COMPOSITION OF STABLE CARBON ISOTOPES IN COMPONENTS OF FOREST ECOSYSTEMS OF CENTRAL SIBERIA
A. S. Prokushkin1,2, D. A. Polosukhina1,2, E. Yu. Novenko2
1Krasnoyarsk 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
2Institute of Geography, Russian Academy of Sciences, Moscow, Russian Federation
Keywords: middle taiga, northern taiga, vegetation layers, functional groups, fungi, soil, stable carbon isotopes, carbon isotope fractionation, intensity of soil organic matter turnover
Abstract
Stable carbon isotopes are widely used in environmental sciences to study physiological, ecological, and biogeochemical processes associated with ecosystem, regional, and global carbon cycles, providing information on various temporal and spatial scales. The study was conducted in forest ecosystems of the middle and northern taiga subzones of Central Siberia. The δ13C composition of the tree, shrub, dwarf shrub, and moss-lichen vegetation layers, fungal fruiting bodies, litter, and soil cover of the studied forests was analyzed. A pronounced δ13C gradient was observed across vegetation layers in forest ecosystems. δ13C values n the biomass of aboveground components of ecosystems ranged from -34.0 ± 1.0 ‰ in the green moss glittering woodmoss ( Hylocomium splendens (Hedw.) Schimp.) of the middle taiga to -23.8 ± 0.8 ‰ in the wood of Gmelin larch ( Larix gmelinii (Rupr.) Kuzen.) growing in the northern taiga. Both the lowest and highest δ13C values were found in the lowest, moss-lichen layer. The tree layer of the studied middle taiga ecosystems is characterized by lower δ13C values in the leaf apparatus compared to the northern taiga stands, reflecting their higher productivity and the degree of discrimination (Δ) of the heavy carbon isotope during photosynthesis. The heavier isotopic composition of the subordinate vegetation layers in the northern taiga forests indicates a reduced canopy effect. Isotope fractionation during soil organic matter mineralization leads to an increase in δ13C values with depth in all studied ecosystems. However, based on the dependence of δ13C values on soil carbon content, which varies with depth, an increased carbon turnover rate (β) was detected in larch soils in the permafrost zone. This is presumably due to post-pyrogenic dynamics of root detritus input, rather than the intensity of mineralization processes.
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