Biogeochemical gradient forms in vadose zone, yet little is known about the assembly processes of microbial communities in this zone under petroleum disturbance. This study collected vadose zone soils at three sites with 0, 5, and 30 years of petroleum contamination to unravel the vertical microbial community successions and their assembly mechanisms. The results showed that petroleum hydrocarbons exhibited higher concentrations at the long-term contaminated site, showing negative impacts on some soil properties, retarding in the surface soils and decreasing along soil depth. Cultivable fraction of heterotrophic bacteria and microbial α-diversity decreased along depth in vadose zones with short-term/no contamination history, but exhibited an opposite trend with long-term contamination history. Petroleum contamination intensified the vertical heterogeneity of microbial communities based on the contamination time. Microbial co-occurrence network revealed the lowest species co-occurrence pattern at the long-term contaminated site. The distance-decay patterns and null model analysis together suggested distinct assembly mechanisms at three sites, where dispersal limitation (42-45%) was higher and variable and homogenizing selections were lower (37-38%) in vadose zones under petroleum disturbance than those in the uncontaminated vadose zone. Our findings help to better understand the subsurface biogeochemical cycles and bioremediation of petroleum-contaminated vadose zones.

生物地球化学梯度在渗流带形成，但对石油扰动下该带中微生物群落的组装过程知之甚少。这项研究在石油污染为0、5和30年的三个地点收集了渗流带土壤，以阐明垂直微生物群落演替及其组装机​​制。结果表明，石油烃在长期受污染的地方表现出较高的浓度，对某些土壤特性产生负面影响，在表层土壤中具有阻滞作用，并随土壤深度而减少。可养分的异养细菌和微生物α-具有短期/无污染历史的渗流带沿深度的多样性降低，但与长期污染历史呈相反的趋势。基于污染时间，石油污染加剧了微生物群落的垂直异质性。微生物共生网络显示，在长期受污染的地点，物种共生模式最低。距离衰减模式和无效模型分析共同表明了三个位置的组装机制不同，在石油扰动下的渗流区中，扩散限制（42-45％）较高，变量和均质选择较低（37-38％）在无污染的渗流区。我们的发现有助于更好地了解石油污染的渗流带的地下生物地球化学循环和生物修复。