Nitrogen export by runoff and sedimentunder different types of land use inWest Tiaoxi catchment

摘要

Five typical land covers in West Tiaoxi catchment of China, including mulberry garden, bamboo forest, pinery, vegetable plot and paddy field, were studied on nitrogen loss in artificial rainstorm runoff and sediment. Triple duplication experiments have been carried out under the artificial rain condition with an intensity of 2 mm.min-1 and lasting 32 minutes in 3 m2 field. Export of various species of nitrogen in runoff and sediment were investigated. The results show that nitrogen loss amount and rate are quite different among five kinds of land covers. The loss of total nitrogen in runoff of mulberry is the largest and that of paddy field is the smallest. Particle nitrogen accounts for 70-90% of total nitrogen in runoff of various kinds of land covers. Loss of dissolved nitrogen in pinery is much higher than in other kinds of land covers, which are similar among them. More detailed species of dissolved nitrogen show their respective features among various land covers. Total amounts of nitrogen loss from the top 10 cm layer of 5 kinds of soils are estimated as high as 4.66-9.40 g.m-2, of which nitrogen loss through sediment of runoff accounts for more than 90%. The rate of total nitrogen losses are ranged in 2.68-14.48 mg.m-2.min-1 in runoff, which is much lower than that of 100.01-172.67 mg.m-2.min-1 in sediment of runoff.