基于PCA的滇西北高原纳帕海湿地退化过程分析及其评价

Abstract

PDF HTML阅读 XML下载 导出引用 引用提醒 基于PCA的滇西北高原纳帕海湿地退化过程分析及其评价 DOI: 10.5846/stxb201205060653 作者: 作者单位: 同济大学环境科学与工程学院污染控制与资源化国家重点实验室，长江水环境教育部重点实验室，上海,同济大学环境科学与工程学院污染控制与资源化国家重点实验室，长江水环境教育部重点实验室，上海,同济大学环境科学与工程学院污染控制与资源化国家重点实验室，长江水环境教育部重点实验室，上海 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目(41171074, U0933601, 40771013) Process analysis and evaluation of wetlands degradation based on PCA in the lakeside of Napahai, Northwest Yunnan Plateau Author: Affiliation: Key Laboratory of Yangtze River Water Environment, Ministry of Education, State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, China,Key Laboratory of Yangtze River Water Environment, Ministry of Education, State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, China,Key Laboratory of Yangtze River Water Environment, Ministry of Education, State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以滇西北高原纳帕海湖滨过度放牧、水文改变协同胁迫(简称GAD)和过度放牧单独胁迫(简称GD)退化湿地为研究对象,将其划分为4个梯度:原生湿地、轻度退化、中度退化、重度退化,采用聚类分析和主成分分析(PCA)在"植物-水体-土壤"系统上进行湿地退化过程、机制探讨及定量评价。沿退化梯度,植物群落演替规律为"水生植物群落→沼泽植物群落→沼泽化草甸植物群落→草甸植物群落",群落结构趋于复杂,向中生植物群落演替;矿化度、总硬度、总碱度、氮、磷等水质指标在GD梯度上升,在GAD梯度下降,水文改变对水质影响显著;土壤有机质、全氮、速效氮含量降低,全磷、全钾有所增加,速效磷和速效钾含量无明显变化规律。基于PCA建立了纳帕海湖滨湿地退化模型,并给出不同程度退化湿地的阈值。 Abstract:Napahai wetland is a unique and seasonal marsh wetland located in the middle of Hengduan Mountains, northwestern Yunnan Plateau. In the recent decades, it has been seriously degraded under human disturbances, mainly including drainage and overgrazing. In the present paper, two kinds of typical degradation transects were established to evaluate the synergistic impacts of overgrazing stress and water regime and the single impacts of overgrazing stress in the lakeside of Napahai. The two transects were further classified into four degradation gradients, including primary wetland(PW), lightly degraded wetland (LW), moderately degraded wetland (MW) and severely degraded wetland (SW). Cluster analysis and principal component analysis (PCA) were conducted to explore the process and mechanism of wetland degradation as well as to evaluate the degree of wetland degradation quantitatively at system level of "vegetation-water-soil". The results were as follows: the numbers of plant families, genera and species as well as species diversity and richness all increased gradually from PW to SW, whereas species evenness remained stable. The plant community succession is in the direction of aquatic plant community→swamp plant community→swamp meadow plant community →meadow plant community. Correspondingly, the community changed towards more complicated structure characterized by the decreasing of helophyte and increasing of hygrophyte and mesophyte. Overgrazing stress changed the inherent mode of plant community succession and accelerated the degraded stage of "swamp meadow community" to some extent, although the direction of succession had not changed. The degradation characteristics of water properties varied in different disturbance type, the water indices of salinity, total alkalinity, total hardness, total nitrogen, ammonia nitrogen, nitrate nitrogen and total phosphorus all increased along the GD gradients, whereas decreased along the GAD gradients, depending on the water regime. Therefore, hydrologic alteration had a significant effect on wetland water properties. The changes of wetland soil properties were similar in the two disturbances. Among them, the contents of organic matter, total nitrogen and available nitrogen decreased, total phosphorous and total potassium (K) increased, whereas the available phosphorous and available potassium (K) showed no obvious changes. The vertical distribution for each nutrient content in the soil profiles of degraded wetlands varied greatly. Soil total phosphorous, available phosphorous and available potassium (K) decreased along the soil depth gradients. It showed that soil nitrogen content was the most obvious characteristics of wetlands degradation. In order to identify the driven factors of wetlands degradation under the multi-factorial stresses, PCA was employed to synthesize the degradation information from multiple aspects as discussed in this paper. Thirty indices based on vegetation, water and soil were simplified into three principal components by PCA, explained 54.8%, 29.1% and 15.9% of the total variance, respectively. PCA results indicated that plant community was the most representative of wetlands degradation, and the soil structures and nutrient contents changed significantly along the degradation gradients of lakeside wetlands, Napahai. By contrast, the contributions made by water nutritional contents were lowest compared with vegetation and soil for wetlands degradation. Based on the three principle components derived from PCA, a multiple linear regression model, PC=0.548×PC1+0.291×PC2+0.159×PC3, was conducted to calculate the scores for each degradation stage, which could be taken to evaluate the wetlands degradation. 参考文献 相似文献 引证文献