Shifts in Dissolved Organic Matter and Microbial Communities Under Continuous Cropping of Aralia continentalis Kitag.: A Comparative Study of 2-, 6-, and 12-Year Durations

Continuous cropping affects soil health, microbial diversity, and organic matter dynamics, but its long-term impacts on soils under <i>Aralia continentalis</i> Kitag. (a medicinally important Northeast China-native plant) remain unclear. This study evaluated effects of 2-, 6-, and 12-year continuous cropping on soil microbial communities, physicochemical properties, and dissolved organic matter (DOM) of bulk soils, and elucidated links between cropping duration and soil health indicators. Results showed that key physicochemical properties (total organic carbon, TOC) and available nutrients (available nitrogen, AN; available phosphorus, AP; available potassium, AK) declined with cropping duration: AN, AP, and AK decreased from 75.24 ± 1.2, 16.39 ± 0.05, and 104.8 ± 0.27 mg·kg^-1 (2 years) to 63.47 ± 1.53, 13.38 ± 0.16, and 88.71 ± 0.94 mg·kg^-1 (12 years), respectively. Microbial diversity increased initially but stabilized after 6 years, with communities shifting from copiotrophic taxa (e.g., Proteobacteria) to oligotrophic taxa (e.g., Acidobacteria). Partial Least Squares Path Modeling (PLS-PM) revealed strong positive correlations between dissolved/organic carbon (DOC/TOC) and microbial diversity, highlighting organic matter's role in sustaining microbial richness. UV-visible and 3D fluorescence spectroscopy indices correlated significantly with microbial diversity, confirming their utility for monitoring DOM quality and microbial dynamics. This study clarifies dynamic interactions between soil properties, microbial diversity, and organic matter under continuous cropping, providing insights for sustainable cultivation of <i>A. continentalis</i>.