[Soil denitrification rates in different type riparian zones in maoershan mountainous region of China].

Soil samples were collected from forested, clear-cut, and grassy riparian zones under forest background and from forested and barren riparian zones under cropland background in the Maoershan mountainous region of China. The samples were incubated in laboratory, and their denitrification potentials were determined by nitrate-deduction method. The results showed that under crop-land background, soil denitrification rate was the highest in forested riparian zone and the lowest in barren riparian zone, with the deduction rate of nitrate varied from 46.79%-91.13% and 15.64% -81.84%, respectively. Under forest background, soil denitrification rate decreased in the order of clearcut > forested > grassy riparian zone, with the deduction rate of nitrate being 42.06%-90.39%, 28.24%-85.73% and 21.44%-83.11%, respectively. The denitrification rate was higher in subsurface layer than in deeper layer, and the denitrification potential was limited by the available carbon and nitrate, being the greatest in the forested riparian zone under cropland background.

[Retaining and transformation of incoming soil N from highland to adjacent terrestrial water body in riparian buffer zone].

Highland soil nitrogen can enter adjacent water body via erosion and leaching, being one of the important pollutants in terrestrial water bodies. Riparian buffer zone is a transitional zone between highland and its adjacent water body, and a healthy riparian buffer zone can retain and transform the incoming soil N through physical, biological, and biochemical processes. In this paper, the major pathways through which soil nitrogen enters terrestrial water body and the mechanisms the nitrogen was retained and transformed in riparian buffer zone were introduced systematically, and the factors governing the nitrogen retaining and transformation were analyzed from the aspects of hydrological processes, soil characters, vegetation features, and human activities. The problems existing in riparian buffer zone study were discussed, and some suggestions for the further study in China were presented.