This study investigates the composition and metabolism of microbial communities in soil pores, focusing on how long-term differences in vegetation history affect the spatial distribution of soil pores and particulate organic matter (POM), and the hydraulic connectivity of small (4-10 μm) and large (30-150 μm) pores. The authors used single- and triple-energy X-ray computed microtomography (μCT) to characterize pore structure and stable isotope probing to identify active microorganisms. They found significant differences in microbial diversity, composition, and life strategies between large and small pores, as well as in responses to added substrate and metabolic pathways. The study also proposes a microbial habitat classification concept based on biogeochemical mechanisms and localization of soil processes, suggesting interventions to mitigate environmental consequences of agricultural management. The results highlight the importance of pore structure and POM distribution in influencing microbial communities and ecosystem processes such as decomposition, nitrogen processing, and carbon sequestration.This study investigates the composition and metabolism of microbial communities in soil pores, focusing on how long-term differences in vegetation history affect the spatial distribution of soil pores and particulate organic matter (POM), and the hydraulic connectivity of small (4-10 μm) and large (30-150 μm) pores. The authors used single- and triple-energy X-ray computed microtomography (μCT) to characterize pore structure and stable isotope probing to identify active microorganisms. They found significant differences in microbial diversity, composition, and life strategies between large and small pores, as well as in responses to added substrate and metabolic pathways. The study also proposes a microbial habitat classification concept based on biogeochemical mechanisms and localization of soil processes, suggesting interventions to mitigate environmental consequences of agricultural management. The results highlight the importance of pore structure and POM distribution in influencing microbial communities and ecosystem processes such as decomposition, nitrogen processing, and carbon sequestration.