoid pigments in needles of spruce undergrowth is in 1−8-year-old stands of birch forests, when the light stream arriving under the canopy does not limit the need of spruce in solar radiation. During this period, the maximum ratios between the components of chlorophyll and the minimum ratios between the light-harvesting and chlorophyll-protein complexes in the energy-converting system of chloroplasts (1.05 : 1.40) are recorded in the needles. According to the authors' data, such proportions in spruce undergrowth correspond to the maximum intensity of photosynthesis and promote the synthesis of carbohydrates in chloroplasts. With increasing the age of the birch forest, due to the formation of the upper shading hardwood canopy, the concentration of pigments in the needles of spruce gradually increases. The maximum concentration of chlorophyll and the minimum ratios between its components in spruce undergrowth are observed in 50−80-year-old birch forests, when the undergrowth is experiencing an acute shortage in solar radiation. Gradual felling in bilberry birch forests with the volume intensity of 45…52 % increase the influx of sunlight under the canopy and lead to a decrease of the concentration of green pigments in the needles in spruce undergrowth, especially chlorophyll b, increase the ratio of chlorophyll a : chlorophyll b, reduce the ratio in the energy-converting chloroplast system between the light-harvesting and chlorophyll-protein complexes to 1.26, while improving the rate of photosynthesis to 2.2−2.4 times and activate the processes in the cell associated with carbohydrate synthesis. The salient degradation of chlorophyll is absent in spruce undergrowth in the bilberry birch forests during winter, although it is usually noted. In the seasonal dynamics of accumulation of green pigments maxima are clearly marked: the first is large in summer, and the second, which is less significant, is observed after the leaf fall, not found in spruce trees.