Effect Of Biochar On Soil Organic Carbon And Microorganism In Saline Alkali Wetland At Western Of Jilin Province

Biochar as a new green functional material,has been widely studied on soil carbon sequestration and remediation of heavy metal pollution.However,there are few studies about the effect on the physicochemical properties,soil organic carbon and microbial community structure of original soil by the biochar in the non-farmland soil ecosystem,and there are many unknown mechanisms about the interaction of the three factors under the addition of biochar.Therefore,the study takes the saline soil in west of Jilin as the research object,uses conventional methods to detect the basic physical and chemical properties,and the phospholipid fatty acid(PLFA)method was used to explore the change of soil microbial biomass and community structure,the stability isotope mixed model was used to analysis the source of soil organic carbon(SOC).In the perspective of functional groups and molecular structure to analysis the stability of SOC and dissolved organic carbon(DOC)by the use of Fourier infrared spectroscopy(FT-IR)and thermal pyrolysis-meteorological chromatography/mass spectrometry(PYGC/MS).Through the relevant analysis and multi-linear regression equation to prove the factors which affecting SOC content,and further elaborate the relationship between soil microbial with soil physicochemical properties,soil organic carbon composition structure and organic carbon chemical structure by means of the structural equation modeling(SEM)and correspondence analysis(CCA).In this experiment,three biochar levels were set up: no biochar(CK,0%),low addition treatment(LK,0.5%,1%,2% biochar was added according to the proportion of biochar with soil),high addition treatment(HK,5%,10%,20% biochar was added according to the proportion of biochar with soil).The test was carried out on the basis of free external interference and the main conclusions of the experiment are as follows:(1)The addition of biochar will increase the content of DOC and soil TP,soil bulk weight(BW),soil TN and soil water content(SWC)values were decreased,SOC and soil p H on biochar added changes almost inresponse.(2)With the increase of biochar addition,the carbon content of coarse particulate organic carbon(CPOC)in soil is increasing,and the proportion of organic carbon contained in CPOC under HK treatment could reach up to 44.24% in total organic carbon,while the carbon content and proportion of fine particulate organic carbon(FPOC)and mineral combined organic carbon(MOC)were decreased.At the same time,with the increase of experimental time also makes the proportion of organic carbon contained in CPOC increased.In addition,the structure of soil organic carbon source also have changed due to the increase of biochar addition,make the contribution of surface plants to organic carbon could reach to 67.65%.(3)The increase of biochar addition will significantly reduce the content of polysaccharide(Ps)in soil organic carbon,but has little effect on the molecular structure of dissolved organic carbon,while the change of the experimental time has significant effect on the molecular structure of soluble organic carbon,in which the proportion of fatty substances(Al)and alkane substances(Alk)increased by 34.82% and 90.01%,respectively,while the proportion of nitrogen-containing substances(Nn)decreased by 45.05%.(4)There is no significant difference between the total amount of soil microbial organisms under LK treatment and CK treatment(P>0.05),both of which are around 265 nmol/g,while the total amount of organisms under HK treatment can reach about 320 nmol/g.In addition,the structure of the microbial community changed very little under the three treatments,bacteria(Bc)dominated the community,followed by actinomycetes(Ac)and fungi(F).The increase of experimental time will significantly reduce the biomass of soil microorganisms(P<0.05),but no significant change in the structure of the microbial community.The biomass of surface vegetation under the HK treatment was 8.63% and 25.05% higher than CK and LK treatment,and there was a significant difference between the vegetation community structure in the three treatments as well,which was reflected in the change of community advantage species,under CK treatment,the advantage was digitaria sanguinalis,under LK treatment,no obvious advantage species,and HK treatment,the dominant species changed into chloris virgate.(5)The relevant analysis shows that there is a significant positive correlation between SOC and C:N,and a significant negative correlation between SOC and DOC/SOC,and the value of the propotion of MOC is the largest factor to inhibit the increase of SOC content,at the same time,the Bc and F in the microbial community are negatively correlated with SOC,but the SOC content is almost immune to the influence of organic carbon molecular structure.The structural equation model shows that soil microorganisms are mainly affected by the physical and chemical properties of soil,the organic carbon physical composition structure and molecular structure have negligible effects on microorganisms.