喀斯特石漠化区不同土地利用方式下土壤有机碳分布特征

为探究喀斯特土壤有机碳分布特征及其对人为干扰的响应,挖掘了2 854个土壤剖面,采集了22 786个土壤样品,分析了贵州省不同土地利用方式下土壤有机碳分布规律;并结合贵州省石漠化防治规划,初步估算了石漠化防治工程的土壤碳增汇贡献。结果表明:贵州省土壤有机碳呈现含量高、密度小的特征。表层土壤(0-20cm)有机碳平均含量25.07g/kg,平均密度仅为4.27kg/m~2。不同用地类型土壤表层有机碳含量大小为灌木林地乔灌木林地灌草地乔木林地弃耕地与荒地草地水田园地旱地与坡耕地;表层碳密度大小为水田灌木林地乔木林地乔灌木林地弃耕地与荒地灌草地旱地与坡耕地草地园地。0-60cm土层土壤有机碳含量对人为干扰较为敏感,60-100cm土层土壤有机碳含量差异较小。实施退耕还林,人工种草及人工造林等石漠化防治工程会明显促进土壤有机碳的积累,到2050年,贵州省0-10,0-20,0-30,0-100cm土层土壤有机碳将增加1.99×10~(13),3.37×10~(13),4.45×10~(13),6.29×10~(13) g。可见,喀斯特地区土壤有机碳具有含量高、密度低的显著特征,石漠化治理能有效增加喀斯特地区土壤碳汇。

Distribution Characteristics of Soil Organic Carbon Under Different Land Uses in a Karst Rocky Desertification Area

To reveal the distribution characteristics of soil organic carbon (SOC) and to study the influence of human activities on SOC in Karst area,22 786 soil samples collected from 2 854 soil profiles were analyzed.Spatial distribution characteristics of SOC under different land uses in Guizhou Province were discussed.Combined with the control plan of rocky desertification in Guizhou Province,carbon sequestration caused by rocky desertification prevention and control was assessed.The results indicated that the SOC content in Guizhou was high,and the SOC density was low.The average SOC content in top soil (0-20 cm) was 25.07 g/kg,but the average SOC density was only 4.27 kg/m2.The SOC content of top soil in different land uses followed the order:shrub lands ＞ arbor-shrub mixed forest lands ＞ shrub grass lands ＞ arbor forest lands ＞ abandoned lands and uncultivated lands ＞ grasslands ＞ paddy lands ＞ garden lands ＞ arid lands and sloping croplands.The SOC density of top soil in different land uses descended in the order:paddy lands ＞ shrub lands ＞ arbor forest lands ＞ arbor-shrub mixed forest lands ＞ abandoned lands and uncultivated lands ＞ shrub grass lands ＞ arid lands and sloping croplands ＞ grasslands ＞ garden lands.The SOC content of top 60 cm soil was sensitive to human disturbance,and small discrepancies were observed among SOC contents of different land uses in deeper soil layers.If the rocky desertification prevention and control project (including returning farmland to forests,construction of artificial pasture,and artificial afforestation) was carried out efficiently,the SOC storage in Guizhou Province would be obviously promoted.Up to year 2050,at calculating depth of 0-10,0-20,0-30 and 0-100 cm,the total SOC sequestration caused by this project would be up to 1.99 × 1013,3.37 × 1013,4.45 × 1013 and 6.29 × 1013g.In conclusion,the SOC of Karst areas was characterized by high content and low density,and the implementation of the rocky desertification prevention and control project was propitious to carbon sequestration in Karst areas.