ISSN 00124966, Doklady Biological Sciences, 2015, Vol. 460, pp. 40–41. © Pleiades Publishing, Ltd., 2015. Original Russian Text © P.Yu. Voronin, V.A. Mukhin, P.V. Konovalov, V.P. Sedelnikov, Vl.V. Kuznetsov, 2015, published in Doklady Akademii Nauk, 2015, Vol. 460, No. 4, pp. 486–487.
The Limitation of Carbon Sink in Western Siberian Forest Ecosystems P. Yu. Voronina, V. A. Mukhinb, P. V. Konovalova, Corresponding Member of the Russian Academy of Sciences V. P. Sedelnikovc, and Corresponding Member of the RAS Vl. V. Kuznetsova Received September 24, 2014
Botanical Garden, Siberian Branch, Russian Acad emy of Sciences (Novosibirsk, Russia).
The gross primary production by photosynthesis (GPP) in the boreal forest zone of Northern Eurasia per hectare annually utilizes tens of tons of atmo spheric carbon as СО2 (CСО2). Note that the plant cover emits a comparable СО2 amount via respiration [1, 2]. The organic carbon as a small positive differ ence between the amounts associated with photosyn thesis and respiration of plant cover (~1%) contributes to the wood and soil pools . Oxidative conversion of the organic substrates of these pools is also consider ably smaller than photosynthesis, not exceeding 1–2 t of emitted CСО2 per hectare of the forestcovered area [3–5].
A decrease in СО2 concentration in the atmosphere reaching several tens of parts per million at the begin ning of the summer season due to the photosynthesis of plant cover and its complete restoration it to the ini tial “background” level caused by an increase in respi ration in the second half of the vegetation period have been observed (Fig. 1). Such a seasonal trend in the atmospheric СО2 concentration agrees well with the concept of a dominant role in the gas exchange of the photosynthetic and respiratory СО2 produced by the plant cover during the carbon cycle of the boreal forest zone . Studies of the seasonal dynamics in atmo spheric СО2 concentration have definitely demon strated that (1) the respiration of plant cover is delayed relative to the photosynthesis, which appears as a
It is commonly accepted that changes in atmo spheric СО2 concentration in the boreal zone of the northern hemisphere display seasonal variation . However, fouryear observations of the atmospheric carbon dynamics over Western Siberia described in this paper demonstrate that these variations display a cyclic pattern for the vegetation period. This suggests a pioneering inference that the plant potential in the boreal zone of Northern Eurasia has an evolutionary genetic limitation in photosynthetic binding of the atmospheric CСО2 excessive relative to the natural average longterm sink in its soil and wood pools.
СО2 concentration, ppm 400
An infrared СО2 sensor, C20 (GSS, United King dom), installed to a Carbologic electronic circuit (IChP Konovalov Pavel Veniaminovich, Russia) was used to monitor (with a periodicity of 1 min) the changes in СО2 concentration. The measurements were conducted in 2010–2013 at the Central Siberian
1 2 3 4 5 6 7 8 9 10 11 12 Months of the year
Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Moscow, 127276 Russia; email: [email protected]
b Yeltsin Ural Federal University, Yekaterinburg, 620002 Russia c Central Siberian Botanical Garden, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Fig. 1. Seasonal trend of the changes in atmospheric СО2 concentration at the level of tree crowns of a midaged pine–spruce stand in the area of the Central Siberian Botanical Garden (Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia) over 4 years (2010–2013); M ± m, n = 4.
THE LIMITATION OF CARBON SINK
decreased atmospheric СО2 concentration observed in May–June; (2) the decreased СО2 concentration of May–June is replaced by its increase in July; and (3) a shortterm equilibrium between photosynthesis and respiration gives place to the prevalence of respiration over photosynthesis to the very emission CСО2 vol umes. The return of СО2 concentration to its back ground level during the vegetation suggests that the decay of soil organic substance and wood pool is lim ited by the refilling of these pools with carbon accounted for by a small positive difference between the values of photosynthesis and plant cover respira tion. The value of seasonal delay in respiration relative to photosynthesis is determined in an evolutionary genetic manner by the specific features in plant pro duction. It is well known that the photosynthesis of a completely developed green leaf under normal natural conditions is confined to the demands for photoassim ilates of the growing organs and tissues . In turn, the demand for photoassimilates is accompanied by tran sition of the photosynthetic carbon in a wood plant from the slowly oxidized accumulation pool to rapidly oxidized growth pool. This is how the equilibrium between photosynthesis and respiration achieved dur ing vegetation basically restricts a potential increase in the photosynthetic sink of carbon. Although the oxidative conversion of dead wood does not directly depend on photosynthesis, it is rather unlikely that the increase in СО2 emission from the natural organic pools of plant cover due to climate warming would considerably shift the atmospheric carbon balance. The possible additional СО2 emission from fungal sources is limited by the size of the wood pool available for decay. Indeed, the fungal emission activity does not exceed a seasonal increase in wood [4, 5, 8]. Therefore, the reported data on an oscillatory dynamics of the atmospheric СО2 concentration in the boreal forest zone limited by the vegetation time sug
DOKLADY BIOLOGICAL SCIENCES
gest the existence of natural limitation on the carbon sink in forest ecosystems and confirm exclusively anthropogenic and abiogeniccarbonate origin of additional atmospheric carbon contributing to its increased atmospheric concentration observed during the past decades. ACKNOWLEDGMENTS The study was supported by the Presidium of the Russian Academy of Sciences under program no. 4 (project no. 4.6.3), Russian Foundation for Basic Research (project no. 120400684), and Presidium of the Ural Branch of the Russian Academy of Sciences (project no. 12S41032). REFERENCES 1. Voronin, P.Yu. and Blek, K.K., Fiziol. Rast., 2005, vol. 52, no. 1, pp. 81–89. 2. Voronin, P.Yu., Dokl. Biol. Sci., 2006, vol. 408, no. 6, pp. 253–255. 3. Schlesinger, W.H., Biogeochemistry: An Analysis of Glo bal Change, San Diego; Academic, 1997. 4. Mukhin, V.A. and Voronin, P.Yu., Ekologiya, 2007, no. 1, pp. 24–29. 5. Kudeyarov, V.N., Zavarzin, G.A., Blagodatskii, S.A., et al., Puly i potoki ugleroda v nazemnykh ekosistemakh Rossii (Carbon Pools and Flows in Terrestrial Ecosys tems of Russia), Moscow: Nauka, 2007. 6. The Global Carbon Cycle: Integrating Humans, Climate, and the Natural World. SCOPE, Field, C.B. and Rau pach, M.R., Eds., Washington: Island, 2004, vol. 62. 7. Mokronosov, A.T., Ontogeneticheskii aspekt fotosinteza (The Ontogenetic Aspect of Photosynthesis), Moscow: Nauka, 1981. 8. Safonov, S.S., Karelin, D.V., Grabar, V.A., Latyshev, B.A., Grabovskii, V.I., Uvarova, N.E., Zamolodchikov, D.G., Korotkov, V.N., and Gitarskii, M.L., Lesovedenie, 2012, no. 5, pp. 44–49.
Translated by G. Chirikova