The Growth Strategy Of Spartina Alterniflora And The Response Of Soil Microbial Diversity To Eutrophication

Salt marshes play a key role in nutrient cycling in coastal ecosystems,acting as converters（both sinks and/or sources）of nutrients,and the increase in nutrient fluxes worldwide has put many salt marshes at risk.Eutrophication may change the fixation process of soil organic carbon pool by changing the structure of ecosystem and material circulation,such as photosynthetic capacity,growth strategy,microbial community structure and metabolic activity of salt marsh plants.In this study,a plot was set up based on the succession sequence of Spartina alterniflora in Yancheng coastal wetland of Jiangsu province.At the same time,an indoor salt marsh soil culture system was constructed.The growth strategy and carbon allocation strategy of S.alterniflora and its photosynthetic carbon were analyzed.Response of plant-soil system distribution and soil microbial diversity to eutrophication.The results show that:（1）The phenotypic plasticity of S.alterniflora under the combination of low nitrogen,low phosphorus and high nitrogen and phosphorus was high,and the addition of nutrients led to the early maturity of S.alterniflora.The change of S.alterniflora biomass carbon-soil organic carbon content has the rule that leaves,stems are larger than roots and soil.At the maturity stage of S.alterniflora seeds,the addition of nutrients led to a decrease in the biomass carbon-soil organic carbon content of S.alterniflora.The combined addition of low nitrogen,low phosphorus and high nitrogen phosphorus increases the distribution rate of leaf and stem biomass carbon and soil organic carbon,and reduces the distribution rate of underground biomass carbon.（2）With the growth of S.alterniflora,¹³C is gradually enriched in the plant-soil system.The combination of low nitrogen,medium phosphorus and high nitrogen phosphorus is beneficial to improve the ¹³C abundance of plant-soil system.In this case,S.alterniflora can fix more new carbon,and it is more conducive to the photosynthetic carbon of S.alterniflora Move to the underground.（3）Nitrogen addition and nitrogen-phosphorus compound addition are beneficial to increase the relative abundance of Proteobacteria and the genus of bacteria such as Marinobacter and Desulfurivibrio under Proteobacteria.Under low nitrogen,low phosphorus and low nitrogen and phosphorus combined addition,S.alterniflora had the largest total number of bacterial species in the soil,and had greater species diversity and uniformity.Under the combination of low nitrogen,low phosphorus and high nitrogen and phosphorus,the diversity of soil fungal community is higher,and the combined addition of nitrogen and phosphorus can increase the diversity of soil fungal genus more than nitrogen and phosphorus alone.The injection of high phosphorus reduced the diversity of fungal communities in the wetland.Salt marsh eutrophication significantly affects S.alterniflora growth strategy,above-ground/underground carbon allocation strategy,and S.alterniflora soil microbial diversity,which further affects the input,output,decomposition,and accumulation of soil organic carbon pool balance,affect the fixed potential of soil organic carbon.Mastering the growth strategy of S.alterniflora and the response mechanism of microbial diversity to eutrophication provide theoretical support for the scientific use of vegetation to regulate the function of soil carbon sink.