Effect Of Three Forest Types On The Water Quality In Liuxihe Small Watershed

The water quality in a forest ecosystem can reflect the physiological chararectristic and the ecological condition of this forest. Based on plot data we have carrired out a research program into the effect of forest types on water quality. With sample water from permanent plots of evergreen broad-leaved forest, Pinus massoniana forest and Phyllostachys edulis forest in Liuxihe Reservoir area in Guangzhou, we have taken EC, DO, COD, solubility phosphate, total phosphorus, total hardness, potassium permanganate index, SO₄^2-, NO₃^- and NH₄⁺ as water quality parameter and mensurated these items, compared the water quality characteristics of throughfall, stemfall, surface flow and soil water during water transfer in different forest types, and then we have tried our best to discover the water quality change mechanism, the results show that the concentration of each Water quality parameter changes a lot when rainfall passing through a forest type, and the each water quality parameter concentration has a increase tendency except for DO and NO₃^-. The concentration for solubility phosphate, total P, total hardness, and NH₄₊ are relatively high for a stand of evergreen broad-leaved forest, the concentration of EC and SO₄^2- are relatively high for a stand of Pinus massoniana, the concentration of DO, COD, the index of potassium permanganate and NO₃^- are relatively high for a stand of Phyllostachys pubescens as well. All water quality items concentration show the same situation for rain water passes through different forest types, i. e. soil water＞surface runoff＞stemfall＞throughfall＞rainfall. These substances pass through soil with rainning water. According to the characteristics of the rainfall and the raining water conflux into reservoir, we divided whole year into three periods, i. e., the abundant water period, the normal water period and the low water period. In the low water period, the concentration of EC, DO, solubility phosphate, potassium permanganate index and NH₄⁺ are the highest, and in the abundant water period the concentration of COD is the highest. We have estimated the water quality by means of the compositive pollution index, the compositive fuzzy index and the compositive gray index methods. With indexes of COD, total phosphorus, potassium permanganate index, SO₄^2- and NH₄⁺ we have graded the Liuxihe Reservoir based on Chiese relative standard of GB3838-2002, and the water of Liuxihe Reservoir rearches to the first grade standard. It is very significant to study the rainfall and raining water passing through each forest ecosystem layer for discovering mineral elements movement and proposing some suggestions for water-collecting forest construction and protection.