The biogeochemical signature of fire shapes the functioning of many ecosystems. Fire changes nutrient cycles not only by volatilizing plant material, but also by altering organic matter decomposition, a process regulated by soil extracellular enzyme activities (EEAs). However, our understanding of fire effects on EEAs and their feedbacks to nutrient cycles is incomplete. We conducted a meta-analysis with 301 field studies and found that fire significantly decreased EEAs by ~20%–40%. Fire decreased EEAs by reducing soil microbial biomass and organic matter substrates. Soil nitrogen-acquiring EEA declined alongside decreasing available nitrogen, likely from fire-driven volatilization of nitrogen and decreased microbial activity. Fire decreased soil phosphorus-acquiring EEA but increased available phosphorus, likely from pyro-mineralization of organic phosphorus. These findings suggest that fire suppresses soil microbes and consumes their substrates, thereby slowing microbially mediated nutrient cycles (especially phosphorus) via decreased EEAs. These changes can become increasingly important as fire frequency and severity in many ecosystems continue to shift in response to global change.

中文翻译：

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火灾降低土壤酶活性并重组微生物介导的养分循环：一项荟萃分析

火灾的生物地球化学特征塑造了许多生态系统的功能。火灾不仅通过挥发植物物质，而且通过改变有机物分解来改变养分循环，这是一个受土壤细胞外酶活性 (EEA) 调节的过程。然而，我们对火灾对 EEA 的影响及其对营养循环的反馈的理解是不完整的。我们对 301 项实地研究进行了荟萃分析，发现火灾使 EEA 显着降低了约 20%–40%。火灾通过减少土壤微生物生物量和有机质底物来减少 EEA。土壤获取氮的 EEA 随着可用氮的减少而下降，这可能是由于火灾驱动的氮挥发和微生物活动减少所致。火灾减少了土壤中获取磷的 EEA，但增加了有效磷，可能来自有机磷的热解矿化。这些发现表明火会抑制土壤微生物并消耗它们的底物，从而通过减少 EEA 来减缓微生物介导的养分循环（尤其是磷）。随着许多生态系统的火灾频率和严重程度不断变化以响应全球变化，这些变化可能变得越来越重要。