Components of C and N cycles in natural and anthropogenic ecosystems of semideserts of the northern Caspian area

Resumo

Changes in the amounts and dynamics of the deposition of carbon and nitrogen in the soil surface of anthropogenic pasture and forest ecosystems created in places of natural steppe and desert plant associations in the Northern Cis-Caspian area were studied. For two years after input, the litter of oak stands (Quercus robur) deposited 1.3 times more carbon and about the same amount of nitrogen as compared to the steppe litter, even though the mass of litter input in the forest plantation was 1.4 times less than that in the grass ecosystem. The values of carbon and nitrogen contents in the soil under steppe vegetation and under plantation were similar, but there was a redistribution of carbon and nitrogen contents in the forest soil. The carbon contents in the forest litter and 0–5 cm layer make up 33% of the contents in the litter and in 0–50 cm soil layer. The respective value was 22% under the steppe vegetation; the nitrogen contents were 2.9 and 2.0%, respectively. Due to intensive grazing, the ecosystems of microdepressions obtain 1.6–1.7 times less carbon and nitrogen than those of virgin plots. This value was 1.4 for the ecosystem of microelevations. A significant decrease in the contents of carbon and nitrogen was observed in the litter and 0–5 cm layer of meadow–chestnut soils of microdepressions under the pressure of intensive grazing.