Effects of land‐use systems on macroaggregate pore structure, hydraulic conductivity, and physical protection capacity

Reclamation of saline–alkali land relies on salt leaching and restoring soil fertility. However, the micro‐scale pore‐architectural changes associated with different land‐use systems remain insufficiently characterized, particularly in relation to their potential implications for water transport and fertility retention. This study selected natural land‐use systems (wasteland [WL] and degraded grassland [GL]) and artificial land‐use systems (upland field [UF] and paddy field [PF]) in Jilin, China, and scanned 5–7 mm macroaggregates for computed tomography imaging. Results showed that WL had a dense structure with low porosity (12.74%), while GL contained many elongated pores (21.74%). Porosity increased in the cultivated soils of UF (27.8%) and PF (22.48%). Network analysis indicated that UF had the highest hydraulic conductivity, whereas PF exhibited a hydraulically restrictive network. Using topological metrics, we identified critical pores within the macroaggregates. In natural systems (WL: two critical pores; GL: three critical pores), these pores resembled root systems. In contrast, the critical pores in UF (two critical pores) and PF (eight critical pores) were morphologically more uniform. Our analysis suggests that the two reclaimed agricultural systems are associated with divergent intra‐macroaggregate pore‐network configurations: UF was characterized by low‐tortuosity vertical pathways, suggesting a higher potential for rapid water transmission, whereas the more compartmentalized pore network in PF may restrict flow and increase the potential for physical protection of soil organic matter. These findings show that land‐use choice can redirect macroaggregate structural development during saline–alkali land reclamation, with implications for balancing salt leaching, hydraulic transport, and fertility retention.