Spatial Variation of Soil Aggregate Stability and Its Multifactorial Driving Mechanism in Mollisol Region: Insights from Latitude, Topography and Plow Layer

This study’s research hypothesis focuses on the effects of latitude, topography, and plow layer on Mollisol aggregate stability in Northeast China: latitude, topographic factors (slope gradient/aspect/position/elevation), and soil depth (0–20 cm top plow, 20–40 cm lower plow, 40–60 cm plow pan) jointly regulate aggregate stability by affecting soil properties, nutrients, and SOC fractions; higher latitude (mid-to-cold-temperate) correlates with higher stability (MWD/GMD/SSI), topographic factors have weaker effects; key controlling factors differ by layer (POC/clay in plow layer/plow pan, MOC for SSI in all layers); soil properties (pH, BD, particle composition) and nutrients (TN/TP/TK) vary with latitude, indirectly regulating stability via SOC fractions. Data were collected from five hilly regions (JT, LS, BX, HL, NJ) covering a mid-to-cold-temperate latitudinal gradient, with 3 slopes/location and 3 sample points/slope (upper/middle/lower), sampling 3 soil layers. On-site, slope aspect/gradient/elevation were recorded; ~1 kg undisturbed/fresh samples per layer were collected, air-dried, ground, sieved for tests. Ring knife samples measured BD and field water-holding capacity. Laboratory methods: BD (ring knife), mechanical composition (pipette), pH (potentiometric), TN (semi-micro Kjeldahl), TP (molybdenum-antimony colorimetry after HClO₄-H₂SO₄ digestion), TK (flame photometry after NaOH fusion), MWD/GMD (wet sieving), SSI (aggregate composition), SOC fractionation (wet sieving: 10 g soil + 100 mL 5 g L⁻¹ sodium hexametaphosphate, shaken, sieved, fractions >250 μm (cPOC), 53–250 μm (fPOC), MOC by difference). All samples were tested in triplicate; data (site characteristics, soil indices, aggregate stability) were presented as mean ± standard deviation (P < 0.05). Significant findings: pH, BD, silt, cPOC, TK decreased with latitude; fPOC, MOC, TN, TP, macroaggregate (>2 mm), clay, MWD/GMD/SSI increased; topographic factors correlated with silt, clay, cPOC, pH. db-RDA/VPA showed latitude (53.04%) was dominant driver, topographic factors (11.05%) weaker. PLS-SEM showed fPOC dominated plow layer MWD, cPOC/clay dominated plow pan MWD; MOC controlled SSI in all layers. Data were interpreted via descriptive statistics, Pearson correlation, db-RDA/VPA/PLS-SEM, and mechanism analysis. When using data, check triplicate reliability, select indicators by objectives, and analyze factors comprehensively, supporting Mollisol structure research and soil conservation.