STRUCTURE OF FRACTIONAL PHYTOMASS INCREMENT IN YOUNG PINE STANDS OF DIFFERENT DENSITY IN KRASNOYARSK FOREST-STEPPE
V. E. Aryasov, A. A. Onuchin
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 felling, tree stand density, wood increment, branch increment, root increment, needle increment, photosynthesis
Abstract
As part of long-term study conducted in Krasnoyarsk forest-steppe, the dynamics of the increment of major phytomass fractions (stems, roots, branches, needles) of young pine stands formed on former agricultural lands were analyzed. It was found that, in early ontogenesis, the maximum phytomass increment is characteristic for overstocked tree stands with an initial density of 40.7 thousand trees/ha. However, by the age of 17, these stands experience a decline in productivity due to intensified intraspecific competition for resources, which negatively affects photosynthesis efficiency. In contrast, in stands with lower density, including those with thinning treatments, phytomass increment shows a stable positive trend with increasing tree stands of 9-20 age. It was established that under natural competitive conditions, the proportion of stem fraction increment decreases with age, whereas in stands subjected to thinning, its contribution increases, reaching 62 % of total increment over a 20-year period. The obtained data emphasize the necessity of comprehensively considering all phytomass fractions when assessing the capacity of stands to absorb atmospheric carbon dioxide. Thus, accounting only for stem mass increment results in almost a twofold underestimation of the carbon sequestration potential of overstocked young pine stands. The study results should be taken into account when assessing the carbon balance of forest ecosystems in the context of international carbon trading. It has been shown that regulating the density and spatial structure of stands allows optimizing their functional purpose - from creating carbon farms focused on CO2 sequestration to organizing industrial plantations prioritizing target assortments production. Thus, silvicultural practices, including thinning, serve as a key tool for managing the productivity and ecosystem services of forest stands.
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