| The effect of elevated atmospheric CO2 concentration on invasions of exotic plants is one of the research hotspots of current invasive ecology.However,related researches have mainly focused on aboveground ecosystems,and relatively few researches have been done on belowground ecosystems,especially on soil organisms.Mycorrhiza is a symbiotic relationship between fungal symbiot and roots of various plants,which is a kind of widespread phenomenon of plant mutualism.More than 90% of plants can form different types of mycorrhiza with mycorrhizal fungi.Arbuscular mycorrhizal fungus(AMF)is the most widely distributed mycorrhizal fungus and has the largest number of host plants.Mycorrhizae may enhance the competitiveness of invasive plants by increasing absorption of soil nutrients and enable invasive plants to expand rapidly in new habitats.Studies on the effects of elevated atmospheric CO2 concentration on mycorrhizal fungi of invasive and native plants can contribute to invasive plant management and restoration of damaged ecosystems.In order to determine the differences in the effects of atmospheric CO2 enrichment on soil physicochemical properties and AMF infection rate for co-occurring invasive versus native plants,we grew the invasive plant Xanthium strumarium and two co-occurring native plants under ambient and doubled atmospheric CO2 concentration for consecutive years.The main results of this study are as follows:1.Elevated atmospheric CO2 concentration affected the physical and chemical properties of rhizosphere soils from the three plants.Doubled atmospheric CO2 concentration significantly reduced total potassium contents in rhizosphere soils of Xanthium strumarium and X.sibiricum,significantly increased total nitrogen content in rhizosphere soil of X.strumarium,and significantly increased total nitrogen and available nitrogen contents in rhizosphere soil of Bidens biternata.2.There were a large number of hyphae,cysts,and typical arbuscular structures in cells and between cells of the cortical tissue of the root segments of X.strumarium,and X.sibiricum.In the ambient atmospheric CO2 concentration,,the invasive plant X.strumarium can obtain high mycorrhizal infection rate in a short period of time,while two native plants B.biternata and X.sibiricum take a long time.Under the doubled CO2 concentration,all the three plant species of mycorrhizal infection are increased and the increase of X.strumarium was lower,which also indicated that it could quickly obtain higher mycorrhizal infection.3.AMF infection rates increased significantly with training time for B.biternata and X.sibiricum grown under both atmospheric CO2 concentrations.Under doubled atmospheric CO2 concentration,AMF infection rate significantly increased with training time for X.strumarium,while the change in AMF infection rate was not significant for the invader grown under ambient atmospheric CO2 concentration.4.Mycorrhizal fungi could help plant to absorb soil nutrients,especially phosphorus.Mycorrhizal infection rates increased significantly with the increase of soil p H values and organic matter contents for the three plants grown under both atmospheric CO2 concentration.Doubled atmospheric CO2 concentration increased soil carbon content for all plants,decreasing plant nitrogen uptake.Mycorrhizal infection rates are negatively correlated with soil contents of total phosphorus,available phosphorus,and available potassium for the three plants grown under doubled atmospheric CO2 concentration.Under ambient atmospheric CO2 concentration,howecer,AMF infectin rates were only correlated negatively with soil total phosphorus contents. |
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