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.

目前学界尚未形成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）丰度的核心影响因素的整合性认知，在干旱区这一研究缺口尤为突出。本研究以地中海盆地全域草原的裸露与植被覆盖微生境为研究对象，评估了不同气候、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；干旱度及pH值、砂粒含量、电导率等其他非生物因子，对AOA/AOB丰度比值的调控强度显著高于土壤肥力。氨氧化细菌在植被覆盖微生境中丰度更高，而对胁迫环境具有高耐受性的氨氧化古菌则在裸露地表区域更为富集。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则在肥力更高的生境中占据主导地位。进一步分析显示，干旱度与pH值对AOA、AOB基因相对优势度的影响，最终由多年生植被驱动的局域尺度环境变化所决定。因此，在干旱区这类空间异质性较强的生态系统中，这两类微生物存在相互排斥与生态位分化现象，提示二者可能具备功能互补性。