We identified a suite of steroid biomarkers in sediments and surface soils around Lake Ximencuo, a typical glacial lake in the Nianbaoyeze region, eastern Qinghai-Tibet Plateau (QTP). Various sterols, stanols, sterones, and sterenes appear in the sediments and surface soil samples. Among these steroids, plant-derived β-sitosterol and the 5α-stigmastanol that is derived from it exhibit high relative abundances. Notably, we found that the relative abundance of 5α-stigmastanol and the 5α-stigmastanol/n-alkanol ratio in a core of Lake Ximencuo sediment increased significantly in the last 200–300 year. These biomarker changes are broadly consistent with the growth of human settlement and the rapid development of animal husbandry in this region, which resulted in the former nomadic pastoral lifestyles gradually being transformed into permanent settlements since the early eighteenth century. The environmental and cultural changes led to greater delivery to soils around the lake of β-sitosterol that was transformed into 5α-stigmastanol by microbial communities in soil horizons, which include aerobic and anaerobic bacteria, and eventually surface runoff transport of the increased abundance of 5α-stigmastanol into Lake Ximencuo. We further postulate that the progressively greater human impacts in the Nianbaoyeze region over the past 200–300 year have modified the kinds of microbes that participate in the biogeochemical cycles of local soils.

我们在西门措湖周围的沉积物和表层土壤中鉴定了一套类固醇生物标志物，西门措湖是青藏高原东部念保叶泽地区的典型冰川湖。沉积物和表层土壤样品中出现各种甾醇、甾烷醇、甾酮和甾烯。在这些类固醇中，植物来源的 β-谷甾醇和由其衍生的 5α-豆甾醇表现出较高的相对丰度。值得注意的是，我们发现 5α-豆甾醇和 5α-豆甾醇/ n的相对丰度近200-300年西门措湖沉积物岩心烷醇比显着增加。这些生物标志物的变化与该地区人类聚居地的增长和畜牧业的快速发展大体一致，导致从18世纪初期开始，原游牧牧民生活方式逐渐转变为永久性聚居地。环境和文化的变化导致 β-谷甾醇更多地输送到湖周围的土壤中，β-谷甾醇被土壤层中的微生物群落转化为 5α-豆甾醇，其中包括好氧和厌氧细菌，最终地表径流输送增加的 5α 丰度-豆甾醇入西门措湖。