Dynamics of carbon pools in post-agrogenic sandy soils of southern taiga of Russia

A soil chronosequence study, covering the ecosystems of 3, 20, 55, 100, and 170 years of self-restoration in southern taiga zone, shows that soil organic content of mineral horizons remains relatively stable during the self-restoration. This does not imply, however, that SOM pools remain steady. The C/N ratio of active SOM reached steady state after 55 years, and increased doubly (from 12.5 - 15.6 to 32.2-33.8). As to the C/N ratio of passive SOM, it has been continuously increasing (from 11.8-12.7 to 19.0-22.8) over the 170 years, and did not reach a steady condition.The results of the study imply that soil recovery at the abandoned arable sandy lands of taiga is incredibly slow process. Not only soil morphological features of a former ploughing remained detectable but also the balance of soil organic matter input and mineralization remained unsteady after 170 years of self-restoration.Until recently, a lot of arable lands were abandoned in many countries of the world. Predominantly caused by economic crises, the most abandonment was found in Russia, reaching 578000 km2 in the years 1961-2007 [1-3]. As a consequence, the soils of these sites underwent the process of natural restoration or self-restoration.A recent chronosequential study on the succession of vegetation, profile morphology, and soil properties of post-agrogenic sandy soils under self-restoration of the southern taiga zone in the European part of Russia showed that the vegetation developed towards spruce forest and the soils towards natural Podzols with an accumulation of thick raw humus layers [4]. Additional podzolization features were found in respect to morphology and chemical properties like pH, exchangeable cations, and nutrition dynamics. Although these changes happened rather fast, the ploughing features were still evident after 170 years of self-restoration, as found in other studies [1,2,5,6].Since every land-use change causes a disturbance of the long-termed adjusted balance of soil organic