Comparative Study On The Rhizosphere Soil Microbial Community And Soil Nutrients Of Invasion Composite Plants

The plants rhizospheric soil microbial community plays a very important role in the successful invasion of Asteraceae plants.To study whether there are general patterns in the changes of microbial communities and soil factors in the rhizosphere soils of Flaveria bidentis(L.)Kuntze.],Bidens pilisa L.and Ambrosia artemisiifolia L.over time.Our study was carried out at the homogeneous park,using PLFAs method and Biolog method and traditional method to compare the soil microbial community structure and function.The results are as follows:(1)The rhizosphere soil pH and invertase activity were significantly reduced;The activity of acid phosphatase was significantly reduced(except for the mixed treatment of B.pilosa and Melilotus suaveolens Ledeb);the nitrate nitrogen content decreased significantly(except for Flaveria bidentis(L.)and B.pilosa mixed with Melilotus suaveolens Ledeb);the available phosphorus content increased(except for Flaveria bidentis(L.)and B.pilosa mixed with Melilotus suaveolens Ledeb,and the mixed treatment of Ambrosia artemisiifolia L and Chenopodium serotinum L.).(2)In 2017,the total amount of PLFAs in the rhizosphere soil of three exotic Asteraceae plants increased significantly;the content of Gram-positive bacteria increased significantly(except the mixed treatment of B.pilosula and Setaria viridis);the content of actinomycetes increased significantly(except the mixed treatment of B.pilosula and Melilotus suaveolens Ledeb);the value of G~-/G~+was decreased significantly with increasing invasion time(except the mixed treatment of Ambrosia artemisiifolia L and Setaria viridis).With the increase of the invasion years,there are both similarity and difference in the changes of the rhizosphere fatty acid of the three exotic Asteraceae species:in 2017,15:1 iso G was not detected in the rhizosphere of three kinds of Asteraceae,in addition 15:1?6c,i 17:0 3OH and 20:1?7c were not detected in the rhizosphere of F.bidentis,and 13:1 at 12-13 was not detected in the rhizosphere of B.pilosa.In 2017,17:1 anteiso A was newly detected in the rhizosphere of F.bidentis and B.pilosa.,while in the rhizosphere of F.bidentis also newly detected 10:0 2OH,i 16:0 3OH,and i 20:0.The contents of 16:0,20:4?6,9,12,15c,18:1?9c,18:1?7c,i 15:0,and a 15:0 in the rhizosphere of the three Compositae plants are mainly affected by the three kinds of exotic plants,and increased significantly with the invasion time.(3)With the increase of the invasion years,the diversity of soil microbial community and its ability to use different types of carbon sources changed significantly.The utilization of sugars in B.pilosa and Ambrosia artemisiifolia L(except for the mixed treatment of B.pilosa and Melilotus suaveolens Ledeb)was significantly reduced;the utilization of lipids,carbohydrates and amino acids was reduced when the three kinds of exotic plants were mixed with Chenopodium serotinum L..The ability of Ambrosia artemisiifolia L to use the four types of carbon sources decreased over time when mixed with Melilotus suaveolens Ledeb.The structure and function of soil microbial communities and soil nutrient and soil enzyme activities of the three kinds of exotic plants changed with the invasion time,and these changes were significantly different due to the changes of the native plant species in the invasion domain.