岷江上游地区近30年森林生态系统水源涵养量与价值变化

Forest water conservation and its benefits in upper reaches of Minjiang River in recent 30 years

根据岷江上游地区自然地理环境条件的差别,将该区森林植被划分为暗针叶林、其它针叶林、阔叶林和灌木林等4个类型,利用年降雨量、林冠截流量数据、径流系数以及“影子价格”等方法,计算和评述了该区森林生态系统水源涵养效益;并利用遥感4期影像分析了岷江上游地区森林生态系统水源涵养量的变化原因。结果表明:2000年岷江上游森林生态系统年水源涵养量最高,为1·3892×1010m3,经济价值为93·07亿元。去除降雨量的影响后,在各时期年降雨量为705mm的情况下,岷江上游地区1986年的水源涵养量最高,为1·3348×1010m3,经济价值为89·43亿元;1995年水源涵养量下降,为1·2320×1010m3,经济价值为82·54亿元;2000年水源涵养量及经济价值与1995年基本持平。造成这一现象的主要原因是20世纪90年代岷江上游森林景观受到人为的严重破坏,而随后实施的“天然林保护工程”与“退耕还林还草”政策,加强了人工植被恢复建设,改善了森林生态系统,使森林生态系统水源涵养量有所恢复。

Based on the differences of physical geography, the forest in the upper reaches of Minjiang River was divided into four types, i. e. , dark coniferous forest, other coniferous forests, broadleaf forest, and shrubbery. The benefits of water conservation by these forest types were calculated by using relevant indicators such as annual rainfall, crown cover interception, runoff coefficient, and ‘ shadow price＇ , and the variations in water conservation were analyzed according to the four remote sensing images in different times. The results indicated that in 2000, the annual water conservation by the forest ecosystems was 1. 3892 × 10^10 m^3, and the economic value was 93.07 hundred million Yuan RMB. After deducting the rainfall effect, the annual water conservation and economic value were 1. 3348 × 10^10 m^3 and 89. 43 hundred million Yuan RMB in 1986, and 1. 2320 × 10^10 m^3 and 82.54 hundred million Yuan RMB in 1995, respectively, with the water conservation and economic value in 2000 being at the similar levels in 1995. The main reason of these variations was that in 1990s, the forest landscape in the upper reaches of Minjiang River was severely destroyed by human activities, while the policies ‘ protecting natural forest＇ and ＇ returning cultivated land into forest- and grassland＇ implemented subsequently promoted the establishment of artificial vegetation, improved forest ecosystem, and gradually restored the water conservation by forest ecosystem.