| The previous focus of plant invasion ecology mostly focused on the macroscopic organism level,but more and more studies have shown that the interaction between invasive plants and soil microorganisms has a profound influence on the adaptability and competitiveness of invasive plants and plays an important role in their further invasion.As the breakthrough point,this thesis with bamboo invasion of broad-leaved forest soil nitrogen transformation rate determined by indoor culture method,and combined with T-RFLP and quantitative PCR method to research the bamboo in the process of its invasion of broad-leaved forest soil bacteria,fungi community structure change,and then using quantitative PCR to bacteria,fungi and nitrogen mineralization related functional genes are analyzed in abundance,in order to explore the bacteria,fungi community and its role in the process of functional groups in the bamboo plant invasion.In addition,we compared the relative contribution of soil bacterial and fungal on nitrogen transformation by determining the nitrogen transformation rates after adding inhibitors.Finally,this paper aims to explore the seasonal characteristics of the effect of bamboo invasion on soil net nitrogen transformation and tries to elucidate the microbial mechanism.The result showed that:1.Soil net nitrogen mineralization rates significantly increased after bamboo invasion in Wuyi Mountain,and the soil inorganic nitrogen in the bamboo forest was more abundant than that of broad-leaved forest.Under the condition of laboratory incubation,the net nitrification of bamboo forest was stronger in the short term(7 days),but the soil net nitrification ability of evergreen broad-leaved forest was stronger under relative long-term(28 days)cultivation conditions.There was a seasonal difference in the effect of bamboo invasion on evergreen broad-leaved forest on the mineralization of soil nitrogen.The net nitrogen mineralization rate was the highest in summer in bamboo forest and was the lowest in spring in evergreen broad-leaved forest.There were significant differences in organic matter content,carbon nitrogen ratio and inorganic nitrogen content in soil in different seasons,which was closely related to the change of microbial species and abundance.2.Compared to fungal community,bacterial community was more sensitive to bamboo invasion,and this became obvious in the spring soil.3.There was a significant decrease in mineralization gene(apr)abundance of soil bacteria caused by bamboo invasion,while the abundance of ammonia-oxidizing bacteria gene(AOB)and lignin degradation genes(lcc)increased significantly(P<0.05).F: B,AOB gene abundance were both significantly positively corelated with soil nitrification rates,lcc gene abundance was significantly positively corelative with soil organic matter content and net nitrogen mineralization rates,indicates that fungal,especially the lcc gene plays an important role in the form of ammonium nitrogen.Combined environmental parameters with functional genes,we found that the significant rise of soil celulose degradation gene cbh I and lignin degradation gene lcc had positive effects on soil nitrogen mineralization and nitrification in spring soil,while the influence of environmental parameters on gene abundance variation was not significant in autumn soil.4.Both bacterial and fungal play important roles in the transformation of soil net nitrogen.After adding different inhibitors on three types of forest caused by bamboo invasion,we found soil fungal had more contribution on net nitrogen mineralization than bacteria under the evergreen broad-leaved forest,while the opposite result appears in the bamboo forest soil.5.The autotrophic nitrification is the main form of nitrification in the soil under the three typical vegetation types caused by bamboo invasion on evergreen broad-leaved forest.With the decrease of soil acidity after invasion,the contribution of soil fungal on soil nitrification is also increased,while the specific reasons need to be further studied and confirmed. |
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