Postagrogenic development of Retisols in the middle taiga subzone of European Russia (Komi Republic)

Reforestation on abandoned agricultural lands is widespread in the belt of boreal forests. We analyzed the morphological and physicochemical properties of a Plaggic Glossic Retisol (Siltic, Cutanic) site that had been abandoned either 7, 19, or 85 years ago, as well as a Glossic Stagnic Retisol (Siltic, Cutanic) as a control. Involvement of forest soils in agricultural use results in the degradation of organic horizons, which are not restored until many decades after the termination of active agricultural use. Arable soil horizons were preserved and were clearly identified 85 years after the land had been abandoned. The morphological features of the eluvial and subeluvial horizons were determined at all sites. Soils at sites that had been abandoned for 7 and 19 years showed lower acidity and higher base saturation compared to the background soil. Total carbon stocks were lower at the abandoned sites. The slow increase of carbon stocks after the soil had been abandoned is caused by C increase as in the organic as in the topsoil mineral horizons. Soils that had been abandoned for 7 and 19 years contained less water-extractable forms of C and N than the control and 85-year forest soils. Agricultural use leads to a reduction in C stocks of forest soils. The postagrogenic soil C sequestration rate was estimated to be 30-40 g.m(-2).yr(-1).