No evidence that conifer biochar impacts soil functioning by serving as microbial refugia in boreal soils

It is well established that application of biochar to soils can promote soil fertility, which ultimately may enhance plant growth. While many mechanisms have been proposed explain this, one specific mechanism, the “microbial refugia hypothesis,” suggests provide physical protection for microbe from microfauna otherwise exert top-down control on microbial biomass and activity. We tested hypothesis by incubating two boreal with without derived a wood mixture tree species (Picea abies Pinus sylvestris), nematodes. measured phospholipid fatty acids (PLFA) as relative measure biomass, several variables indicative activity, including extractable nutrient concentrations (NH4+, NO3−, PO4−), heterotrophic N2-fixation, respiration. Contrary our expectations, we found itself did not stimulate or Furthermore, nematode addition stimulated rather than depressed bacterial PLFA groups. Finally, interactive effects between treatment never worked in way supported hypothesis. Our findings suggest typical applied same stimulatory effect activity has shown some other ecosystems, enhanced growth response sometimes observed environments likely due mechanisms, such direct supply amelioration pH.