Study On Mechanical And Chemical Control Of Invasive Plant Spartina Alterniflora In Yellow River Delta

Since Spartina alterniflora was introduced to the Yellow River Delta(YRD)in Shandong Province in 1990,it has rapidly spread in the salt marsh wetlands,and seriously threatened the safety of the native ecosystem of the coastal wetlands in YRD.Therefore,the effective control of this exotic species is urgent.In this study,the S.alterniflora was eliminated by mechanical(mowing)or chemical control(spraying herbicides),aiming to find the best mowing technique and herbicides which can effectively killing S.alterniflora,and then provide scientific support for S.alterniflora controlling technology.The research results are as follows: 1.The effect of mowing control on the growth and reproduction of S.alterniflora(1)Mowing time has a great influence on the control effect.Mowing with low stubble in the early stage of reproduction of S.alterniflora has the best weeding effects.The density of S.alterniflora was reduced by 99.8% and the earing rate was only 3.4%,which effectively inhibited the sexual reproduction of S.alterniflora.The rhizomes had the lowest vitality,so the asexual reproduction ability of S.alterniflora was the weakest.(2)Multiple mowing with low stubble can completely eliminate S.alterniflora,but increasing the mowing frequencies will increase the control cost.The experiment suggested that S.alterniflora had minimum plant density and spikeing rate in the treament with twice mowing and low stubble.Thus it was the most efficient and cost-effective methods for elimateing S.alterniflora.(3)The height of stubble after mowing seriously affected the density of new sprouts of S.alterniflora.The density and earing rate of S.alterniflora in the plots with low stubble were significantly lower than that of the CK plots.In the plots with high stubble,there was a higher density of new sprouts of S.alterniflora than that in the plots with low stubble.Even if the high stubble was mowing four times,more than 30% of S.alterniflora could germinate new seedlings and bear seeds.(4)Mowing with low stubble significantly reduced the vitality of rhizomes of S.alterniflora,while mowing with high stubble had very limited inhibition for the vatility of rhizomes.The change of rhizome vitality was consistent with the density variation of new seedlings of S.alterniflora after mowing,which indicated that the rhizome vitality determined the asexual reproductive capacity of S.alterniflora.2.Effect of herbicides on the growth and reproduction of S.alterniflora(1)Haloxyfop-r-methyl has the best weeding effects on S.alterniflora,which can kill the aboveground part of S.alterniflora resulting in complete inhibition of the sexual reproduction,and completely inhibit the asexual reproduction of S.alterniflora in the next year.(2)Cyhalofop-butyl also has a good control effect on the elimination of S.alterniflora,that can completely inhibit the growth and the earing of S.alterniflora,but the inhibition the asexual reproduction of rhizomes is as good as haloxyfop-r-methyl.Glyphosate can completely inhibit the sexual reproduction of S.alterniflora,but it cannot inhibit the asexual reproduction of S.alterniflora in the following year.(3)Herbicides could poison some macrobenthic animals in a short time,but there was no significant difference in the number of benthic animals between the herbicide treatment and CK treatment after one year.The impact of herbicides on the environment is closely related to the dosage and application time of herbicides.In future studies,the optimal application time and minimum dosage of herbicides need to be explored to minimize the environmental impact.