| The invasion of alien species is one of threats to species diversity loss. This thesis intendsto launch exotic species Sonneratia apetala invasion risk comprehensive research in the lightof intrusion problem of the Sonneratia apetala used as the research object, Zhuhai Qi’ao Ⅰslandmangrove wetland served as the research base. Based on the invasion risk model, combinedwith the alien species invasion process, influence factors and unique mangrove wetlandenvironment, construct exotic species invasion risk assessment index system, determineevaluation index, through expert inquiry and related literature review to determine theassessment standard, use the application of fuzzy analytic hierarchy process to determine theindex weight, obtain data from three respects，including intrusion，environment informationand influence, then uses the fuzzy comprehensive evaluation method to make a qualitative andquantitative assessment of Sonneratia apetala invasion risk, determine their invasive risk grade,aimed at comprehensively and objectively reflecting the Sonneratia apetala invasion risk level,and finding out the influence on the results of Max factor, targeted for management departmentto manage, reduce risk, and help people to get a comprehensive understanding of Sonneratiaapetala ecological, biological characteristics, to balance introduction and ecological systemsafety，healthy and stable relations, meanwhile, it has the important theory and the practicalsignificance to ensure society and economy sustainable development.Results show：（1） Ⅰn Zhuhai Qi ao Ⅰsland mangrove reserve, the strongest of resistance, the semi lethaltemperature of-3.733°C, cold hardiness of the worst species Sonneratia caseolaris, semilethal temperature of3.733°C. Zhuhai Sonneratia apetala semi lethal temperature thanHainan Sonneratia apetala lethal low temperature3.941°C, description of Sonneratia apetalacold resistance enhancement, has the extremely strong adaptive capacity. Sonneratia apetala seedlings semi lethal temperature of1.945°C, than adult plant height of3.139°C, the coldhardiness of difference than adult plants.（2） The two parts of the Acanthus ilicifolius （stems, leaves）all had all elopathic influenceon S.apetala, the intensity of aerial parts were greater than the underground sections, each partof the interaction strength increased with increase of concentration; the influence ofgermination, except the underground sections0.1g ml-1, could promote the sprouting rootspeed, the rest showed a significant and very significant inhibitory effect, ground sections0.4gml-1,0.5g ml-1group, field germination were40%and0%; in the aspect of impact on thequality of the seedlings, Acanthus ilicifolius emerged two very significant laws, namely“highconcentrations inhibit and low concentrations promote”, the water content decreased withincrease of two part’s concentrations. Acanthus of Sonneratia apetala seedlings had significanteffect （P <0.01）, in the acanthus woodland Sonneratia apetala seedling density of1lines/16m2, height is1.1cm, but in the absence of Acanthus woodland density has reached70lines/m2, higher2.3cm.（3） Sonneratia apetala seedlings mainly appears in the September to Decemberfrequently, mainly concentrated in the forest edge and naked beach. Sonneratia apetalaplantation in December only in seedling emergence, the density is0.06strains/m2, not containⅡ class nursery in forest margins, Sonneratia apetala seedling density of Ⅰ grade reached12.5slines/m2, Ⅱ grade seedlings is2.5lines/m2, in the nude beach also in December the biggestdensity, Ⅰ grade seedlings reached6lines/m2, Ⅱ grade seedling lines0.31/m2, Ⅰn the Acanthusilicifolius communities, Sonneratia apetala seedlings appeared only in December, Ⅰ gradeseedling density reached0.5lines/m2, do not found Ⅱ grade plantation. After a winter lowtemperature environment, by March, forest margins and nude beach seedling density decreasessubstantially, respectively in0.25lines of/m2,0.06lines/m2.（4） Although the Sonneratia apetala can produce large numbers of seeds every year,but75%will be eaten by sea rat,20.54%outward diffusion,2.2×10-4%germination,4.46%were stored. seeds spreaded by seawater are mainly concentrated in the area of slow water flow, the beach can be reached600m. After a year, Sonneratia apetala seed is mainly empty anddecayed seeds, alive seeds only exist the forest0-10cm soil layer, and the germinationpercentage and vitality are less than10%, that reveal Sonneratia apetala survival period lessthan one year.（5） As the Sonneratia apetala age increases, the mudflat height gradually increased, from3aged Sonneratia apetala to9aged Sonneratia apetala, average annual increase10cm, thisshow Sonneratia apetala can quickly promote deposition. Acanthus ilicifolius were the majorcommunity under Sonneratia apetala forest. With S. apetala age increasing, Acanthusilicifolius plants density, height, coverage, biomass, maturity rate were ascending，Acanthusilicifolius plants density, height in the Kandelia candel forest were the lowest within them,there not exist the growth of of Acanthus ilicifolius in the the Aegiceras corniculatum forestand nude beach plot; Root-top ratio of Acanthus ilicifolius tends to1:1with S. apetala ageincreasing, stems-leaves ratio were increasing accompanied by S. apetala age raising and wereapproaching to the comparison; That show: The local species, Acanthus ilicifolius, has begun tosettle and grow under S. apetala forests after it control Spartina alterniflora growth and spread,meanwhile, growing is well.Ⅰt is appropriate for benthic animal living under Sonneratia apetal forest. Ⅰn the survey,found a total of16families,18species of benthic animal, in5aged Sonneratia apetal exist9species, density is350inds/m2, diversity index H′is1.96, evenness index J′is0.95, bothmore than native species Aegiceras corniculatum and Acanthus ilicifolius community diversityindex and evenness index.（6） Sonneratia apetala can improve soil texture, can make the soil clay content increased,with the increase of Sonneratia apetala plantation, soil pH decreased, in fertility, soil organicmatter content, microbial biomass carbon content, total phosphorus, total nitrogen, totalpotassium increase with age of Sonneratia apetala increasing. Ⅰn the soil biological activityinfluence, β-glucosidase, dehydrogenase and phosphatase activity increase with age increase ofSonneratia apetala increasing. （7） Ⅰn the5000mg/kg body weight, Sonneratia apetala fruit and leaves can’t influencerats behavior,14d mortality rate was0, and semi-lethal dose (LD50) is greater than5000mg/kgbody weight, proved to be non-toxic substances; toxic to fish, species, the fruit aqueous extracttoxicity intensity exceed leaves aqueous extract to the same fish, under the same aqueousextract, the sensitivity of the mudskipper is stronger than zebra fish,24h LC50>48hLC50>72hLC50>96hLC50>1000mg L-1, proved to be low toxic substances, according to the above,Sonneratia apetala will not pose biological toxicity hazards.（8） Used evaluation index system to assess Sonneratia apetala invasion risk,show thatSonneratia apetala invasion （R1）, adaptability（R2）, spreading （R3） and hazard （R4） risk grade isrespectively0.72,0.72,0.28,0.1, corresponding to the level of Ⅱ （high）, Ⅱ （higher）, ⅠⅤ （lower）,Ⅴ （low）. Sonneratia apetala invasion risk value of R is0.01, the corresponding grade of Ⅴ,namely the risk is very low. |
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