Recent studies have shown that invasive earthworms can dramatically reduce native biodiversity, both above and below the ground. However, we still lack a synthetic understanding of the underlying mechanisms behind these changes, such as whether earthworm effects on soil chemical properties drive such relationships. Here, we investigated the effects of invasive earthworms on soil chemical properties (pH, water content, and the stocks and fluxes of carbon, nitrogen, and phosphorus) by conducting a meta-analysis. Invasive earthworms generally increased soil pH, indicating that the removal of organic layers and the upward transport of more base-rich mineral soil caused a shift in soil pH. Moreover, earthworms significantly decreased soil water content, suggesting that the burrowing activities of earthworms may have increased water infiltration of and/or increased evapotranspiration from soil. Notably, invasive earthworms had opposing effects on organic and mineral soil for carbon and nitrogen stocks, with decreases in organic, and increases in mineral soil. Nitrogen fluxes were higher in mineral soil, whereas fluxes in organic soil were not significantly affected by the presence of invasive earthworms, indicating that earthworms mobilize and redistribute nutrients among soil layers and increase overall nitrogen loss from the soil. Invasive earthworm effects on element stocks increased with ecological group richness only in organic soil. Earthworms further decreased ammonium stocks with negligible effects on nitrate stocks in organic soil, whereas they increased nitrate stocks but not ammonium stocks in mineral soil. Notably, all of these results were consistent across forest and grassland ecosystems underlining the generality of our findings. However, we found some significant differences between studies that were conducted in the field (observational and experimental settings) and in the lab, such as that the effects on soil pH decreased from field to lab settings, calling for a careful interpretation of lab findings. Our meta-analysis provides strong empirical evidence that earthworm invasion may lead to substantial changes in soil chemical properties and element cycling in soil. Furthermore, our results can help explain the dramatic effects of invasive earthworms on native biodiversity, for example, shifts towards the dominance of grass species over herbaceous ones, as shown by recent meta-analyses.

中文翻译：

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土壤化学颠倒：蚯蚓入侵对土壤化学性质影响的荟萃分析

最近的研究表明，侵入性蚯蚓可以大大减少地上和地下的本地生物多样性。然而，我们仍然缺乏对这些变化背后的潜在机制的综合理解，例如蚯蚓对土壤化学性质的影响是否会推动这种关系。在这里，我们通过荟萃分析研究了侵入性蚯蚓对土壤化学性质（pH 值、含水量以及碳、氮和磷的储量和通量）的影响。入侵的蚯蚓通常会增加土壤 pH 值，这表明有机层的去除和更多富含碱的矿质土壤的向上迁移导致土壤 pH 值的变化。此外，蚯蚓显着降低了土壤含水量，这表明蚯蚓的挖洞活动可能增加了土壤的水分渗透和/或增加了土壤的蒸散量。值得注意的是，侵入性蚯蚓对有机和矿质土壤的碳和氮储量具有相反的影响，有机质减少，矿质土壤增加。矿质土壤中的氮通量较高，而有机土壤中的通量不受侵入性蚯蚓的存在的显着影响，表明蚯蚓在土壤层之间动员和重新分配养分并增加土壤中的整体氮损失。仅在有机土壤中，蚯蚓对元素库的影响随着生态群丰富度的增加而增加。蚯蚓进一步减少了铵盐储量，对有机土壤中硝酸盐储量的影响可以忽略不计，而它们增加了矿质土壤中的硝酸盐库存但不增加铵库存。值得注意的是，所有这些结果在森林和草原生态系统中都是一致的，强调了我们发现的普遍性。然而，我们发现在现场（观察和实验设置）和实验室中进行的研究之间存在一些显着差异，例如对土壤 pH 值的影响从现场到实验室设置都有所降低，需要仔细解释实验室发现。我们的荟萃分析提供了强有力的经验证据，表明蚯蚓入侵可能导致土壤化学性质和土壤元素循环发生重大变化。此外，我们的结果可以帮助解释入侵蚯蚓对本地生物多样性的巨大影响，例如，草类物种在草本物种上的主导地位转变，