Contributions of biotic and abiotic factors to soil aggregation under different intensities

Soil aggregation is a hierarchical and complex process mediated by both abiotic and biotic factors, and is crucial for preventing erosion.This study aimed to providing new insights into the role of biotic and abiotic factors on soil aggregation amid various thinning intensities and exploring mechanisms of aggregation. A survey involving four thinning treatments (T0: no thinning, T10: low-intensity thinning, T20: medium-intensity thinning, and T50: high-intensity thinning) of Pinus tabulaeformis plantation was conducted to explore mechanisms of soil aggre-gation and quantify the significance of selected biotic and abiotic factors effects on aggregation using structural equation models. Comprehensive models that included soil physicochemical properties, microbial community, root, and microarthropods were established. Compared to no-thinning, medium-intensity thinning contained about 1.8 times more mean weight diameter (MWD). The levels of total phospholipid fatty acids (totPLFAs), arbuscular mycorrhizal fungi (AMF), mycorrhizal colonization rate (F), and total microarthropods were signif-icantly higher in T20 than in other thinning treatments. The structural equation model indicated that the abiotic, biotic, and abiotic/biotic factors accounted for 35%, 82%, and 92% of the variation on MWD, respectively. MWD depended on the positive influence of F, totPLFAs, and AMF. Microorganisms were positively affected by total microarthropods and negatively affected by Diptera. Overall, the medium-intensity thinning (T20) was beneficial to the stability of soil aggregates. Also, biotic factors were more vital in determining soil aggregation than abiotic factors. Of note, soil microarthropods actd on aggregates by influencing microorganisms rather than directly affecting aggregation.