The Research On The Landscape Successions And The Carbon Storage Of Hong-hu Wetland In China

Wetland landscape is a hot research field in the past decade, and wetland carbon storage is one of the essential elements in the study of global climate change and ecological security. As the seventh largest freshwater lake in China, which owns the most abundant wetland resources in the world, the Honghu Lake wetland is typical and representative among the Yangtze River. Therefore, research into Honghu wetland landscape and carbon storage has great significance for China's wetland ecology security, protection and rational utilization.With3S technology support, this paper collected the Landsat series, CBERS02-CCD and ALOS remote sensing data of Honghu City during the period1974-2010, a total9images for eight different time slots, had set up a wetland resource space database, combined ground auxiliary information, and extracted wetland information using object-oriented image segmentation approach; On this basis, by employing principles of landscape ecology,23landscape pattern index were selected to carry out analysis of temporal and spatial variation of Honghu wetland landscape and its succession, and to reveal the wetland type change of landscape change and transfer characteristics. Using Markov and CA-Markov model, the future landscape changes of the wetland over time were predicted and analyzed, while utilizing high-resolution ALOS images of the entire study area, carbon density and carbon storage were estimated for target landscape types. The main conclusions are as follows:(1) Referring to "International Convention on Wetlands" and the State Forestry Administration published "Technical Specification for wetland inventory", and considering the actual situation of Honghu wetlands, the interpretation standard of remote sensing classification was proposed. Through wetland information extraction using object-oriented approach, the appropriate segmentation parameters were determined as:the spatial parameter, the color parameter and the minimum area parameter are10,10and120respectively.(2) Spatial and temporal analysis of wetland variation using23selected landscape indices suggests that, over the past36years, the number of wetland landscape patches in the study area increased significantly, and the degree of fragmentation increases. Increasing human activities main factor affecting the landscape patch number and the landscape fragmentation, leads to the rising of landscape fragmentation and the increases of Shannon evenness index and the Shannon diversity index. Land types undulating patch number changes are cropland, farm ponds and paddy fields/winter paddy field. The fastest growing of area appears for freshwater ponds, and more than90%of the area increase is from rice/winter paddy field conversion.(3) Dynamic analysis of the contribution rate and retention rate of landscape composition moving-in or-out reveals the position and role of different landscape components'characteristics in the overall change of the landscape, describes the general features of landscape dynamics and the internal driving mechanism; for changes in landscape type dynamic, the landscape transfer activity and fluctuant of the city was analyzed, through investigating into the landscape center changes, the centroid position of each direction and the partial offset Shift for landscape types were calculated, visually representing the temporal evolution of landscape components.(4) CA-Markov and Markov models were used to predict the pattern of Honghu landscape, and the predicted results were compared with the interpretation results. Comparison shows that:CA-Markov and Markov models have both achieved satisfactory estimation, can provide scientific and reasonable projections for the Honghu landscape pattern change, and CA-Markov has higher prediction accuracy as to model estimation precision.(5) Carbon storage of Honghu wetland were carried out on organic carbon from soil and vegetation carbon storage, results show that the soil organic carbon density of Honghu is4.557-67.519kg/m2, the soil organic carbon density of each soil type rank as:Bottom mud> Floodplain wetland> Marshes> Woodland> Cropland; the total soil carbon reserves is3.537x107t, of which the lake bottom sludge carbon storage takes45%, accounts to1.597x107t, carbon storages rank as:Bottom mud> Woodland> Cropland> Marshes> Floodplain wetland; Honghu plant organic carbon content of carbon density and storage of calculation results show that the organic carbon density of plants is4.93-63.03kg/m2, carbon density rank of the vegetation types is: Woodland> Marshes> Farmland> Aquatic> Floodplain wetland; the total plant carbon reserves is1.74x106t, carbon storage of farmland takes59%, accounts to1.02x106t, carbon storage rank is:Farmland> Woodland> Aquatic> Marshes> Floodplain wetland.