Abstract: With the upper reaches of Gongbiela River in the northeast part of Xiaoxing’an Mountains as test area, this paper studied the hydrochemical characteristics of the streams in forest and swamp during the period of June～September 2004. The results indicated that the hydrochemistry of forest and swamp streams belonged to calcium-bicarbonate type Ⅰ (C^Ca₁). The pH value, mineralization rate, total hardness, and HCO₃^-, SO₄^2-, Ca²⁺, Mg²⁺ and Fe concentrations of forest streams were lower than those of swamp streams, while the concentrations of total N, total P, Cl^-, K⁺, and Na⁺ were in adverse. In both of the streams, the contents of heavy metal elements such as Fe, Mn, Cu, Zn, Cd, Hg and Pb were lower than the classⅠin Environmental Quality Standards for Surface Water (EQSSW) of China. The concentrations of total N and P in forest streams were （0.27±0.04） mg·L^-1 and （0.040±0.005） mg·L^-1, respectively, being significantly higher than those (（0.21±0.02） mg·L^-1 and （0.025±0.004） mg·L^-1) in swamp streams. Swamp wetland had a stronger ability in depositing and adsorbing N and P, with more NH₄⁺-N adsorbed than NO₃^--N, and also had a stronger ability on the reduction and release of Fe, with the Fe content (（0.26±0.05） mg·L^-1) in its streams obviously higher than that in forest streams.

Key words: Grey system, GM model, Forest stand volume, Hydrological element