Comparison of metrics to reveal the role of soil fauna in soil health assessment in peat meadow restoration

Understanding the nuances of soil health is more important than ever to improve the quality and sustainability of agroecosystems. However, it is poorly understood how the variety of metrics currently in use to evaluate soil health relate to each other, and in what situations their use is not sensitive enough to indicate environmental changes. The use of faunal co-occurrence networks is a novel, potentially valuable tool that has hitherto received little attention in the context of soil health. Here, we used a meadow land-use intensity gradient to compare the response of a number of soil community metrics, including chemical and ecological indicators as well as faunal co-occurrence network parameters. Our findings indicate that the examined metrics displayed distinct, often contrasting patterns to one another, and that network analysis detected patterns that strongly aligned with the land-use effects. This pattern was qualitatively different from patterns arising from traditionally used metrics. The soils with conventional farming, that is, the least regenerative land-use, generally scored well in traditionally used metrics, including C:N ratio, faunal abundance and the ratio of Acari to Collembola. Regenerative farming was comparable with conventional farming in all conventional metrics—however, network analysis revealed that the soil faunal communities under regenerative farming had the highest species connectivity out of all research areas potentially due to grazing increasing the connectivity of faunal networks. Overall, these results suggest that network analyses are best suited to capture subtle land-use intensity differences while traditional metrics performed well in big changes. While more research is needed to better interpret soil faunal co-occurrence networks, our findings imply that it could be a useful method to provide further insight in aspects of soil health.