景观类型与景观格局演变对洪泽湖水质的影响

基于Landsat序列遥感影像数据解译进行了景观类型分类，分析了2008—2018年洪泽湖16个监测点位水质数据变化特征，从流域尺度研究了景观类型和景观格局演变对湖区水质的影响机制.研究结果表明，洪泽湖区主要水质风险指标为总氮（TN）和总磷（TP），淮安南区域TN和TP浓度较高.2000年之前洪泽湖流域内景观类型主要为旱地（43.3%），2000年后主要景观类型逐渐转变为水田（37.7%）和建设用地（23.6%）.建设用地、水田、入湖河流、围圩和围网养殖面积与湖区TN和TP浓度呈显著正相关，林地和草地面积与TN和TP浓度呈显著负相关.围圩养殖面积对TN浓度变异解释度最高，建设用地面积对TP浓度变异解释度最高，分别为47.6%和43.2%.近20年洪泽湖流域景观破碎度增大，斑块密度指数（PD）和蔓延度指数（CONTAG）与湖区TN、TP浓度呈显著正相关.建设用地、围网和围圩养殖面积增加以及景观破碎化增强与湖区TN和TP浓度上升密切相关.减少围圩和围网养殖的面积比例，控制建设用地和水田规模，降低生态空间景观破碎度，是维护和修复洪泽湖水质安全和水生态健康的重要抓手.

Effects of landscape types and landscape pattern evolution on water quality of Hongze Lake

Landscape types were classified based on Landsat remote sensing image data interpretation, and water quality changes at 16 monitoring sites in Lake Hongze from 2008 to 2018 were analyzed, the influence mechanism of landscape type and landscape pattern evolution on lake water quality was studied at watershed scale. The results showed that the main water quality risk indicators were total nitrogen (TN) and total phosphorus (TP) in the Lake Hongze region, and the concentrations of TN and TP were higher in the southern Huai''an region. Before 2000, the main landscape types in the Lake Hongze Basin was dry land (43.3%), and after 2000, the main landscape types gradually changed to paddy field (37.7%) and construction land (23.6%). The areas of construction land, paddy field, inflow rivers, purse seine and ring-fence fisheries were significantly positively correlated with TN and TP concentrations, while the areas of woodland and grassland were significantly negatively correlated with TN and TP concentrations. The explainability of ring-fence fisheries area to TN concentration variation was the highest and construction land area to TP concentration variation was the highest, 47.6% and 43.2%, respectively. In recent 20 years, the landscape fragmentation increased, and the patch density index (PD) and the contagion index (CONTAG) were significantly positively correlated with the TN and TP concentrations in the Lake Hongze Basin. The increase of construction land, paddy field, purse seine and ring-fence fisheries area and the increase of landscape fragmentation are closely related to the increase of TN and TP concentration in the lake area. Therefore, reducing the area ratio of purse seine and ring-fence fisheries, controlling the scale of construction land and paddy field, and reducing the fragmentation degree of landscape patches in ecological space are the important measures to maintain and restore the water quality safety and ecological health of Lake Hongze.