Ecological Stoichiometry And Arbuscular Mycorrhizal Fungi Diversity Of Spartina Alterniflora In Duliujian River Estuary

Spartina alterniflora is a salt tolerant herb,which was introduced into China from the United States in 1979.At present,Spartina alterniflora is widely distributed in the eastern coastal provinces of China.The distribution area in China spans about 22 latitudes,and largescale Spartina alterniflora communities have been formed.As an alien species,Spartina alterniflora rapidly colonizes and spreads in some suitable areas,encroaches on the niche of indigenous species,and brings many negative effects on the local ecological environment and species diversity.Arbuscular mycorrhizal fungi(AM fungi),as an important part of plant rhizosphere soil ecosystem,play an important role in the invasion process of alien plants.At present,there are few systematic studies on the interaction between Alien Species Spartina alterniflora and AM fungi in its rhizosphere soil,especially in high latitudes.In order to explore the ecological distribution characteristics of AM fungi in rhizosphere soil of Spartina alterniflora in high latitude area,the seasonal dynamic sampling survey of Spartina alterniflora and its rhizosphere soil at different elevations(from land to sea,from high to low,A,B,C,D and E zones)in Duliujian River Estuary Wetland of Tianjin was conducted in June,August and October 2020.In order to provide data and theoretical support for the study of ecological invasion mechanism of Spartina alterniflora,the ecological stoichiometry characteristics of Spartina alterniflora and the temporal and spatial changes of AM fungi colonization in different elevation sample plots were analyzed.Combined with highthroughput sequencing technology,the diversity and temporal and spatial changes of AM fungi in rhizosphere soil of Spartina alterniflora were obtained.The main results are as follows:1 The time dynamic change rule of the growth parameters of Spartina alterniflora community was as follows: the plant height,diameter and biomass increased with time,while the density decreased gradually.In horizontal space,the density and biomass of Spartina alterniflora increased with the decrease of elevation,while the plant height and diameter decreased.2 The results showed that the C / N ratio and C / P ratio of roots and stems were significantly higher than those of leaves,and they were higher than the average of global wetland plants,indicating that the carbon fixation capacity of Spartina alterniflora was strong;N / P ratio was less than 14,which indicated that Spartina alterniflora was limited by nitrogen.Carbon,nitrogen and phosphorus are closely related among the organs of Spartina alterniflora,and they interact with each other to participate in the material circulation and energy flow in the plant.3 The temporal and spatial changes of soil factors are complex.(1)Time dynamic change rule: salinity,organic carbon,total nitrogen,alkali hydrolyzable nitrogen and available phosphorus showed a "V" rule,with time change,first decreased and then increased,that is,the content in August was lower than that in June and October.Because of the characteristics of soil phosphorus,the time change is not significant.(2)Among the vertical soil layers,except for D area and E area,the fluctuation range of soil layers is larger due to the tidal action,the organic carbon,total nitrogen,total phosphorus,alkali hydrolyzable nitrogen and available phosphorus decrease with the decrease of soil layer.(3)Except p H and salinity increased with the decrease of elevation,other soil factors were the highest in area B and decreased in two directions,which was related to the optimum height range and invasion years of Spartina alterniflora.(4)Person correlation analysis showed that soil organic carbon was significantly positively correlated with total nitrogen,total phosphorus,alkali hydrolyzable nitrogen and available phosphorus,indicating that soil nutrient content was limited by soil organic carbon content.Salinity significantly affected the contents of available phosphorus and available nitrogen in rhizosphere soil of Spartina alterniflora.4 The ecological stoichiometric characteristics of the rhizosphere soil of Spartina alterniflora were that the ratio of carbon to nitrogen was higher than the global average,and that of Spartina alterniflora area was higher than that of bare beach area,indicating that the invasion of Spartina alterniflora increased the ratio of carbon to nitrogen in the rhizosphere soil of Spartina alterniflora.The ratio of nitrogen to phosphorus is far lower than the national level,indicating that nitrogen is the limiting nutrient element in this region,which is the same as that of plants.There were no significant differences in C / N,C / P and N / P in the rhizosphere soil of Spartina alterniflora among the three soil layers,which accorded with the dynamic balance theory of ecological stoichiometry.5 TThe results showed that soil factors had significant effects on the ecological stoichiometry of Spartina alterniflora,and the main influencing factors were p H and organic carbon content,but the relationship between soil nitrogen and phosphorus content was not significant,indicating that the growth of Spartina alterniflora in this study area was not limited to the limitation of soil nutrients.6 The mycelial colonization rate and total colonization rate of AM fungi reached the maximum in August,the vesicle colonization rate decreased with time,and the arbuscular colonization rate fluctuated unsteadily;The spore density of AM reached the peak in August;Among the vertical soil layers,it gradually decreases with the deepening of soil layer;At the spatial level,B area was the highest,and with the elevation decreasing,Spartina alterniflora area was higher than the light beach area,which indicated that Spartina alterniflora invasion increased the spore density of AM fungi.7 According to person correlation analysis,soil temperature,salinity,organic carbon,total nitrogen and total phosphorus were positively correlated with AM fungal colonization,while p H was negatively correlated,indicating that there was a close correlation between AM fungal colonization in rhizosphere soil of Spartina alterniflora and soil factors.8 Using high-throughput sequencing technology,a total of 7 genera,6 families,4 orders and 1 class of AM fungi were identified in this study,which were glomus,paraglomus,acaulospora,diversispora,Scutellospora,Gigaspora and archaeospora,Glomus is the dominant genus.The results showed that salinity,organic carbon,C / N ratio,available phosphorus and alkali hydrolyzable nitrogen were correlated with AM fungal community abundance.In conclusion,due to the tidal effect of Duliujian River estuary wetland,Spartina alterniflora has its most suitable growth elevation area,and the growth parameters change with the elevation change.Spartina alterniflora invasion will change the distribution of nutrient elements in rhizosphere soil,and further affect the structure and diversity distribution of AM fungal community.The ecological stoichiometry of Spartina alterniflora and its rhizosphere soil is closely related to the diversity of AM fungi.