近30年太湖沉水植物优势种遥感监测及变化分析

Remote sensing monitoring and analysis of dominant species of submerged vegetation in Taihu Lake over last 30 years

利用1985—1986年、1995—1996年、2004—2006年和2014—2015年多时相遥感影像数据,构建了水生植物分类决策树模型,结合沉水植物的生活史差异,研究太湖近30年沉水植物优势种的演替模式。4个时期的沉水植物遥感分类总体精度与Kappa系数依次为64.86%和0.59,70.83%和0.65,63.93%和0.50,64.94%和0.60。研究表明:1985—2015年马来眼子菜由东山湾向西山岛、东太湖向南太湖扩张,竺山湾、梅梁湾的苦草呈锐减的趋势,近年来梅梁湾的沉水植物只有菹草1种,湖心区一直未监测到沉水植物,东太湖沉水植物分布面积最广、种类最多。近30年太湖沉水植物演替主要经历4个阶段,依次为苦草-眼子菜型、小眼子菜型、金鱼藻-伊乐藻型和眼子菜-伊乐藻型阶段。水体富营养化和围网养殖是沉水植物演替的主要原因。

Multi-temporal remote sensing image data over the periods from 1985 to 1986,from 1995 to 1996,from2004 to 2006,and from 2014 to 2015 were used to construct a classification tree（ CT） model for aquatic vegetation. With consideration of the differences in phenological information of submerged vegetation in Taihu Lake,the succession of the dominant species of submerged vegetation in the lake over the last 30 years was studied. The overall accuracies and Kappa coefficients of the remote sensing classification results for the four periods were64. 86% and 0. 59,70. 83% and 0. 65,63. 93% and 0. 50,and 64. 94% and 0. 60,respectively. The results show that Potamogeton malaianus has expanded from Dongshan Bay to Xishan Island,and from East Taihu Lake to South Taihu Lake from 1985 to 2015. There was a declining trend in the growth of Vallisneria spiralis in the Zhushan and Meiliang bays. There was only one kind of submerged vegetation（ i. e.,Potamogeton orispus） in Meiliang Bay in recent years. No submerged vegetation was found in the central part of the lake. The submerged vegetation was widely distributed in East Taihu Lake,with the most species. The submerged vegetation has experienced the following four stages of succession in the last 30 years： Vallisneria spiralis-Potamogetonaceae,Potamogeton pusillus,Ceratophyllum Demersum-Elodea nuttalli, and Potamogetonaceae-Elodea nuttalli. Eutrophication and aquatic breeding are the main factors leading to the succession of submerged vegetations in Taihu Lake.