Carbon Fluxes of Recent High-latitude Steppes

Modern high-latitude steppes (HLS) serve as unique information sources about the Late Pleistocene 'mammoth' steppe because of the many similarities between these ecosystems. HLS were vast and zonal in the Late Pleistocene and now have small exclave positions on steep slopes under S, SW and SE aspects in the modern climate. Over a three-year period we studied two types of relict HLS on the Kolyma Lowland, Siberian Arctic, a region where steppes were widespread in the Late Pleistocene. Modern vegetation predominately belongs to the xerophytic-steppen florogenetic complex of North East Asia and resembles other steppe coenosises of the North-East Siberia. HLS soils have high organic matter content and their thermophysical and physico-chemical properties, and the structure of soil profiles, differ from properties of zonal soils of sparse larch taiga. The vegetation season starts 10-20 days earlier than on other landscapes of the area. Daily and seasonal ecosystem productivity is bimodal with morning and afternoon daily peaks and small resting of plant productivity in the period of high summer temperatures. The polar day increases the photosynthesis time on average 3 - 4 hours per day compared with zonal steppes of Eurasia. The steppe carbon budget has a positive carbon balance. Fast seasonal melting - freezing of HLS shorten both the period and volumes of the autumn-winter CO2 emission, which are significant in zonal landscapes. This has an important paleogeographic meaning. We suppose that this effect contributed significantly to the reduction of the atmospheric concentration of CO2 in the glacial time of the Late Pleistocene, when steppe and tundra-steppe ecosystems of the 'mammoth' biome were zonal.