5Hill A R. Nitrate removal in stream riparian zones. Journal of Environmental Quality, 1996, 25(4) : 743-755.
6Gilliam J W, Skaggs R W. Controlled agricultural drainage to maintain water quality. Journal of Irrigation and Drainage Engineering, 1986, 112(3):254-263.
7Herzon I, Helenius J. Agricultural drainage ditches, their biological importance and functioning. Biological Conservation, 2008, 141(5): 1171-1183.
8Alexander R B, Smith R A, Schwarz G E. Effect of stream channel size on the delivery of nitrogen to the Gulf of Mexico. Nature, 2000, 403(6771): 758-761.
9Lenat D R, Crawford J K. Effects of land use on water quality and aquatic biota of three North Carolina piedmont streams. Hydrobiologia, 1994, 294(3): 185-199.
10Turner M G, Gardner R H, O'Neill R Y. Landscape Ecology in Theory and Practice: Pattern and Process. New York: Springer-Verlag, 2001.
