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• We performed a meta-analysis to synthesize the rhizosphere effect on soil gross nitrogen mineralization rate. • It was 81% on average, being significantly higher in woody (than non-woody species) and in ECM associated species (than AM associated species). • It was positively correlated with the rhizosphere effects on soil C mineralization rate, microbial biomass nitrogen, phenol oxidase activity and root biomass. • Its variations were mainly controlled by soil microbial variables and plant factors rather than climatic factors.
Rhizosphere effects play crucial roles in determining soil carbon (C) and nitrogen (N) cycling. However, the rhizosphere effect on soil gross nitrogen (N) mineralization (Nmin) has not been quantitatively assessed on the global scale. Here we performed a meta-analysis of compiled data from 24 publications and 37 species to synthesize the rhizosphere effect on soil gross Nmin and its influencing factors. We found that the rhizosphere effect significantly enhanced soil gross Nmin by 81% on average. Such rhizosphere effect was significantly higher in woody species than in non-woody species, and higher in ECM (ectomycorrhizal) associated species than in AM (arbuscular mycorrhizal) associated species. Moreover, the variations of the rhizosphere effect on soil gross Nmin were correlated with those on soil C mineralization, phenol oxidase activity and root biomass rather than with other plant (growth form and mycorrhizal association) and climatic (mean annual temperature and precipitation) factors. These results support the ‘microbial activation’ and ‘microbial N mining’ hypotheses of rhizosphere effects and indicate the coupling of soil C and gross N mineralization in the rhizosphere. Overall, these findings provide novel insights into the rhizosphere effect on soil gross Nmin among plant growth forms and mycorrhizal associations, and improve our mechanistic understanding of soil N dynamics in the rhizosphere. |
