Differential responses of soil arthropods to the application of biogas slurry and biochar in a coastal poplar plantation

As critical drivers of ecosystem functionality, soil fauna are sensitive to soil management such as organic amendments. However, the effects of organic amendments on soil fauna communities are poorly understood. Here, we evaluated the differentiated responses of soil arthropod communities to the application of biogas slurry (BS) and biochar (BC) in a newly established poplar plantation on reclaimed coastal land. Compared with the control, the application of BS increased the abundance of soil arthropods by 113–253%, whereas the application of BC decreased it by 35–74%. Furthermore, the total taxonomic richness and Shannon index of the soil arthropods increased under the BS treatments and decreased under a high-dose BC treatment. Arthropod abundance and diversity under the BS treatments correlated with the increased biomass (46–76%) of leaf litterfall, fine roots, and undergrowth vegetation, elevated soil water and nitrogen concentrations (28–254%), as well as neutralized soil pH. In contrast, arthropod abundance and diversity under the BC treatments were correlated with decreased fine root biomass and increased soil alkalinity. These results suggested that BS and BC applications exert different effects on arthropod communities, probably linked with the differential direction and extent of the modification on plant food resource and soil variables in the newly reclaimed coastal lands. • Biogas slurry (BS) increased arthropod abundance and diversity in saline soils. • BS positively affected soil arthropods through bottom-up control of plant production. • BS was preferable amendment to promote soil fertility and arthropod development. • Biochar negatively affected arthropods due to increased pH and decreased root biomass.