Study On The Adaptability Of Deyeuxia Angustifolia Kom. Encroachment And Its Effect On Soil Microorganisms In The Subalpine Tundra Of Changbai Mountain

Under the influence of global change and human activities,the ecosystem of Changbai Mountain has undergone great changes,one of which is the encroachment of Deyeuxia angustifolia(Komarov)Y.L.Chang(D.angustifolia)from low altitude to high altitude tundra.Researchers have found that D.angustifolia encroachment could lead to the decline in native plant diversity,and could change the plant community structure significantly in the tundra.Factors contributed to the expansion of D.angustifolia into the tundra have also been identified.However,how D.angustifolia quickly adapted to the harsh environment of the tundra in a short time and the impact of its upward expansion on the tundra ecosystem has not yet been fully explored.Therefore,based on the biological characteristics of encroachment plants,this paper mainly studied the molecular basis and nutrient characteristics of the encroachment of D.angustifolia to tundra,explored the rapid adaptation mechanism of D.angustifolia.The impact of D.angustifolia encroachment on tundra ecological functions was also investigated by studying the effects of D.angustifolia encroachment on soil microbial communities.The main contents are as follows:1.Using AFLP and MSAP molecular marker technology,genetic and epigenetic analysis of 17 natural D.angustifolia populations in the tundra on the western slope of Changbai Mountain were carried out.Environmental factors were measured and statistically analyzed at the same time.AFLP results showed that the Shannon information index(I)and the percentage of polymorphic loci(PPL)of D.angustifolia were 0.035 and 6.79%,respectively,which indicated that the genetic diversity of D.angustifolia was relatively low in the population level.Significant genetic variation among populations(Phi PT=0.946,P<0.001)was manifested by AMOVA.MSAP results showed that the Shannon information index(I)and the percentage of polymorphic loci(PPL)of D.angustifolia were 0.038 and 9.21%,respectively,which indicated that the epigenetic diversity of D.angustifolia was relatively low in the population level.Significant epigenetic variation among populations(Phi PT=0.866.946,P<0.001)was shown by AMOVA.In addition,the DNA methylation level of D.angustifolia was relatively high(28.35%).Pearson correlation results showed that the genetic diversity of D.angustifolia were significantly positively correlated with soil total nitrogen(TN),nitrate nitrogen(NO₃^--N)and moisture,and significantly negatively correlated with soil carbon-nitrogen ratio(C/N),total potassium(TK)and p H(P<0.05).Only soil p H and soil temperature were significantly negatively correlated with epigenetic diversity of D.angustifolia(P<0.05).Under the condition of relatively low genetic diversity and genetic variation,D.angustifolia may expand its ecological niche through epigenetic regulation,which may be one molecular basis for its rapid expansion and its adaptation to the tundra environment.The soil environment,especially sufficient nitrogen,high soil moisture and relatively low soil p H may provide a suitable environment basis for the colonization and expansion of D.angustifolia in the tundra.2.To explore the dynamic characteristics of leaf eco-stoichiometry and its driving factors during the encroachment of D.angustifolia,the contents of carbon,nitrogen and phosphorus of D.angustifolia leaves and soil physicochemical properties in different levels of encroachment at three elevations in the tundra on the western slope of Changbai Mountain were detected.C:N:P stoichiometry of D.angustifolia varied significantly with the increase of elevation and encroachment level,but the variation pattern was not consistent,showing significant heterogeneity of elevation and encroachment level,and indicating the adaptation of D.angustifolia to the complex and changeable tundra environment.Mantel test and RDA results showed that the differences in leaf nutrient content and stoichiometry of D.angustifolia were mainly determined by soil total nitrogen(TN),available phosphorus(AP),ammonium nitrogen(NH₄⁺-N),and moisture.The average LN:LP was 16.82 and was greater than 16 in most samples,indicating that the growth of D.angustifolia in the alpine tundra of Changbai Mountain was mainly limited by phosphorus.3.Using the third generation full-length 16S r RNA and ITS high-throughput sequencing technology(Pac Bio Sequel),we investigated the composition of soil bacterial and fungal communities at different encroachment levels of D.angustifolia in native shrubs and herbaceous communities at three elevations in the tundra on the western slope of Changbai Mountain,and predicted the biological functions of microorganisms.Physicochemical properties and enzymatic activities of different soil samples were also compared.Soil analysis showed that D.angustifolia encroachment significantly affected the soil properties of the herbaceous communities(P<0.001)but not the shrubs communities(P=0.404).Further analysis found that all indicators of soil properties,except for AP and catalase,were significantly affected by D.angustifolia encroachment(P<0.05).However,changes of most indicators differed across vegetation types and encroachment levels.D.angustifolia encroachment did not induce significant changes in the?-diversity(number of observed OTUs,Shannon,Chao1,Faith's PD)of soil microbial communities in shrubs and herbaceous soils(P>0.05),and these impacts differed across elevations and plant types.D.angustifolia encroachment significantly affected soil microbial community composition(PERMANOVA:P<0.05),but this effect depended on D.angustifolia encroachment levels.LEf Se results showed that 40 bacterial indicator taxa and 57 fungal indicator taxa shifted significantly in response to plant encroachment,some of which were involved in soil biogeochemical cycle.Microbial biological function prediction results showed that the encroachment of D.angustifolia led to changes in the relative abundance of some microbial functional genes involved in carbon and nitrogen cycling,and the changes in microbial community structure led to the variation in microbial functional potential.Mantel test,RDA/CCA,and Spearman correlation analysis showed that soil properties were significantly correlated with changes in soil microbial(bacterial and fungal)communities,and soil TOC,TN,C/N,moisture,sucrase,and ALP were the main driving factors of soil microbial community variation.In conclusion,this study analyzed the species characteristics for the rapid adaptation of D.angustifolia to the complex and changeable environment in the subalpine tundra of Changbai Mountain,and explored the distribution patterns and driving factors of soil microbial communities under the impact of D.angustifolia encroachment along an elevation gradient in the subalpine tundra of Changbai Mountain.The results of the study preliminarily determined the adaptability of D.angustifolia itself,as well as the response of soil microorganisms,a key biological factor of the tundra ecosystem,to the encroachment of D.angustifolia.The results will be providing a scientific basis for biodiversity conservation and ecological security strategy formulation in the Changbai Mountain.In addition,the research results have extremely important reference value for a deep understanding of the internal mechanism and ecological effect of species encroachment.