Understanding the change in function of the biological community under different soil conditions is key to effective soil quality monitoring and mitigation of soil degradation. Current measures of biological soil quality suffer from drawbacks with most techniques having high expense, low throughput or a narrow focus on one component of the community. The aim of this study was to assess the use of volatilomics as a method to profile the soil microbial community and compare the technique to phospholipid fatty acid (PLFA) profiling as a measure of biological soil quality. An agricultural grassland soil (Eutric Cambisol) was subjected to a range of stresses in replicate laboratory mesocosms. Treatments included the imposition of hypoxia/anoxia by flooding with freshwater or saltwater in the presence or absence of plant residues. The volatile organic compound (VOC) and PLFA profile of each treatment was then compared to unamended mesocosms. We hypothesized that the VOC fingerprint of soil would be highly responsive to changes in microbial metabolic status/functioning and thus provide a complementary approach to PLFAs for evaluating soil biological health. We also hypothesized that the VOC profile would have greater discriminatory power than PLFAs for determining differences between soil treatments. A headspace solid phase microextraction (HSSPME) method coupled with gas chromatography quadrupole-time of flight mass spectrometry (GC/Q-TOFMS) was used to analyse the broad spectrum of VOCs produced by each soil. Across all soil treatments 514 unique VOC peaks were detected. Overall, VOCs showed greater sensitivity than the PLFA analysis in separating soil quality treatments. Eighteen individual VOCs were identified which were primarily responsible for this separation (e.g. indole, α-ionone, isophorone, 3-octanone, p-cresol, 2-ethyl-phenol). Anaerobic soils amended with residues showed the greatest separation from other treatments, with most of this differentiation associated with ten individual VOCs. The anaerobic soils also showed a significant reduction in the number of VOCs emitted but an increase in total VOC emissions. In conclusion, our findings provide evidence that soil VOCs rapidly respond to changes in soil quality and therefore hold great potential as a novel functionally relevant diagnostic measure of biological soil quality.

了解不同土壤条件下生物群落功能的变化是有效监测土壤质量和减轻土壤退化的关键。当前的生物土壤质量衡量标准存在缺点，因为大多数技术具有高费用，低通量或仅关注社区一个组成部分的缺点。这项研究的目的是评估使用挥发性有机物作为土壤微生物群落概况的一种方法，并将该技术与磷脂脂肪酸（PLFA）谱图进行比较，以衡量生物土壤质量。在复制的实验室介观环境中，农业草原土壤（Eutric Cambisol）受到了一系列压力。处理方法包括在存在或不存在植物残渣的情况下，通过用淡水或盐水淹没来施加缺氧/缺氧。然后将每种处理的挥发性有机化合物（VOC）和PLFA曲线与未经修改的介观膜进行比较。我们假设土壤的VOC指纹对微生物代谢状态/功能的变化具有高度的响应性，因此为PLFA提供了一种补充方法来评估土壤生物健康。我们还假设，在确定土壤处理之间的差异时，VOC谱比PLFA具有更大的判别力。顶空固相微萃取（HSSPME）方法与气相色谱四极杆飞行时间质谱（GC / Q-TOFMS）结合用于分析每种土壤产生的VOC的广谱。在所有土壤处理中，检测到514个独特的VOC峰。总体而言，挥发性有机化合物在分离土壤质量处理方面显示出比PLFA分析更高的敏感性。对甲酚，2-乙基苯酚）。用残留物改良的厌氧土壤与其他处理方法的分离程度最大，其中大多数差异与十种单独的挥发性有机化合物有关。厌氧土壤中的挥发性有机化合物排放量也显着减少，但总挥发性有机化合物排放量却有所增加。总之，我们的发现提供了证据，表明土壤VOC对土壤质量的变化迅速做出反应，因此具有作为生物土壤质量的新功能相关诊断手段的巨大潜力。