2.2. Preparation of soil coresAfter sampling, undisturbed subsamples were excised from thefield cores at a depth equivalent to 6e10 cm. The excised sampleswere used to prepare the different structure treatments. A third ofthe samples was left intact and was used for the “undisturbedstructure” treatment. A second third of the samples was sieved to<5 mm. This treatment was called the “sieved structure” treatment.The final third of the samples was disaggregated by shaking inwaterwith glass beads, according to the protocol proposed by Balesdentet al. [33]. This ensured the disruption of all aggregates > 50 mm. Thesoil suspension was then air-dried and sieved to <5 mm into artificialaggregates. This final treatment was named the “dispersedstructure” treatment. The soil in both disturbed treatments wascompacted with a hydraulic press to obtain the same bulk density asthat of the undisturbed treatment (1.4 g cm3). To ensure that therewas no gradient in bulk density, the soilwas packed in layers. In total,17 samples were prepared for each physical structure treatment.Nine per treatment were used for the preparation of themicrocosmsas described below, three to establish thematric potential curves andfive for X-ray micro-CT analysis.In the literature it is commonly observed that disturbing soilstructure (by grinding, sieving or through drying and wettingtreatments) induces an immediate flush of carbon mineralisation.The increased C mineralisation rate generally lasts for a few days upto a maximum of 4 weeks [13,17,34e37]. In order to exclude the Cmineralisation flush from the incubation, the treated samples werepre-incubated for two months at 20 C and 31.5 kPa
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