SPECIFICITY OF INCREMENT OF YOUNG PINE STANDS OF DIFFERENT DENSITY IN KRASNOYARSK FOREST-STEPPE IN THE CONTEXT OF EFFICIENCY OF ASSIMILATION APPARATUS
A. A. Onuchin, V. E. Aryasov, A. M. Schemberg
Krasnoyarsk Science Centre of the Siberian Branch of Russian Academy of Science, V. N. Sukachev Institute of Forest, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk, Russian Federation
Keywords: young pine stands, care logging, tree stand density, needle increment, wood increment, carbon sequestration, photosynthesis
Abstract
Synchronous observations of the dynamics of wood and needle increment in young 22-year-old pine stands on former agricultural lands in Krasnoyarsk forest-steppe were conducted. It was found that overcrowded stands (the initial density of which was 40.7 thousand pcs./ha) reach the maximum wood increment at the age of 15 years, after which a steady decrease is observed. Stands with an initial density of 10.8 thousand trees/ha, as well as stands, the density of which as a result of thinning at the age of 8 years was reduced to 2.9 thousand trees/ha, demonstrate a continuing increase in wood increment throughout the observation period. At the same time, in the variant with thinning, stabilization and some decrease in the increment of needle mass are observed at the age of 18 years, while stands that have not undergone thinning, regardless of the initial density, retain a tendency to increase the increment of needle mass. The apparent paradox of a decrease in wood increment at a certain age with simultaneous preservation of the tendency to increase needle increment in densely densified young growth and a decrease in needle increment with simultaneous preservation of the tendency to increase wood increment in a stand undergoing thinning is explained by an increase in the efficiency of the assimilation apparatus under conditions of low competition for environmental resources. This fact is confirmed by special studies of the efficiency of needle photosynthesis in densely densified pine forests and tree stands where trees produce under conditions close to free growth. The results obtained may be useful in growing stands for various purposes.
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