青弋江流域土地利用/景观格局对水质的影响

研究不同空间尺度的景观组成与结构对水质的影响对于水质保护具有重要意义。青弋江为长江下游最长的支流，人类活动可能通过多种方式对水质产生影响。以青弋江流域为研究对象，基于Google Earth遥感数据和水质实测数据，采用冗余分析（RDA）和Spearman相关性分析，探讨了土地利用/景观格局对水质的影响。研究结论为：（1）以采样点为中心建立的100、200、500、1000、2000 m 5种尺度缓冲区中，500 m半径圆形缓冲区景观组成对水质的解释率最高，枯水期与丰水期对水质的解释率分别为46.30%和43.10%。（2）土地利用类型中，耕地和建设用地面积与NH₄⁺-N、TP、EC呈正相关，对水质具有负面效应；林地面积与DO呈正相关，对污染物起到净化作用；土地利用综合程度指数与污染指标呈正相关，表明人类活动强的区域，水质变差。（3）景观格局指数中，PRD在丰水期与NH₄⁺-N、TP浓度为负相关，相关系数分别为-0.656、-0.540，表明随斑块丰富度密度的增大，流域生态系统更加稳定；LPI与DO浓度在枯水期为显著负向相关，相关系数为-0.653，SHAPE_AM与NH₄⁺-N、TP呈显著正向相关，表明随人类活动强度的增大，水质恶化；FRAC_AM与水质的关系无法得到合理的解释。通过多角度分析，在一定程度揭示了青弋江流域的生态水文过程，有利于土地利用管理和水质保护，进而促进资源的可持续利用。研究结果可为政府相关职能部门进行决策时提供参考。

Responses of water quality to land use & landscape pattern in the Qingyijiang River watershed

It''s great significance for water quality protection to figure out the effects of landscape composition and configuration in different spatial scales. The Qingyijiang River is the longest branch of lower Yangtze River, the water quality of rivers is influenced by human activities in variety of ways. Taking the Qingyijiang River basin as the research objective, this paper adopted the redundancy analysis (RDA) and Spearman correction analysis to initially explore the impacts of the land utilization and landscape pattern on the water quality, which based on the Google Earth remote sensing data and water quality measurement data. The results are: (1) Among the five buffer scales of 100, 200, 500,1000 and 2000 m established based on sampling point, the landscape composition of the 500 m radius circular buffer zone had the highest interpretation rate of water quality, and the interpretation rates of the low flow period and the high flow period were 46.30% and 43.10%, respectively. (2) In land use types, farmland area and building land area were positively correlated with ammonia nitrogen (NH₄⁺-N), total phosphorus (TP) and electrical conductivity (EC) and produced negative effect on water quality. However, forest land area was positively related to dissolved oxygen (DO), which played a vital role in purifying pollutants. Comprehensive index of the land use was positively related to the polluted indicator, which meant the water quality was increasingly deteriorating in the area with highly intensive human activities. (3) The landscape pattern indexes suggested that patch richness density (PRD) was negatively related to the density of the NH₄⁺-N and TP. The relative indexes were -0.656 and -0.540 respectively, which indicated that the watershed ecosystem became more stable with the increase of PRD. The density of the largest patch index (LPI) was negatively associated with the density of DO in the low flow period, the relative index was -0.656, while area-weighted mean shape index (SHAPE_AM) was positively related to the density of the NH₄⁺-N and TP. The above-mention demonstrated that the growing intensity of human activities would result in the deterioration of water. The relationship between area-weighted mean patch fractal dimension (FRAC_AM) and water quality can not be well described.Through multi-angle analysis, this study revealed the eco-hydrological processes in the Qingyijiang River watershed, and thus is beneficial to land use management and water quality protection, and sustainable use of resources. This may be useful for the relevant functional departments of the government to make decisions.