Effect Of Flaveria Bidentis Invasion On Plant Community And Soil Biological Community Of Invaded Soil

Invasive plants poses a serious threat to the biodiversity of the invasion site due to their strong reproductive and competitive abilities in most cases.At present,the invasive plant Flaveria bidentis has invaded a large regions of north China,which has caused serious effect to the ecological environment,and caused a large loss to agricultural production and economic development in China.It is of great theoretical value to explore the effect of F.bidentis on the plant community and soil biological community of the invaded region through the research of the rules,mechanism and scientific prevention and control countermeasures of the invasion by F.bidentis,In this paper,the field investigation and the homogenous garden experiment were used to study the effect of F.bidentis invaded on the plant community and soil biocenosis characteristics.The main findings were as follows:1.The difference of plant community diversity,soil physical and chemical factors as well as soil microbial community structure between F.bidentis-invaded soil and non-invaded soil of JH,CZ,HS and AY(Jinhai in Tianjin,Cangzhou in Hebei,Hengshui in Hebei and Anyang in Henan,respectively)has been analysed.The results showed that the plant community diversity index of F.bidentis-invaded soil(JH,CZ and HS)was significantly decreased and the physical and chemical properties of four F.bidentis-invaded soil have been changed.The fungi PLFA,total PLFA,fungi/bacteria and gram-negative bacteria/gram-positive bacteria in different F.bidentis-invaded soil were significantly increased due to the plant invasion,while the Margalef richness index of soil microorganisms was significantly reduced,and there were regional differences.The results of RDA and correlation analysis showed that the contents of nitrate nitrogen and total nitrogen had greater influence on plant community than other physical and chemical properties,while the content of ammonium nitrogen had larger impact on soil microbial community structure.Except for the Margalef index,there was a significant negative correlation between the plant community diversity index and the diversity index of soil microbial community.2.A common garden experiment was conducted to monitor the dynamic growth of plant communities in invaded and non-invaded soils,and further determined the growth and physiological variables of four indigenous plants—Setaria viridis,Bidens maximowicziana,Chenopodium glaucum,and Kochia scoparia.The results showed that the plant community diversity index of F.bidentis-invaded soil was less than that of non-invaded soil,but this difference gradually decreased with time.Flaveria bidentis had significant effect on the growth index of native plants,but this effect was species-specific.The net photosynthetic rate,stomatal conductance,and transpiration rate of the four native species grown in native soil were significantly higher than those of plants grown in the invaded soil,signifying the suppression effect of F.bidentis on native vegetation.However,the specific leaf area(SLA),specific root length(SRL),and specific root area(SRA)of the four native species grown in invaded soil were significantly higher than those of plants grown in native soil,indicating species-specific tolerant strategies to competition from the invader.3.The difference of soil nematode community structure between F.bidentis-invaded soil and non-invaded soil has been analysed.The results showed that the community structure of soil nematode was changed by the invasion of F.bidentis,the abundance of soil nematode was reduced significantly,and the species of soil nematode has increased.The Fungivores nematodes(Fu)was increased significantly,while the plant parasitic nematodes(Pp)were lower than that in non-invaded soil significantly.The evenness index(J)and maturity index(PPI)of the invasive soil nematodes were decreased and the wasilewska index(WI)was increased,the plant parasitic nematode maturity index(PPI)and wasilewska index(WI)were significantly correlated with soil microbial community.Comprehensive analysis showed that Flaveria bidentis invasion changed the soil microbial community structure and soil nematode community structure,the nutrients of the F.bidentis-invaded soil were changed gradually,and inhibited the growth of the native plants growthed in F.bidentis-invaded soil,and the diversity of plant communities in F.bidentisinvaded soil was reduced,but the response of different species to the invasion of F.bidentis showed interspecific difference.and there were regional differences.It provides a theoretical basis for understanding the impact of invasive species on community structure and soil ecosystem and for the restoration of invasive habitats.The results of this paper provides a theoretical basis to understand the influence of invasive species on the native community structure and soil biological community with time and master the rules of invasion,carry out effective prevention and control,to restore invaded habitats as well.