Sounds of the underground reflect soil biodiversity dynamics across a grassy woodland restoration chronosequence

Abstract

Fifty-nine percent of species on Earth inhabit the soil. However, soils are degrading at unprecedented rates, necessitating efficient, cost-effective, and minimally intrusive biodiversity monitoring methods to aid in their restoration. Ecoacoustics is emerging as a promising tool for detecting and monitoring soil biodiversity, recently proving effective in a temperate forest restoration context. However, understanding the efficacy of soil ecoacoustics in other ecosystems and bioregions is essential. Here, we applied ecoacoustics tools and indices (Acoustic Complexity Index, Bioacoustic Index, Normalised Difference Soundscape Index) to measure soil biodiversity in an Australian grassy woodland restoration chronosequence. We collected 240 soil acoustic samples from two cleared plots (continuously cleared through active management), two woodland restoration plots (revegetated 14-15 years ago), and two remnant vegetation plots over 5 days at Mount Bold, South Australia. We used a below-ground sampling device and sound attenuation chamber to record soil invertebrate communities, which were also manually counted. We show that acoustic complexity and diversity were significantly higher in revegetated and remnant plots than in cleared plots, both in-situ and in sound attenuation chambers. Acoustic complexity and diversity were also strongly positively associated with soil invertebrate abundance and richness, and each chronosequence age class supported distinct invertebrate communities. Our results provide support that soil ecoacoustics can effectively measure soil biodiversity in woodland restoration contexts. This technology holds promise in addressing the global need for effective soil biodiversity monitoring methods and protecting our most diverse ecosystems.