Spruce Assimilation Apparatus in Plantations at the Polytric Cutting
At an early stage of stand development we can consider the viability and potential of formation of valuable forest plants by the characteristics of development and functional state of the assimilation apparatus of trees. We studied the assimilation apparatus of the 36-year-old spruce plantations in the polytric cutting in the Northern taiga subzone of Arkhangelsk region. The needle mass of different ages, emerging in different parts of the crown, was determined. Morphological and biometric indicators of photosynthetic apparatus were established. The average longevity of needle is 10.7 years in spruce plantations cultivated between the rows of pine crops, and 7.7 years in plantations in the open area. Moreover, the longevity of the photosynthetic apparatus in the top of a crown is 4…8, in the middle part - 9.5…10.5, at the bottom - 9.5…13.5 years, depending on the habitat. Comparing biometrics of spruce needle, planted by different methods of cultivation, we can conclude, that the plants located on microelevations have better growth conditions in this forest type, and consequently, have the highest indicators of length, width, thickness and square of a needle. One of the important characteristics of a production phytocenoses process is a leaf-area index, which is considered as the most convenient value for comparing the productivity of ecosystems. This ratio largely determines the degree of transformation of environmental factors and photosynthetic activity of plants by the forest phytocenoses. Each type of plant community is characterized by a certain measure of the leaf-area index of woody vegetation. The size of the leaf surface decreases in process of advance to the North, deterioration of drainage and increase of excessive moistening. In the studied artificially regenerated stands of spruce the leaf-area index is 2.17…15.68 ha/ha, which indicates the properly matched technology of planting in these site conditions. The crops are provided by favorable conditions to develop and reach the indicators that are close to the Hylocomium group of the middle taiga subzone.