Mechanism Of Biochar On The Mediation Of Plant-soil Negative Feedback Of Lycium Barbarum L.

Soil sickness caused by long-term monocropping of Lyclium barbarum L.(L.barbarum)is the main problem restricting the sustainable development of L.barbarum plantation in the arid and semi-arid areas of northwest China.The issue has severely hindered local economic development and caused a loss of income for farmers.Exploring related soil improvement measures is particularly essential for the sustainable development of L.barbarum plantation.Previous studies have shown that biochar can modify soil properties,maintain soil nutrient,microbial community function,and diversity,and has been widely used in soil improvement.However,the effect of biochar in alleviating the soil sickness of L.barbarum is still unclear.Our study detected the impacts of biochar amendments on soil abiotic and biotic properties by using meta-barcoding sequencing,CLPP,soil enzyme activity assay under both greenhouse and field conditions.The main research results of our study are as follows:1.Under the greenhouse condition,the optimal concentration of biochar applied to the soils of the L.barbarum field is 2%.At this concentration,the biochar amendment increased the fresh shoot weight of L.barbarum seedlings by approximately 25.4%-34.0%,but significantly reduced the survival rate of seedlings in some field.As compared with the control,two successive years'biochar application(15 t·hm-2)increased the stem diameter of L.barbarum samplings by 17.4%in the field condition.These results indicate that the amendment of biochar can partly promote the growth of L.barbarum in both greenhouse and field conditions.2.The biochar amendment increased the soil available phosphorus content and decreased the nitrate and ammonium nitrogen contents.Enzyme activity analysis found that biochar promoted soil urease and cellulose activities,but inhibited sucrase,acid phosphatase,and dehydrogenase activities.Short-term biochar treatment in the greenhouse promotes soil carbon mineralization in the high-organic field but induces carbon accumulation in low-organic soil.The results of community-level physiological profiling(CLPP)showed that the biochar amendment promoted the utilization rates of L-arginine,a-D-lactose,D-glucosamine acid,and L-a-glycerol phosphate,while inhibited the utilization of Tween 80 of the L.barbarum rhizosphere microorganisms.These results indicate that the short-term treatment of biochar modified the content of soil available nitrogen and phosphorus and altered the activities of soil enzymes and the patterns of soil microbial metabolism in the greenhouse condition.3.The sequencing results of 16s rDNA v4 and ITS2 regions showed that the biochar amendment inhibited the a diversity of rhizosphere bacterial community and soil fungal community under greenhouse condition.The compositions of the bacterial and fungal communities were not affected.The relative abundance of Proteobacteria was enriched by the biochar amendment in some fields,whereas Actinomycetes,Acidobacteria,Chloroflexi,and Bacteroidetes showed an opposite pattern.At the genus level,the proportions of Lysobacter,Ilumatobacter,Devosia,and Noviherbaspirillum were differently affected by the biochar amendment.The genera of Fusarium,Gibberella,Alternaria,Lophotrichus,and Botryotrichum are the dominant soil fungal populations of L.barbarum field,which relative abundance higher than 1%.Among them,the relative abundance of Fusarium is as high as 38.3%?52.4%.The application of biochar enriched plant pathogens' relative abundances,including Fusarium,Gibberella,Colletotrichum,and Botryotrichum in different soils.Combined with the result of the biochar amendment on the survival rate of L.barbarum seedlings under greenhouse condition,our results suggested that the application of biochar might promote the occurrence of soil-borne diseases and disturb plant health by interfering with the antagonistic activities of specific bacterial populations(i.e.,Bacillus,Lysobacter and Ilumatobacter)to plant pathogenic fungi.4.In the field condition,the application of biochar:increased the soil pH,while decreased the concentration of ammonium nitrogen.The activity of cellulose was stimulated,whereas the dehydrogenase activity was inhibited by biochar.These results are consistent with that of the laboratory experiments.Principle coordinate analysis(PCoA)showed that the biochar amendment altered the community structure of both soil bacteria and fungus,whereas the a diversity of the soil microbial communities did not change in L.barbarum field.Biochar stimulated the relative abundance of Proteobacteria and Ascomycota.At the genus level,the biochar amendment promoted the accumulation of Fusarium,Chrysosporium,and Rhizopus in the soil of L.barbarum field.Pearson's correlation analysis showed that the relative abundances of Fusarium and Rhizopus positively correlated with cellulose activities and negatively correlated with dehydrogenase activity.These results confirmed that the application of biochar further induced the proliferation of fungal plant pathogens(i.e.,Fusarium)in the monocropped fields,which might increase the incidence of soil-borne disease of L.barbarum.Based on these results,we purpose that biochar is not suitable for soil improvement in L.barbarum cultivation system.5.Our results indicated that the effects of biochar amendments on soil properties,enzyme activities,and some soil microbial populations are consistent.These consistencies were suggesting that the experiments performed in the greenhouse condition can partially replace the field experiments to study the mechanisms of soil sickness for perennial plant species.The replacement will shorten the research period of plant-soil negative feedback and accelerate the development of soil improvement measures for the perennial plant species cultivation system.