1978年以来5个时期南四湖区土地利用格局及土壤有机碳储量

Land Use Pattern and Soil Organic Carbon Storage in Nansihu Lakes Area for 5 Periods since 1978

以1978年、1987年、1998年、2008年和2018年南四湖区的遥感影像为数据源,采用监督分类方法,对遥感影像进行人机交互目视解译,得到5个时期南四湖区各种土地利用类型的分布和面积数据;在沼泽、水产养殖区、水稻田和旱地中各设置了8个采样点,采集表层(0~15 cm深度)土样,测定土样中的溶解性有机碳、轻组有机碳和重组有机碳的含量,计算出各种土地利用类型表层土壤有机碳密度和碳储量。研究结果表明,受水文变化和人类活动干扰的影响,随着时间的推移,5个时期南四湖区天然湿地(湖泊、河流、沼泽)面积在不断减少,人工湿地面积(水产养殖区、水稻田、人工水渠)在不断增加;随着土地利用方式的改变,南四湖区土壤碳储量也发生了明显变化,沼泽表层土壤的溶解性有机碳密度和轻组有机碳密度都相对最大,水稻田表层土壤的重组有机碳密度相对最大。虽然水产养殖区和水稻田面积的增加,使其表层土壤重组有机碳储量增加了921.58×10~3t,但是,天然湿地的丧失,使得2018年南四湖区表层土壤碳储量比1978年减少了136.34×10~3t。

Based on the remote sensing images of Nansihu Lakes area in 1978,1987,1998,2008 and 2018,human-machine interactive visual interpretation was conducted using supervised classification to obtain the data of distribution and area of each type of land use in Nansihu Lakes area for 5 periods.Eight sampling sites were set up in marshes,fishponds,paddy fields and dry land,respectively,and soil samples were collected in the sampling sites.The contents of dissolved organic carbon,light fraction organic carbon and heavy fraction organic carbon in the soil samples were measured.Moreover,the density and storage of organic carbon of each types of land use were calculated.The results showed that the areas of natural wetlands(lakes,rivers,marshes)in Nansihu Lakes area decreased,while the areas of artificial wetlands(fishponds,paddy fields,artificial canals)increased,due to the hydrological changes and interference of human activities during 5 periods.The soil organic carbon storage in Nansihu Lakes area has undergone significant changes with the change of land use ways.The highest dissolved organic carbon density and light fraction organic carbon density were occurred in the top soils of the marshes,and the highest heavy fraction organic carbon density was occurred in the top soil of paddy fields.The heavy fraction organic carbon storage in the top soil increased by 921.58×103 ton due to the increased area of fishponds and paddy fields,however,the total soil organic carbon storage in the top soil in Nansihu Lakes area decreased by 136.34×103 ton because of significant shrinkage of natural wetlands.