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Intra-aggregate pores play an important role in controlling soil processes on a micro-scale. Differences in parent materials, pedogenic processes, land use, and management practices can have a substantial effect on their characteristics. The goal of this study is to examine intra-aggregate pore characteristics using X-ray computed microtomography (μCT) images in soils of two contrasting parent materials and of contrasting land use and management. In addition, to quantify pore characteristics in aggregate exterior and interior layers we have developed an approach for aggregate boundary delineation in μCT images. Soil aggregates from a Hapludalf under Long Term Ecological Research conventional tillage treatment (LTER-CT) and native succession vegetation treatment (LTER-NS) in southwest Michigan, and from an Ustochrept under native succession vegetation and bare soil in northeast China were used. The LTER-CT aggregates had significantly greater macro- porosity (>14.6 μm in diameter) than those of LTER-NS. The LTER-NS aggregates had more large pores (>97.5 μm) and more small pores (