Soil-resistant organic carbon improves soil erosion resistance under agroforestry in the Yellow River Flood Plain, of China

Soil organic carbon (SOC) pool within different agroforestry systems is less documented. This study therefore investigated the relationships between soil parameters, concentrations of SOC pools, and soil erodibility under four agroforestry systems (Chinese ash ( Fraxinus chinensis Roxb ) forestland (CK), Chinese ash forestland and soybean ( Glycine max (Linn.) Merr. ) farmland (AS), Chinese ash forestland and peanut ( Arachis hypogaea Linn. ) farmland (AP), and Chinese ash forestland and chrysanthemum ( Arachis hypogaea Linn. ) farmland (AC)) in Yellow River Flood Plain in China. Among the compared agroforestry systems, AS had the highest easily oxidizable carbon (1.69 g kg −1 ), particulate organic carbon (1.60 g kg −1 ), dissolved organic carbon (30.23 g kg −1 ) and microbial biomass carbon (17.71 g kg −1 ), AC had the lowest (1.09 g kg −1 , 0.82 g kg −1 , 22.29 g kg −1 , and 12.34 g kg −1 , respectively). The non-easily oxidizable carbon (NOC) and mineral-associated organic carbon of AS (respectively, 5.71 g kg −1 and 5.96 g kg −1 ) were the greatest, whereas both were far lower under AC (respectively, 2.40 g kg −1 and 2.48 g kg −1 ). The ranking for soil carbon fractions concentrations was AS > CK > AP > AC. Structural equation modeling analysis revealed that soil capillary porosity and the active SOC pool (C a ) had positive effects on soil erodibility factor (K) (standardized coefficient = 0.27 and 0.33, respectively), while pH, the ratio of carbon to nitrogen (C/N), and the resistant SOC pool (C r ) each negatively affected K (standardized coefficient = − 0.46, − 0.33 and − 0.59, respectively). Further, the redundancy analysis results supported a decisive role for soil parameters and carbon fractions in determining soil erodibility. The result of this study implies that agroforestry can strengthen soil erodibility resistance. Altogether, these findings suggest the effects of the resistant SOC pool warrants explicit consideration when studying the dynamics of soil erosion resistance.