Interactive Effects of Land Use and Climate on Soil Organic Carbon Storage in Western Siberian Steppe Soils

Abstract

Soils store much more carbon (C) than all terrestrial plants and the Earth's atmosphere together, and the C exchange between soils and atmosphere largely influences the CO2 contents in the atmosphere. While converting native ecosystems into agricultural land in the past caused a huge historical release of C into the atmosphere, an optimization of the management of agricultural soils offers the possibility of restoring parts of the previously lost C in the soil. However, in this respect, interrelationships of land use and soil management with climate change must be considered. In this chapter, land use and climatic effects on soil organic carbon (SOC) stocks in the large western Siberian grasslands will be evaluated and scenarios of future development of SOC storage will be given. A combination of soil analysis along a climatic gradient from the forest steppe to the dry steppe and a modelling approach with the Lund-Potsdam-Jena managed Land (LPJmL) model revealed, that since their cultivation soils of the Kulunda steppe lost about 20-35% of their organic C. Surprisingly, not only particulate organic C was affected but likewise also organic C located within mineral-organic associations was lost, and the proportion of the lost C is independent from the climatic conditions. Parts of this lost organic C can be restored by abandoning arable land. However, due to political and economic constraints, this does not seem to be likely. Minimum or zero tillage may provide an option to increase the organic C storage in western Siberian steppe soils, but the potential effect may be limited. The LPJmL model simulates a continuing climate-change driven C loss from soil, which corroborates results of soil analysis along the climatic gradient. The management of SOC stock has to be evaluated also for its effect on soil erosion, water deficiency and nutrient shortage.