Based On MaxEnt And 3S Technology Simulating The Suitable Habitat Distribution For Two Endemic Plants In Hainan Island Under Climate Change

Modelling potential distribution ranges for species is an effective and important means of protection and breeding work for wildlife,especially for the rare and endangered species or the narrow and specific species.It is of great significance to define the suitable habitat distribution of species and its restrictive distribution factors for their protection and further study.Impatiens hainanensis and Dendrobium sinense both are endemic species to Hainan Island.I.hainanensis is endemic plants to limestone region and D.sinense is a typical orchid epiphyte.Habitat distribution of both they is extremely narrow,and they have strict requirements on habitat.In recent years,because of the distruction of human activities,the habitat of these two species has been damaged seriously,so it is urgent to define their suitable habitat distribution areas and to protect them.In this paper,based on field investigation records of species occurrence sites and 18 environmental factors which were important to the growth of I.hainanensis and D.sinense,Maximum Entropy(MaxEnt)algorithm and 3S technology were used to predict the distribution ranges of I.hainanensis and D.sinense in current period.The suitable habitat distribution of these two species were predicted and their distribution change were analyzed under RCP4.5 and RCP8.5 climate scenario in 2050s and 2070s.At the same time,the dominant environmental factors and their suitable range to I.hainanensis and D.sinense were discussed.The main results of this study are as follows:(1)The indicative value of all four evaluation metrics of model simulation results for these two species were above 0.9,indicating the result is exactly accurate and the MaxEnt model can effectively predict the potential suitable habitats for I.hainanensis and D.sinense,(2)The current potential suitable habitat areas for I.hainanensis in Hainan Island is approximately 4,194.2 km2,totally accounts for 12.0%of land areas on Hainan Island.Slope,precipitation of driest quarter,precipitation of driest month and coefficient of variation of precipitation seasonality were the four main environmental factors which influencing the distribution of I.hainanensis.The appropriate scope of these four major factors for I.hainanensis:slope was 16-50°,precipitation of driest quarter was 22-50 mm,precipitation of driest month was 6-13mm,coefficient of variation of precipitation seasonality was 72.5-82%.I.hainanensis tends to grow in the habitat with low precipitation,large variation of precipitation seasonality.(3)The current potential suitable habitat areas of D.sinense in Hainan Island was about 537.9 km2,totally accounts for 1.5%of land areas on Hainan Island.Elevation,max temperature of warmest month,mean annual temperature and min temperature of coldest month were the four domain environmental factors.The suitable range of these four factors:elevation was 1,070-1,600 m,max temperature of warmest month was 24.5-29 ?,mean annual temperature was 16.5-19.5 ?,min temperature of coldest month was 7.2-10.6?.D.sinense tends to grow in the high mountain environment with cool temperature,low temperature of warmest quarter and elevation above 1000m.(4)In the future 2050s and 2070s,the suitable habitat of I.hainanensis may be increased under the two climate scenarios of RCP4.5 and RCP8.5.The suitable habitat of I.hainanensis may be changed from fragmentation to continuous,and it's distribution tends to expand eastward.The suitable habitat of D.sinense may be slightly reduced and may move towards to higher altitude areas.