荒漠化重建地区土壤有机碳时空动态特征--以陕西省榆林市为例

以陕西省榆林市这一典型区为例探讨干旱、半干旱荒漠化重建地区SOC时空动态特征及其驱动因素。数据基础为1982年土壤普查和2003年重复采样。结果表明:(1) 在耕层(0~20 cm)、1 m深(0~100 cm) 和全剖面(母质层以上整个土体) 等三个剖面层次上,土壤有机碳密度(SOCD)和储量(SOCS)时空动态分异明显,其中耕层最为显著。(2) 在区域水平上,耕层、1 m深和全剖面SOCS分别增加10.12 Gg、19.06 Gg和20.10 Gg,其中东南部丘陵沟壑区显著高于西北部风沙草滩区。(3) 在土类水平上,风沙土类中各土种SOCD及其变化悬殊,其中流动风沙土和半固定风沙土SOCD最低、增加量最小,固定风沙土初始SOCD最高、减少量最大;反之,黄绵土类中各土种SOCD较高,增加量显著。该研究证明植树造林种草、可持续农业耕垦等土地利用和管理方式的变更能显著提高荒漠化地区土壤固碳能力。

Temporal-spatial Dynamic Analysis of Soil Organic Carbon in Inversed Desertification Area: a case study in Yulin County, Shaanxi Province

Soil organic carbon (SoC) is considered to be a key index in evaluation of soil quality, soil degradation and soil C sequestration. In order to discuss the temporal-spatial dynamics of SoC in reversed desertification area, Yulin County is taken as a case. Data of SoC were obtained based on the Second National Soil Survey in 1982 and re-sampling in 2003. Methods to soil sampling, SoC determination, soil organic carbon density (SoCD) and storage (SoCS) calculation are soil auger, K₂Cr₃O₇ oxidation and FeSO₄ titration and area-weighted mean values, respectively. On average, SoCD and SoCS and their changes vary between different soil groups, soil C pools and sub-areas. During 1982 and 2003, soil organic carbon density (SoCS) for arable layer (0-20 cm), 1-m depth (0-100 cm) and whole profile (100±10 cm) increase 0.15 kgm_-2, 0.29 kgm_-2 and 0.31 kgm_-2 respectively, being equal to increments of SoCS of 10.12 Gg, 19.06 Gg and 20.10 Gg, correspondingly. As for soil C pools, arable layer is much more sensitive to climate change, land use/management and other human activities than 1-m depth and whole profile. With regard to soil group and sub-area, the change of SoCD of sandy soil distributed in the northwest is much less than that of loessal soil distributed in the southeast, thus per unit area SoCS in the northwest is lower than the southeast. As far as soil genus, the SoCD of moving sandy soil and semi-fixed sandy soil is significantly lower than that fixed sandy soil, and sandy loamy loessal soil is less than light loamy loessal soil, which indicate that there is great potential to increase SoC in the study area. These data demonstrate that afforestation, agroforestry, tillage of soil and water conservation, and other soil restoration countermeasures can enhance soil C sequestration and mitigate the atmospheric concentration of CO₂.