Background and aim When soil is rewetted after drought, typically a transient pulse of mineralization and other microbial processes occur. This “Birch effect” translates into a temporarily elevated soil carbon dioxide efflux (SCE) and may alter nutrient availability. While rewetting effects on SCE have been frequently studied, effects on soil nutrient supply have rarely been considered despite potential relevance for plant nutrition during post-drought recovery. Methods We investigated the magnitude of the post-drought rewetting effect on SCE, ion exchange membrane-derived soil nutrient supply rates and leaf stoichiometry in a drought experiment in the Austrian Alps. We conducted the experiment on a managed grassland (MG) and a nearby abandoned grassland (AG). Results Under drought, soil moisture depleted faster at MG than at AG. Upon rewetting, the SCE pulse was significantly larger at MG than at AG, whereas N, P and K supplies were more strongly stimulated at AG. A large, transient rewetting effect on soil K supply (MG: +363 ± 132%; AG: +821 ± 195%) was reflected in elevated K in leaves of Leontodon hispidus . Conclusions Rewetting can alter post-drought nutrient availability in mountain grasslands, with particularly pronounced effects on soil K supply.

中文翻译：

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干旱后的再润湿触发了管理和废弃山地草原的大量钾释放和叶子化学计量的变化

背景和目的 当土壤在干旱后重新润湿时，通常会发生矿化和其他微生物过程的短暂脉冲。这种“桦树效应”转化为暂时升高的土壤二氧化碳外排 (SCE)，并可能改变养分的有效性。虽然经常研究再润湿对 SCE 的影响，但很少考虑对土壤养分供应的影响，尽管在干旱后恢复期间与植物营养有潜在相关性。方法 我们在奥地利阿尔卑斯山的干旱试验中研究了干旱后再润湿对 SCE、离子交换膜衍生的土壤养分供应率和叶片化学计量的影响程度。我们在管理草地 (MG) 和附近的废弃草地 (AG) 上进行了实验。结果 在干旱条件下，MG 的土壤水分消耗速度比 AG 快。再润湿后，MG 处的 SCE 脉冲明显大于 AG，而 N、P 和 K 供应在 AG 处受到更强烈的刺激。对土壤钾供应（MG：+363 ± 132%；AG：+821 ± 195%）的大的、瞬时的再润湿效应反映在Leontodon hispidus 叶子中钾的升高。结论 再润湿可以改变山地草原干旱后养分的有效性，对土壤钾供应的影响尤其显着。