| Due to the increasing environment fluctuation and anthropogenic disturbance, the capability of soil to maintain ecological function has attracted more concerns for the agricultural soil managements. The current studies focus on responses of soil microbial communities in response to disturbance/stress and its contribution to soil ecosystem functional stability, but few experimental work has been conducted on the effect of soil biotic interactions from the perspective of soil fauna, which occupies key positions in the structure of soil food web. Earthworms may have an indirect effect on soil ecosystem functional restoration.In this study, the laboratory and field experiment have been combined to investigate how earthworm could impact on soil functional recovery after disturbance. In a microcosm experiment, the effects of earthworms on soil ecosystem functional restoration have been investigated under a transient stress (heating to50℃for24h); Then, in the field plots which subject to metam-sodium fumigation stress, the effect of vermicompost on soil functional restoration has been studied in a natural condition. The main results are as followed.(1) The microcosm experiment indicated that soil dissolved organic carbon (DOC), microbial biomass carbon (MBC), basal respiration (BR) and metabolic quotient (qCO2) were remarkably influenced by heating stress (P<0.05). Earthworms enhanced BR and MBC significantly (P<0.05), but did not affect soil microbial biomass nitrogen (MBN). Besides, earthworms facilitated the dispersal of soil microorganisms and promoted colonization or establishment of alien microbes. As shown by many more Escherichia coli strains DH5a marked with the green fluorescent protein (GFP) were isolated from soil in the presence of earthworm. Compared with the control, combined inoculation of earthworms and microorganisms that following heat stress significantly enhanced MBC, MBN and DOC (P<0.05). Furthermore, inoculation of earthworms only or combination with microorganisms significantly decreased soil qCO2after heating stress. (2) As a popular used agricultural nematicide, metam could eliminate soil nematodes efficiently, and also decreased significantly MBC, MBN and BR (P<0.01). Application of vermicompost and PGPR microbial agent to soil could increase significantly soil available nutrient including nitrogen, phosphorus and potassium, MBC and BR (P<0.05), as well as the harvest yield and quality of spinach (P<0.05). Moreover, compared with single application of PGPR microbial agent, combined application of vermicompost and PGPR microbial agent enhanced resilience of soil ecosystem function (i.e. soil MBC, MBN, BR, the harvest yield and quality of spinach) following fumigation stress. Bacterivorous nematode was the dominant trophic group in all plots. Application of vermicompost and PGPR following fumigation stress significantly increased the total numbers of nematodes and nematode channel ratio (NCR)(P<0.05).To summarize, this study investigated effects of soil biotic interactions of microorganism with earthworm or its byproducts (i.e. vermicompost) on soil functional restoration following typical stresses such as heating and fumigation. It demonstrated that the positive effects of earthworm or vermicompost on functional recovery of soil ecosystem. Importantly, the present study integrated both field and laboratory experiment in order to comprehensively recognize the effects of earthworms and understand the inherent mechanisms. |
