黄河泥沙冲/沉积区土壤有机碳不同组分空间特征及变异机制

黄河泥沙是黄河下游陆地地貌类型形成的物质来源,泥沙沉积改变了地表土壤结构和有机碳含量水平。基于室内外实验和空间地统计分析方法,文中对开封—周口土壤有机碳组分的空间特征和影响因素进行了分析。在0~100 cm土壤中TOC、AOC、NOC的含量分别为0.05~30.03 g/kg、0.01~8.86 g/kg和0.02~23.36 g/kg,表层0~20 cm的TOC、AOC、NOC高于下层,同一土层中TOC的变化幅度和含量差异性最大,AOC最小,NOC介于二者之间。NOC的含量对TOC的贡献大于AOC。空间地统计学研究显示,TOC、AOC、NOC的块金系数在0.50~0.67之间,具有中等程度的空间相关性,TOC、AOC、NOC的含量受结构因素和随机因素的共同作用,且二者的作用强度接近。空间上,自表层向下层,土壤TOC、AOC和NOC的整体变化趋势较为一致,高值区与低值区之间过渡明显,NOC和AOC的含量及空间变化能较好地反映TOC的空间变化和碳积累区域。分析发现,黄河泥沙冲/沉积区分布、农业耕作过程和耕作历史是影响区内土壤有机碳及其组成含量和空间分布的主要因素,而有机物的输入量、土壤颗粒物组成及二者的动态关系是影响土壤结构体形成和有机碳含量的关键因素,提高有机物的含量和改善土壤结构是提升土壤质量、实现区内农业持续发展的有效途径。

Spatial characteristics and variation mechanism of different soil organic carbon components in the alluvial/sedimentary zone of the Yellow River

Sediment from the Yellow River is the main material source in the formation of several landform types in the lower reaches of the Yellow River. This sediment deposition changes the surface soil structure and its organic carbon content. Here, the distribution characteristics of soil organic carbon components and their influencing factors were analyzed in the Kaifeng and Zhoukou areas based on field investigations, laboratory experiments and spatial analyses. The statistical results showed that the TOC, AOC and NOC contents were 0.05-30.03 g/kg, 0.01-8.86 g/kg and 0.02-23.36 g/kg, respectively. Contents were higher in the surface (0-20 cm) layer than those in the lower (20-100 cm) layer, and the sequence of change from high to low content in a single layer was TOC, AOC and NOC. The NOC content contributed to TOC more than AOC did. The geostatistical characteristics obtained by using the GS+ software showed that the nugget coefficients of TOC, AOC and NOC were between 0.50 and 0.67, with a moderate degree of spatial correlation. This indicates that structural and random factors commonly influence variations in TOC, AOC and NOC, and that the action intensity between them is similar. The overall trend in all areas was that the contents of TOC, AOC and NOC were relatively consistent with those from the 0-20 cm to the 20-100 cm layer, although a transition from high-value region to low-value region was obvious. The spatial distribution and the statistical characteristics of TOC, AOC and NOC contents indicates that the high-value region is located in the area less affected by sediment, and the low-value region is located in the area which the Yellow River floods. The old riverway of the Yellow River has a value somewhere in between. In flooded areas, the TOC, AOC and NOC contents were the lowest in the burst place, and then contents gradually increased in the direction of water flow and passed area. Spatial variation in the NOC and AOC contents reflected the regions of TOC spatial variation and accumulation well. Throughout history, the banks of the Yellow River have been overflowed, causing river realignment and serious flooding. The resulting sediment deposition changed the surface particulate matter composition and soil organic matter content. It was found that the distribution of deposited sediment in the flooded area and old riverway of the Yellow River, the farming process and the cultivation history were all important factors affecting SOC composition content and spatial distribution. In addition, the organic matter input, soil particle composition and their dynamic relationship were the key factors affecting soil structure and organic carbon components. In short, increasing organic matter content and improving soil structure are effective ways to improve soil quality and to achieve sustainable regional agricultural development.