Dynamics of carbon storage in phytomass and soil humus in Northern Eurasia during the last climatic macrocycle

Phytomass of terrestrial vegetation and soil humus are considered to be the most important sinks of carbon, and therefore their changes during glacial–interglacial macrocycle may influence considerably the carbon balance. Spatial reconstructions of paleovegetation and paleosols at the key intervals within the macrocycle, namely the Mikulino (Eemian) Interglacial ∼ 125 ka BP, the Last Glacial Maximum 20–18 ka BP, and the Holocene optimum ∼ 5.5 ka BP made it possible to estimate quantitatively the phytomass and soil humus carbon in Northern Eurasia (within the limits of the former Soviet Union). With the phytomass in modern (potential) vegetation taken as 100%, phytomass accumulated in vegetation which existed in Northern Eurasia 125, 18–20 and 5.5 ka BP amounts to 150%, 27% and 129%, respectively. The estimated carbon storage in soil humus for the same intervals is 149.2%, 23% and 128.8% of the present-day value. The values are similar to those previously calculated for the East European Plain except for LGM, where phytomass calculated for the whole territory of Northern Eurasia is relatively higher than that calculated for the East European Plain (27% and 6%). The same tendency is seen in the carbon storage in paleosols dated to the LGM 23 and 15% respectively. The difference in relative phytomass and carbon storage calculated for Eastern Europe and for Northern Eurasia may be attributed to the fact that degradation of forest and steppe vegetation was less pronounced in continental Siberia than in Eastern Europe.