Functioning of the Leaf Apparatus, Root System and Biological Productivity of Siberian Larch on the Level of the Organism in Ontogeny (the Case of Larch Forests of the Arkhangelsk Region)

The ecological, physiological, agrochemical, balance methods of investigation, characteristics of soil and climatic conditions of habitats and the results of model experiments carried out by the authors, are used to obtain quantitative data on the operation of the leaf apparatus, root system and indicators of biological productivity and carbon deposition by plants of Siberian larch in ontogeny. Tabular data of the root, needle, trunk and branches mass given per one hectare for the stands of Iа–V yield classes of the Arkhangelsk region are converted to an average (by weight) plant by age. Biological productivity is determined by a relative increase in the dry weight of a plant in the comparison periods, net productivity of photosynthesis according to the formula given by A.A. Nichiporovich (1955), and mineral productivity by the method of V.M. Lebedev (1998). The nature of the plant reaction on the depletion of soil resources with age, affecting physiological, functional and morphological processes and biological productivity of plant sis established. In the forest stands of all yield classes from 25 to 300 years, we observe a decrease in the net and biological productivity of photosynthesis and carbon deposition, depending on the yield class, by 4.1–8.1, 15.7–19.9, 5.6–10.7 times, respectively, and the absorption of nitrogen, phosphorus and potassium by 20.4–42.2, 24.3–53.1, and 24.0–50.2 times, respectively. The indicators change dramatically to the age of 75–80 years, and then they relatively stabilize, remaining at a low level. The ratio of the root potential to the photosynthetic potential during ontogeny in creases by 4.5–5.4 times. The supply of plants with nutrients to maintain photosynthesis has increased, the biological productivity has not decreased as sharply as the net productivity of photosynthesis and mineral productivity. The presented data significantly supplement our knowledge of biology of woody plants, contribute to the expansion of research in the field of ecology and physiology of woody plants and serve as a theoretical basis for the development of agricultural methods for managing the production process. The proposed complex physiological analysis of tables of plant phytomass allows us to obtain quantitative data on the operation of the leaf apparatus and the root system of woody plants at the level of the organism in ontogeny, and to establish the nature of their interconnection. In the forest stands of all yield classes a nonspecific adaptive reaction is activated in response to a decrease in the absorption of mineral elements. This leads to the growth of the active part of the root system relative to the surface of needles to increase the supply of elements to the aerial part of the plant in order to maintain photosynthesis at the vital level and stabilize biological productivity.