Preliminary Study On The Stable Carbon And Nitrogen Isotopic Compositions Of Primulina Tabacum Hance

At present,the population of Primulina tabacum are still endangered.To better protect the key national protected species P.tabacum,The plant diversity of 14distribution sites with P.tabacum in Guangdong,Guangxi,Hunan and Jiangxi Province have been surveyed.By determining the stable carbon and nitrogen isotopic constitution(?¹³C,?¹⁵N)on plant vegetative organs,surface soil and rock of each P.tabacum population in 14 distribution sites.Preliminary study the relationship between the stable carbon and nitrogen isotopic composition of different vegetative organs and environmental factors.The main research conclusions are as follows:?1?Among all the distribution sites?there are 11 sites?in which P.tabacum have been found,there are also found some species of Pteris spp.are always live in the same environment with Primulina tabacum.So Pteris plants can be useful as indicator to find the environment which is suitable for Primulina tabacum to survey.?2?Based on the geographic information of the 11 locations of P.tabacum,the potential geographic distribution sites of P.tabacum are predicted by MaxEnt software.The result shows that except Guangdong,Guangxi and Hunan provinces,Jiangxi province,there are not any province have high suitable areas for P.tabacum.Both training AUC and training AUC in the model evaluation indexes are over 0.9991.The main climatic factors affecting the potential suitability sites of P.tabacum are the solar radiation,the cumulative permutation importance of solar radiation on March and September is as high as 94.44%.Since 24 climatic and environmental variables are used in this prediction,the prediction of the potential suitability of P.tabacum can be more accurately.In the future,more environmental variables should be used to predict the accurate suitability area,so as to explore the new distribution sites of P.tabacum.?3?In all samples?including plants,soils and rocks?,the element contents are arranged as C>H>N>S,and plants>soils>rocks.there are not significant difference among the C/N values of roots,stems,and leaves from P.tabacum and its same family plants.The C/N values of rock are much bigger than plants and soils,and there are also not significant relationship between rocks and soils.The values of soils are significant positive correlation with plants'C/N values?average C/N values of roots,stems and leaves?.?4?The?¹³C of sample plants are between-40.47^-29.92‰,and the?¹⁵N are between-13.38‰³.72‰.The?¹³C in different vegetative organs of sample plants are not significant difference.There are significant difference between the?¹⁵N of root and leaf.But the significant difference on?¹⁵N are not exist either during root and stem or leaf and stem.And the?¹⁵N of root is smaller than the?¹⁵N of leaf.It is because leaf can uptake atmospheric nitrogen sources.The?¹³C of all the plant samples are larger than-25‰obviously shows that the photosynthetic pathway of P.tabacum,Chirita eburnea and Ch.fimbrisepala are Calvin Cycle.?5?There are significant positive correlation on?¹³C during sample plants and surface soil.So it shows that?¹³C of surface plant is mainly factor on?¹³C of surface soil.There are significant negative correlation during the nitrogen content and the root?¹⁵N of plant samples,it shows that as the nitrogen content of soil increases,the Carbon deposition in rhizosphere will be strengthened(the increase of soil nitrogen content will promote the release of organic compounds containing ¹³C from roots).?6?The climate factors?regional annual mean temperature and annual mean precipitation?can not influence the?¹³C and?¹⁵N of different vegetative organs of P.tabacum,unless to change the factors of limestone cave where P.tabacum living.