| Biochar and rhizobacteria could potentially promote soil nutrition condition,plant growth and plant nutrient accumulation as soil amendments.The diversity of soil microbial is an essential indicator for soil fertility and ecological environment changes,which always belongs to the soil ecological research tpics.The object of our research was to determine the effects of applications of PGPR and 3 levels of biochar on Eucalyptus growth,soil microbial amount,soil physicochemical properties,soil enzyme activities,soil microbial functional diversity,soil microbial community diversity,and thus provide a reference for the optimum soil physicochemical environment reg?lation for eucalyptus growth and explore the mechanism of biochar and PGPR affect soil microbial diversity.Biochar applied in our study was made from wheat straw,and was used at three application levels(0 t/hm2,20.0 t/hm2,40 t/hm2).The following treatments were evaluated:(1)no PGPR and no biochar applied(M0B0),(2)5×1010cfu/m L PGPR(hereafter referred to as MB0),(3)20.0 t/hm2 biochar(B20),(4)5×1010 cfu/m L PGPR plus 20.0 t/hm2 biochar(MB20),(5)5×1010 cfu/m L PGPR plus 40.0 t/hm2 biochar(MB40).We used the traditional agar plate dilution method,biology eco-plate,and Illumina high-throughput sequencing methods to determine the relationship between soil microbial diversity and soil physicochemical properties and the mechanism of the reaction of soil microbial diversity to biochar and PGPR amendments via soil microbial amount,enzyme activities and microbial diversity.The main res?lts are shown as follow:(1)Soil nutrient contents and physicochemical property were influenced by biochar and PGPR applications.All of the treatments significantly decreased soil nitrate nitrogen content in relative to the control.All of the treatments significantly decreased soil TN.All of the treatments significantly influenced SWC and soil EC.(2)Applications of biochar and PGPR influenced soil microbial amount in the Eucalyptus plantation.Soil Bacteria amount dominated among the three microbial groups.Soil fungi amount diverse significantly(p < 0.01)between treatments and the control.Soil actinomyces amount was significantly and negatively correlated with soil TN,TP and TK(p < 0.001;p < 0.001;p < 0.05)while showed positively(p < 0.001;p < 0.01)relationships with soil p H and EC.(3)Soil enzyme activities were not significantly affected by all of the treatments except for soil sucrase.MB0 significantly decreased soil sucrase activity in relative to M0B0.Soil catalase activity was positively and negatively correlated with soil fungi and actinomyces amount(p < 0.05),soil urease activity was negatively and significantly correlated to soil actinomyces amount(p < 0.01).Besides,soil protease activity was positively and significantly related to soil nitrate nitrogen(p < 0.01),whereas negatively correlated to SWC(p < 0.05).Soil urease activity was positively and significantly(p < 0.01)correlated to soil TP.Soil sucrase was positively correlated to soil ammonium nitrogen(p < 0.05),p H(p < 0.05)and EC(p < 0.05).Soil catalase activity showed negatively and significantly correlated with soil nitrate nitrogen(p < 0.01),TN(p < 0.001),TP(p < 0.001),whereas positively and significantly correlated to soil p H(p < 0.05).(4)Applications of biochar and PGPR affected soil AWCD,microbial functional diversity,and carbon use efficiency.The PCA factors for microbial carbon use capacity showed that MB20 significantly increased soil microbial community metabolism capacity during our trial period.(5)Applications of biochar and PGPR affected soil bacterial community diversity,and soil nutrient contents were significantly related to soil dominant bacteria.The Pearson correlations between soil microbial diversity index and soil nutrient contents showed that OTUs,ACE and Chao index was significantly and negatively correlated to soil ammonium nitrogen,Shannon index significantly and negatively correlated to soil TN.The correlation analysis between dominant bacteria and soil physicochemical properties showed that soil TK was mainly affected soil Proteobacteria?Bacteroidetes?Cyanobacteria,soil p H mainly affected soil Chloroflexi?Planctomycetes?Verrucomicrobia,and soil nitrate nitrogen and TP was mainly affected by soil Firmicutes?Actinobacteria?Cyanobacteria.(6)Effects of applications of biochar and PGPR on Eucalyptus growth increased with the growing time and the improvement of PGPR on Eucalyptus growth was timed-released.MB0 significantly increased Eucalyptus diameter after the one-year application.Besides,MB0 significantly increases the root,stem,foliar biomass and the total biomass.(7)The RDA for soil nutrient content,soil physicochemical properties,soil microbial community diversity,Eucalyptus growth and nutrient contents of each part of Eucalyptus showed that biochar and PGPR affected nutrient contents of each part of Eucalyptus via reg?lating soil nitrate nitrogen,TP,EC and TK,and thus influencing Eucalyptus growth.Besides,biochar and PGPR affected Eucalyptus growth and biomass through reg?lating soil dominant bacteria,such as the relative abundance of Chloroflexi ? Rokubacteria ?Firmicutes?Gemmatimonadetes?Acidobacteria.Biochar and PGPR affected nutrient contents of each part of Eucalyptus via reg?lating the soil bacterial richness index and microbial evenness induces.(8)Biochar application has no signicant improvement on eucalyptus growh,but signiciantly increases soil structure and the environment for microbial growth;PGPR application could significantly increase microbial vigor and eucalyptus growth.The applications of biochar and PGPR on eucalyptus plantation should take the soil condition into consideration,and also with soil improvement,encalyptus planting sustainable development and biodiversity. |
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