In grasslands, N mineralization and nitrification are important processes and are controlled by several factors, including the in situ microbial community composition. Nitrification involves ammonia oxidising archaea (AOA) and bacteria (AOB) and although AOA and AOB co-exist in soils, they respond differently to environmental characteristics and there is evidence of AOA/AOB niche differentiation. Here, we investigated temporal variation in N mineralization and nitrification rates, together with bacterial, archaeal and ammonia-oxidiser communities in grassland soils, on different geologies: clay, Greensand and Chalk. Across geologies, N mineralization and nitrification rates were slower in the autumn than the rest of the year. Turnover times for soil ammonium pools were <24 h, whilst several days for nitrate. In clay soils, bacterial, archaeal, AOA, and AOB communities were clearly distinct from those in Chalk and Greensand soils. Spatially and temporally, AOA were more abundant than AOB. Notably, Nitrososphaera were predominant, comprising 37.4% of archaeal communities, with the vast majority of AOA found in Chalk and Greensand soils. AOA abundance positively correlated with nitrate concentration, whereas AOB abundance correlated with ammonium and nitrite concentrations, suggesting that these N compounds may be potential drivers for AOA/AOB niche differentiation in these grassland soils.

在草原上，氮矿化和硝化是重要的过程，并受包括原位在内的几个因素控制微生物群落组成。硝化涉及氨氧化古细菌（AOA）和细菌（AOB），尽管AOA和AOB共存于土壤中，但它们对环境特征的反应不同，并且有AOA / AOB生态位分化的证据。在这里，我们调查了在不同地质条件下（包括粘土，格林沙和粉笔）的草地土壤中氮矿化和硝化速率的时间变化，以及细菌，古细菌和氨氧化剂的群落。在整个地质地区，秋季的氮矿化和硝化速率均比一年中的其余部分要慢。土壤铵池的周转时间小于24小时，而硝酸盐的周转时间为几天。在粘土土壤中，细菌，古细菌，AOA和AOB群落与白垩和格林沙土的群落明显不同。在空间和时间上 AOA比AOB丰富。值得注意的是亚硝酸盐球菌占主导地位，占古细菌群落的37.4％，绝大多数的AOA存在于粉笔和格林沙土中。AOA的丰度与硝酸盐浓度呈正相关，而AOB的丰度与铵盐和亚硝酸盐的浓度呈正相关，表明这些N化合物可能是这些草地土壤中AOA / AOB生态位分化的潜在驱动力。