Cycle of Biophilic Elements in the Litter of Native and Anthropogenic Ecosystems in the Northern Caspian Semidesert

Abstract

The turnover rate and the main mechanisms of accumulation of biophilous elements (C, N, P, K) in the litters of native, forest, and pasture ecosystems of the Northern Caspian region (Volgograd oblast, Dzhanybek Experimental Station of the Institute of Forest Science, Russian Academy of Sciences) were assessed from the data of a four-year-long field experiment on the decomposition of dominant plants of steppe and desert phytocenoses, falloff of introduced oak (Quercus robur L.), and sheep feces from rangeland. It was shown that the litter of native steppe associations accumulates 16–19 times more carbon and nitrogen and 2–2.5 times more potassium and phosphorus as compared with the litter of pastures. The accumulation of C, N, P, and K in the litter of native desert plant communities is 1.5 times more intensive than in the litter of pasture communities. The reserves of C, N, P, and K in the litter of oak plantation exceeds 5–8 times that in the steppe litter. The rates of C and N cycling calculated as the ratio of stock to input mass is 6–7 times slower in the litter of oak plantation than in the litter of steppe community. This corresponds to a lower decomposition constant of oak leaves as compared with decomposition constants of dominant plants of steppe communities. The rate of litter decomposition in phytocenoses with sparse vegetation (steppe pasture and desert native and pasture communities) is an order of magnitude higher than in the native steppe associations, which is related to increased physicochemical decomposition of plant residues under sunlight. Specific features of litter formation should be taken into account when assessing the stability of anthropogenic ecosystems in the region.