中国中东部平原及周边地区土壤有机碳分布与变化趋势研究

Research on soil organic carbon distribution and change trend in middle-east plain and its vicinity in China

依据多目标区域地球化学调查数据对比研究中国中东部地区土壤有机碳分布与变化特征。中东部平原及周边地区河北、河南、湖北、湖南、广东与海南等6省经黄河、长江纵贯南北,由较高纬度带到较低纬度带,跨越温带、亚热带和热带地区的截然不同的自然景观,调查面积约33.4万km2,表层土壤(0～0.2m)碳储量为906.84Mt,平均碳密度为2 716.93t/km2。连接更高纬度带的东北平原土壤碳密度,中东部地区由高纬度带至低纬度带碳密度呈现高低高低的规律性变化,即3 327.8t/km2(东北平原)2 207.39、2 421.02t/km2(河北、河南)3 442.15、3 942.92t/km2(湖北、湖南)2 255.90、2 936.72t/km2(广东、海南)。不同生态系统碳密度均值比研究发现,由高纬度带至低纬度带农田与城市系统均值比呈反向变化,农田趋高,城市趋低。与第二次土壤普查相比,中东部地区20年期间土壤有机碳总计增加115.18Mt,占14.5%,年均增加5.76Mt。但有机碳增加比例极不平衡,由高纬度带至低纬度带增加比例及变化速率呈显著降低趋势乃至负增长。其中农田、城市系统变化比例呈现增长,呈下降趋势的由大至小为潮间带、河流、湖泊、草原、森林及沼泽等。

Soil organic carbon in middle-east China can be studied by comparison based on the data obtained by multi-purpose regional geochemical survey. The middle-east plain covers the terrain of Hebei, Henan, Hubei, Hunan, Guangdong and Hainan provinces, ranging from relatively higher latitude to low latitude and crossing temperate zone, subtropical zone and tropical zone. More than 334000 km2 were covered in the multbpurpose regional geochemical survey. Top soil（0- 0.2 m）carbon storage is 906.84 Mt and average carbon density is 2716.93 t/kin2. Including the higher soil carbon density in the northeastern plain, the carbon density in mid- dleeast regions of China exhibited the changing pattern of high-＋low-＋high-＋low from the northeastern plain downward to Hainan Province, that is 3327. 8 t/km2 （northeastern plain-→2207. 39, 2421.02 t/km2 （Hebei and Henan）→3442. 15, 3942.92 t/km2 （Hubei and Hunan）→2255.90, 2936.72 t/km2（Guangdong and Hain an）. The soil carbon density in agricultural ecosystem and urban ecosystem presented different changing rule from higher latitude to lower latitude, i. e. , in agricultural farmland it changes from low to high, and in urban soil from high to low. The soil organic carbon increased by 14.5%（totally increasing 115.18 Mt and annually averaging 5.76 Mt/a） during past 20 years compared to the value achieved by the second soil reconnaissance. However organic carbon did not increase evenly. The rising rate decreased from low latitude to high latitude, and organic carbon increased in agricultural and urban ecosystem but decreased in tideland, rivers, lakes,grassland, forest and swamp.