Holocene; Paleogeography; Eastern Europe; Radiogenic isotopes; Primary succession; Pedogenesis; Sequestration; Nutrient cycling; Retrogression

Soils represent a key component of the global carbon (C) cycle containing 2 to 3 times more C than the atmosphere. Understanding the dynamics of soil carbon storage is crucial for the prediction of its potential and future feedback to climate change. Traditionally, it has been accepted that millennia are required for soils to reach their C storage capacities. For the first time, we investigated long-term soil development on sedimentary substrate under semi-natural temperate forest, using a unique chronosequence of 26 landslides ranging in age from 4 to ~13,000 years. Both carbon and nitrogen (N) stocks in the 0e30 cm of mineral soil increased rapidly and reached levels resembling that of undisturbed sites already within 100 years of pedogenesis. The mineral soil C stock then did not change while the N stock decreased significantly in older landslides ( 900 years). Phosphorus (P) in <2mm soil showed a rapid increase in the first 100 years followed by a slow decrease. This decrease was significant also for total soil P (including rocks) and may be caused by leaching, erosion and wood harvest. In contrast, the O horizon C, N and P stocks increased linearly throughout the chronosequence. The C:N, N:P, C:P ratios increased along the chronosequence in mineral soil but not in O horizon. Further experiments are needed to explain the mechanisms behind the observed dynamics of C and N. The possible mechanisms include saturation of soil mineral surfaces, the decreasing availability of soil phosphorus or erosion.