| In the recent20years, the spread and explosion of Merremia boisiana in Hainan has significantly threatened biodiversity and ecosystem functioning, bring serious negative impact on the ecological environment. This study choose M. boisiana as the main test materials, carry out field investigation and garden experiment research respectively, from the effects of the invasive plants on soil physical and chemical properties and the plant-soil feedback to discuss M. boisiana possible mechanism of the invasion, so as to deepen the understanding of mechanism of plant invasion, at the same time, it will also provide theoretical basis for the control of the harmful plants and the ecological restoration. The results are as follows:1. The influence of different concentration of aqueous extracts of M. boisiana and a native non-invasive congener M. vitifolia on soil chemical properties and three categories of enzyme activities was analyzed and compared for exploring the impacts of native harmful plant M. boisiana on soil ecology. With the increase in the concentration, the aqueous extracts of M. boisiana increased the soil pH, total nitrogen, soil organic matter, available potassium, nitrate nitrogen, total phosphorus, ammonium nitrogen, available phosphorus, content and the activities of urease, sucrase and phosphatase, but did not affect total potassium content. With the increase in the concentration, the aqueous extracts of M. vitifolia also increased the content of soil available nutrients and the activities of sucrase and phosphatase, but have no significant effect on soil total potassium content and the activity of urease. Compared with the aqueous extracts of M. vitifolia, the aqueous extracts of M. boisiana had more significant effects on soil pH, total phosphorus, ammonium nitrogen, available phosphorus content and the activities of urease. At the highest concentration (0.5g·mL-1), total phosphorus, ammonium nitrogen, available phosphorus, and urease content in soil with the aqueous extracts of M. boisiana were1.13,1.52,1.31and2.19times of those in soil with the aqueous extracts of M. vitifolia. At the concentration of0.25g·mL-1, total phosphorus, ammonium nitrogen, available phosphorus, and urease content in soil with the aqueous extracts of M. boisiana were1.06,1.51,1.26and1.88times of those in soil with the aqueous extracts of M. vitifolia. At the concentration of0.125g·mL-1,total phosphorus, ammonium nitrogen, available phosphorus, and urease content in soil with the aqueous extracts of M. boisiana were1.07,1.64,1.23and1.39times of those in soil with the aqueous extracts of M. vitifolia. The improvement of soil nutrients may provide favorable conditions for the growth of M. boisiana and it could also promote its advantage when competing with native plants. This may be one of the ecological mechanisms underlying its invasion success and rapid expansion. 2. Through the analysis of soil physical and chemical properties, soil enzyme activities and soil microbial community with the change in the level of invasion by M. boisiana. The results showed that with the increase in the coverage, M. boisiana increased the soil total nitrogen, organic matter, available potassium, nitrate nitrogen, ammonium nitrogen, available phosphorus, content, reduced the soil total phosphorus content, did not affect total potassium content, and also increased the activities of urease, sucrase and phosphatase. At the same time, the quantity of cultivable soil microbe groups in the heavily-covered soil was significantly more than that in the non-covered soil. Total nitrogen, organic matter, nitrate nitrogen, ammonium nitrogen, available potassium and available phosphorus content in the heavily-covered soil was2.57g·kg-1,44.96g·kg-1,17.42mg·kg-1,8.96mg·kg-1,12.67mg·kg-1,1.37mg·kg-1, which was10.28,4.40,1.57,2.30,1.90and1.83times as that in the non-covered soil. The activities of urease, sucrase and phosphatase in the heavily-covered soil was0.52mg·g-1,3.39mg·g-1and7.70mg·g-1, which was2.26,2.92and1.39times as that in the non-covered soil; the numbers of fungus, bacterium and actinomycetes were14.70×103CFU/g,5.88x107CFU/g and6.03×105CFU/g, which was2.21,3.95and2.86times as that in the non-covered soil. The results indicate that M. Boisiana changed soil microbial community structure, which changed the soil physical and chemical properties and enzyme activities, probably creating a favorable soil environment for itself. This may be one of the ecological mechanisms underlying its invasion success and rapid expansion.3. In order to examine the role of soil fungi play in the growth and competition between M. boisiana and P. scandens, fungicide was added into the heavy-covered soil and non-covered soil to control soil fungi and at the same time cultivation of M. boisiana and P. scandens was conducted by using a pot experiment. When M. boisiana separately, the biomass in heavy-covered soil is1.63times of the local plant soil; In the process of applying fungicide, the biomass in covered soil is1.45times of the local plant soil. When M. boisiana mixed with P. scandens, in the absence of fungicide treatment, M. boisiana increased than when individual growth, especially in the M. boisiana covered soil, M. boisiana mixed with P. scandens, the biomass is significantly different from the biomass of M. boisiana grow alone, and the biomass cultivated together with P. scandens was1.35times than that of when it was planted alone. But the competition ability was impaired obviously when it was planted with companion plants in soil with fungicide, to show that the soil fungi are good for M. boisiana in competition of P. scandens. P. scandens grows alone and was impaired obviously covered soil, without fungicide treatment and with fungicide treatment, the biomass of P. scandens in local soil is1.83times and1.7times higher than in covered soil. The plant biomass of P. scandens cultivated together with M. boisiana were no significantly different from the biomass grow alone, but after fungicide treatment, mixing plant biomass is1.45times higher than that of when it was planted alone. The feedback effects of soil fungi are more conducive to the growth of M. boisiana, M. boisiana and soil microorganisms are form a stable interaction, it will be more conducive to the formation of M. boisiana monodominant communities.4. M. Boisiana, P. Scandens, M. vitifolia and L. binectariferum were planted in the same scale core soil background, to detect the effects of different plants on soil characteristics, The results showed that the total nitrogen, pH value, urease and sucrase content as well as the number of fungi, bacteria and actinomycetes in. M. boisiana soil were significantly higher than that of non-vegetation soil, the available potassium, available phosphorus content and organic matter were significantly lower than that of non-vegetation soil; The:total nitrogen, available potassium, organic matter content and pH value, in P. scandens soil were significantly higher than that of non-vegetation soil, The activities of urease, sucrase and phosphatase content as well as the number of actinomycetes and bacteria were significantly higher than that of non-vegetation soil; The available potassium, pH value, phosphatase and urease content as well as the number of actinomycetes in M. vitifolia soil were significantly higher than that of non-vegetation soil; The pH value, organic matter, available potassium content, sucrase and urease content as well as the number of actinomycetes in L. binectariferum soil were significantly higher than that of non-vegetation soil. The study was to know about the growth adaptabilities of four plants to the soils of five different types, found M. boisiana and P. scandens grow better in the soil that they had grow, their biomass were significantly higher than that of in the other soil, the ratio of root to shoot of M. boisiana and P. scandens are higher only in the soil that they had grow. In this experiment, three kinds of local plant biomass also showed the biomass decreased significantly in the M. boisiana soil, it is proved that M. boisiana soil does indeed has certain inhibitory effect on the local plant. Further growth to some extent, feedback experiment also illustrates the M. boisiana quickly spreading mechanism, which has a strong ability to adapt to the soil environment, can quickly improve their leaf biomass, through higher aboveground biomass to obtain more photosynthetic resources. It has played a significant role to establish their population quickly. |
PDF Full Text Request