Study On The Potential Habitat Impact Of Climate Change On Hopea Exalata Based On MaxEnt By

Hopea exalata has the characteristics of small distribution but concentrated distribution.However,the current cognitive restrictions on the habitat selection conditions of Hopea exalata are not conducive to the comprehensive and effective protection of Hopea exalata.This paper studies the potential distribution in Sanya,and analyzes the macro environmental variables such as climate and topography that affect the distribution of Hopea exalata so as to provide theoretical support for the local and ex situ protection of Hopea exalata.56 environmental variables such as climate factor,soil factor,elevation,slope direction,runoff accumulation and solar radiation were obtained by selecting the environmental variables related to the growth of Hopea exalata.The main environmental variables affecting the potential distribution of Hopea exalata were analyzed by using MaxEnt model after the environmental variables were screened by principal component analysis.BCC_CSM1.1 model was used to analyze the change of the potential distribution of Hopea exalata in the future climate from the perspective of centroid migration and fitness index change.Finally,the AUC value of MaxEnt model test data is 0.992,and the AUC value of training data is 0.991.And the AUC value of test data and training data are both greater than 0.9 in future climate,so the simulation effect of the model is good.The contribution rate and importance value of each environmental variable to the model under the historical climate are obtained.The results show that the contribution rate of bio₁4 to the model is 41.4%,and the importance is 42.3%;The contribution rate of elevation to the model is 17.9%,and the importance is 34.8%;The contribution rate of bio-19to the model is 12.8%,and the importance is 7.7%;The contribution rate of t_gravel to the model is 5.2%,and the importance is 9.5%.The centroid ’s coordinates of region of core-suitable of Hopea exalat under the historical climate conditions is 109°39’30"E,18°22’46"N;The centroid ’s coordinates of region of core-suitable under the RCP4.5 scenario is 109°39’11"E,18°22’ 23 "N;The centroid ’s coordinates of region of core-suitable under the RCP 8.5 scenario is 109 °39’25" E,18°22’ 05"N;The centroid’s coordinates of region of core-suitable under the RCP 6.0 scenarios is 109°39 ’13"E,18°21’25 "N.The centroid’s coordinates of region of core-suitable under the RCP 2.6 scenarios is 109°39’04"E,18°22’14"N.The main conclusions of this study are as follows:（1）The main environmental variables that affect the potential adaptive area of Hopea exalat are BIO₁4,DEM,BIO₁9,and t_gravel.The suitable growing conditions of Hopea exalat are as follows:There is a lower precipitation demand in dry and cold seasons;The proportion of gravel in the upper soil is required to be lower,and the growth probability of Hopea exalat is almost 0 when the proportion of gravel reaches 15%;The altitude range of the suitable growing region of Hopea exalat is 200～400m.（2）The suitable range of Hopea exalat is mainly in Ganshiling of Sanya.In the future,under the four scenarios of rcp8.5,rcp6.0,rcp4.5 and rcp2.6,from the perspective of centroid migration,it is found that the centroid of the core suitable area of Hopea exalat moves southward.From the change of fitness index,it is found that the potential fitness areas of Hopea exalat all tend to extend to the South and northwest of Ganshiling nature reserve.