Diversity Of Orchid In Hainan Tropical Rainforest National Park And Its Priority Protection Strategy

As one of the most advanced and evolved plant groups in the world,orchids have their unique charms that have been impressed by people since ancient times.However,in recent years,the diversity of orchids has been greatly threatened due to ecological specialization,extremely stringent habitat conditions and anthropogenic disturbances.The Hainan Tropical Rainforest National Park has just been established,covering all the important nature reserves of the island and integrating the most precious biological resources.It is imminent to carry out the protection of rare and endangered animals and plants,mainly orchids.In this context,the research takes wild orchids in the national park as the research object.First,evenly lay out the sample lines and squares in the whole area to find out the basic situation of orchid resources,and compare the differences in the diversity of orchids in different regions and different altitudes from both horizontal and vertical directions;afterwards,the CCA method was used to explore the influence of habitat on the species composition,and the GLM model was used to fit the response of the richness and abundance of orchids to the habitat;finally combined the above-mentioned research results use comprehensive scoring and the Dobson method to rank priority protected species and areas.The main conclusions are as follows:（1）The survey found a total of 209 species of orchids in 74 genera,of which 11 are endemic species,and 16 species are only distributed in Hainan;life type is complete,the terrestrial orchid mainly include Cranichideae,Orchideae,and Coelogyninae;epiphytic orchid mainly include Malaxideae,Podochileae and Vandeae（which with obvious tropical and subtropical property）;R/T value of the genus and species is significantly higher than that of whole Hainan Island.（2）Bawangling had the highest Margalef richness index(D_MG=13.43),while the Shannon-Wiener diversity index（H’=3.71）and Pielou evenness index（E=0.77）of Wuzhishan are both the largest,the maximum value of the Simpson dominance index appears in the Jianfengling（λ=0.21）;the richness index of epiphytic orchids is the highest in Yinggeling(D_MG=3.79),while the diversity index and evenness index of this type of orchid in Bawangling are the highest（H’=2.85,E=0.82）,the dominance index of the Limushan is the largest（λ=0.20）;species number of‘ep./li.’orchid is the largest,and the diversity trend of each branch is the same as that of all species;the maximum richness index and diversity index of terrestrial orchid appear in Wuzhishan(D_MG=3.84,H’=2.63),Janfengling and Bawangling have the maximum values of evenness and dominance index respectively（E=0.83,λ=0.64）;the maximum dominance of the‘te./li.’type orchid appears in the Diaoluo,and the relationship between other index is the same as the overall situation.（3）It can be seen that no matter whether it is overall or for a certain life type,orchid in geographically adjacent area will always have a higher similarity coefficient;among them,the similarity of orchid in the Bawangling and Yinggeling always has the highest similarity,the number of species they share reaches 103,and all orchid or‘te./li.’orchid reached a moderately similar（Cj=0.5393;0.5714）,while the‘ep./li.’orchid have reached a very similar level（Cj=0.7857）;Limushan and Jianfengling,which are the farthest apart,their orchid have the lowest similarity（Cj=0.3758）.（4）The richness of orchid shows a“hump”trend in the vertical direction（R²=0.9228;0.921;0.8827）,all species and two major life-type orchid have their species richness peaks at H₄;the analysis result based on the diversity index also point out the high diversity of orchid in the H₄band,but the maximum value of the orchid diversity index（H’=2.67）of the terrestrial category will slightly shift upward to the elevational band of H₆;for all species or epiphytic orchid,the evenness index and the dominance index have their own minimum（E=0.5828;0.5959）and maximum（λ=0.1667;0.1874）in the H₃.（5）In terms of all species,there are 95 and 109 species in H₂ and H₃ and H₃ and H₄elevational bands respectively,the compositional similarity coefficients of orchid in these two groups both exceeded 0.5,reaching a moderately similar level;the epiphytic orchid have a higher degree of similarity,in the 4 elevational bands from H₂ to H₅,the similarity between two adjacent elevation bands or one elevation band apart exceeds 0.5;te.&‘te./li.’orchid in each elevation band have not reached a moderately similar level.（6）The 6 habitat factors ranked by CCA explained 6.2%of the total variation of species composition（p=0.002）,and the most explained variation was elevation（1.2%）,and karst and valley topography also have a significant explanation rate（0.6%;0.4%）;whether it is in a univariate model or a full model,the effect of vegetation type,topography,aspect,and slope on species richness variation is very significant（p<0.01）;elevation has a significant effect only in the full model（Wald=2.160,p=0.0404,Coefficient=3.319100e-04）;in addition,the canopy closure and interference degree do not show a significant driving effect on the richness of orchids;among the 5 types of vegetation,Liquidambar formosana forest（Co.=-0.6;-7.6）has significant negative effects in both the univariate model and the multiple model;the valley（Co.=0.37;3.4）and Karst（Co.=0.85;7.8）topography can significantly promote the increase in the richness of orchids;as the number of plots on the steep slope of the southeast slope increases,the species of orchids tend to increase.Except for the independent effects of canopy closure（Wald=3.102,p=0.0654）and interference degree（Wald=3.936,p=0.123）,the effects of other habitat factors on abundance in the univariate regression model are all extremely significant level（p<0.01）,but the effect of aspect in the multiple regression model is no longer significant（p>0.05）,that is to say,in the actual living environment of orchids,the habitat heterogeneity brought about by the aspect cannot drive the obvious variation of the abundance of orchids in a small area.（7）Among all 1,844 plots deployed in the survey,only 33 plots had relatively primitive habitat conditions and were not significantly disturbed;the environment of most plots was disturbed and destroyed by extremely stringent habitat conditions and anthropogenic disturbances,of which anthropogenic factor accounted for 78.69%.According to the comprehensive scoring method,Cymbidium insigne,Cym.lii,Anoectochilus hainanensis,Phaius hainanensis,Dendrobium sinense,Den.chrysanthum,Phalaenopsis hainanensis,Liparis bautingensis,Oxystophyllum changjiangense,and Rhynchostylis gigantea are selected as priority protection top 10 species;Dobson method pointed out that the order of priority protection areas is Wuzhi Mt.>Maoyang>Exian-Wangxia>Limu Mt.>Sanjiao-Lomei Mt.>Qingchun Mt.>Nankai-Mengya>Yajiadaling Mt.>Chahekou>Nanba River-Rainforest valley>Jiaxi>Heiling Mt.>Shiqing waterfall>Mahuo Mt.>Dongwu-Futou Mt.>Zapo-Shijie>Jianfengling fifth division>Diaoluohoushan Mt..The top 7 areas can protect 78.30%（>75%）of indicator orchid,and the protection rate of all area reaches 92.45%.