In order to explore the karyotype characteristics and evolutionary relationship of different populations of Sophora alopecuroides， the karyotype characteristics and evolutionary of six natural geographic populations distributed in Inner Mongolia， Gansu， Ningxia were analyzed respectively， and chromosome conventional slicing technology was used. The results showed that the number of chromosomes in six populations of S. alopecuroides was constant，2n=2x=36. There were two types of central centromere（m） chromosome and sub-central centromere（sm） chromosome in three populations. Chromosomes of most populations were only central centromere chromosome except for Population 3 in Wuwei， Gansu， with central centromere and sub-central centromere chromosome. The average arm ratio of chromosomes ranged from 1.19 to 1.37， the length ratio was between 1.72 and 2.19， and the karyotype asymmetry coefficient was from 54.30% to 57.17%. There were three types of karyotypes including 1A， 3A and 2B for S. alopecuroides. The karyotype asymmetry coefficient of population 3 of S. alopecuroides was the largest and the evolutionary degree was the highest， while those of population 19（Ordos， Inner Mongolia） was the smallest and the lowest. Cluster analysis showed that the six populations of S. alopecuroides were aggregated into two major branches of A and B. Branch A could be divided into two subclades of C and D. Among them， population 5（Wuwei， Gansu） and population 13（Alxa， Inner Mongolia） were clustered into subclade C， which had the closest relationship， whereas population 3 was clustered into subclade D alone， which was relatively distant with two populations from subclade C. Similarly， branch B could be further divided into subclade E and subclade F respectively. Subclade E was consisted of population 19 and population 43（Ordos， Inner Mongolia）， which had the closer relationship， while Subclade F only contained population 17（Yinchuan， Ningxia）， which had the relatively distant with two populations from subclade E. In this study， the chromosome number， karyotype characteristics and evolutionary trend of S. alopecuroides were discussed at the population level， which provided cytological evidence for further studying the system and evolution， and genetic diversity of germplasm resources of S. alopecuroides.
To clarify the codon usage pattern and phylogenetic relationship of the chloroplast genome between Ranunculaceae and Paeoniaceae， 33 species of Ranunculaceae and seven species of Paeoniaceae were used as materials， and the analysis software CodonW， online software CUSP， and R software were used to analyze the codon characteristics of chloroplast genes， while the MAFFT software， MEGA software were used for phylogenetic analysis respectively. The results showed that the chloroplast genomes of Paeoniaceae and Ranunculaceae （except Columbine） had a high consistency of high frequency codons， with 29 high frequency codons， which were basically biased towards ending with A/U， but the optimal codon were different. The codon bias of the chloroplast genome of Ranunculaceae and Paeoniaceae was mainly influenced by natural selection， and the codon bias of the chloroplast genome of Paeoniaceae was more affected by natural selection than that of Ranunculaceae. The phylogenetic relationship based on the complete chloroplast genome sequence and the CDS sequence of the chloroplast genome showed that although the phylogenetic relationship based on the complete chloroplast genome sequence and the chloroplast genome CDS sequence of Paeoniaceae was different， they could be divided into the peony group and the peony group. The phylogenetic relationship of Ranunculaceae based on the entire chloroplast genome sequence did not conform to the classification relationship of Chinese flora， but it supported the division of Ranunculaceae into four subfamilies and 14 families. The analysis results supported that Paeoniaceae were independent from Ranunculaceae and Ranunculus， and were classified into Saxifraga.
The perennial fern Pteris vittata（Pteridaceae） is a hyperaccumulator of arsenic and is used for remediation of soils contaminated by heavy metals. In order to identify the characters that the P.vittata sporophyte thrives in xeromorphic rocky environments and hyperaccumulates ions， the brightfield and epifluorescence microscopy were used to investigate the anatomical structures and histochemical features of this species. The results were as follows： （1）The structure of the rhizome， adventitious roots and leaves of P. vittata sporophytes were all primary structures， the adventitious roots had an vascular bundles， endodermis with Casparian band， lignified sclerenchyma layers， cortex， rhizodermis. （2）The rhizomes had a dictyostele， endodermis， cortex， epidermis， cuticle. （3）The stipes had a single vascular bundle with a central endodermis， cortex， sclerenchyma layers， while the epidermis had a cuticle. The pinnae had bifacial mesophyll with palisade tissue and spongy tissue， the epidermis had a cuticle. （4）The surfaces of the rhizodermis and the root hairs were pectin-rich and underlain by a lignified cortex， and permeability tests using a berberine tracer showed that these structures retained large volumes of berberine. In summary， the suberized endodermis， lignified sclerenchyma layers， bifacial mesophyll， and a cuticle， all of which reflect an adaption to xeromorphic rocky environments. The result of the berberine permeability test are consistent with the hyperaccumulation of ions by P. vittata.
Based on the survey of orchid resources in the lower Yarlung Zangbo River region， the priority protection value of each endangered plant was quantitatively calculated using multiple evaluation indexes to determine the endangerment level and priority protection sequence of rare and endangered orchids in the region by combining data collection and specimen review. The endangerment level of 156 species of endangered orchids in 60 genera in the lower Yarlung Zangbo River region was evaluated， among which 15 species were in critically endangered（CR） status， 46 species in endangered（EN） status， 78 species in vulnerable（VU） status and 17 species in near threatened（NT） status； the priority protection range value was 0.853 9-0.416 8， among which 45 species were classified as Class Ⅰ protected plants， 72 species as Class Ⅱ protected plants， and 39 species as Class Ⅲ protected plants.The results of this study differ greatly from the endangered degree and priority protection level of various protected plant lists， and most of the orchids are under enhanced threat in this region， which is consistent with the real survival status of these orchids in the lower Yarlung Zangbo River area， and the protection of orchids in this region is urgent and should be given sufficient attention.
In order to better understand the origin of plant， phylogenetic differentiation and evolution process of flora， to promote the protection of endemic plants， endemic flora regions in Northeast China were systematically investigated respectively， including the species composition， family structure and genus structure， life-form composition， flora characteristics and geographical distribution. The results showed that：①There were 289 species of Chinese endemic plants， 109 species of endemic plants of Northeast China， 154 species of endemic plants of Changbai flora region， 16 species of endemic plants of Daxing’anling flora region， 10 species of endemic plants of Mongolia steppe flora region and 20 species of endemic plants of Northern China flora region. ②Among all kinds of endemic plants， herb were the most， and perennial herbs were the most dominant， while trees， shrubs and vines were the less. ③Chinese endemic plants were densely distributed in Daxing’anling Mountains and Changbai Mountains. ④The concentrated distribution areas of endemic plants of Northeast China were distributed along the main mountains in Northeast China， indicated that the endemic plants of Northeast China mainly originated from mountains. ⑤Changbai flora region had high level of endemism， showed the mature nature of the flora. Daxing’anling flora region， Mongolia steppe flora region and Northern China flora region had low level of endemism， showed the young nature of the flora. ⑥Endemic plants of Changbai flora region were densely distributed in Changbai Mountains. The endemic plants of Daxing’anling flora region were evenly distributed， and the endemic plants of Mongolia steppe flora region and the endemic plants of Northern China flora region were scattered.
To reveal whether the testa and endosperm are main factors restricting the seed germination of Sinopodophyllum hexandrum， anatomical structure of seed in different germination stages（1， 7， 14， 21 and 28 d） of S. hexandrum were observed by using the tissue sectioning microscopy， and morphological characteristics of plants were investigated after the germination seeds sowing 7-210 d. The seed of S. hexandrum was composed of testa， endosperm and embryo. The testa contained episperm and endopleura， the episperm was compact and regular and it was composed of palisade cells and epidermal cells from outside to inside， and the endopleura was composed of 5-6 layers sponge cells. The endosperm accounted for most of the seed， included micropylar endosperm and outer endosperm. The embryo consisted of radicle， hypocotyl and cotyledons， surrounded by the compacted testa， multilayer-micropylar endosperm and outer endosperm. During the germination stage， the radicle and hypocotyl began to elongate from 1-7 d， two cotyledons separated from 7-14 d， the radicle broke through the micropylar endosperm and testa from 14-21 d， the radicle， hypocotyl and cotyledons continued to expand and elongate from 21-28 d. 3 function leaves and 5 adventitious roots were formed on average after seeding for 210 d. The compacted testa（physical dormancy） and multilayer endosperm（mechanical dormancy） were the two main factors that restricted seed germination of S. hexandrum.
To improve the characteristics of the spore，elater and oil body of Lophoziaceae and to provide detailed information for classification，the morphology of 11 species of the Lophoziaceae was observed by scanning electron microscopy， 6 species provided for the morphological characteristics of spore and elater，and 9 species provided for oil body. The results showed that：①The spores of 6 species of Lophoziaceae were spherical， near spherical or elliptical with brown， reddish-brown or yellowish brown respectively. The spore size of them were from 10-16 μm belonging to MI type，and their faces near pole were usually concave. The ornamentation of the above spores were verrucose，clavate，spinate，granular or short baculite respectively. ②The elaters of 6 species of Lopholoziaceae were densely bispiral with obtuse both ends，and their cuticle were smooth or granulate.③The oil bodies of 9 species of Lophoziaceae were spherical，elliptical or oval，with the diameter between 3-10 μm. The detailed description and illustration on morphological evidence of spores，elaters and oil bodies of 11 species of Lophoziaceae might provide the elemental data for the systematic taxonomy and evolution of Lophoziaceae.
In order to reveal the distribution pattern of genetic variation and haplotype geographical distribution pattern of Allium macrostemon， and to infer the refugia in the quaternary glaciation， the chloroplast gene fragments（psbA-trnH， rps16 and trnL-F） and nuclear gene fragments（ITS） of A. macrostemon in 14 regions of China were analyzed respectively. The results showed that the genetic diversity of A. macrostemon chloroplast gene（cpDNA） was lower than that of nuclear gene（nrDNA） （cpDNA：HT=0.868； nrDNA：HT=0.890）. The AMOVA analysis of cpDNA and nrDNA showed that the genetic variations occurred mainly among populations （cpDNA：92.84%； nrDNA：98.40%）， there was significant genetic differentiation among populations（cpDNA：Nst=0.918，Gst=0.866，Fst=0.928；nrDNA：Nst=0.984，Gst=0.855，Fst=0.984）， and had an obvious phylogeographical structure in A. macrostemon populations（Nst>Gst）. A total of 11 chloroplast and 14 nuclear haplotypes were identified in the A. macrostemon populations. The haplotype network and geographical distribution map showed that the chloroplast haplotype H3 and nuclear DNA genotype H1 had the highest frequency and were located in the center of the network structure， which might be the ancient haplotype. In addition， the glacial refuge hypothesis suggested that the region with high genetic diversity， ancient haplotype and more endemic haplotype might be the glacial refugia of A. macrostemon. Therefore， it was speculated that in the quaternary glaciation， A. macrostemon might be multiple glacial refuges in Dapanshan， Tianshui and Tonghua. The analysis could provide references for the evolution of similar herbs and enrich our understanding of the molecular phylogeography of herbaceous plants in East Asia.
Saxifraga sect. Ciliatae Haworth belonging to Saxifraga Tourn. ex L. has highly species richness， but phylogenetic relationships within the section have not been well resolved. S. subsect. Hirculoideae Engl. is the largest subsection in sect. Ciliatae， which is mainly distributed in the Qinghai-Tibet Plateau and its surrounding areas. Based on the morphological characteristics， the subsect. of Hirculoideae was divided into three complex group， and the species attaching to the bumped vein at the leaf submarginal was classified to the S. diversifolia complex. Based on specimen inspection， the morphological and distributional data of 657 specimens from 24 species and two varieties were obtained， and 24 morphological characteristics of each specimen were used for principal component analysis and cluster analysis respectively. A total of 443 geographical distribution records was used to construct the distribution pattern of complex group. The cumulative contribution rate of the first seven principal components with an eigenvalues greater than one was low， only 67.748%. Among the characters of ‘cauline leaves petiolate’， ‘proximal median cauline leaves shape’， ‘inflorescence’， ‘proximal median cauline leaves size’， ‘sepal veins confluent at apex’， and ‘base of leaves cordate’， the contribution value of the first three principal components was large 0.6， could be used as the key characters for classification and identification of S. diversifolia complex. Based on morphological clustering and geographical distribution patterns， S. diversifolia complex could be divided into three branches： Himalayan Branch， Mountains Around Sichuan Basin Branch and Hengduan Mountains Branch（Contained a widespread species： S. egregia）， and the result was also supported by PCA.
Xanthopappus subacaulis is an endemic medicinal plant growing in the alpine meadow of the Qinghai-Tibet Plateau（QTP）. To explore the influence of Quaternary climatic oscillations on the population genetic structure and distribution pattern of X. subacaulis， 3 chloroplast DNA fragments（psbA-trnH， rbcL and psbI-psbK） from 123 individuals of 20 populations were sequenced and analyzed respectively in the present study. The results showed that 6 haplotypes were detected in X. subacaulis， among which H1 was an ancient haplotype. All populations of X. subacaulis had haplotype H1 except for P7. H3， H5 and H6 were private haplotypes， among which H3 was a private haplotype of population P7， and H5 and H6 only existed in P18. H2 and H4 were mainly distributed in the population of Qinghai Lake basin. The total genetic diversity（He） and nucleotide diversity（π） were 3.101 and 0.008 903， respectively. The genetic variation among populations（68.98%） was higher than that within populations（31.02%）， and the genetic differentiation among populations was relatively higher（FST=0.689 85，P<0.01）. The genetic differentiation coefficient NST of populations（0.727） was higher than that of GST（0.656）（P>0.05）， which indicated that there was no obvious phylogeographical structure in the sampling regions. The results of mismatch distributions and neutrality tests revealed that the population of X. subacaulis might have experienced recent expansion. Therefore， the study suggests there are micro-sanctuaries in Qinghai Lake basin of Qinghai Province and Lintan region of Gansu Province during the Quaternary glaciations， and suggests that the Quaternary climate change and QTP uplift shape the modern geographical distribution pattern of X. subacaulis.
Improving reproductive ability of invasive plants might be an important mechanism for successful invasion， but there might be different in variation of reproductive organ traits among the different habitats， especially in the trade-off relationship. The plant Plantago virginica was taken as material， the inflorescences in three habitats including lawn， wasteland and understory， were collected to investigate the differences of morphology， biomass， and the allometric relationship of spikelet and peduncle among different habitats. The results showed that， there were significant differences in most inflorescence morphological and biomass indexes of P. virginica in different habitats. The inflorescences of P. virginica in lawn and wasteland habitats were slender， while that in understory habitat was short and strong. The allometric relationships among different traits of reproductive organs of P. virginica were both conservative and variable， showing different environmental sensitivities. The size dependence of reproductive resource allocation of P. virginica in different habitats was also inconsistent. Therefore， the inflorescence traits and resource allocation of P. virginica in different habitats are both plastic and relatively conservative， which might be an important manifestation of its high invasive ability.
In order to rationally protect and explore the wild poisonous plant resources in the Namjagbarwa region， the distribution of families and genera， the composition of life forms， the toxicity， poisonous parts and toxicological effects of plants were analyzed by field investigation， specimen investigation and related literature books inspection. The results showed that there were 77 families， 167 genera and 242 species of wild poisonous plants in the Namjagbarwa region， among which the dominant families mainly included Araceae， Ranunculaceae， Ericaceae， Fabaceae and Asteraceae respectively. The most poisonous plants with herbaceous life form were 138 species in total. Most of the plant toxic parts were poisonous whole grass， a total of 109 species. There were 184 species with mild poisonous plants， including 50 minor toxic plants， there were only five kinds of highly poisonous and three kinds of strong poisonous. There were 19 poisonous nectar source plants， Scrophulariaceae and Ranunculaceae were dominant； in terms of toxicology， most of them were nervous system poisoning. There were many kinds of poisonous plant resources in the Namjagbarwa region， but there was less use of these resources. It was necessary to strengthen the understanding and protection of poisonous plants， and carry out rational development and explroation.
Inflorescence is a key character affecting plant reproduction and plays an important role in plant taxonomy and phylogeny. The inflorescence types of Discorea nipponica are diverse， but relevant data are few available and often controversial. In order to distinguish the inflorescence types and characteristics of D. nipponica， a morphological observation combined with paraffin sectioning techniques was carried out to investigate the morphological characters， quantitative characters and development process of inflorescences of D. nipponica respectively. The results showed that the female inflorescence was an axillary spike， and had vestigial anther and pollen sac but didn’t produce pollen. The male inflorescence of D. nipponica showed different characteristics from the description of existing data. The male inflorescence was an infinite one composed of scorpion-tailed monochasium， which belonged to the mixed inflorescence with axillary or terminal buds developed， was shaped like spike. The leaves on some lateral branches of male plants degenerated， and axillary inflorescences gradually shortened towards the tip， presenting conical type with the terminal inflorescence. Male inflorescences had higher values than female ones in terms of average length， the number of florets， the density of florets， and flowering time respectively. The study showed that the male and female inflorescences of D. nipponica morphologies were consistent with the evolution from finite to infinite， exhibited relatively primitive features， which ensured the success of pollination and adaptability to the environment.
Akebia trifoliata belongs to Akebia of the Lardizabalaceae family， and it is a dioecious， monoecious woody vine， with economic value for medicine and food. In order to understand the sexual reproduction process of A. trifoliate， analyze the reproductive reasons of the low seed setting rate of this species under natural conditions， and provide a theoretical basis for its hybrid breeding and new variety cultivation，the embryological characteristics of mega-and microsporogenesis and female and male gametophyte development of A. trifoliate were observed by paraffin section technology. The main results showed that A. trifoliata had six stamens with four locules in each， and the anther wall was fully differentiated， and it was composed of epidermis（1 layer）， endothecium（1 layer）， middle layers（2-3 layer） and tapetum（1 layer） from outside to inside， tapetum belonged to glandular type respectively. The cytokinesis of the microspore mother cell in meiosis was of simultaneous type， and the tetrads were arranged in a tetredraltah， mature pollen grain was two-celled. There were little pollen abortion， and abortion occurred at the microspore tetrad stage. The ovary was one locular， parietal placentation， ovules were hemianatropous， bitegminous and crassinucellate. Its megaspore was of monosporogenesis type， and tetrads were linearly arranged. The chalazal end megaspore developed into functional megaspores， which underwent three times consecutive mitosis and further developed into polygonum embryo sac with seven cells and eight nucleus，another three megaspores degenerated. The early development of the stamens in the female flowers was normal， but the microspores did not develop further until the uninucleate pollen grain stage， the tapetum was not completely degraded， and the anther wall did not crack， the degeneration of the carpel of the male flowers was due to the early lack of development，the carpels heal incompletely， and no ovules are produced.The process of the mega-microsporogenesis and development of female and male gametophyte of A. trifoliata were normal， which was not the reason for the low seed setting rate， but may be related to external factors affecting pollination.
Brachytheciaceae is one of the most diverse and problematic taxonomic families in pleurocarpous mosses. In this paper， the morphology of pseudoparaphyllia of 594 specimens in Brachytheciaceae， which belonged to 19 genera and 44 species， were studied. Results were as follows： ①In Brachytheciaceae， pseudoparaphyllia was triangular to semicircular foliose. According to its apical characteristics， pseudoparaphyllia could be divided into two types： truncate or obtuse， and acuminate. ②Except for the genus Brachythecium， morphology of pseudoparaphyllia among the different species in the other 18 genera was basically the same. ③Morphology of pseudoparaphyllia had taxonomic significance in the genus level.
The Qinghai-Tibet Plateau（QTP） is one hotspot of studies about biodiversity， speciation and adaptive evolution. Gentiana algida var. purdomii， belonging to Gentianaceae， is endemic to the QTP and has high value in medicine. Based on populations across the QTP， we assessed its genetic structure， divergence and demographic history based on plastid and nuclear DNA sequences in this study. Palaeo-distribution was also reconstructed by species distribution model. High level of genetic diversity was observed in G. algida var. purdomii. Genetic differentiation was high in plastid data（FST=0.452） but low in ITS data（FST=0.022）， indicating high level of gene flow in G. algida var. purdomii. Neutrality test and mismatch distribution analysis both showed signatures of recent population expansion. Species distribution modelling showed slight range expansion from the Last Glacial Maximum to the present day. Divergence time estimates suggested that the onset of intraspecific diversification generally fell into the Quaternary. The results indicated that the intraspecific divergence in G. algida var. purdomii should be related to geographical isolation and range fragmentation in glaciations. This study provides insights into genetic differentiation， adaptive evolution and conversation in Gentiana as well as alpine plants in the QTP.
To investigate the genetic and phylogeography structure of Artemisia intramongolica， which was an important sand-fixing plant in Hunsandak sandy land in China， the homologous single-copy nuclear genes c9065 and c7847 were developed by transcriptome sequencing， and then eight natural populations of A. intramongolica were studied. The results showed that the total length of c9065 and c7847 were 485 bp and 457 bp， respectively， with 14 and 19 variable loci， and 48 and 40 haplotypes were obtained. Based on c9065 and c7847， the haplotype diversity（Hd） was 0.871 6 and 0.934 8， respectively， and all populations were above 0.8. The total nucleotide diversity（π） was 0.008 2 and 0.005 9， respectively， and all populations were above 0.005， indicating that both species and populations had high genetic diversity. The results of AMOVA analysis showed that 99.398% and 98.908% of genetic variation existed within the populations of A. intramongolica based on c9065 and c7847， respectively， with gene flow（Nm）of 6.810 and 7.270， respectively， much greater than 1， indicating that there was extensive gene exchange among populations of A. intramongolica. Based on c9065， Nst<Gst， although Nst>Gst by c7847， but the difference was not significant（P>0.05）， indicating that A.intramongolica population did not exist phylogeographic structure. The neutral test showed that Tajima’s D values for both nuclear genes were all not significant（P>0.05）， while Fu’s Fs values were all significant（P<0.05）， and combined with the mismatch distribution analysis， A.intramongolica experienced limited population expansion under the neutral mode.
The morphological description of Aster longipetiolatus C.C.Chang was inadequate in the original literature when compared with the specimen which we collected from its type locality， and there was a lack of cytological reports. The detailed morphological and cytological description of A. longipetiolatus were carried out， and the new evidences of plant taxonomical revision would be provided. The results showed that： ①There were some newly-discovered characteristics for A. longipetiolatus. For example， the receptacle was convex， phyllaries 3- or 4-seriate， ray floret staminodes， lamina pilosulose and achenes 5-ribbed； ②Its cytology evidence revealed that the chromosome number was 2n=18 and the karyotype formulae was 2n=2x=16m+2sm， belonged to the type 1A.
To identify the cell types and analyze the transport mechanism of vascular tissue and explore the cell evolution during tree evolution，a comprehensive anatomical study was carried out on a kind of special tracheids of Tetracentron sinense. After slicing and dissociating， the distribution position and morphological characteristics of the special tracheids of the 34-year-old T. sinense were observed by using optical microscope and scanning electron microscope. The results showed that the special tracheids were arranged from the inside to the outside radially in the horizontal of the tree， and ran through the growth ring boundary. Most of them were in one row， and few were in two rows. And each special tracheid was connected with wood ray cells on one or both sides. In the longitudinal direction， the special tracheids were connected individually or with several cells terminally. There were three main types of special tracheids： fusiform without end wall， fusiform with one sloping end wall or with two sloping end walls. The average length of special tracheids was 286.44 μm. Its cross section was quadrilateral. The average tangential width of special tracheids were 55.22 μm respectively. The average wall thickness of special tracheids was 1.53 μm. The two ends of the special tracheids were closed without perforation. The number of pits on the side wall of special tracheids was large and the pit membrane was clearly visible. There were a large number of bordered pits on the wall in tangential section， which were arranged in opposite， alternated and scalariform pitting. The single pits on the radial wall were rounded or ellipse. There were 2-10 pits， arranged in 1-4 rows in per region. There were no pits between the special tracheids and the normal tracheids on the radial wall. The distribution of special tracheids has certain regularity. Compared with normal tracheids， the special tracheids were much shorter in length， and the tangential width were slightly larger. The type and arrangement of the pits were similar to those of the pits on the wall of general hardwood species. The shape of the special tracheid was different from the general vessel in the hardwood， and it was in an intermediate state of the evolution from tracheid to vessel， indicated a certain level of evolution of this type of cell.
To explore the potential suitable distribution and ecological adaptability of Rhodiola tangutica on the Qinghai-Xizang Plateau， based on 38 distribution sites of Rhodiola tangutica across the plateau and seven environmental factors across current and future five periods， a relationship model between the distribution of Rhodiola tangutica and environmental factors was constructed using the MaxEnt model. The potential geographical distribution patterns for the current period（1970-2000） and four future periods（2030s， 2050s， 2070s and 2090s） under the SSP245 scenario were simulated and verified. The findings revealed that： （1）Altitude（Alt） and precipitation of the driest month（Bio14） were the most important ecological factors influencing the geographical distribution of Rhodiola tangutica， contributing rates of 89.3% and 4.9%， respectively. （2）under the current climatic context， the total suitable distribution area of Rhodiola tangutica on the Qinghai-Xizang Plateau was approximately 195.21×10? km2， predominantly situated in the southern and northeastern parts of Qinghai， northwestern Sichuan， and central Xizang. （3）compared with the current period， the total suitable distribution area of Rhodiola tangutica in the next four periods would not change obviously； however， the area of high suitability would increase， with a tendency of concentrated distribution to the central Qinghai-Xizang Plateau.
