遥感用于鄱阳湖区钉螺孳生地的监测

目的　结合遥感技术和地面生态学调查数据区分钉螺孳生地并监测其变化。　方法　从鄱阳湖共选择10 0个调查点 ,75个为从鄱阳湖 5 74块草洲中随机抽取。根据历史调查 (1982～ 1984 ) ,其中 5 0个有螺 ,2 5个无螺 ,另2 5个为非钉螺孳生地调查点。将每个调查点 (面积 10 0 0 0 m2 )分成 10 0格 ,从中随机抽取 2 0格 ,在每格的中央置钉螺调查框 (4m2 ) ,收集框内所有钉螺。收集与地面调查同期的 TM卫片。采用非监督分类法对卫片进行分类并结合地面调查结果区分钉螺孳生地。　结果　分类的敏感性和特异性分别为 90 .0 %～ 95 .6 %和 6 1.1%～ 6 8.6 %。 1999～ 2 0 0 0年 ,鄱阳湖区估算的钉螺孳生地面积变幅为 6 2 3.4～ 76 2 .8km2。　结论　钉螺孳生地与植被覆盖的区域有关 ,卫片分类能用于区分钉螺孳生地确定其范围并监测其随关键因素的波动而造成的变化。

Application of Remote Sensing for Surveillance of Snail Habitats in Poyang Lake, China

Objective To identify snail habitats and monitor the changes by combining remote sensing technique with the ground-based ecological data. . Methods. Of 100 survey sites selected throughout Poyang Lake, 75 were randomly identified from 574 land mass units: 50 were from snail habitats and 25 were from non-snail habitats based on a historical survey (1982-1984); 25 sites with habitats that did not have snails were also selected. Each site, covering .{10 000.} m2, was divided into a grid of 100 cells from which 20 cells were randomly selected. Snails, when present, were collected from a 4 m2 frame placed in the center of the selected cell. Satellite Landsat TM images were obtained for the same period as the ground survey data collected. Unsupervised classification was used to classify the images. Identified land-cover types were correlated with snail habitat. . Results . The sensitivity and specificity of classified snail habitat were 90.^0%-95.^6% and 61.^1%-68.^6%, respectively. Based on the classification, estimated snail habitat areas in Poyang Lake increased from 623.^4 km2 in 1999 to 762.^8 km2 in 2000. . Conclusion . Snail habitats are associated with grassland-covered areas. Classified images can be used to identify snail habitats, determine their areas, and monitor snail habitat changes caused by annual fluctuations of key environmental factors.