Abstract Elevated atmospheric carbon dioxide concentrations (eCO2) are known to significantly impact aboveground vegetation, with cascading effects on belowground systems. However, the effects of altered biogeochemical and hydrological cycles on belowground faunal assemblages remain unclear. Oribatid mites are abundant and hyperdiverse litter decomposers, with the potential to act as bioindicators of ecosystem disturbance. Here, we assessed oribatid mite assemblages under ambient and eCO2 (ambient +150 ppm) at the Eucalyptus Free-Air CO2 Enrichment (EucFACE) facility using high-throughput sequencing of the mitochondrial cytochrome oxidase 1 (COI) gene. Our aims were to i) quantify the effect of eCO2 on mite abundance and diversity, and ii) evaluate metabarcoding as a reliable approach for the rapid assessment of oribatid mite assemblages. Three years of eCO2 exposure resulted in lower soil pH but had no significant impact on mite abundances or oribatid mite assemblage structure. Instead, mite densities were found to correlate negatively with soil NH4+, while oribatid species richness using both morphological and metabarcoding datasets were positively correlated with total soil nitrogen content. Additionally, metabarcoding showed that oribatid mite assemblage structure was correlated with total soil carbon and nitrogen content, and soil pH. However, dissimilarity matrices based on the two approaches were not correlated, indicating that metabarcoding can be used as a proxy for shifts in assemblage structure but cannot be directly compared with morphological datasets. This study demonstrates how metabarcoding can rapidly assess belowground assemblages, providing a useful monitoring tool under current and future climate scenarios.

中文翻译：

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Metabarcoding 螨虫：三年升高的 CO2 对桉树林地中的 oribatid 组合没有影响

摘要 众所周知，大气二氧化碳浓度 (eCO2) 升高会显着影响地上植被，并对地下系统产生连锁效应。然而，改变的生物地球化学和水文循环对地下动物群组合的影响仍不清楚。Oribatid 螨是丰富和高度多样化的垃圾分解者，有可能作为生态系统干扰的生物指标。在这里，我们使用线粒体细胞色素氧化酶 1 (COI) 基因的高通量测序，在桉树自由空气 CO2 富集 (EucFACE) 设施中评估了环境和 eCO2（环境 +150 ppm）下的 oribatid 螨组合。我们的目标是 i) 量化 eCO2 对螨类丰度和多样性的影响，以及 ii) 评估元条形码作为快速评估 oribatid 螨类组合的可靠方法。三年的 eCO2 暴露导致较低的土壤 pH 值，但对螨丰度或 oribatid 螨组合结构没有显着影响。相反，发现螨密度与土壤 NH4+ 呈负相关，而使用形态学和元条形码数据集的 oribatid 物种丰富度与土壤总氮含量呈正相关。此外，元条形码显示，oribatid 螨组合结构与土壤总碳和氮含量以及土壤 pH 值相关。然而，基于两种方法的差异矩阵不相关，表明元条形码可以用作组合结构变化的代理，但不能直接与形态数据集进行比较。这项研究展示了元条形码如何快速评估地下组合，