College of Resources, Sichuan Agricultural University, Chengdu 611130, China.
College of Resources, Sichuan Agricultural University, Chengdu 611130, China.
Sci Total Environ. 2020 Mar 10;707:136049. doi: 10.1016/j.scitotenv.2019.136049. Epub 2019 Dec 11.
Soil aggregate stability and soil organic carbon (SOC) physical sequestration is essential to regulation of anthropogenic climate change. However, relative knowledge remains elusive. The total SOC stock, aggregate stability, capacity of physically protected C, structure of macroaggregates and Al/Fe oxides under rice-wheat rotation (RW), rice-vegetable rotation (RV) and afforested land (AL) were analysed. We chose 1-2 mm macroaggregates for low-temperature ashing (LTA) treatment to mimic natural oxidation to assess the capacity of physically protected C. Using scanning electron microscopy, the N adsorption method, and energy dispersive spectroscopy, we explored the internal structure of macroaggregates under different land use types. All land use types could physically protect over 50% of SOC. AL showed the strongest capacity of C sequestration, followed by RW, which preserved 67.1% and 59.6% of SOC, respectively. After 5 h of LTA treatment, the amount of SOC removed from the macropores in cropland (RW and RV) was higher than that in AL. In micropores with further oxidation, AL and RW both lost only 5% of SOC. Fe oxides were more correlated with C dynamics than Al oxides. Free Fe oxides were associated with the easily oxidised organic matter. Soil aggregate stability significantly correlated with Al/Fe oxides (p < 0.05). The RW and AL had a greater soil aggregate stability than the RV owing to the relatively higher content of Al/Fe oxides. In conclusion, the conversion of RW to RV reduced the mechanical stability of soil aggregates and the capacity of C physical sequestration, while the conversion of RW to AL increased these two properties. Land use change affected C physical sequestration mainly via changes in surface area, pore development and the content of Fe oxides in macroaggregates.
土壤团聚体稳定性和土壤有机碳（SOC）的物理固存对于调节人为气候变化至关重要。然而，相关知识仍然难以捉摸。本研究分析了水稻-小麦轮作（RW）、水稻-蔬菜轮作（RV）和林地（AL）下的总 SOC 储量、团聚体稳定性、物理保护的 C 容量、大团聚体结构和 Al/Fe 氧化物。我们选择 1-2mm 大小的大团聚体进行低温灰化（LTA）处理，以模拟自然氧化，评估物理保护的 C 容量。通过扫描电子显微镜、N 吸附法和能量色散光谱，我们研究了不同土地利用类型下大团聚体的内部结构。所有土地利用类型都能物理保护超过 50%的 SOC。AL 表现出最强的 C 固存能力，其次是 RW，分别保留了 67.1%和 59.6%的 SOC。经过 5 小时的 LTA 处理后，农田（RW 和 RV）中大孔隙中 SOC 的去除量高于 AL。在进一步氧化的微孔中，AL 和 RW 仅损失了 5%的 SOC。Fe 氧化物与 C 动态的相关性大于 Al 氧化物。游离 Fe 氧化物与易氧化的有机物有关。土壤团聚体稳定性与 Al/Fe 氧化物显著相关（p<0.05）。RW 和 AL 的土壤团聚体稳定性大于 RV，这是由于它们含有相对较高的 Al/Fe 氧化物。总之，RW 向 RV 的转化降低了土壤团聚体的机械稳定性和 C 的物理固存能力，而 RW 向 AL 的转化增加了这两个特性。土地利用变化主要通过改变大团聚体的表面积、孔隙发育和 Fe 氧化物含量来影响 C 的物理固存。
