滇池湖滨带植被时空变化及其对滇池总磷浓度的影响

滇池是中国最大的高原淡水湖泊,是长江上游生态安全格局的重要组成部分。自2008年起政府在滇池湖滨带大规模退耕还草还林,以恢复滇池及其湖滨生态。湖滨带植被对滇池总磷浓度的影响是一个长期过程,需要通过遥感长时间连续监测的数据来评价。本文以滇池和滇池湖滨带为研究区,从空间分布、季节差异2个角度,结合入湖河流总磷负荷,研究2005—2018年滇池湖滨植被时空变化对滇池总磷浓度的影响。主要结论如下：① 滇池总磷浓度由湖缘向湖心逐渐降低,并且北部和南部偏高;2005—2018年,滇池总磷浓度呈现显著下降趋势;② 2011—2018年滇池总磷浓度显著减小与湖滨带植被的拦截作用密切相关;③ 2005—2018年滇池湖滨带草本和木本植物面积都显著增加,增加最剧烈的年份是2010—2011年;④ 相比于平水期和丰水期,枯水期NDVI与强影响区总磷浓度负相关关系最强,且木本植物NDVI与强影响区总磷浓度负相关性强于草本。本文利用长时间序列数据评价滇池总磷浓度与其湖滨植被的响应关系,可为滇池湖泊生态恢复提供科学依据。

The Spatiotemporal Changes of Vegetation in Lakeshore of Dianchi Lake and Its Impact on Total Phosphorus Concentration in Dianchi Lake

Dianchi Lake, the largest plateau freshwater lake in China, is an important part of the ecological security pattern in the upper reaches of the Yangtze River. In order to restore the ecology of Dianchi Lake and its lakeside, farmland along the lake has been converted to grasslands and forests on a large scale since 2008. The influence of vegetation in the lakeside on the total phosphorus concentration in Dianchi Lake is a long-term process, and it needs to be evaluated through long-term continuous monitoring data based on remote sensing. In this paper, Dianchi Lake and its lakeshore are taken as research areas. From the perspectives of spatial distribution and seasonal differences, combined with the annual change of total phosphorus load of the rivers flowing into the lake, the effect of the spatial and temporal changes of the vegetation in the lakeside on the total phosphorus concentration in Dianchi Lake from 2005 to 2018 was studied. The main conclusions in this paper are as follows: (1) In terms of the spatial variation, the multi-year average of total phosphorus concentration in the Dianchi Lake gradually decreases from the edge of the lake to the center, and it is higher in the north and south. From the aspect of temporal changes, the annual average of total phosphorus concentration in the Dianchi Lake shows a significant downward trend from 2005 to 2018. (2) The significant reduction of total phosphorus concentration in Dianchi Lake from 2011 to 2018 is closely related to vegetation in the lakeside , and the growth of vegetation has a certain degree of interception on the input of total phosphorus. (3) The results of vegetation extraction show that the area of herbs and woody plants in the lakeside of Dianchi Lake increased significantly from 2005 to 2018, and the period with the most dramatic increase in both was from 2010 to 2011. (4) Compared with the normal water period and the high water period, the NDVI of herb and woody plants has the strongest negative correlation with the total phosphorus concentration in the strongly affected area during the low water period, and the negative correlation between the NDVI of woody plants and the concentration of total phosphorus in the strongly affected area is stronger than that of herbs. This paper studied the response relationship between the total phosphorus concentration in Dianchi Lake and vegetation on its lakeshore based on long-term remote sensing data, and provided scientific basis for the ecological restoration of Dianchi Lake.