Mixed forest plantations can efficiently filter rainfall deposits of sulfur and chlorine in Western China

Forest filtering is a well-known and efficient method for diminishing atmospheric pollutant (such as SO₄^2- and Cl^-) inputs to soil and water; however, the filtering efficiencies of forests vary depending on the regional vegetation and climate. The rainy area of West China has suffered from heavy rainfall and human activity, which has potentially resulted in large amounts of sulfur and chlorine deposition, but little information is available regarding the filtering effects of typical plantations. Therefore, the migration of SO₄^2- and Cl^- from rainfall to throughfall, stemflow and runoff were investigated in a camphor (Cinnamomum camphora) plantation, a cryptomeria (Cryptomeria fortunei) plantation and a mixed plantation in a 9-month forest hydrology experiment. The results indicated the following: (i) The total SO₄^2- and Cl^- deposition was 43.05 kg ha^-1 and 5.25 kg ha^-1, respectively. (ii) The cover layer had the highest interception rate (60.08%), followed by the soil layer (16.02%) and canopy layer (12.85%). (iii) The mixed plantation resulted in the highest SO₄^2- (37.23%) and Cl^- (51.91%) interception rates at the forest ecosystem scale, and the interception rate increased with increasing rainfall. These results indicate that mixed plantations can effectively filter SO₄^2- and Cl^- in this area and in similar areas.