不同空间特征尺度下景观格局对水质的影响

Effects of landscape pattern on water quality under different spatial characteristic scales

探究空间特征尺度下景观格局与水质的关系,对正确揭示格局如何影响水体污染迁移过程具有重要意义。本研究以福建省闽江流域为例,划分子流域、河岸和圆形缓冲区3种空间尺度,收集流域内26个监测断面的水质数据,基于Landsat-8影像分析景观格局特征。利用半变异函数、冗余分析等手段,识别各空间尺度的特征尺度,探讨在空间特征尺度下景观格局对水质的影响。结果显示:(1)闽江流域水质总体达到Ⅱ类标准,但仍存在超标水质,主要由水产禽畜养殖所致。(2)河岸尺度的特征尺度在1000 m缓冲区,而圆形缓冲区的特征尺度在2000 m。(3)子流域尺度景观格局对水质的总解释最强,达58.4%,其次为河岸(45.2%)、圆形缓冲区尺度(38.4%)。(4)林地的聚集程度和城镇最大斑块指数是影响水质的主要景观格局变量。上游汇水单元是未来水资源管理的关键区域,减少污染排放,增大林地优势和聚集程度,打破大面积建成区的连续性,有助于净化水质。

Exploring the relationship between landscape pattern and water quality at the spatial characteristic scale is of great significance to revealing the impacts of landscape pattern on water pollution migration.In this study,water quality data were collected from 26 monitoring sections in the Minjiang River basin in Fujian Province,which was divided into three spatial scales as sub-watershed,riparian buffer zone,and circular buffer zone.Landscape pattern characteristics were analyzed based on Landsat-8 images.Each spatial characteristic scale was identified to examine the impacts of landscape pattern on water quality under the spatial characteristic scale by means of semivariogram and redundancy analysis.The results showed that:(1) water quality of Minjiang River basin generally met the Level Ⅱ standard.However,there were still polluted waters that exceeded the Level Ⅲ standard,which was mainly caused by aquaculture and livestock breeding.(2) The characteristic scale of riparian zone was in 1000 m buffer zone,while the one of circular zone was in 2000 m.(3) Landscape pattern at sub-watershed had the strongest overall interpretation of water quality,up to 58.4%,followed by riparian buffer zone(45.2%) and circular buffer zone(38.4%).(4) Forest cohesion and urban largest patch index were the main landscape pattern variables affecting water quality.The upstream catchment is the key area for future water resources management.Reducing the discharge of pollution,increasing the advantage and aggregation of forest,and breaking the continuity of extensive built-up areas,could help improve water quality.