Effects of riparian vegetation on soil organic carbon andtotal nitrogen distribution - a case study of Wenyu River, Beijing

Riparian ecosystem is an ecological ecotone that occurs between river and terrestrial ecosystems. Riparian ecosystems are normally sensitive and vulnerable ecological niches. There are vast changes in riparian vegetation systems due to human disturbances of river systems. Thus this study analyzed the effects of 7 riparian vegetation systems on the contents and spatial distributions of soil organic carbon and total nitrogen in Wenyu River in Beijing. The results showed that riparian vegetation mainly affected soil organic carbon and total nitrogen in the surface soil layer, especially in the 0~5 cm soil layer, with relatively minimal effect on below the 5 cm soil layer. The impact of vegetation on the content and distribution of soil total nitrogen and organic carbon was significant. While soil total nitrogen and organic carbon decreased with increasing soil depth, vertical variations among the 7 vegetation systems were different. The rate of decrease in soil organic carbon and total nitrogen with soil depth was significantly higher under natural grasslands, abandoned farmlands and forests than under farmland ecosystems. In the 0~30 cm soil profile, the average content of soil organic carbon was highest under Populus simonii forestland (9.54 g·kg^-1), followed by natural grassland (9.33 g·kg^-1), pear orchard (9.18 g·kg^-1), Rhus typhina forestland (8.89 g·kg^-1), abandoned farmlands (7.91 g·kg^-1), corn field (7.22 g·kg^-1) and then soybean field (7.17 g·kg^-1). Also the average soil total nitrogen was highest under natural grassland (1.30 g·kg^-1), followed by P. simonii for-estland (0.91 g·kg^-1), pear orchard (0.90 g·kg^-1), R. typhina forestland (0.83 g·kg^-1), abandoned farmlands (0.80 g·kg^-1), corn field (0.72 g·kg^-1) and then soybean field (0.70 g·kg^-1).