Jensen Johannes L, Schjønning Per, Watts Christopher W, Christensen Bent T, Obour Peter B, Munkholm Lars J
Department of Agroecology, Aarhus University, Blichers Allé 20, 8830 Tjele, Denmark.
Department of Sustainable Agricultural Sciences, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, United Kingdom.
Geoderma. 2020 Apr 1;364:114181. doi: 10.1016/j.geoderma.2020.114181.
The combination of concurrent soil degradation and restoration scenarios in a long-term experiment with contrasting treatments under steady-state conditions, similar soil texture and climate make the Highfield land-use change experiment at Rothamsted Research unique. We used soil from this experiment to quantify rates of change in organic matter (OM) fractions and soil structural stability (SSS) six years after the management changed. Soil degradation included the conversion of grassland to arable and bare fallow management, while soil restoration comprised introduction of grassland in arable and bare fallow soil. Soils were tested for clay dispersibility measured on two macro-aggregate sizes (DispClay 1-2 mm and DispClay 8-16 mm) and clay-SOM disintegration (DI, the ratio between clay particles retrieved without and with SOM removal). The SSS tests were related to soil organic carbon (SOC), permanganate oxidizable C (POXC) and hot water-extractable C (HWC). The decrease in SOC after termination of grassland was greater than the increase in SOC when introducing grassland. In contrast, it was faster to restore degraded soil than to degrade grassland soil with respect to SSS at macro-aggregate scale. The effect of management changes was more pronounced for 8-16 mm than 1-2 mm aggregates indicating a larger sensitivity towards tillage-induced breakdown of binding agents in larger aggregates. At microscale, SSS depended on SOC content regardless of management. Soil management affected macroscale structural stability beyond what is revealed from measuring changes in OM fractions, underlining the need to include both bonding and binding mechanisms in the interpretation of changes in SSS induced by management.
在长期实验中，将土壤退化与恢复情景相结合，在稳态条件、相似土壤质地和气候下设置对比处理，这使得洛桑试验站的海菲尔德土地利用变化实验独具特色。我们利用该实验中的土壤，在管理措施改变六年后，对有机质（OM）组分和土壤结构稳定性（SSS）的变化速率进行了量化。土壤退化包括草地转变为耕地和裸地休耕管理，而土壤恢复则包括在耕地和裸地休耕土壤中引入草地。对土壤进行了两种大团聚体尺寸（DispClay 1 - 2毫米和DispClay 8 - 16毫米）的粘土分散性测试以及粘土-土壤有机质解体（DI，去除和未去除土壤有机质时回收的粘土颗粒之比）测试。SSS测试与土壤有机碳（SOC）、高锰酸盐可氧化碳（POXC）和热水可提取碳（HWC）相关。草地终止后SOC的减少大于引入草地时SOC的增加。相比之下，在大团聚体尺度上，就SSS而言，恢复退化土壤比退化草地土壤更快。管理变化对8 - 16毫米团聚体的影响比对1 - 2毫米团聚体更明显，表明较大团聚体对耕作引起的粘结剂破坏更敏感。在微观尺度上，无论管理措施如何，SSS都取决于SOC含量。土壤管理对宏观结构稳定性的影响超出了通过测量OM组分变化所揭示的范围，这突出了在解释管理引起的SSS变化时需要同时考虑粘结和结合机制。
