DYNAMICS OF CARBON STORED IN SOIL HUMUS AND PHYTOMASS IN THE COURSE OF THE LAST CLIMATIC MACROCYCLE ON THE NORTHERN EURASIA TERRITORY

Soil humus and phytomass of terrestrial vegetation are among the principal carbon pools on continents. Estimates of the carbon dynamics in the past are necessarily based on data on its amounts stored in paleo-vegetation and fossil soils (buried under younger sediments). Of particular interest are extremely warm intervals within the last 125,000 years: the Eemian (Mikulino) Interglacial optimum ~125 ka BP and the Holocene optimum 5.5 ka BP, with mean global temperature about 1.8 to 2°C and 0.8 to 1.0°C above the present-day values, respectively. An example of reverse situation is provided by the Last Glacial Maximum (about 18 ka BP). The analysis of carbon dynamics is based on detailed spatial reconstructions of vegetation and soils in Northern Eurasia (within the limits of the former Soviet Union). The estimated values of carbon stored in terrestrial vegetation and soil humus appeared to be greatly different not only when the warm interglacial epochs are compared with the LGM. The differences are quite noticeable when three warm intervals (the last interglacial, the Holocene optimum and the present days) are compared. It is noteworthy that amounts of carbon stored in phytomass and those stored in soil humus (defined as percentage of their modern values) appeared to be close to each other: about 150% at the Mikulino Interglacial; 120 and 128.2% in the Holocene optimum; 27 and 25% at the LGM). One should bear in mind that the values given above represent "instant characteristics" of the processes different in rate. If the phytomass (even that of forests) takes a few tens to a few hundreds of years to accumulate, carbon in soil humus is stored in the course of many centuries.