Understanding the impact of agricultural land use on the soil prokaryotic communities in connected downslope sites is crucial for developing sustainable strategies to preserve ecosystem properties and mitigate agriculture’s environmental impacts. In this study, we investigated topsoil samples collected at three time points in 2022 (March, June, and November) from two adjacent catenas, reaching from hillslope to floodplain. The catenas differed in land use (extensive grassland vs. extensive cropland) at the top and middle parts, while the floodplain remained an extensive grassland due to legal restrictions. Using quantitative real-time PCRs and metabarcoding, we assessed prokaryotic abundance and prokaryotic community composition. Results show higher bacterial abundance in the cropland-influenced floodplain part across all time points compared to the grassland-influenced floodplain part. Temporal dynamics revealed a progressive decrease in the shared prokaryotic communities of the floodplain parts, peaking at the summer sampling time point, indicating a significant influence of the respective management type of the agricultural sites over the bacterial and archaeal communities of the floodplain parts. Differential abundance analyses identified several nitrifying taxa as more abundant in the cropland-influenced floodplain. Upstream land use also influenced the prokaryotic network of the cropland-floodplain, with some cropland taxa becoming keystone taxa and altering network morphology, an effect not observed in the grassland-influenced floodplain. These findings suggest that upstream agricultural land use practices have exerted a long-term influence on the floodplain prokaryotic communities over the past three decades. Moreover, there is evidence suggesting that these prokaryotic communities may undergo a potential reset during winter, which requires further investigation.

了解农业用地对相连下坡地点土壤原核生物群落的影响，对于制定可持续战略以保护生态系统特性和减轻农业对环境的影响至关重要。在这项研究中，我们调查了 2022 年三个时间点（3 月、6 月和 11 月）从两个相邻的 catenas 收集的表土样本，从山坡到洪泛区。顶部和中部的土地用途（大面积草原与大面积农田）不同，而由于法律限制，洪泛区仍然是广阔的草原。使用定量实时 PCR 和元条形码，我们评估了原核生物丰度和原核生物群落组成。结果显示，与草原影响的洪泛区部分相比，在所有时间点上，受农田影响的洪泛区部分的细菌丰度更高。时间动力学显示洪泛区部分共享的原核生物群落逐渐减少，在夏季采样时间点达到峰值，表明农业地点的相应管理类型对洪泛区部分的细菌和古细菌群落有显着影响。差异丰度分析确定，几个硝化分类群在受农田影响的洪泛区中更为丰富。上游土地利用也影响了农田-洪泛区的原核生物网络，一些农田类群成为关键类群并改变了网络形态，这种影响在受草原影响的洪泛区中没有观察到。这些发现表明，在过去三十年中，上游农业土地利用做法对洪泛区原核生物群落产生了长期影响。 此外，有证据表明，这些原核生物群落可能会在冬季经历潜在的重置，这需要进一步调查。