The soil microbiome unveils strong imprints of artificial erosion after 27 years

Abstract

Soil erosion is a severe and widespread form of land degradation worldwide, and is being exacerbated by effects of climate change, such as increased storm frequency and intensity. It is important to study the impact of soil erosion on the soil microbiome because soil microbes are crucial drivers of many important soil biological processes in agriculture. In 2016 and 2017, we sampled a simulated soil erosion field trial established in 1990 to investigate the effects of different depths of topsoil removal and restorative soil amendments on soil pH, microbial biomass carbon (MBC) and the activities of enzymes that mediate C, nitrogen (N), phosphorus (P), and sulfur (S) cycling, plus the diversity and composition of soil prokaryotic (bacteria and archaea) and fungal communities. The one-time (1990) treatments consisted of a split-plot combination of three depths of topsoil removal (0, 10, and 20 cm) as main plots, and three restorative soil amendments (check, topsoil, and cattle manure) as subplots. Soil pH was higher in the eroded treatments than the noneroded treatment, but the opposite was observed for MBC and the activities of β-glucosidase (C cycling) and N-acetyl-β-glucosinidase (C and N cycling). The restorative amendments did not affect soil pH, MBC, or enzyme activities. The relative abundances of the archaea Thaumarchaeota was higher in noneroded treatments than in eroded treatments, but the reverse was observed for the bacteria Chloroflexi, Gemmatimonadetes, Planctomycetes, and Verrucomicrobia. For fungi, the relative abundance of Basidiomycota was lower in eroded treatments than in the noneroded treatment, but the opposite was true for Mortierellomycota. The β-diversity analyses also showed different prokaryotic and fungal community structures between eroded and noneroded treatments, but the restorative amendment effects were less distinct. Therefore, soil erosion and excavation can have lasting imprints on the soil microbiome, particularly negative imprints on total microbial biomass and its C and N cycling potential, while imprints of restorative measures such as manure or topsoil amendment were not as strong. A single desurfacing event has effects that last for decades, and our efforts to reverse them are largely ineffective when applied only once.