Study On The Suitable Growing Area Of Bromus Tectorum L. In China And Its Key Influencing Factors

Taking Bromus tectorum L.,a malignant weed in farmland in Northwest China,as the research object,this paper studied the geographical distribution of Bromus tectorum L.through literature review,distribution sample plot investigation and plant reproductive ecology research methods.Combined with climate change,based on GIS,the maximum entropy model was used to predict the suitable area of Bromus tectorum L.in China,The key environmental factors affecting the occurrence and distribution of Bromus tectorum L.were analyzed,and its ecological adaptability was analyzed by simulating the field environment indoors.The research results not only revealed the reasons for the increasingly serious harm of Bromus tectorum L.,but also laid a theoretical foundation and data support for the comprehensive prevention,control and utilization of Bromus tectorum L.The main results are as follows:1.Geographical distribution pattern of Bromus tectorum L.and prediction of its potential suitable areaBased on the geographical distribution data of Bromus tectorum L.in China,combined with the current climate data and future climate change scenarios(2050s and 2070s under RCP 8.5 scenario),the maximum entropy model(Max Ent model)is established to determine the dominant environmental factors affecting the distribution of Bromus tectorum L.Geographic Information System(GIS)was used to divide the suitable growing areas of Bromus tectorum L.in China,and ROC curve was used as the accuracy evaluation index of simulation.The results show that Max Ent model has excellent simulation effect(AUC=0.965);Under the current climate conditions,the suitable area of Bromus tectorum L.is 2.5 534×10~6 km~2,mainly distributed in the northeast of Qinghai Province,the areas bordering Qinghai Province in Gansu Province,the northwest of Sichuan Province and the northwest of Xinjiang;Among them,the main environmental factors affecting the distribution of Bromus tectorum L.are altitude,bio12(annual precipitation),bio9(average temperature in the driest quarter)and bio15(seasonal variation coefficient of precipitation).Their contribution rates are 45%,17.5%,9.7%and 9.7%respectively,and the cumulative contribution rate is 81.9%;In RCP 8.5 Compared with the current situation,the potential distribution area of sparrow is 23.2%～23.5%,which is higher than that of the current situation Under scenario RCP 8.5,2070s is higher than 2070s,the distribution area of potential high suitable area of Bromus tectorum L.decreased by 8.9%in 2050s;In conclusion,the potential distribution area of Bromus tectorum L.under the climate change scenario shows a trend of expansion in the future,and Under RCP 8.5scenario,2070s is higher than 2050s,the distribution area of suitable areas in 2050s tends to decrease.2.Study on reproductive allocation of Bromus tectorum L.at different altitudes and habitatsIn order to explore the reproductive allocation of Bromus tectorum L.in different altitude gradients and habitats,the differences of reproductive characteristics and resource allocation of Bromus tectorum L.in flower and fruit stage at five altitude gradients and three different habitats at the same altitude in Qinghai were studied by quadrat investigation method and drying weight method.The results showed that the plant height of Bromus tectorum L.decreased gradually with the increase of altitude,and there were differences in the plant height of Bromus tectorum L.in different habitats;There was no significant correlation between reproductive allocation and nutrient allocation in flower and fruit stage and altitude(P>0.05),and there was no significant correlation between reproductive allocation in flower and fruit stage and aboveground biomass in five altitude zones(P>0.05);The reproductive distribution and nutrient distribution of Bromus tectorum L.in flower and fruit stage in 15different habitats in Qinghai Plateau showed very significant differences(P<0.01).In conclusion,Bromus tectorum L.reproductive allocation is disturbed by the external environment,but altitude is not the only reason to determine its reproductive allocation,and the phenotypic plasticity of different habitats of Bromus tectorum L.is high.3.Physiological response of Bromus tectorum L.to three kinds of stressIn recent years,salt stress has become a hot spot in plant research,combined with the temperature and humidity affecting the survival of Bromus tectorum L.Taking Bromus tectorum L.in Qinghai Plateau as the research object,the differences of physiological and biochemical properties of weedy Bromus tectorum L.under three different types of stress were systematically discussed by using low temperature,PEG-6000 and Na Cl treatment to simulate the form of stress.The adaptability to adverse conditions was reflected by measuring the content of soluble protein,the activities of antioxidant enzymes such as superoxide dismutase,chlorophyll and proline,and then the correlation was analyzed.The results showed that the seed germination rate and average bud length of Bromus tectorum L.decreased under three stress conditions.The average plant height,average leaf length and aboveground biomass of Bromus tectorum L.seedlings decreased under low temperature and drought stress,while the above indexes fluctuated under salt stress.(1)During low temperature stress,the contents of soluble protein,pro and pod increased with the decrease of temperature;The activities of SOD and cat showed an irregular trend with the decrease of temperature.(2)With the increase of PEG concentration,the changes of cat and SOD fluctuated,and proline,soluble protein and pod increased.(3)With the strengthening of Na Cl stress level,the changes of cat,SOD and pod showed a fluctuating state,and proline and soluble protein showed an increasing trend.(4)The results of correlation analysis showed that soluble protein and pod were significantly negatively correlated with temperature;Proline was positively correlated with the concentration of PEG-6000,while soluble protein and pod were positively correlated with the concentration of PEG-6000;There was a very significant positive correlation between pro content and Na Cl concentration,and there was a significant positive correlation between soluble protein and Na Cl concentration.In conclusion,abundant physiological and biochemical regulation mechanisms are involved in the adaptation of Bromus tectorum L.to stress,and there is a certain correlation among various physiological and biochemical substances,which reflects the ability of Bromus tectorum L.to resist stress,weaken its own damage and adapt to environmental changes.