Community Characteristics Of Ageratina Adenophora In Liangshan Prefecture Of Sichuan Province And Its Adaptability To Soil

Ageratina adenophora is a perennial poisonous weed of the genus Eupatorium in the daisy family,Compositae.This invasive species invaded into China through the Sino-Burmese border in 1940s.A.adenophora grows profusely in Yunnan,Guizhou,Sichuan,Guangxi,and Tibet,causing a huge ecological disaster,and immeasurable economic losses to agriculture,forestry,animal husbandry and fishery.Thereby A.adenophora is regarded as the most harmful invasive species in China,and urgently needs to be prevented from spreading and effectively controlled.A.adenophora interacted with the soil to achieve the successful invasion.Liangshan Prefecture is severely invaded with more than 14.1%covered by A.adenophora,the prefecture possesses multiple soil types,with various physiochemical and biological properties.With regards to this,in this paper the author selected more than 50 typical and representative A.adenophora communities in 5-7 counties(cities)of Liangshan Prefecture,Sichuan Province,to explore the relationship of community characteristics with native plant species,spatial and temporal distribution of plant nutrients,dynamic variation of nutrients absorption,soil chemical and biological properties,and the effects of soil heavy metals on the absorption and growth of A.adenophora,which enriched our understanding of the invasion mechanism of A.adenophora from the perspectives of plant nutrition,soil science,and ecotoxicology,and provided scientific data for converting A.adenophora into an organic fertilizer resources.The main findings are as follows:1)A total of 155 plants were observed in the sampling plots of A.adenophora communities.The?~2 test showed that the main species in A.adenophora communities were not significantly negatively related.The main dominant species had similar adaptability to the environment,and competitons were found in utilizing the surviving resources;PC and OI values demonstrated that A.adenophora has close correlations with Bidens pilosa,Artemisia sylvestris,Digitaria sanguinalis,and Clinopodium polycephalum,that is,they probably appeared simultaneously;the community stability analysis indicates that the invasion of A.adenophora lowered the stability of previous plant communities.2)The nitrogen,phosphorus,and potassium contents of A.adenophora plants varied with habitats,ranging in 0.46%~1.51%,0.07%~0.55%,and 0.74%~1.77%,respectively,which were significantly greater than the neighboring plants,and their variation coefficients were significantly lower than the soil.This indicated that A.adenophora has a strong competitiveness in nutrients uptake,and can adapt to both fertile and barren soil environments.With these specialities A.adenophora established its own ecological advantages,supplanted native plant species,and finally established the single superior community.A.adenophora absorbed nutrients the fastest in spring and accumulated the most in summer,leaves>stems>roots.The average concentrations of nitrogen and phosphorus were greater than that of rice,corn,and wheat straw,and the potassium concentration was equivalent to that of corn and wheat straw.A.adenophora is a potential source of organic fertilizer.3)A.adenophora plants were observed on different soil types,showing extremely strong adaptability to various soils.In the rhizosphere soil of A.adenophora,the effective nutrients,activities of most enzymes,microbial biomass,autogenous nitrogen-fixing bacteria and ammonia-oxidizing archaea were significantly greater than those in the non-rhizosphere.Although there were differences among soils,A.adenophora generally decreased the diversity of bacteria and fungi,and increased the dominance index,indicating that A.adenophora can affect soil chemical and biological properties and adapt it to its own growth.In the rhizosphere of red soil,yellow soil,and purple soil,the richnesses of pathogenic fungi such as Cryptococcus terreus,Phialophora verrucosa,and Pleosporales were significantly higher than that in the non-rhizosphere,indicating that A.adenophora accumulated soil-borne pathogens in the rhizosphere,harmless to itself,but improved the competitiveness with neighboring plant species.4)The contents of heavy metals in different A.adenophora communities varied greatly,which was the lowest in farmland and woodland,while reached the serious pollution level in rare earth mining area(Pb and Cd),waste cinder yard(Hg),and lead-zinc mining area(Pb).Nevertheless,the heavy metals in A.adenophora did not increase with the increase of soil heavy metal contents,and the contents and enrichment coefficients were lower than or similar to those of most neighboring plants,which indicated that A.adenophora is unbiased to heavy metals,and can antagonize excessive absorption.The contents of heavy metals in decomposed A.adenophora were significantly lower than the national organic fertilizer standard,indicating that extremely low risk of soil pollution was exposed in in-situ application of decomposed A.adenophora,which laid a scientific foundation for the resourceful utilization of A.adenophora.To sum up,A.adenophora has strong adaptability to various soils regardless of soil fertility,soil moisture content,and heavy metal content.And A.adenophora also establishes its own ecological advantages through nutrients uptake and altering rhizosphere soil properties,thereby reduces native plant community stability and achieves successful invasion.Meanwhile,A.adenophora possesses abundant nutrients,huge biomass,and safe contents of heavy metals in the aboveground part,it is a potential source of organic fertilizer,this lays a foundation for the prevention and utilization as a fertilizer source.