【作者】 戎慧；

【导师】 彭世揆；

【作者基本信息】 南京林业大学 ， 森林经理学， 2011， 硕士

【摘要】 森林和湿地两大生态系统分别作为“地球之肺”和“地球之肾”,共同为地球构筑了强大的生态安全屏障。同时两者之间息息相关、相互依存,他们的动态变化常常是具有一定的联系性,因而只研究其中一种的变化是片面的。建设和保护好森林与湿地生态系统是林业部门承担的重要职责,而森林与湿地的动态监测则是森林与湿地保护的一项重要内容。本文以浙江省余杭区为研究区,利用1994年与2008年TM影像,探索森林与湿地动态监测的方法以及余杭区从1994至2008年将近二十年内森林与湿地的变化情况。研究结果表明：(1)本文主要采用三种变化监测的方法,包括分类后比较法、多时相数据直接分类技术、变化信息的提取技术。分类后比较法的监测精度主要取决于分类方法的选择。本文引入纹理信息,对两期数据分别进行最大似然法和决策树法进行分类,结果显示后者的精度高于前者。最后通过类别叠加分析得到变化类别和变化统计结果。多时相数据直接分类法相对前者合理性较强,减少出现实际不存在变化类别,并且只进行一次分类。难点在于变化类别的确定,有时相当繁琐。变化信息的提取技术主要采用图像差值法和变化向量分析法,难点在于变化阈值的确定,本文采用基于Kappa系数的阈值计算方法以及双窗口变步长阈值搜寻算法来确定阈值,并且选取精度最高的变化—未变化二值图,最后再对变化信息进行分类。(2)变化结果显示：1994年森林占地40146.66hm2；2008年森林占地41618.97 hm2；1994年湿地占地4380.75hm2；2008年湿地占地9680.85hm2。从1994年到2008年,森林覆盖较为稳定,而湿地覆盖面积显著增加。森林一部分转化为农田以及建筑用地,增加部分由农田转化而来；湿地的增加主要来自于农田的转化。(3)对两期森林状况采用Riitters模型进行景观破碎化分析,1994年到2008年,尽管森林覆盖面积有所上升,但森林内部破碎化程度加重,2008年穿孔森林是1994年的7.32倍、斑块森林是1994年的1.84倍、过渡森林是1994年的1.27倍。造成森林破碎化程度加剧的主要驱动力为人为干扰。根据AI指数的分析,从1994年到2008年随着建筑用地的急剧扩张,对森林的干扰逐渐上升,而人为干扰中农田干扰则有逐渐减弱的趋势。(4)从1994年到2008年,余杭区人工湿地增加明显而天然湿地比重下降。研究区内人工湿地主要包括水库及养殖水面,人工湿地的破碎化剧烈升高,主要由于余杭区重视水产养殖的发展,积极发展渔业,人工养殖水面相应增加且彼此之间缺少连通性。更多还原

【Abstract】 Forest and wetland as two big ecological systems of the earth are regarded as "lung" and "kidneys" of the earth.They are closely related and interdependent and construct a powerful ecological security barrier for the earth.The dynamic changes of them have a certain relation, therefore,only researching one change is not comprehensive.It is an important responsibility of foestry department to Construct and protect forests and wetlands ecosystems, and the dynamic monitoring forests and wetlands is the important content of forest and the wetland protection.Using TM images data of 1994 and 2008, this paper aims at comparing different change detection techniques to assess their effectiveness for detecting changes of forests and wetlands from 1994 to 2008 inYuhang,Zhejiang provice. Following are the conclusions from this study:(1)This paper describes three change detection methods, including the post-classification comparison method,the multitemporal composition classification and the change detection techniques based on pixels.The detection accuracy of post-clsssification method depends on the choice of classification methods. Taking advantage of the approach of texture analysis,this study compares Maximum likelihood classification and decision tree classification and the result shows that the accuracy of the latter is better than the former. Finally, we get change category and change statistical results by overlay analysis. Compared to post-classification comparison method, multitemporal composition classification,which is more reasonable, only requires classification once and reduces the occurrence of the Unrealistic changes. But it is difficult to determinate the change category. Change detection techniques based on pixels mainly use the image difference method and the Change Vector Analysis(CVA), which is difficult to determine the appropriate changing threshold. In this paper, we choose Double Thresholding algorithm based on the Kappa and a new method named Double-Windows Flexible Pace Searching algorithm to determine image segmentation threshold, and select the most accurate change binary image,to classify(2)The changed results show that the area of forest and Wetland were 40146.66 hm2 and 4380.75hm2 in 1994 while there were 41618.97 hm2 and 9680.85 hm2 in 2008. From 1994 to 2008, forest cover was more stable,while wetland coverage area increased significantly. Part of the forest changed into farmland or building lands,changed from farmland. The increase of Wetland is mainly because of farmland transformation.(3) By Riitters Model, Compared to 1994, although the overall forest cover rate in Yuhang District has increased in 2008, forest fragmentation has accelerated due to a decreased proportion of interior forest and an increased proportion of perforated, patch and transitional forests. Perforated forest in 2008 was 7.32 times that of 1994, patch forest was 1.84 times that of 1994 and transitional forest was 1.27 times that of 1994. That human disturbance accelerates forest fragmentation from the 1980s to 2008.According to the analysis of Association Index, Rapid urbanization during 1994 to 2008 is considered to be the main driving force for this deterioration,while the interference of field is a gradual weakening trend.(4)From 1994 to 2008, artificial wetland increased obviously and natural wetland proportion dropped in yuhang district. Artificial wetland mainly includes reservoirs and aquaculture, and artificial wetland fragmentation dramatically rise, mainly due to the development of attention for aquaculture in yuhang district,and water aquaculture increase but lack of connectedness.更多还原