Invasive Biological Characteristics And Chemical Control Of Galinsoga Parviflora Gav.

In this paper,the invasive specie G.parviflora Gav.was studied,the invasion status of G.parviflora Gav.in Hohhot was investigated by field investigation,and the phenological characteristics of G.parviflora Gav.were studied by observing and recording the effects of phenological period,growth rate,seed yield and different buried depth on seed germination.The photosynthetic light response and diurnal variation of G.parviflora Gav.were measured by CIRAS-3 portable photosynthesizer,and its photosynthetic characteristics were systematically analyzed.The effects of G.parviflora Gav.on plant diversity in invasive areas were studied.The types and concentrations of chemical herbicides were screened out through chemical control experiments.The results of the study were showed as follows:?1?A total of 48 sites of invasion and distribution of G.parviflora Gav.were identified in Hohhot:except Wuchuan,The rest of the county districts were found to have its distribution,of which 38 were concentrated in four districts.The types of invasive habitats are diversified,including green belts,farmland,roadside,disturbed by buildings,vegetable gardens,orchards,etc.Among them,green belts are the most common ones and shade areas are preferred.G.parviflora Gav.can adapt to a variety of environmental types and provide favorable conditions for its invasion into new areas.In Hohhot,G.parviflora Gav.seedlings began to emerge in early May and entered budding stage in early June,flowering stage in mid-June.Then the plants entered the state of edge-growing and lace-setting from early July to early November.Most of plants died in early December.So far,G.parviflora Gav.had completed its life cycle of more than 200 days.The seed yield of mature G.parviflora Gav.per plant was 7020-14508.Its vigorous vitality and huge fruiting amount have laid an important foundation for the success of the invasion.When the buried depth of G.parviflora Gav.seeds was 0cm,2cm,4cm,6cm and 8cm,they can germinate and emerge.The average germination rate was negatively correlated with seed burial depth.Statistical analysis of variance showed that deep seed burial?8cm?delayed the initial germination time and duration of hyacinth seeds,but had no effect on the germination rate.Therefore,in the process of propagation and diffusion,even if buried by soil,it can germinate,grow and reproduce,which provides an important guarantee for invasion.?2?The diurnal variations of leaf temperature,stomatal conductance,transpiration rate and water vapor pressure deficit were single-peak curves,and the diurnal variation of intercellular CO₂ concentration was"V"type.The diurnal variation of net photosynthetic rate of G.parviflora Gav.showed a bimodal curve at the peak of growth and a single peak at the end of growth.It was related to photosynthetic effective radiation,stomatal conductance,intercellular CO₂ concentration and transpiration rate,among which transpiration rate had the greatest influence.The photosynthetic light response curve of G.parviflora Gav.showed that it rose straight at first(I<200?mol.m^-2.s^-1),then rose slowly(200?mol.m^-2.s^-1<I<1000?mol.m^-2.s^-1),finallydecreased slightly(I>1000?mol.m^-2.s^-1).The best fitting model for photosynthetic response of G.parviflora Gav.was a new model developed by Ye et al..G.parviflora Gav.had no higher light saturation point,but its light compensation point was very low.It shows that although it can not make good use of strong light,it can make good use of photosynthesis under unfavorable conditions of light shelter,which is suitable for main types of its invasive habitats.?3?There are 77 species of wild plants belonging to 59 genera and 24families in 22 sample plots.Compositae,Gramineae and Chenopodiaceae are the main families.Compositae plants account for 22.078%,Gramineae plants for 18.182%,Chenopodiaceae plants for 7.792%.There were twenty-four common plants.Through the analysis of the relationship between the important value and diversity index of G.parviflora Gav.,it was found that the four indexes showed a similar downward trend compared with CK in control group.With the increase of the important value of G.parviflora Gav.,Shannon-Wiener index?H'?,Simpson index?D_i?and Pielou index?J?decreased significantly or extreme significantly?P<0.05 or P<0.01?.It indicated that the invasion of G.parviflora Gav.had adverse effects on plant diversity in its distribution area.?4?Nine kinds of herbicides were used to control G.parviflora Gav..The concentration of herbicides and control effect were analyzed and the ED₅₀ and ED₉₀ were calculated.Comparing the concentration of herbicides needed to effectively control G.parviflora Gav.,the effect of the content of herbicides on Soil and environment,and the main types of habitats invaded by G.parviflora Gav..It was considered that 25%octyl Bromophenyl nitrile was the best herbicide for controlling the stem and leaf of G.parviflora Gav.,and23.5%ethofluoroethercould be used as a pretreatment agent for controlling G.parviflora Gav.effectively.