Drought and rainfall events will become more frequent and intense with climate change. At the same time, soil moisture is one of the major factors controlling soil microbial processes such as carbon cycling. When challenged with drought there are two main growth responses microorganisms can use: (1) they can maintain growth rates during drought (i.e., resistance) and (2) they can recover growth rates faster when the drought ends (i.e., resilience). Microbial communities are shaped by multiple other factors in the soil environment, however how those impact drought responses remain unclear. Here we investigate how climate (estimated as aridity index) and soil properties determine microbial growth resistance and resilience to drought across a climate gradient in Europe. To test this, we exposed the different soils to a standardised drought cycle in controlled conditions. We assessed bacterial growth, fungal growth and respiration during soil drying to determine resistance and in high resolution during three days after rewetting to estimate resilience to drought. We found that alpha diversity was the strongest driver of both bacterial drought resistance and resilience, which occurred via changes in soil pH. This shows the importance of diversity for sustaining bacterial functions during drought stress. A secondary driver of bacterial drought resistance and resilience was the aridity index was also an important driver, where bacterial communities from more arid climates had higher resistance and resilience to drought. Fungal communities were both more resistant and resilient compared to bacteria, but this was independent of other measured environmental factors. Bacterial resilience was partly linked with differences in community composition. Our results suggest that if sites are exposed to increased aridity due to climate change or are managed to promote bacterial diversity, they will have higher bacterial growth rates during drought perturbations, which could potentially promote soil carbon storage.

中文翻译：

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欧洲气候梯度中的微生物耐药性和抗旱能力


随着气候变化，干旱和降雨事件将变得更加频繁和强烈。同时，土壤水分是控制土壤微生物过程（如碳循环）的主要因素之一。当受到干旱的挑战时，微生物可以使用两种主要的生长反应：（1） 它们可以在干旱期间保持生长速率（即抵抗力）和 （2） 当干旱结束时，它们可以更快地恢复生长速率（即恢复力）。微生物群落受土壤环境中的多种其他因素影响，但这些因素如何影响干旱反应仍不清楚。在这里，我们研究了气候（估计为干旱指数）和土壤特性如何决定欧洲气候梯度中微生物生长的抵抗力和对干旱的恢复力。为了测试这一点，我们在受控条件下将不同的土壤暴露在标准化的干旱周期中。我们评估了土壤干燥过程中的细菌生长、真菌生长和呼吸作用，以确定抗性，并在再润湿后三天内以高分辨率评估了对干旱的恢复力。我们发现 alpha 多样性是细菌抗旱性和恢复力的最强驱动因素，这是通过土壤 pH 值的变化发生的。这表明多样性对于在干旱胁迫期间维持细菌功能的重要性。细菌抗旱性和恢复力的次要驱动因素是干旱指数也是一个重要驱动因素，其中来自更干旱气候的细菌群落对干旱具有更高的抵抗力和恢复力。与细菌相比，真菌群落的抵抗力和弹性都更强，但这与其他测量的环境因素无关。细菌恢复力部分与群落组成的差异有关。 我们的结果表明，如果地点因气候变化而暴露于更干旱的环境中，或者被设法促进细菌多样性，那么在干旱扰动期间，它们的细菌生长速度会更高，这可能会促进土壤碳储存。