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Effects Of Simulated Root Glucose Exudates On Soil Biochemical Transformation In Pinus Tabulaeformis Forest

Posted on:2022-08-25Degree:MasterType:Thesis
Country:ChinaCandidate:R C WangFull Text:PDF
GTID:2480306515961259Subject:Soil and Water Conservation and Desertification Control
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The research on plant rhizosphere process and regulation mechanism has become the most active and sensitive research field in soil science.Root exudates,as an important medium for the energy exchange and information transmission of the root-soil-microbe interface material,how to drive the material circulation in the soil,the biological and non-biological processes of changes in the microbial community are not yet fully understood.In this study,the most abundant glucose in root exudates was selected as the experimental material,and the typical Pinus tabulaeformis ecosystem in the Loess Plateau was used as the research object,through the field simulation experiment in the PVC pipe,4levels of glucose concentration were set(CK,C1,C2,C3 were 0,0.05,0.5,2g G·kg-1 dry soil),the effects of different concentrations of glucose on soil nutrients,soil enzyme activities and their stoichiometry,soil carbon and nitrogen turnover,and soil microbial community structure characteristics of Pinus tabulaeformis were studied.The main results are as follows:(1)The effect of glucose addition on soil physical and chemical properties and carbon and nitrogen nutrient content.Glucose addition significantly changed soil total phosphorus(TP),water-soluble phosphorus(WSOP),pH,water-soluble nitrogen(WSON),ammonium nitrogen(NH4+-N),soil organic carbon(SOC),nitrate nitrogen(NO3--N),C/P,N/P content of different carbon and nitrogen components,but it has no significant effect on soil total nitrogen(TN),water-soluble carbon(WSOC),available phosphorus(SAP),C/N,etc.Specifically,with the increase of glucose addition,TP,WSOP and pH kept increasing in the range of0.42?0.5g·kg-1,143.48?189.82 g·kg-1,8.18?8.57 g·kg-1,and reached the highest under C3 treatment;WSON and NH4+-N keep decreasing in the range of 4.46?11.7 mg·kg-1 and11.65?40.74 mg·kg-1respectively;SOC,NO3--N,C/P,N/P are in the range of 6.53?7.36 g kg-1respectively,first increase and then decrease at C1 Or C2 treatment reach the maximum value;the effect on TN,WSOC,SAP,C/N is not significant.(2)Effect of Glucose Addition on the Conversion of Soil C and NGlucose addition significantly increased the release rate and amount of CO2,the21-day culture experiment results showed that different amounts of glucose added to the CO2 release rate were not linear,but fluctuating;the average release rate of CO2 increased significantly with the increase of glucose addition,and the three levels of addition increased by 7.8%,22.8%,and 114.3%respectively;the effect of glucose addition on soil net nitrogen conversion and N2O release rate has a threshold effect,the net mineralization rate of soil nitrogen under the four treatments was 0.11,0.32,0.40,and 0.07(mg C kg-1 soil d-1),the net ammoniation rates are-0.29,-0.38,-0.24,and-0.04(mg C kg-1 soil d-1).Respectively,and the net ammoniation rates are 0.32,0.70,0.53,and 0.04,respectivelyrespectively,It can be seen that the performance of the first three glucose treatments promotes the above three indicators,and the inhibitory effect under high glucose treatments,the net nitrogen conversion changes from increasing to decreasing,and the N2O release rate will also decrease.(3)Effects of Glucose Addition on Soil Enzymes and StoichiometryGlucose addition significantly affected the soil microbial biomass,with the increase of glucose addition,microbial biomass carbon(MBC),MBC/MBN,MBC/MBP have been increasing in the range of 196.37?334.54,22.42?38.18,4.41?8.81(mg·kg-1),respectively;The microbial biomass nitrogen(MBN)first increased and then decreased in the range of8.88?11.47mg·kg-1,the microbial biomass phosphorus(MBP)and MBN/MBP were in the range of 39.15?45.78mg·kg-1,and the range of 0.21?0.26 was fluctuating trend,Glucose addition significantly affects soil enzyme activities.With the increase of glucose addition,BG,NAG,LAP and AP first increase and then decrease in the range of 27.84?58.34,4.42?7.44,71.12?106.82,152.59?392.64(nmol·g-1·h-1),respectively.Addition of low-concentration carbon Promotes enzyme activity,but it inhibits enzyme activity when added at high concentrations.(4)The effect of glucose addition on the microbial communityWith the increase of glucose concentration,the soil bacterial community Chao1 index and Shannon index increased first and then decreased in the ranges of 3019-5163 and8.64-10.94,respectively,and had no significant effect on the fungal community Chao1index and Shannon index,from the PCoA analysis and the species stacking diagram,it can be seen that the bacteria classes with higher relative abundance are:?-Proteobacteria and Bacteroides,while the fungi classes with higher relative abundance are:Faecomycetes and Cystomycetes.Lefts analysis showed that the bacterial community was more sensitive to glucose drop than the fungal community.The explanation rates of the effects of soil nutrients and biological factors on bacterial communities were 30.69%and 27.18%,respectively;The explanation rate of the influence on the fungal community was 30.06%and 26.01%,respectively.The addition of glucose concentration has a significant impact on the bacterial genus of R-strategy microorganisms,but has no obvious effect on the fungal genus of K-strategic microorganisms,indicating that glucose addition has little disturbance to the overall species composition of the fungal community and has a significant impact on the overall composition of the bacterial community.In conclusion,this study shows that by adjusting the secretion of glucose in root exudates,Pinus tabulaeformis can not only reshape the composition and structure of microorganisms,but also affect the process of nutrient conversion,carbon and nitrogen conversion,enzyme activity and stoichiometric changes in the soil..
Keywords/Search Tags:Soil nutrients, Transformation of carbon and nitrogen, Enzyme activity, Microbial community, root exudates
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