红树林空间分布遥感监测精度的影响因素及应对措施

Influence factors and measures of remote sensing monitoring precision of mangrove space distribution

为提高红树林空间分布遥感监测结果的准确性和可靠性,分析了现有研究中存在的突出问题及其原因:不同研究者得到的同一区域和相同(或相近)年度的红树林面积相差很大;同一研究者得到的同一区域相邻监测期的红树林面积变化剧烈,明显不符合红树林空间演变规律。结合长期监测实践,讨论了影响区域和地方尺度红树林空间分布遥感监测精度主要因素。分析认为:遥感图像的空间分辨率、海水淹没情况、信息提取策略、实地调查验证等是影响红树林空间分布遥感监测精度的主要因素。我国区域和地方尺度红树林空间分布遥感信息提取宜采用优于1 m、处于低潮位、滩涂裸露的高分辨率遥感数据;在作多期遥感信息提取时,须确保相邻监测期间红树林斑块范围的变化符合其空间演变规律;必须开展深入细致的地面调查工作,全面了解各个海湾的红树林分布状况和特点,并在实地逐一修正红树林斑块边界。

Improvement of area accuracy and reliability is highly important for the dynamic monitoring of mangrove forests based on remote sensing.In this study,two serious problems present in certain studies addressing mangrove dynamics were analyzed： one was that in the same region and same year,the mangrove areas reported by different researchers varied greatly,and the other was that the area of mangrove forests in a region or gulf changed dramatically in a short period.The main factors affecting the accuracy of mangrove area surveys using remote-sensing data at regional and local levels were discussed based on the practical experience of monitoring of mangrove dynamics from many years.The spatial resolution of remote-sensing images,tidal height,protocol for extraction of information on mangrove distribution,and field validation were the most important factors affecting the accuracy of mangrove areas based on remote sensing.We suggested that remote-sensing data of extremely high resolution（1 m or below） should be used to extract information of mangrove areas at regional and local levels in China; tides were low,and the beach was exposed when the image was acquired.When remote-sensing information from two or more periods is extracted,the area of mangrove patches should be prevented from changing dramatically between adjacent periods.Furthermore,a basic prerequisite for any image-analysis approach is the conduction of an intensive field study; the characteristics of mangrove distribution in each gulf or bay should be investigated by field work,and then,the patch boundary should be revised individually in the field.