| Metasequoia is famous for China’s unique relic plant around the world,and therefore it is known as"living fossil".It has been the key species of our government’s protection and monitoring management since it was rediscovered,and it has been listed as a primary protection plant.At present,Native metasequoia population is pushed on the verge of recession and extinction due to some reasons such as climate change,environmental damage,human disturbance and others.Therefore,this study is aimed to adopt the different research methods to research on the growth,change and suitability of native Metasequoia population through the collection of field investigation data,climate data,tree growth data and others of wildlife habitat of native metasequoia population,and then put forward reasonable countermeasures for the protection of native metasequoia population in Xingdoushan National Nature Reserve of Hubei Province,so as to provide the scientific basis for the protection and management of habitats of native metasequoia population.The main results are acquired as follows:1.Through the analysis of climate data of the 65 year of habitats of native metasequoia population,it is well learned that the local temperature shows a rising trend while precipitation,average relative humidity,average wind speed and sunshine duration all show a descending trend.In winter,the temperature rise is the main factor of average annual temperature increase.Being mainly affected by the extreme high temperature in January and the extreme low temperature in October,both of the annual extreme high and low temperatures show an upward trend.The rise of average temperature is mainly regulated and controlled by the high temperature in May.The increase of average low temperature is affected by the decrease of low temperature in the winter of February.The decrease of average relative humidity is main factor of the decrease of annual average relative humidity in spring and August.Meanwhile,the decrease of precipitation is also the most obvious in spring and August and the average wind speed declines most significantly in spring.In terms of hours of sunshine,its decrease becomes mostly significant in the December of winter.2.The tree ring and annual ring of metasequoia are respectively used to build three chronologies,namely standardization,difference and auto-regression.Through the analysis of correlation between chronology and climatic factor,it is found that except for the influence of climate factor,last year’s climate also had a certain influence on the growth of metasequoia,and the effect of temperature on the radial growth of metasequoia is most significant.In terms of the season,the influence of spring climate factor plays a dominant role to the growth of annual ring of metasequoia.The rise of extreme high temperature and the average high temperature promote the growth of the metasequoia and the increase of extreme low temperature,and the decrease of average low temperature and average relative humidity restricts the growth of metasequoia.From the perspective of lunar climate factor,the climate factor from May to September accounts for a large proportion in affecting the growth of metasequoia,the decrease of average relative humidity and precipitation has a hindrance to the radial growth of metasequoia.Through the correlation research between average wind speed and sunshine duration and the growth of tree-ring of metasequoia,it is found that the correlation only exists in a few months.3.Based on the correlation degree of the chronology of tree ring of metasequoia and climate factor,it sets up a climate reconstruction model.Through the test of model,it can be seen that the effect of model is better,which can reflect the climate change trend in the area of study in a certain extent.Meanwhile,it is learn from the relationship model that the main growth seasons of metasequoia are from May to September.Also,the winter’s low temperature promotes the dormancy of metasequoia,accumulating energy for the growing season.The model is built by the selected climate factor.The selected factors finally determine that the model has better fitting effect that can effectively predict the radial growth of metasequoia.4.The radial growth model is established by using the data of tree ring of metasequoia.The optimal growth model is evaluated as D=61.44*(1-e-0.01*T)0.86.The model is characterized of good fitting effect.From the results of analysis of growth process of metasequoia,it is shown that the metasequoia within 50 years tree age still has exuberant vitality.In the model of diameter at breast height of tree,the prediction accuracy of multivariate composite model is higher than that of single variable model.Model 4 h=17.7508+0.0042d2+0.0001d3,22(h=128.1449e-49.9808/d+69 7668),5 1(h=e,5.3671-3.07371nH-0-9.5212/t-28.31741nN/d+544.2804/dt+206.7969/d)and 52(h=0.4994H00.0507(BA)0 3521N0.0196e0.1972/t+8 6632/d)are the four best models,in which model 4 is a linear model and the other three are nonlinear models.Tree age is not the most important variable in the study of tree height,the prediction accuracy of tree height can be enhanced by considering tree age in the selection of model.When the dimensionality of standing tree,site and environmental characteristic factors are reduced by using the random forest method,it is found that the eight factors in the standing tree,such as DBH,height of tree,crown diameter and tree age in the data of standing tree,and longitude,latitude,elevation and slop direction in the data of site,play an optimized effect to the classification of growth status of native metasequoia population and can effectively ensure the classification accuracy.The combination of two classification methods of random forest and SVM is combined with multi-source information can effectively conduct the predication of classification to the health type of metasequoia.5.From a study on the suitability of habitats of native metasequoia population,the results show that:among the weights obtained by analytic hierarchy process,the weight of human activity factor is the highest,and the altitude factor is second.The most suitable area for the survival of metasequoia is the valley area in the southwest of the protection area,and the northeast is the suitable area for survival of native metasequoia population.The mostly unsuitable areas are mainly the living area in the central area and surrounding mountains environment.The most suitable,suitable and unsuitable areas of the protection area respectively account for 26.95%,41.01%,and 32.04%.6.According to the investigation results of native metasequoia population,with the factors that can affect the population of metasequoia,the research proposes to strength the monitoring and management of metasequoia in the central area,raise the awareness of the protection of the people,increase the special fund for protection,implement the contract responsibility system,carry out ecological immigration,build a professional team of metasequoia protection,and regularly organize the academic exchange so as to ensure the effective protection of metasequoia population.In conclusion,although climate change trend of native metasequoia population is relatively weak,it still has a certain effect on the growth of metasequoia.The growth of metasequoia can be effectively predicted by climate factor.The results of adaptive class division show man-made interference and altitude play an important effect to the classification of suitable level of metasequoia,and therefore it is necessary to strengthen the force of supervision on the protection of metasequoia,eliminate the human disturbance,raise the awareness of the protection of the people,and restore the natural environment of the protective area.This study provides a scientific basis for the protection and management of the native metasequoia population in the future,and provides a reference for the protection of other species. |
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