东北黑土有机碳的分布及其损失量研究

为了分析东北黑土土壤有机碳(SOC)的分布特征及其开垦以来黑土SOC的损失程度,我们于2004～2005年在黑龙江和吉林两省采集了32个自然黑土剖面样品,在每个自然黑土样品附近对应采集32个景观条件相似的耕作黑土样品。结果表明,自然黑土样品0～30cm土层SOC含量平均为32.20 g kg-1,最高可达63.46 g kg-1,黑龙江省自然黑土SOC含量(34.55 g kg-1)高于吉林省(23.80 g kg-1)。耕作土壤SOC平均含量为22.71 g kg-1,远低于自然土壤。受温度的影响,随着纬度的增加,自然黑土与耕作黑土SOC含量逐渐递增。由于土壤侵蚀以及耕垦和去除作物残留物等农业管理措施的综合作用,使得耕作黑土表层SOC含量小于自然黑土。与自然黑土相比,耕作黑土0～10cm土层SOC损失量在26.84%～46.57%之间,亚表层损失相对较少。黑土SOC含量下降也是土壤水土流失致使黑土层变薄的一个直接表现。耕作黑土表层流失厚度可以通过自然与耕作黑土剖面SOC含量的分异差值来估算。通过对土壤剖面上SOC的分布进行校正剔除土壤侵蚀的影响后得到的同等深度SOC含量的差值才可视为由耕作以及有机质输入量差异等因素造成的SOC损失量。未经校正而进行的自然黑土和耕作黑土同一深度SOC含量的比较可能过高估计了农业管理措施对土壤SOC损失量的影响。

Distribution of Soil Organic Carbon and Its Loss in Black Soils in Northeast China

To analyze the distribution characteristics of soil organic carbon(SOC) in and its loss in Black soil since it was reclaimed,a total 32 pair of soil profiles were collected in Heilongjiang and Jilin provinces in Northeast China in 2004 and 2005.Soil samples were collected in pairs with one from virgin soil profiles which had not been cultivated and the other from nearby cultivated soil profiles.Average contents of SOC at a 0-30 cm depth in virgin soils were 32.20g kg-1,a maximum up to 63.46g kg-1.Average SOC content at this depth in virgin soils in Heilongjiang Province(34.55g kg-1) was higher than in Jilin Province(23.80g kg-1).For cultivated soils the average SOC content at 0-30cm depth was 22.71 g kg-1,far less than in virgin soils.Due to the effect of temperature SOC increased with increasing in latitudes.The SOC loss from cultivation was attributed to a combination of surface soil erosion and agricultural practices including tillage and removal of plant residues.Compared with SOC in virgin soils,the amount of SOC loss at 0-10 cm depth accounted for 26.84-46.57% in cultivated soils which was more than in subsurface soils.SOC decrease is a direct response to soil layer thinning caused by water and soil erosion.The soil thickness eroded of cultivated soil can be estimated by the difference of SOC contents in cultivated and virgin soil profiles.Only with calibration and eliminating the effect of soil erosion,the difference of SOC at the same depth between virgin and cultivated soils was SOC loss caused by tillage and the different input of organic materials.The SOC loss at the same depth in virgin and cultivates soils without calibration possibly overestimated the influence of agricultural practices on SOC loss.