Microbial activity increases after rewetting dry soil, resulting in a pulse of carbon mineralization and nutrient availability. The biogeochemical responses to wet-up are reasonably well understood and known to be microbially mediated. Yet, the population level dynamics, and the resulting changes in microbial community patterns, are not well understood as ecological phenomena. Here, we used sequencing of 16S rRNA genes coupled with heavy water (H218O) DNA quantitative stable isotope probing to estimate population-specific rates of growth and mortality in response to a simulated wet-up event in a California annual grassland soil. Bacterial growth and mortality responded rapidly to wet-up, within 3 h, and continued throughout the 168 h incubation, with patterns of sequential growth observed at the phylum level. Of the 37 phyla detected in the prewet community, growth was found in 18 phyla while mortality was measured in 26 phyla. Rapid growth and mortality rates were measurable within 3 h of wet-up but had contrasting characteristics; growth at 3 h was dominated by select taxa within the Proteobacteria and Firmicutes, whereas mortality was taxonomically widespread. Furthermore, across the community, mortality exhibited density-independence, consistent with the indiscriminate shock resulting from dry-down and wet-up, whereas growth was density-dependent, consistent with control by competition or predation. Total aggregated growth across the community was highly correlated with total soil CO2 production. Together, these results illustrate how previously "invisible" population responses can translate quantitatively to emergent observations of ecosystem-scale biogeochemistry.

中文翻译：

---

特定分类群的微生物生长和死亡率模式揭示了加利福尼亚草地土壤对再湿润的明显的暂时种群响应。

重新润湿干土壤后，微生物活性增加，导致碳矿化和养分利用率的脉动。对润湿的生物地球化学反应已被很好地理解并且已知是微生物介导的。然而，人们对种群水平的动态以及微生物群落模式的变化并没有很好地理解为生态现象。在这里，我们结合16S rRNA基因的测序以及重水（H218O）DNA定量稳定同位素探测，以评估响应于加利福尼亚年草原土壤中模拟的湿润事件的种群特异性生长率和死亡率。细菌的生长和死亡率在3小时内对变湿迅速做出反应，并在整个168小时的培养过程中持续不断，并在门廊水平观察到连续生长的模式。在预先湿润的社区中检测到的37个门中，有18个门中有生长，而有26个门中有死亡率。在湿润的3小时内可以测量到快速的生长和死亡率，但是具有鲜明的特征。3 h的生长主要是由变形杆菌和Firmicutes中的特定类群决定的，而死亡率在分类学上是广泛分布的。此外，在整个社区中，死亡率表现出密度独立性，这与干dry和湿透引起的不加区分的休克相一致，而生长则是密度依赖性的，与竞争或掠夺控制相一致。整个社区的总聚集生长与土壤CO2总产量高度相关。这些结果加在一起说明了以前如何“隐身”