| Under the background of the increasingly serious problem of soil salinization and the increasingly prominent contradiction between land supply and demand,the rational development and utilization of coastal saline-alkaline land resources is of great significance.In this study,the ecological restoration effect of Jerusalem artichoke on coastal saline-alkali soil was studied through long-term positioning experiment.The high purity inulin was extracted from Jerusalem artichoke by hot water extraction method,and the effect of inulin on the growth of functional bacteria in soil was studied.The interaction mechanism of rootmicroorganism-salt tolerant plants in the process of ecological improvement of saline-alkali land was discussed,which could provide guidance for the introduction and domestication of salt-tolerant plants and ecological restoration of saline-alkali land.The results are as follows:1.Compared with the original Suaeda salsa habitat soil,the salt content and p H value of the soil planted with Jerusalem artichoke decreased by 84.38% and 3.23%,respectively.The contents of organic matter,alkali hydrolyzable nitrogen and available phosphorus increased by 0.52,2.75 and 1.24 times,respectively.It indicating that the physical and chemical properties of coastal saline-alkali soil were significantly improved by planting Jerusalem artichoke in successive years.In addition to catalase,the activities of urease,sucrase and alkaline phosphatase in the rhizosphere of Jerusalem artichoke soil increased by70.91%,117.44% and 143.50%,respectively,compared with those in Suaeda salsa soil.2.Planting Jerusalem artichoke promoted the proliferation of soil microorganisms,and the quantity of soil bacteria,fungi and Actinomycetes increased by 1-2 orders of magnitude.The number of soil functional bacteria such as nitrogen-fixing bacteria,silicate bacteria and phosphate-solubilizing bacteria increased by 2 orders of magnitude,but the microbial diversity decreased.The relative abundance of Actinomarinales and Acidobacteria increased by 12.68% and 9.30% in the rhizosphere soil of Jerusalem artichoke,respectively.The relative abundance of Actinomarinales and Acidobacteria was positively correlated with the contents of available phosphorus,alkali hydrolyzable nitrogen,and the activities of urease,invertase and alkaline phosphatase.Compared with Suaeda salsa planting soil,the abundance of common functional bacteria such as Arthrobacter,Bradyrhizobium and Pseudomonas in Jerusalem artichoke planting soil was significantly increased,and Azorhizobium was the unique genus in the rhizosphere soil of Jerusalem artichoke,which indicated that planting Jerusalem artichoke in successive years could optimize the soil microbial community structure,which was of great significance The soil biological activity increased with the increase of probiotics.3.The extraction and purification process of inulin from Jerusalem artichoke was optimized by single factor test and orthogonal test,and a process of inulin extraction from dry Jerusalem artichoke slices without crushing step was determined.The optimum extraction conditions were as follows: the ratio of dry Jerusalem artichoke slices to water was1:20,the extraction temperature was 80℃,the extraction time was 60 min,the relative energy consumption was less,and the extraction rate of inulin was higher.The crude extract was purified by phosphoric acid-lime milk method and ion-exchange resin method,and then freeze-dried to obtain a kind of inulin powder with high purity and good quality.4.Four rhizosphere growth promoting bacteria were screened from the rhizosphere soil of Jerusalem artichoke,which could fix nitrogen,soluble phosphorus,release potassium and produce IAA.The four strains were identified as Serratia sp.,Enterobacter sp.,Pseudomonas sp.and Variovorax sp.The effect of inulin on the growth of 4 strains of bacteria was analyzed.It was found that inulin as a carbon source could promote the growth of 4 strains of bacteria and increase the proliferation rate of bacteria.Among them,Serratia sp.and Enterobacter sp.had the highest utilization efficiency of inulin,which indicated that inulin from Jerusalem artichoke could affect soil microorganisms and promote the proliferation of soil functional bacteria. |
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