| Invasive plants have a significant impact on the local economy and the ecological environment,that also has attracted widespread attention.Exploring the biological control of invasive plants has gradually become a research hotspot.The interaction between invasive plants and native plants has been the focus of research,that in the aspects of allelopathy and competition have been carried out.This study focused on the three invasive species Bidens pilosa,Eupatorium catarium and Wedelia trelobata,that had invaded the vast area of Hainan Island.It was explored the biological control methods through the study of the interspecific interaction mechanisms.The allelopathic interaction among invasive plants and the allelopathic effects of native species and Melicope pteleifolia on invasive plants,and the growth competition between Carmona microphylla and invasive plants.The main results are as follows:(1)A study on biological control through allelopathic effects between invasive plants.The seeds of invasive plants are treated with the extract of other invading plants,and the effects of seed germination are observed to study the allelopathic effects between the invasive plants.The results show that there is a strong mutual inhibition between B.pilosa(concentration of 30-50g/L)and E.catarium(concentration of 30-50g/L),and the inhibition increased with the concentration of the extract.W.trelobata(concentration of 15-50 g / L)shows different degrees of promotion to B.pilosa and E.catarium.The strong mutual inhibition between the B.pilosa and E.catarium can be used for biological control.In addition,catechol and 2,3-butanediol are used for single compound experiment that widely distributed in three invasive plants.The results show that catechol has strong inhibitory effects on seeds germination and seedling growth of B.pilosa and E.catarium in the concentration(1-10mmol/L).The seeds germination and seedling growth of B.pilosa and E.catarium are inhibited at low concentrations(1mmol/L).When the concentration is slightly higher,the seeds of the B.pilosa and the E.catarium could not germinate at all.2,3-butanediol also strongly inhibit the seeds germination and seedling growth of B.pilosa and E.catarium at the same concentration(1-10mmol/L),and the inhibition increased with concentration.In contrast,B.pilosa is more sensitive to 2,3-butanediol than E.catarium.Bothchemicals are expected to be used to develop herbicides.(2)A study on the biological control of the allelopathic effects of native plants on invasive plants.Treatment of seeds germination of B.pilosa and E.catarium with five kinds of Hainan native plants M.azedarach,M.apelta,M.pteleifolia,Alocasia macrorrhiza and Piper sarmentosum extract(15-50g/L concentration).The results show that M.pteleifolia and A.macrorrhiza have no significant effect on seed germination of invasive species.M.azedarach,M.apelta and M.pteleifolia have significant inhibitory effects on B.pilosa and E.catarium,especially the extract of M.azedarach.When the concentration is higher(30g/L),the seeds of two invasive species are basically unable to germinate,and the inhibitory effect on the germinated seedlings is also the strongest,which makes M.azedarach more restrained against the M.apelta and M.pteleifolia.The inhibitory effect of the extracts of M.azedarach,M.apelta and M.pteleifolia on E.catarium is as follows: M.azedarach>M.pteleifolia > M.apelta,and the inhibitory effect on B.pilosa was M.azedarach> M.apelta > M.pteleifolia.In contrast,M.azedarach has the most allelopathic inhibition potential.It can be considered as a biological inhibitor of these two invasive plants,which is easy to obtain and has no hidden dangers of environmental pollution.(3)A study on the growth competition control of native plants and invasive plants.C.microphylla is mixed with the invasive plants B.pilosa and W.trelobata in the sample(1 m ×1 m)for a one-year experiment to observe the growth competition with different quantities.The results show that the C.microphylla showed a certain inhibition trend on the height of B.pilosa.The more the number of mixed C.microphylla,the more obvious the trend.The inhibitory effect on the biomass of B.pilosa is the most significant in the treatment of 12 or 8C.microphylla mixed with 30 B.pilosa.The biomass of B.pilosa is significantly lower than the control group of 8 strains(P=0.035)or 30 strains(P=0.019)B.pilosa.In terms of photosynthesis,the photosynthesis rate of B.pilosa in the treatment group of 12 or 8 mixed with C.microphylla is the smallest.The photosynthetic rate of B.pilosa is lower than that mixed with different plant number of C.microphylla.The C.microphylla shows inhibition trend.For the W.trelobata,C.microphylla has significant inhibitory effects on the coverage,and the tendency of inhibition is enhanced with the increase of the relative number of C.microphylla.The coverage of W.trelobata in the group of 12 C.microphylla mix with 30 W.trelobatais is significant lower than control group in four determination(P<0.05).In terms of photosynthesis,the net photosynthetic rate of the W.trelobatais is lower than that in the control group.the C.microphylla shows a certain inhibition trend.W.trelobata is a perennial invasive herb,which the C.microphylla as a perennial shrub species,the "race" results between them need long-term observation.For the native species C.microphylla,the height,crown,base diameter,coverage and biomass are inhibited by two invasive plants,and the inhibition by B.pilosa is stronger.The impact of W.trelobata on C.microphylla is not significant.In terms of photosynthesis,the height of C.microphylla increased less than that of the invasive herb during the growth period of one year.The photosynthesis inhibition effect on the C.microphylla is more obvious while the B.pilosa is higher than C.microphylla.When the B.pilosa are aging,the illumination limits of C.microphylla are greatly reduced.For the biomass,the biomass of C.microphylla which mixed with B.pilosa is lower than that in control group or mixed with W.trelobata.On the whole,during the growth period of one year,the inhibitory effect of B.pilosa on the C.microphylla is stronger than W.trelobata.B.pilosa is an annual herb,while the C.microphylla is perennial shrubs.The results may be more valuable for the control of invasive plants if the experiment lasts for more than several years.Summarily,in this study the results of C.microphylla "besieging" two invasive plants showed a certain inhibition trend.C.microphylla is a shrub species whose growth is relatively slow,but its crown is large,branches are thick,and the blocking advantage of other plants can not be underestimated.Therefore,it is expected that C.microphylla might be a species to control the two invasive plants.The specific effects also require long-term continuous observation. |
