Data from: Vascular plants mediate the effects of aridity and soil properties on ammonia-oxidizing bacteria and archaea

An integrated perspective of the most important factors driving the abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in natural ecosystems is lacking, especially in drylands. We evaluated how different climatic, abiotic, and nutrient-related factors determine AOA and AOB abundance in bare and vegetated microsites from grasslands throughout the Mediterranean Basin. We found a strong negative relationship between the abundance of AOA genes and soil fertility (availability of C, N, and P). Aridity and other abiotic factors (pH, sand content, and electrical conductivity) were more important than soil fertility in modulating the AOA/AOB ratio. AOB were more abundant under vegetated microsites, while AOA, highly resistant to stressful conditions, were more abundant in bare ground areas. These results suggest that AOA may carry out nitrification in less fertile microsites, while AOB predominate under more fertile conditions. Our results indicate that the influence of aridity and pH on the relative dominance of AOA and AOB genes is ultimately determined by local-scale environmental changes promoted by perennial vegetation. Thus, in spatially heterogeneous ecosystems such as drylands, there is a mutual exclusion and niche division between these microorganisms, suggesting that they may be functionally complementary.

目前学界尚缺乏针对自然生态系统中驱动氨氧化细菌（ammonia-oxidizing bacteria, AOB）与氨氧化古菌（ammonia-oxidizing archaea, AOA）丰度的关键因子的整合性认知，在旱地生态系统中这一缺口尤为显著。本研究以地中海盆地全域草原的裸地与植被覆盖微生境为研究对象，探究气候、非生物及养分相关因子对AOA与AOB丰度的调控作用。研究发现，AOA基因丰度与土壤肥力（碳、氮、磷的有效性）呈显著负相关关系。在调控AOA/AOB丰度比值方面，干旱度及其他非生物因子（pH值、砂粒含量与电导率）的影响力显著强于土壤肥力。AOB在植被覆盖微生境中丰度更高，而对胁迫环境具备较强抗性的AOA则在裸地区域占据优势。上述结果表明，AOA或可在肥力较低的微生境中介导硝化过程，而AOB则在肥力更高的环境中占据主导地位。本研究结果显示，干旱度与pH值对AOA与AOB基因相对优势度的影响，最终由多年生植被驱动的局地环境变化所决定。因此，在旱地等空间异质性较高的生态系统中，这两类微生物存在相互排斥与生态位分化现象，提示二者在功能上具备互补性。