作 者 ：李裕元,邵明安,郑纪勇,李秋芳
期 刊 ：生态学报 2007年 27卷 6期 页码：2279~2287
关键词：土壤有机碳密度；黄土高原北部；水蚀风蚀交错带；人工草地；植被恢复与重建；土地利用变化；
Keywords:soil organic carbon density, northern Loess Plateau, artificial grassland, vegetation recovery and reconstruction,
摘 要 ：草地的恢复与重建是黄土高原生态建设的重要内容，探讨草地恢复过程中土壤有机碳密度（SOCD）的变化规律对于合理评价北方水蚀风蚀交错带地区生态恢复的环境效应及其对土壤碳固存潜力的影响具有重要的理论价值。以黄土高原北部水蚀风蚀交错带地区不同生长年限的紫花苜蓿（Medicago sativa）人工草地及其退化后形成的次生草地为主要研究对象，探讨了SOCD的动态变化特征。结果表明，研究区0~100 cm土体的SOCD普遍较低，变化范围为1.18 ~2.81 kg C m-2，略高于地球上荒漠带的水平（1.4 kg C m-2），显著低于黄土高原中部(4.46~9.95 kg C m-2)与全国（11.52 ~12.04 kg C m-2）的平均水平。但是当土地利用方式由农田转变为人工草地以后，以及随着人工草地向长芒草（Stipa bungeana）次生天然草地的自然演替，SOCD均有不同程度的增加，增加幅度最大可达72%，土壤表现为明显的碳汇。不同土地利用方式0~100 cm SOCD的变化顺序为：灌木林地（2.11 kg C m-2）>次生天然草地（1.95 kg C m-2）>人工草地（1.91 kg C m-2）>弃耕地（1.69 kg C m-2）>农田（1.68 kg C m-2），但统计差异不显著，意味着植被恢复对土壤碳固存的影响相对较小，该地区土壤固存CO2的潜力并不大，发育较好的次生天然草地0~100 cm土体SOCD平均仅为 2.20 kg C m-2。对SOCD垂直变化的分析结果表明表层SOC主要固存于表层0~20 cm土壤，而且与0~100 cm 土体的SOCD具有显著的线性相关性，由表层观测值可以有效估计0~100 cm土体的SOCD，估计误差为9.9 %（0.18 kg C m-2）。
Abstract:Grassland recovery and land reconstruction in the Loess Plateau are critical constituents of regional ecological construction. Exploration of soil organic carbon density (SOCD) changes during the process of grassland recovery is important in assessing environmental changes, as well as suggesting estimates of soil carbon sequestration in the dissected area of wind-water erosion in north China. Soil was found to be a slight carbon sink during recovery processes in the agro-pastoral area of the northern Loess Plateau with SOCD, being (2.11 kg C m-2) in scrubland > (1.95 kg C m-2) in secondary natural grassland > (1.91 kg C m-2) in artificial grassland > (1.69 kg C m-2) in abandoned farmland and > (1.68 kg C m-2) in farmland. However, these differences were not statistically significant, suggesting that impacts of vegetation recovery on SOCD were relatively slight and that the potential for CO2 sequestration in local soils is not large. Changes of SOCD had been studied in Medicago sativa grasslands of different ages and in the secondary natural grassland of abandoned land in Liudaogou catchment, in Shenmu county of Shaanxi province. Results showed that SOCD were generally low, ranging from 1.18 to 2.81 kg C m-2. Values of 1.4 kg C m-2 are also typically found in desert areas and such values are significantly lower than values for the central Loess Plateau. In the central Plateau, values range from 4.46 to 9.95 kg C m-2, with a national average of 11.5-12.0 kg C m-2 for China. SOCD increased at varying rates when land use patterns changed from farmland to artificial grassland or changed further to the secondary natural Stipa bungeana grassland. SOCD under well-developed Stipa bungeana grassland improved only slightly to 2.20 kg C m-2. Vertical changes in SOCD revealed that soil carbon was mainly sequestrated in the surface layer of 0-20 cm. Furthermore, SOCD in this layer was significantly correlated with an average value for the whole 0-100 cm profile. So SOCD, in the 0-100cm layer, can be well estimated using values for the 0-20 cm layer, with an estimation error of only 9.9 % (0.18 kg C m-2).