草海湿地小流域土地利用与景观格局对氮、磷输出的影响

识别主要污染物和污染源对草海湿地生态系统的保护与管理具有重要的现实意义.基于2012年5—10月6个小流域的水质观测数据、土地利用结构与景观格局指数,研究了草海湿地入湖小流域氮、磷输出的时空变化规律及其与景观格局的关系,以期为草海湿地综合治理提供参考.结果表明,草海湿地北面建设用地面积比例呈西北、东南方向逐渐降低和景观破碎度逐渐减小的趋势,具有明显的城市-城郊-农村的景观格局梯度,景观格局影响流域水质.多元统计分析表明,小流域氮磷输出受景观组成属性和空间属性综合影响,城镇建设用地百分比与TN、TP和COD呈显著正相关关系(r分别为0.995、0.978和0.996,p0.01),景观破碎度(CONTAG、ED、MPS)和多样性(SHDI)与水质(TN、TP、COD)具有显著的相关关系,CCA的第一排序轴解释了建设用地面积比例、景观指数与水质指标相关性的96.0%.可见,威宁城镇化快速发展威胁了草海湿地生态安全,需进行草海周边城镇化进程的调整和控制.

Effects of land-use and landscape pattern on nitrogen and phosphorus exports in Caohai wetland watershed

Identifying the main pollutants and sources of pollution has important practical significance for the protection and management of the Caohai wetland ecosystem in Guizhou Plateau. Based on the water quality data, land use structure and landscape pattern metrics of six sub-watersheds in Caohai from May, 2012 to October, 2012, the spatial-temporal variation characteristics of TN, TP released from sub-watersheds and flowed into lake in Caohai and its relationship with the landscape patterns were studied, to provide guidance for the comprehensive management of Caohai wetland. The results show that the northern land area of Caohai watershed landscape had a gradually decreasing trend from northwest to southeast, with the gradual reducing of landscape fragmentation, and exhibited an obvious City-Suburb-Rural landscape pattern gradient that greatly affects the water quality. The multivariate statistical analysis shows that the nitrogen and phosphorus release from a small watershed were comprehensively influenced by landscape composition and spatial attributes. It is also found a positive correlation between the portion of urban construction area with TN, TP and COD content (the r value is 0.995, 0.978 and 0.996 respectively, p<0.01). The landscape fragmentation degree(CONTAG, ED, MPS) and landscape diversity were dramatically related to water quality (TN, TP, COD). The result of CCA indicated that the first ordination axis could explain 96.0% of the correlations between construction land ratio, landscape index and water quality indicators. The rapid development of urbanization gravely threats the ecological security of Caohai, and which needed to further adjustment and control.