Impacts of earthworms and their excreta on peat soil properties and bacterial community

Abstract

Peatlands store 20–30 % of the global soil carbon (C). Earthworms simultaneously increase net C stabilization and net C mineralization. But little is known about the impact of earthworm invasion on the C cycling in peat soils. Earthworm excreta, such as casts and mucus, have been shown to affect soil chemistry and microbes, the former representing gut process and the latter are secretions from earthworms as they dig burrows. Therefore, this study evaluates the separate effects of the presence of earthworms, casts, and mucus on the soil chemistry, soil microbial community, and the enzymes of peat soil. The results indicated that earthworms and their casts had significantly negative effects on peat soil dissolved organic C, microbial biomass C, pH and polyphenol oxidase, and had positive effects on phenolic matters, hydrolase activity, bacterial diversity, and metabolic functions. The effects of mucus on polyphenol oxidase, phenolic matters and bacterial evenness were similar to those of earthworms, but the effects on other soil properties were different. Earthworms and their excreta selectively promote or inhibit the survival of some soil bacteria, e.g., the relative abundance of Bacteroidetes was increased and Acidobacteria and Rokubacteria was reduced after earthworm entering. This research provides evidence that earthworms change soil properties primarily through gut processes (casts), indicates the negative effect of earthworms on peat soil C, and call for the monitoring of soil fauna in degraded peatland to protecting C stocks in peatlands.

Keywords

• Peatlands
• Soil organic carbon
• Soil enzyme activity
• Soil fauna
• Bacterial diversity