Analysis On The Distribution Characteristics Of Quercus Section Cyclobalanopsis

Understanding the suitable distribution range of forest dominant species and the impact of climate change on their distribution is the basis for the protection and utilization of forest resources.Asian subtropical evergreen broad-leaved forest is rich in species and high endemism.However,in the context of global climate change,the distribution dynamic of this vegetation is not clear.The Quercus section Cyclobalanopsis belongs to the Fagaceae,widely distributed in the eastern Himalayas to southern Japan,and China’s Qinling-Huai River to the Malay Archipelago.It is the important tree species that constitutes East Asian tropical and subtropical evergreen broad-leaved forests,and it has important ecological functions.Based on the construction and comparison of the simulation effects of different species distribution models,this study analyzed the species diversity distribution pattern of the Quercus section Cyclobalanopsis and its distribution dynamics under different climate scenarios by the ensemble model.It aims to provide important basic data and guidance for the protection and restoration of subtropical vegetation types in our country and provide an important theoretical basis for the introduction and domestication of Quercus section Cyclobalanopsis,the formulation of conservation measures,and the protection of endangered tree species.The main results are as follows:(1)Comparison of models for the potential distribution of different speciesA total of 54 and 83 distribution points for Q.lamellosa and Q.macrocalyx were collected.According to the 8 climatic variables screened by each,Maximum Entropy Model,Artificial Neural Network,Generalized Linear Model,Generalized Additive Models,and Random Forest were used to simulate the current(1950-2000)potential distribution area,and build the ensemble model based on single models.The simulation results show that the potential distribution areas of the two target species in current were more consistent with the actual distribution points;The main potential distribution of Q.lamellosa was in the Himalayas-Hengduan Mountains area;the main potential distribution area of Q.macrocalyx was concentrated in southern China to the territory of Vietnam;Random forest and generalized linear models have higher accuracy(specific parameters),and generalized additive models have the lowest accuracy(specific parameters).The TSS value and AUC value of the ensemble model were much higher than other single models.(2)Potential distribution and diversity pattern of Quercus section CyclobalanopsisA total of 6246 distribution samples of 88 Quercus section Cyclobalanopsis species were collected,and the kernel density analysis method was used to evaluate the species diversity of Quercus section Cyclobalanopsis.The result shows that Nanling Mountains area was the diversity center of Quercus section Cyclobalanopsis.Selected 24 widespread and dominant species to simulate the potential distribution area by the ensemble model.The model results showed that the average AUC and TSS value were 0.92±0.06 and 0.76±0.14,respectively.The modeling results were stable and the model performance were good;Dominant environmental factors that affected the potential distribution of Quercus section Cyclobalanopsis were annual mean temperature(Bio01),Isothermality(Bio03),Temperature Annual Range(Bio07)and Precipitation of Warmest Quarter(Bio 18);It could be seen that there were positive/negative skew correlation between the habitat suitability of most Quercus section Cyclobalanopsis species and temperature or precipitation related factors;The results of the current potential distribution suitability showed that the distribution of the higher suitable areas for species in the Quercus section Cyclobalanopsis were roughly consistent with the trend of the south Himalayas,Hengduan Mountains,Xuefeng Mountains,Nanling,Luoxiao Mountains and Wuyi Mountains;The areas with higher suitability in the southwest were mainly concentrated in the southern foothills of the Himalayas and the Hengduan Mountains.The areas with higher suitability in South China were concentrated in the south of the Nanling Mountains.The areas with higher suitability in Central and East China were mainly concentrated in Xuefeng Mountain,Nanling Mountain Range and Wuyi Mountain Range.The regions with higher suitability in Southeast Asia were mainly concentrated in Vietnam and Laos.(3)The impact of climate change on the species distribution of Quercus section CyclobalanopsisBased on the results of the ensemble model,the potential distribution of species in Quercus section Cyclobalanopsis in the Last Glacial Maximum(about 22,000 years ago)and the future(2041-2060,2081-2100)were inferred.The results show that the species a diversity in Central and East China has decreased to varying degrees under different climate scenarios;The suitable distribution area of Quercus section Cyclobalanopsis migrates northward with time and climate change;Since the LGM,the suitable areas for species in southwest have been reduced,while species distributed in other regions have expanded to varying degrees;Under future climate scenarios,the suitable areas for the Quercus section Cyclobalanopsis distributed in the southwest,Central and Eastern China would shrink to varying degrees.The tree species of Quercus section Cyclobalanopsis distributed in South China and Southeast Asia would be expanded.Species distributed across regions showed a variety of patterns according to the different regions in which they were located.The results of this study show that the reliability and accuracy of the combined model simulation results are high and can be used in production practice.Nanling is the diversity center of Quercus section Cyclobalanopsis.It is recommended to establish an ecological corridor in this geographic unit,and take different forest management measures adopted for migrated out,migrated in and reserved areas,so that species can better cope with future climate changes.