Abstract: The chemistry of rainfall,throughfall and stemflow was measured continuously for three years (1994～1996) in two Chinese fir forests with different distances from pollution source in Nanping,Fujian. Precipitation chemistry was dramatically altered upon passage through forest canopies at both sites.The pH values in throughfall decreased slightly,but EC values were significantly higher because of its higher ion concentrations than in rainfall. Stemflow showed extremely acidification and nutrient enrichment.Acidity of rainfall and throughfall showed some seasonal patterns,generally with minimal pH values in summer,maximal in winter.However,the EC values of precipitation exhibited strong seasonal patterns practically identical to that for ion concentrations,consistently with minimal values in summer months,intermediate in spring and fall,and maximal in winter,which appeared highly dependent on rainfall amount.Close correlation exited between acidity and sulfate in stemflow,but hydrogen concentrations in rainfall and throughfall were strongly related to acid-base ratios R,which equals to (SO₄^2-+NO₃-)/(Ca²⁺+Mg²⁺).Lastly the distances from pollution sources produced significant effects on precipitation chemistry.

Key words: Chinese fir forest, Rainfall, Throughfall, Stemflow, Chemical composition, Seasonal dynamics