Study On The Distribution And Potential Suitable Area Of Rare And Endangered Plant Cercidiphyllum Japonicum

Cercidiphyllum japonicum is a kind of dioecious deciduous tree of Cercidiphyllaceae.There are only two species of the family of Cercidiphyllaceae in the world.Because of its primitive status in system evolution and its important value in the study of plant phylogeny.Now it is on the list of wild plants under second-class state protection in China.This article mainly takes the rare and endangered plant C.japonicum as the research object,and studies its distribution from two parts: the geographical distribution pattern and the prediction of potential suitable areas.In the part of the geographical distribution pattern,70 fossil records of plants of the family Cercidiphyllaceae have been collected through related literature and online information,and combined with the data of paleogeology and paleoclimate,the geological distribution of plants of the family Cercidiphyllaceae was statistically analyzed.Through the collection and selection of National Plant Specimen Resource Center and related literature,464 pieces of distribution data of C.japonicum were obtained,and combined with the data of 19 climatic factors under current climatic conditions to carry out a statistical analysis of the distribution status of C.japonicum.In the prediction part of the prediction of potential suitable areas,we screened the 7 climatic factors that had the greatest influence on the distribution of C.japonicum by Jackknife and Variance Inflation Factor.Combined with the climate factors under the future 2050s(2040-2060)and 2070s(2060-2080)from the Worldclim and distribution data of C.japonicum,we predicted and analyzed the potential suitable areas of C.japonicum by Max Ent model.In the part of the geographical distribution pattern,the statistical results show that:(1)The plant of the family Cercidiphyllaceae originated in the late Cretaceous period.The excellent geographical and climatic conditions from the Late Cretaceous to the Tertiary period were very suitable for the survival,evolution and spread of the family Cercidiphyllaceae.Its distribution range has gradually expanded,and its distribution center has gradually shifted from North America to Eurasia.At the end of the Tertiary period,the climate began to deteriorate.During the Quaternary period,the glacial period and the interglacial period alternated,and the temperature decreased and increased periodically.Most parts of North America and Europe were covered by glaciers,and the family Cercidiphyllaceae was gradually extinct in these places.East Asia is less affected by glaciers,and “shelters” have been formed in parts of China and Japan.Therefore,C.japonicum have been preserved in these places,forming the present China-Japan distribution pattern.(2)The current horizontal distribution range of C.japonicum in Japan is138.358°～145°E and 35.52°～43.485°N.In China,the horizontal distribution range is101.507°～119.68°E and 23.614°～36.169°N.The vertical distribution range in China is650～2 700 m,and it is concentrated between 1 000～2 000 m.The distribution area covers 13 provinces(municipalities directly under the Central Government),130districts(counties),and more than 55 nature reserves.The vegetation division covers 2regions and 7 zones,the climate division covers 6 first-level divisions and 13second-level divisions,and the flora covers 2 Kingdom,3 Sub-kingdom,6 Region,and17 subregion.In the prediction part of the prediction of potential suitable areas,the research results show that:(1)The MaxEnt model has a good ability to simulate and predict the potential suitable areas of C.japonicum,with all AUC values more than 0.9.The annual precipitation(Bio12)and the min temperature of coldest month(Bio6)can provide more useful information for the prediction of the potential suitable areas for C.japonicum.(2)Under the current climatic conditions,the potential suitable areas for C.japonicum are mainly distributed around the Hengduan Mountains-Qinba Mountains-Hubei,Chongqing and Hunan Mountains.At the same time,the Nanyang Basin,Huaiyang hills and parts of the eastern part are also within the range of suitable areas.Under future climatic conditions,the range of potential suitable areas has not changed much compared with the current one,but the area of suitable areas is generally in a shrinking trend.(3)There are two extreme forms of species diffusion: Unlimited dispersal and No dispersa.Under these two diffusion methods,the potential suitable area of C.japonicum is shrinking.This shows that climate change will indeed have a negative impact on the distribution of C.japonicum.(4)As the potential suitable area of C.japonicum spreads to the Yunnan-Guizhou Plateau,where the altitude is higher,and at the same time,there is a partial shrinks at the junction of Anhui Province and Henan Province in the northeast,its distribution center is gradually shifting to the southwest.