黑土坡耕地有机碳变化及固碳潜力分析

Organic carbon change and carbon sequestration potential of sloping farmland in the black soil area

东北黑土区自开垦以来有机质含量逐渐降低,有机碳库长期处于亏缺状态,理论上也具有较大的固碳潜力。以典型黑土区长期传统作业的坡耕地(30—60 a)为研究对象,通过测定不同坡位(坡上侵蚀区和坡下沉积区)、不同土层(表土和底土)有机碳分布特征,估算不同开垦年限黑土固碳潜力及其恢复至固碳潜力所需的时间。结果表明:(1)总有机碳、有机碳密度以及碳饱和水平均表现为沉积区显著大于侵蚀区,表土显著大于底土,且均在开垦30a坡耕地达到最大值;(2)固碳潜力表现为侵蚀区(1.24—2.89 kg/m^2)显著大于沉积区(0.79—1.04 kg/m^2),底土(0.83—3.59 kg/m^2)显著大于表土(0.6—2.53 kg/m^2),随着开垦年限的增加表现为开垦30 a显著小于开垦40 a、60 a;(3)黑土坡耕地(30—60 a)侵蚀区和沉积区土壤(0—50 cm)达到固碳潜力分别需要20—181 a和13—66 a。黑土坡耕地固碳潜力的时空变异性在农业经营以及修复管理过程中需引起重视,以实现黑土资源的可持续利用。

Soil organic matter has gradually decreased since the original reclamation of black soil in Northeast China,and the organic carbon pool has maintained a deficient state for an extended period,which in theory leads to a greater carbon sequestration potential.Based on sloping farmlands(30—60 a)in a typical black soil area,the organic carbon distribution characteristics of different soil layers(topsoil and subsoil)at different slope positions(upper-slope eroded area and lower-slope deposit area)were investigated.Besides,the sequestration potential of organic carbon on sloping farmlands with different reclamation years and duration to meet the carbon sequestration potential were estimated.The results showed that:(1)the total organic carbon,the organic carbon density,and the carbon saturation level in lower-slope deposition areas and in the topsoil layer were significantly greater than those in upper-slope eroded areas and subsoil layer,respectively.All their maximum values were found to occur on sloping farmland with 30 years of reclamation.(2)The carbon sequestration potential of upper-slope eroded areas(1.24—2.89 kg/m^2)and subsoil(0.83—3.59 kg/m^2)was significantly higher than that of lower-slope deposition areas(0.79—1.04 kg/m^2)and topsoil(0.6—2.53 kg/m^2),respectively.The potential of carbon sequestration was significantly lower in farmland with 30 years of reclamation than that in farmlands with 40 years and 60 years of reclamation.(3)It will take 20—181 a and 13—66 a to achieve carbon sequestration potential in upper-slope eroded areas and lower-slope deposition areas of sloping farmland(30—60 a)in black soil(0—50 cm),respectively.Therefore,more attention should be paid to the spatial-temporal variability of carbon sequestration potential on sloping farmland in the process of agricultural operation and restoration management,to realize the sustainable potential of black soil resources.