State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, Shaanxi 710061, China; CAS Center for Excellence in Quaternary Science and Global Change, Xi'an 710061, China; National Observation and Research Station of Earth Critical Zone on the Loess Plateau of Shaanxi, Xi'an, 710061, China.
State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, Shaanxi 710061, China; CAS Center for Excellence in Quaternary Science and Global Change, Xi'an 710061, China; National Observation and Research Station of Earth Critical Zone on the Loess Plateau of Shaanxi, Xi'an, 710061, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Sci Total Environ. 2022 Feb 25;809:151155. doi: 10.1016/j.scitotenv.2021.151155. Epub 2021 Oct 21.
Soil aggregates (SA) play crucial roles in soil organic carbon (SOC) sequestration. Different SA fractions contribute differently to the sequestration of SOC. However, few studies have examined the factors controlling SA fractions and associated SOC contents across a watershed. Soil samples were collected at 0-10 cm (surface layer) and 10-20 cm (subsurface layer) from 88 sites across a semi-humid watershed (1.1 km) on the Loess Plateau, China. These samples were separated into macroaggregates (MA), microaggregates (MI), and silt + clay fractions (SC) by wet-sieving, and SOC content of each fraction was determined. The objectives were to: 1) investigate the spatial variability of SA fractions and associated SOC contents as well as their main controls across an entire watershed, and 2) explore the linkages between soil aggregation and SOC sequestration. The bulk and aggregate SOC contents of all SA fractions showed moderate variability, with coefficient of variations of 23.3-31.9%. Geostatistical analysis indicated that the spatial patterns of SA fractions and SOC content varied with aggregate size. From combined Spearman's correlation analysis and structural equation modelling, we found that soil texture was an important control on the spatial variability of all SA fractions and associated SOC contents. Vegetation dynamics and management practices associated with land use were also important controls on MA and MI and their associated SOC contents, especially in the surface layer. However, SC and its associated SOC content were more sensitive to eco-hydrological processes related to topography. Among the land uses, grassland had the greatest SOC sequestration potential. The fine roots of herbs can wrap MI in MA and increase SOC content within MA, which is the primary mechanism responsible for SOC sequestration in grasslands. These results indicate that using vegetation with fine root systems for restoration is a good strategy to increase SOC sequestration in this region.
土壤团聚体（SA）在土壤有机碳（SOC）固存中起着至关重要的作用。不同的 SA 组分对 SOC 的固存贡献不同。然而，很少有研究考察控制整个流域内 SA 组分及其相关 SOC 含量的因素。本研究在中国黄土高原半湿润流域（1.1km）采集了 88 个点位的 0-10cm（表层）和 10-20cm（次表层）土壤样品。这些样品通过湿筛法分离为大团聚体（MA）、微团聚体（MI）和粉粒+黏粒组分（SC），并测定了每个组分的 SOC 含量。本研究旨在：1）调查整个流域内 SA 组分及其相关 SOC 含量的空间变异性及其主要控制因素，2）探讨土壤团聚体与 SOC 固存之间的联系。所有 SA 组分的 bulk 和 aggregate SOC 含量均表现出中等程度的变异性，变异系数为 23.3-31.9%。地统计学分析表明，SA 组分和 SOC 含量的空间格局随团聚体大小而变化。综合 Spearman 相关分析和结构方程模型分析结果表明，土壤质地是控制所有 SA 组分及其相关 SOC 含量空间变异性的重要因素。与土地利用相关的植被动态和管理措施也是 MA 和 MI 及其相关 SOC 含量的重要控制因素，特别是在表层。然而，SC 及其相关 SOC 含量对与地形相关的生态水文过程更为敏感。在各种土地利用方式中，草地具有最大的 SOC 固存潜力。草本植物的细根可以将 MI 包裹在 MA 中，增加 MA 内的 SOC 含量，这是 SOC 在草地中固存的主要机制。这些结果表明，利用具有细根系统的植被进行恢复是增加该地区 SOC 固存的一种有效策略。
