Water quality of throughfall and stemflow in planted forest in Guangxi, China

摘要

In this study, throughfall and stemflow samples were collected from six forest stands (EU1 = 1 year-old Eucalyptus; EU3 = 3 year-old Eucalyptus; EU7 = 7 year-old Eucalyptus; AM = 7 year-old Acacia mangium; PL = 13 year-old Pinus massoniana Lamb and BL= mixed broadleaved softwood) during storm events in 2009. Water quality indicators including turbidity, color, pH, chemical oxygen demand (COD), total phosphorus (TP) and total nitrogen (TN) were measured on the water samples collected from different durations of the throughfall and stemflow. The experiment results clearly demonstrated that the water quality of throughfall and stemflow was substantially modified by tree canopy and the effects differed significantly among forest stands. Overall, the canopy water quality effect was significantly stronger in 3 year and 7 year old Eucalyptus stands than in other forest stands. Significant acidification, nutrients enrichment and organic matter accumulation in the throughfall and stemflow were observed inthe Eucalyptus forest stands. The throughfall concentrations of COD ranged from 86+10 to 894±106 mg L"' and TN ranged from 0.29±0.03 to 3.1±1.0 mg L'1 for different rainfall events on 3 year-old Eucalyptus, which showed the strongest overall effect. Similar patterns were also observed on stemflow water quality but the effects were more pronounced. In addition, within-event throughfall and stemflow patterns indicated that the impacts of tree canopy on precipitation water quality diminished over the rainfall duration. The results provided the essential information for developing best management practices in planted forests for the purpose of water quality protection.