喀斯特石漠化综合治理区表层土壤有机碳时空动态特征与趋势探讨

以中国南方喀斯特地区具有代表性的贵州为例,选取三个典型石漠化综合治理示范区,以2006年4月野外监测和2009年4月重复采样的数据为基础,分析喀斯特脆弱生态区实施石漠化综合治理工程的土壤有机碳时空动态特征和发展趋势。结果表明:经过3年的石漠化综合治理,不同等级石漠化样地表层土壤有机碳密度增幅不一,其中轻、中度石漠化样地提升幅度最大,无、潜在石漠化样地次之,强度石漠化样地最小;不同工程措施下表层土壤有机碳密度特征表现为:封山育林育草>退耕还林还草>坡改梯;增幅表现为:退耕还林还草>封山育林育草>坡改梯。石漠化治理过程中,随着轻度以上石漠化土地面积的减少,表土碳储量进一步增大,而且表层土壤有机碳多分布于潜在和无石漠化区。随着石漠化综合治理进程的推进,表土有机碳密度可能呈S型曲线增长,但由于潜在、无石漠化区多为基本农田,土壤有机碳密度将在较长时间内保持相对平稳的状态。而轻、中度石漠化样地在治理初期其表土有机碳密度增幅将最快。因此,采取有效的土地利用方式与加强可持续管理对提高表层土壤的固碳潜力具有非常重要的意义。 

Spatial-temporal dynamic features and tendency of the topsoil organic carbon in integrated rehabilitating karst rocky desert

Taking the Guizhou Province,a representative karst area,for example,three typical demonstration areas for integrated rehabilitation to karst rocky desertification is chosen in the study.Based on the field monitored data in April 2006 and repeated sampling data in April 2009,the spatial-temporal dynamic characteristics of the topsoil in fragile environment under integrated rehabilitating is analyzed.The result proves the following items.After 3 years rehabilitation,the increase in topsoil organic carbon density at different plots of different desertification grades is different with each other.The amount of the increase in topsoil organic carbon density at mild and moderate rocky desertification plots is the largest,inconspicuous or potential rocky desertification plots is the second,and the serious rocky desertification is the smallest.Organic carbon density of the topsoil under different engineering measures manifests as： closed treatment 〉 recovering farmland to forests and grassland 〉 the project of transforming slope to terrace.While the growth manifests as： recovering farmland to forests and grassland 〉 closed treatment 〉 the project of transforming slope to terrace.Along with the decreases in land area of mild rocky desertification grade or more seriously desertification grade,the carbon storage of the topsoil increases further,and the carbon storage of the topsoil mainly exists in potential rocky desertification plot or not deserted region.The growth trend of topsoil organic carbon density perhaps presents the ＂S＂ pattern along with the rehabilitation,but the organic carbon density of topsoil in inconspicuous and potential rocky desertification plots will keep steady state in a long time for those lands are the basic farmland generally.At the mild and moderate rocky desertification plots,the increase in topsoil organic carbon density is the largest in early rehabilitation stage.So take effective methods of land use and strengthen sustainable management is of extremely vital significance in improving the carbon sequestration.