Land-use, stream order and stream water physical and chemical qualities
土地利用、溪流级别与溪流河水理化性质的关系

Stream water sampling was conducted along the Ash River continuum from 1st order to 5th order in the Maoershan Experimental Forest of the Northeast Forestry University, near Maoershan Township, Shangzhi City, Heilongjiang Province. The pH, turbidity, concentrations of NH~ 4-N, NO~- 3-N and PO~(3-) 4-P were measured/analyzed. Forest coverage, surrounding land-use type and landscape characteristics of each sampling location were recorded. Land-use category was later determined from recent aerial photos and field observations for each sampling location. Water quality variables were evaluated in response to changes in stream order and land-use types. Both stream order and land-use (forest, agriculture and urban) were positively correlated to pH, turbidity, concentrations of NH~ 4-N, NO~- 3-N and and dissolvable phosphate. Although water quality was better in the forested 1st-2nd order streams, the concentration of dissolvable phosphate and inorganic N were more than 30 and 100 times higher, respectively, than those in the comparable pristine forested streams in temperate North America. Soil erosion, lack of riparian protection, grazing, over fertilization and frequent disturbances likely contributed to eutrophication of the streams.