摘 要 ：通过对天山中部天山云杉（Picea schrenkiana var.tianschanica(Rupr.)Chen et Fu）不同郁闭度、林龄天然林区内，降水在转化过程中各环节（包括大气降水、穿透水、地表径流、地下渗水）的水质变化规律，以及森林生态系统不同层次对水质的影响对比分析。结果表明：（1）天山云杉林生态系统对降雨的水质影响，随郁闭度和林龄的增加而增强。在林龄相同的条件下，表现为:0.2＜0.4＜0.6＜0.8；在郁闭度为0.8的条件下，表现为:幼龄林＜中龄林＜成熟林＜近熟林；（2）大气降水透过林冠层后，水中的养分含量显著增高，表现为溶解氧含量减小，氨氮、COD、BOD、总磷、钾含量增加；（3）穿透水转化为地表径流，水中的溶解氧浓度进一步降低，COD、BOD、总磷、钾的含量升高，氨氮浓度降低；（4）总地下渗水的各项水质指标均明显优于大气降水,土壤层是森林生态系统净化水质的关键层。（5）通过对各集水区域水质指标定量化综合评价，天山云杉林生态系统内的水质质量表现为：7月份＞9月份＞8月份；（6）利用主成分分析方法（PAC）构建的水质综合评价多元线性模型，具有很强代表性，能很好地用于水质的等级评价。
Abstract:Forest is titled as “green reservoir” which has incredible ecological functions, such as: reserving water, depurating water quality, etc. Therefore, understanding the effects of different components of the forest ecosystem on water quality is significant. In this study, the Picea schrenkiana var.tianschanica natural forest was taken as the object in the middle Tianshan mountains at Tianshan Forest Ecosystem Research Station. There are totally eight sample plots according to the forest canopy density (0.2, 0.4, 0.6, and 0.8) and forest age (young forest (0-60a), middle\\aged forest (60-100a), nearly mature forest (100-120a), and mature forest (120-160a)) in this area. In the plant growing season (July, August, September), all of water samples in the condition of rainfall over 30mm were collected using high-density polyethylene plastic bottle and detected in Xinjiang Environmental Monitoring Station. The water quality changes during rainfall transformation process were investigated on rain fall, through fall, surface runoff and underground seepage water. The water samples were analyzed chemically to determine the effects of different ecosystem components on water quality. The results showed that: (1) The influence of forest ecosystem on water quality of rainfall was enhanced as the canopy density and forest age increased. When forests were in same age, the sequence of this influence on water quality was canopy density of 0.2＜0.4＜0.6＜0.8. When canopy density was 0.8, the sequence of forest influence on water quality was young forest＜middle-aged forest＜mature forest＜near mature forest; (2)When the rainfall entered forest canopy, the nutrient content in water was significantly increased as dissolved oxygen decreased and ammonia nitrogen, COD, BOD, total phosphorus as well as potassium content increased; (3) When the through fall turned into surface runoff, the concentration of dissolved oxygen in water further declined, along with COD, BOD, total phosphorus and potassium content increased. Meanwhile, the ammonia nitrogen concentration remarkably decreased; (4) The soil layer had strong decontaminating ability and high nutrient accumulation function in natural forest ecosystem. The water quality indicator of total underground seepage was much better than those of precipitation, indicating that forest soil layer is the most critical layer of the forest ecosystem. (5) The sequence of the water quality in the forest ecosystem scored by quantitative and comprehensive assessment on was July＞September＞August; (6) The multi-factor line model established by principal component analysis (PAC) method was representative and can be better used for comprehensive assessment on water quality.