Abstract: Quantitative study on chemical properties of rain water in forests is of great significance to accurate assessment of concentrations of nutrient elements recycling within forest ecosystem. A tract of planted bamboo forest and a tract of natural secondary forest in a low-mount-hilly area of North Zhejiang, located in the mid-subtropics was selected as subject in the study to explore spatio-temporal variation of various ions in waters of  throughfall, surface runoff, and watershed effluent, relative to forest type. Results show that 1) compared with the bamboo forest, the natural secondary forest had a denser canopy capable of intercepting rainfall and a thicker litter layer capable of holding water, thus greatly reducing throughfall, and surface runoff; 2) concentrations of various ions varied sharply in the precipitation, displaying an order of SO₄^2->NO₃^->Na⁺ >Cl^->K⁺ >Ca²⁺>NH₄⁺ >Mg²⁺; 3).leaching coefficient of Na⁺ with throughfall in the bamboo forest and natural secondary forest was 0.49 and 0.85 respectively, and those of the others increased to various degrees, manifesting positive leaching; 4) compared with rainfall, surface runoffs in both forests demonstrated positive leaching of all the ions, with leaching coefficient varying between 1.12 - 10.16, and K⁺  and NO₃^- on the higher side and Na⁺ and NH₄⁺  on the lower; 5). watershed effluent was a bit lower than rainfall in K⁺  and NH₄⁺ concentration, with net leaching coefficient being 0.90 and 0.21, but higher in Ca²⁺ and Mg²⁺ concentration, with net leaching coefficient being 7.55 and 23.78; and 6) the differences between the two forests in chemical properties of rain water at different levels were manifested in ion concentration. All the ions were higher in concentration in rain waters of all the levels in the natural secondary forest than in the bamboo forest, except Na⁺ and Mg²⁺.

Key words: throughfall, runoff, watershed effluent, rain water chemical properties, forest