Being Blessed by Qomolangma: The Diversity and Local Knowledge of Wild Edible Plants Used by Chenthang Sherpa People to Treat Seasonal Food Shortage

Background Wild edible plants (WEPs), which are identied as non-cultivated and non-domesticated plants for food. WEPs provided food, nutrition, herbs and other plant products for people in underdeveloped areas, such as the Everest region, to maintain their daily lives. Chenthang Town is the only Sherpa ethnic township in China. The core purpose of this research is to investigate, collect, and record the WEPs and related local knowledge and functions in the Sherpa community. Looking forward to answering the ultimate question,

Sherpa people in China remains a blank. Therefore, it is necessary to investigate the WEPs and related local knowledge of the Sherpa in China.
Local people living in rural areas and remote areas usually supplement their daily diet by using WEPs, and have accumulated a wealth of plant knowledge. The ecological conditions and cultural signi cance of WEPs seem to affect local people's knowledge and consumption of WEPs [34]. The diversity and function of the plants in the local environment are closely related to the local people's understanding of the plant world in the surrounding environment. Therefore, the core purpose of this research is to investigate, collect and record the WEPs and their local knowledge and functions in the Sherpa community. Looking forward to answering the ultimate question, why did they choose these plants?
Speci cally, the purpose of this study was to investigate, collect and record the traditional use of WEPs and relative local knowledge accumulated by Sherpa people in China. The present study aims to answer the following questions: (1) What plants are consumed by Sherpa people, and how to prepare? (2) What plants are important to the local community, And why? (3) What functions did these plants provide? (4) Why did Sherpa people choose these plants? 2 Material And Methods

Study sites
Chenthang Township which is the only Sherpa ethnic township in China, located in Mount Everest national nature reserve of southeast Qinghai-Tibet plateau, and the border between China and Nepal ( Fig. 1). Its total area is 430.62 square kilometers. There are 133.4 km 2 virgin forest, and the forest coverage rate is 98 percent, but the arable land area which slope is above 45° is only 59.87 hectares [35].
Based on 2016 demographics, there are 2,387 herdsmen in 513 households in the town, including 2,362 Sherpa, accounting for 99 percent of the total number [36]. The elevation of Chenthang Town is from 2040 to 5,500 meters. And the annual frost-free period is around 200 days, and the annual average rainfall is over 1000mm. The annual average temperature is 13.76℃, and the annual extreme minimum temperature is 1℃. Due to the effect of warm moist air ows in the Indian Ocean, forming a subtropical monsoon climate. All the materials going in and out of Chenthang Town depend on manpower and livestock, because of geographical limitations [35]. Even now, Chenthang Town even haven't a vegetable marketplace. The grain output of Chenthang Town in 2010 was 148.46 tons [35], which is not enough to meet the food demand of Sherpa. Wind damage [37], hail damage [38], earthquake [39] and other natural disasters caused serious damage to farmland and pasture in Xigaze area. Moreover, Xigaze City was one of the three main battle elds for poverty alleviation in the Xizang Autonomous Region [40].
The Sherpa language is a dialect of Dbus-gtsang Tibetan language, which is written in Tibetan alphabet [31]. Sherpa traditional houses are made of timber or bamboo, Sherpa people are housed in sheds while grazing animals. The houses were built in a special form, usually with herringbone roofs, surrounded by thick walls made of stones and covered with thin planks. The main local crops are nger millet, winter wheat, corn, buckwheat, potatoes and other crops. And the stable food is Tsamba made of nger millet. The main economic activities are logging and harvesting of medicinal plants, which are either sold in cash or traded for other goods and services [35]. In 1990s, people in Chenthang exchanged daily necessities in Riwu town 100 kilometers away. Carrying special products such as timber, medicine and bamboo baskets, they had to walk from Chenthang to Riwu Town about 5 to 7 days.

Field work and data collections
The eld works were carried out in the six Sherpa communities of Chenthang Township (Table 1), from September 2019 to August 2020. First, we visited the township committee for obtaining the eld work permission. We explained our purpose to committee leaders and asked for helps which mainly included providing local guides, introducing us to local villagers and other necessary eldwork assistance. The WEPs and related local knowledge were collected by semi-structured interview and direct observation. All of the eld works were carried out with informed consent. Because of the relative backwardness of the educational conditions, most of local people especially the aged community members could not communicate uently in mainstream Chinese language. Therefore, the eld works were performed with the assistance of local guides. The informants of semi-structured interview were selected randomly from the local community members, and we mentally chose older people as the priority informants. The Semistructured interview was used to get information on the local knowledge of WEPs which was provided by local people. Vernacular names, life forms, use parts, use, collect seasons, economic values, and culture signi cances of plants were recorded. The direct observation was used to record the image and video data of the local uses of WEPs with digital camera. Meanwhile, the voucher specimens were collected. The semi-structured interviews were performed based on the following questions: 1) Would you mind to list some wild plants you often consume and which of them are edible? 2) Where are you collect them and when are their harvest seasons?
3) For these wild edible foods, could you tell us how to cook them for food? 4) Besides foods, do you use them for other purposes? And what are these purposes? Could you tell us some traditional/old story or legend about these plants?

Information document and plant specimen identi cation and preservation
During the interview, we used a portable notebook to record information, and then organized the information into an Excel sheet (Microsoft Corporation, http://www.microsoft.com/) in a uni ed format, with "one plant to one local name" as a basic unit. We are trying to record all the information provided by the informants into the excel sheet. The entire interviews were conducted in the Sherpa language which were translated into Mandarin by the local guidance. The vernacular name of the plants were recorded in Sherpa language which was written in Tibetan alphabet [31,41].
During the eld survey, with the help of local guides, we collected plant specimens based on the principle of one plant with one vernacular name. Digital photos were also taken for later identify the scienti c taxa of plants. The collection of the voucher specimens and the photographing of the photos were obtained with permission of the informants and the local community management department. And the specimen identi cation was performed and stored in the herbarium of Kunming Institute of Botany, Chinese Academy of Sciences (KUN). Due to objective factors, we did not collect a voucher specimen of Cardamine purpurascens. But this specimen was identi ed based on the video taken by the Sherpa (see additional le 1

Data Analysis
We adopted Use-report (UR) and Cultural Important Index (CI) as an ethnobotanical index.
Use-report (UR) was the sum of information on local utilization and knowledge [45,46]. A use report is that a speci c use of an ethno-species cited by an informant. In this study, all the scienti c taxa of plants are consistent with the ethno-species.
Cultural Important Index (CI) was de ned as the sum of the percentage of respondents who mentioned various uses for a certain useful plant. In this study, we used CI to evaluate the importance of WEPs in the daily diet of Sherpa people. Also, CI considers the various uses of each plant, and the dissemination of knowledge (for each use-category of each plant). In other words, the diversity of the plant's uses and degree of recognition of the informants to each use-category were included. It can evaluate the comprehensive utilization value of each useful plant. When u = 1, i.e. when the plant only one usecategory, CI and RFC index equal in value, but they refer to different meanings [45]. CI is calculated by the following formula: In order to evaluate the comprehensive utilization value of each edible plant, we calculated the CI value. In addition, we calculated CI values for different use-categories of each plant in order to understand the acceptance of the unique use-category of a particular plant.

WEPs categories
These species were identi ed into 78 ethno-species by local people, and the vernacular name of each ethno-species was recorded. In this study, we interviewed a total of 78 informants who provided us with 1,199 use-reports. These use-reports were classi ed into 6 use-categories ( Table 2). The most frequent use-category was "fruit" (485 use-reports), followed by "vegetable" (451 use-reports), "substitute grain" (102 use-reports), "healthcare food" (78 use-reports), "seasoning" (36 use-reports) and "beverage" (47 usereports). Plants that could be used as a direct starch supplement (e.g., tuberous or rhizome of some plants) or processed into starch (e.g., acorns) Substitute grain 10 102 Plants that could be added to dishes or soups to increase the avor of food

Seasoning 9 36
Plants what could be processed into home-made liqueurs or alcoholic beverages and processed into herbal teas Beverage 6 47

The most popular WEPs
In total, we collected 84 plant taxa and 50 of them exceeded 10 use-reports. But there were only 1 usereport for six plants and 10 plants from 2 to 5 use-reports. TheWEPs CI value ranged from 0.01 to 0.77.
According to the URs and CI value of ethno-species, the top 5 popular ethno-species were (Solena amplexicaulis, CI = 0.77), (Arisaema utile, CI = 0.65), (Actinidia venosa, CI = 0.59), (Schisandra grandi ora, S. neglecta, S. sphaerandra, CI = 0.58), (Urtica membranifolia, CI = 0.58) ( Table 3). These plants have been used by the Sherpa for a long time, and most of the plants are still being used. For example, until now, from May to July every year, local women went together to collect the tender stems and leaves of A. utile, and dried them naturally for winter consumption.

Collecting calendar of WEPs
According to the description of the local people, we recorded the farming season and collection time of each plant, and drew a collecting calendar of WEPs (Fig. 2). There are 8 circles in Fig. 2, corresponding to six use categories and two agricultural activities. The circle is divided into 12 equal parts, one part represents one month. The shade of green to indicate the number of plant species collected in each part of each circle. The deeper the green, the more plant species are collected. The Sherpa collect WEPs almost throughout the year, except for January and February. The most concentrated period of wild vegetable collection was from May to July and wild fruit was mainly from September to October. Substitude grain was mainly collected from July to November. Most of the used parts of spice and healthcare plants are roots or seeds, which are collected from July to November (Fig. 2).
The top 5 ethno-species are displayed outside the circle. The larger the picture, the higher the frequency of being cited. The position of the picture represents the time when the plants were collected. Solena amplexicaulis was collected from June to November. Arisaema utile was collected from May to October. Actinidia venosa was collected from September to November. Schisandra sphaerandra was collected from August to November. Urtica membranifolia was collected from May to July.

The important WEPs
Based on the information provided by the informant, we carried out a quantitative analysis and the results showed that there were some WEPs that were very important to the Sherpa people. These plants were collected seasonally and used for multiple purposes or mentioned frequently (Table 3).
" " (Solena heterophylla) was the most frequently cited plants in the recorded plants. Local people collect S. heterophylla for multiple purposes. The young leaves could be collected and cooked as vegetable, and the matured fruits could be collected as seasonal fresh fruits. It should highlight that the starch-rich tuber root of S. heterophylla is one of the important substitude grain sources for Sherpa people during the periodic and aperiodic famine. S. heterophylla is also used by other indigenous tribes settle in Himalaya region. Our previous study showed that the species was consumed as fruit by Monpa in eastern Himalaya [47,48]. Besides, S. heterophylla is also used in local medicine. Sherpa people in Nepal consumed small amounts of fruit or root cream to treat throat infections associated with fever, and often ate ripe fruit to ensure that abdominal ulcers were cured [31]. Traditionally, Hani ethnicity took the tuber root of the species in decoction to treat stomachache in south Yunnan, China [49]. " " (Arisaema utile) was the most frequently cited substitude grain (CI Grain =0.53). From August to November, its tubers are collected and prepared as substitude grain to treat seasonal food shortage. The tender stems and leaves of A. utile are local wild vegetable, and they were dried naturally and stored for cooking in winter or during major festivals. Sometimes, the Sherpa digs A. utile back and plants it in the homegarden so that it can be eaten at any time. The fresh fruits of Araceae plants are local herbal medicine to treat atulence and gastrointestinal discomfort in southern western Ghats, Tamil Nadu, India [50]. Khampa Tibetan people stir-fried young leaves of Arisaema erubescens as a supplementary vegetable and used tubers to relieve cough and treat hemoptysis and pneumonia in Northwest Yunnan, China [51].
" " (Actinidia venosa) was the most mentioned wild edible fruit (UR = 46, CI Fruit =0.59). It is an important and easily available wild edible fruit for the Sherpa to supplement vitamin C from September to November. Previous studies also showed that many species of Actinidia are rich in vitamins [7,47,52].
" " (Schisandra grandi ora, S. neglecta, S. sphaerandra) was another very important wild edible fruit that supplements nutrients seasonally, with 45 use-reports. The local name of " " has three plant taxa.
Sometimes, locals collected a large bag of " " and ate it when the family rests while working in the farm. In China, S. chinensis, a traditional Chinese medicine, has been widely used in medicine and health food in recent years. It contains a variety of chemical components in the treatment of the central nervous system, cardiovascular and cerebrovascular system, hypoglycemic, liver protection and other aspects of potential pharmacological activities [53][54][55]. " " (Urtica membranifolia) was the most mentioned wild edible vegetable (UR = 45, CI Vegetable =0.58). It is an important source of vegetables for Sherpa people from May to July every year, and is often processed into a paste and eaten with potatoes.

Resilience and resistance of Sherpa food systems
WEPs are still an important part of the daily diet in many remote areas and underdeveloped areas, which is especially obvious during seasonal food shortages [22]. Due to the different growth cycles of plants in nature, the collection of wild plants in many places has obvious seasonality [10,52]. The acquisition of WEPs was closely related to the shortage of cultivated food resources [11]. When normal food supply mechanisms were destroyed, such as famine, wild food was very important for the poor and the landless. The growth of crops takes time, and wild vegetables can grow quickly, which enhances the resistance of the local food system [4].
In the past, the Sherpa in Chenthang lived on hunting, and on this basis, they formed a "hunting culture" suitable for their economic life [35]. Previously, there was no land, and the agricultural management method was slash and burn cultivation. Based on 2010 statistic, Chenthang has a population of 2093 and an annual grain output of 148.46 tons, with an average of about 80 kilograms of per person [36]. Moreover, the native fruit trees only have Prunus mira Koehne and Walnut, which are low productivity and seasonal restrictions. And due to the huge altitude gradient, a diverse climate gradient is formed in Chenthang, which creats a diversity of wild plants. Therefore, WEPs are chosen by Sherpa people (and there is no other choice) as an important source of nutrients such as vitamins, minerals, and trace elements. The survey results showed that the diverse WEPs collected at different time periods provided different functions and services for the Chentang Sherpa people at speci c time periods (Fig. 3).

Carbohydrate supplement
WEPs played an important role in supplementing staple food under normal circumstances [56]. From January to March, and from August to November, there were a period of food shortage. "When there was a shortage of food, from January to March, we collected ' ' (Cyclobalanopsis gambleana) to be processed into our for consumption. From August to November, we collected ' ' (Arisaema utile) to be processed into our for consumption" The oldest woman described.
Chentang Town is under heavy snow from January to March, Sherpa people mainly consume the stored grain to survive. So every August and September, Sherpa women collect the nuts of C. gambleana, process them into starch and store them, and consume it in winter. Locals told us that the meal made from the starch of C. gambleana lls them up all day. In 2009, Liu tested the starch content of C. gracilis and C. glauca, the former content was 20.9%, and the latter was 26.2% [57]. In Asia and the Mediterranean basin Fagaceae plants were widely used for cooking, pasture, building materials, and the most used parts were nuts [20,47,58,59]. We can speculate that genus of Cyclobalanopsis has a certain content of starch.
After July, the staple food of the locals was almost every day potatoes. From August to November, A. utile is collected, processed and consumed. In Nepal, tuber of Arisaema intermedium was important wild supplementary food, which could be used as a condiment under normal circumstances and also be used as an emergency food ration during poor harvests and food shortages [60]. In dried tubers of A. elephas, yunnanense and erubescens, the starch content was 15.37%,61.60% and 52.91%, respectively, among the three kinds of starch, and the amylopectin content ranged from 29.1-32.0% [61]. The starch content of A. utile needed further research.
In addition, other WEPs are also used as seasonal alternatives to grain consumption. the roots of Solena heterophylla were dug out, mashed, boiled into porridge or dried and ground into our to make Tsampa. And in winter, Sherpa people also baked the rhizomes of Polygonatum verticillatum, P. oppositifolium, P. cirrhifolium and Paris polyphylla as food. Here are a few less-known but not missed alternative grain plants, namely the root tubers of Equisetum hyemale and bamboo seed that are also consumed as a source of starch. And the tuber of E.hyemaleis rst recorded as edible. All of these substitude grain plants provide an important starch supplement to help them survive food shortages.

Nutrition supplement
WEPs are an important alternative source for people in remote and poor areas to obtain nutrients and biologically active compounds, such as vitamin and mineral, in addition to cultivating vegetables and fruits [62]. In remote areas with inconvenient transportation, wild vegetables were the main source of vitamins for local people, especially women and children [63].
Wild vegetables, regarded as healthy and bene cial foods, were rich in trace elements, cellulose, avonoids, saponins and vitamins [64]. From May to July each year, a large number of wild vegetables are collected and consumed, some of which are consumed as soon as they are collected, while others are processed and stored. Such as the tender stems and leaves of A. utile, the tender leaves of Polygonatum odoratum and Pteridium revolutum, which were naturally dried and stored for consumption when there were no vegetables in the winter or there are in big festival like weddings. And wild fruit also collected.
Some studies had shown that WEPs contributed nutrients to human and revealed the nutrients contained in these plants. Yang analyzed the dry samples of P. revolutum and found it contained 29.42% protein, 7.4% soluble sugars, 16.27% crude ber, 1.05% crude fat, potassium content 3772 mg/100 g, and magnesium content 377 mg/100 g, calcium content 215 mg/100 g, iron content 5.589 mg/100 g, manganese content 10.420 mg/100 g, which were much higher than cabbage and spinach [65].
According to the determination, the leaves of Urtica laetevirens from May to July contained from 23.73-34.75% of crude protein and 17 kinds of amino acids. And aspartic acid and serine reached the maximum value (3.33%) in June, and histidine and threonine reached the maximum value (2.52%) in May. Minerals and vitamins had higher levels from May to July, and then showed a downward trend [66]. The analysis of the nutritional components of Schisandra chinensis showed that crude protein content of S. chinensis was from 10.67-11.69% after entering the mature period, and Schisandrin was from 2.63 to 5.47 g/kg. And it contained 7 amino acids and essential elements (P, K, Mg, Fe, Zn and Cu) that are necessary for the human body [67]. Kiwifruit was rich in minerals and vitamins, which could enhance human immunity, digestion, and metabolism, and improve nutritional status [68].
People in different regions of the world were still consuming WEPs, but the important contribution of these plants to human diet was still not recognized in developed regions [62]. The research of wild edible vegetables could clarify the importance of WEPs to the rural dietary structure, while also providing potential trace element resources for the urban population [69]. The further scienti c utilization and development of WEPs would help provide protection for human nutrition, especially people in remote areas.

4.2.3Healthcare supplement
WEPs usually have the function of medicine and food. And wild vegetables not only provide minerals and vitamins but can be used as medicine for people's food security and health [10,70]. For example, it was found that WEPs have anti-cancer (especially breast and stomach cancer), anti-in ammatory, antioxidant and anti-diabetic effects through the study of 56 kinds of wild vegetables [71]. In our study, 11 WEPs we collected have medicinal functions. The methods of preparation, local names, parts used and the ailments treated of these plants were recorded. The results are consistent with the statistics of common and endemic diseases -dysentery, intestinal parasitic diseases, arthritis and so on -in Chenthang town by Xigaze City and Dingjie County health Station in Xizang Autonomous Region [72,73]. I have to mention an interesting phenomenon. Polygonatum verticillatum, P. oppositifolium, P. cirrhifolium and Paris polyphylla were traditionally used as edible plants instead of herbs in Chenthang. The leaves of these plants were consumed as soup, and rhizomes were roasted in winter to supplement starch. With the opening of Chenthang, Sherpa people learned some medical knowledge from tourists and drug dealers. Now they know how to use the roots of these plants to cook a decoction to treat cold. The exchange of information affects the dissemination of knowledge to some extent.

Socio-economic supplement
Local people could earn extra income by selling some of the economic WEPs [10]. And local people usually sold wild edible plants to urban residents and tourists in the market to increase their income [74].
With economic and social development, Chenthang Town welcomes tourists from all over the world with an open attitude. With the help of the Chinese government, some wild vegetables and fruits such as Pteridium revolutum and Vaccinium glaucoalbum were processed into products by Sherpa people and sold to tourists (Fig. 3). Moreover, the long-standing bamboo thangka of Sherpa was also made into products. Although bamboo thangka could be produced only three months in a year, there was a pro t of 150,000 yuan in 2016, which helped 15 poor households get rid of poverty [75]. But while wild plants increase local income, excessive collection has caused a certain degree of damage to the local plant Page 14/23 community. In recent years, drug dealers had come to Chenthang Town to purchase these medicinal plants in large quantities, resulting in the overharvesting of these plant resources. Studies have shown that because of huge market potential and the uncontrolled collection of medicinal plants, which has led to the disappearance of the herb from its natural habitat [76]. Unsustainable collection had also led to a decrease in the population of some edible plants with high market prices [51]. While WEPs are threatened, the local knowledge associated with them is also under risk. While developing the economy, we must pay attention to sustainable development based on the local ecological environment and biological resources. Therefore, it is necessary and urgent to systematically investigate and record local knowledge of plants and local biological resources.

cultural implications
Many WEPs also had cultural value, some of which were used in religious and cultural activities and were considered sacred. Some vegetables also had a certain social and cultural carrier function, accompanying their collection and donation activities, as a link to promote internal communication in the community [77]. Sherpa people had a long history of bamboo weaving. With the rise of stainless steel and plastic appliances, bamboo weaving appliances have gradually lost their advantages, so bamboo weaving skills are facing a crisis of loss. They combined traditional bamboo weaving techniques and thangka painting techniques to create bamboo weaving thangkas. The bamboo slices processed by them are as thin as a cicada's wing and as tough as a pampas grass, covering it on the text, and the text is clearly visible. Weaving these thin bamboo slices into thangkas not only retains the true qualities of thangkas, but also adds new agility to the thangkas. It is extremely artistic and this is the inheritance of national culture [35]. The utensils used in their homes, such as fruit baskets, and fruit plates, were all made of bamboo [75]. Therefore, bamboo weaving has become a cultural symbol of the Sherpa. In our research, there are 26 kinds of plants with two or more use-categories, which also demonstrate the importance of these plants for local survival and as a cultural heritage.
The diversity of parts and methods of using WEPs also presents the unique food culture of Sherpas to a certain extent. The purpose of local people using wild plants varies according to their priority of needs [11,50,78]. Plants are usually used by people for various purposes, such as food, medicine, fuel, and economic income. In Chenthang, there is a very interesting phenomenon. For example, the Solena heterophylla in this study, the Sherpa only developed the function of food. In Yunnan, thousands of miles away, the Hani people use used S. heterophylla tuber decoction to treat stomachache [51]. The rhizome of Equisetum hyemale were found to be eaten for the rst time. Polygonatum verticillatum, P. oppositifolium, P. cirrhifolium and Paris polyphylla which were famous Traditional Chinese Medicine, were traditionally used as wild vegetable and substitute grain plants instead of herbs by Sherpa people. Although study had shown different geographical conditions, vegetation types and cultures may in uence the use of wild plants in different areas [78]. In other words, people in different regions have strong regional and cultural characteristics in the selection and utilization of WEPs. Further research should focus on this issue.

Detoxi cation and potential safety hazards
Although WEPs have many advantages, there are also some concerns. Wild species which often contain compounds toxic to humans, such as nitrates, oxalic acid [62], excessive consumption of high levels may give cause problems for human health. Therefore, it is necessary to consider the toxic compounds contained in these wild edible vegetables [79].
In the long-term living practice, Sherpas have also developed special methods to make themselves eat safer. For example, Sherpas call the process of removing tannins from nuts of Cyclobalanopsis gambleana "Remove black water". After the collected nuts are shelled and processed into large particles, they are wrapped into leaves of the azalea and washed continuously with water. When the "black water" is removed, the large particles of nuts will turn yellow. "If the harvested nuts are not processed, they will taste bitter. Furthermore, if you eat too much, you will get constipation." the locals told us. The reason may be that the tannins were not completely removed [80].
(Arisaema utile) is a multifunctional plant, and its tuber detoxi cation process is known to Sherpas as "Squeeze the juice". Fresh tubers are processed into large pellets and then wrapped in azalea leaves, and then a heavy stone is pressed on them. After about 15 days, there is no juice owing out and the sourness can be smelled, and the detoxi cation process is completed. In the process of processing, if you do not take protective measures, your hands will be swollen, itchy, or even peeling. At this time, you need to apply some butter. The cause of the adverse reaction may be that the calcium oxalate needle crystals contained in the Araceae hadn't been removed cleanly [81].
But local knowledge alone is not enough to manage food safety. Some WEPs can still have some side effects after being processed. For example, fresh tubers of the Solena amplexicaulis are often processed into porridge by Sherpa people, but even being heated and stewed for a long time, locals still fell the chin itch and stomach upsets after eating the porridge. Therefore, applying modern scienti c methods to detect and monitor the toxicity of these edible plants and raising public awareness of food safety based on scienti c research can fundamentally solve the problem. Future research could pay more attention to the local knowledge of food safety.

Conclusion
In total, the study examined 84 species of WEPs used by the Sherpas, belonging to 62 genera in 40 families. The local name of each Botanical taxa was recorded. Sometimes a local name has multiple Botanical taxa. The results showed that the most frequently mentioned family by the informants was Rosaceae, following by Urticaceae. According to the URs and CI value of ethno-species, the top ve popular plants were (Solena amplexicaulis), (Arisaema utile), (Actinidia venosa), (Schisandra grandi ora, S. neglecta, S. sphaerandra), (Urtica membranifolia). We interviewed 78 informants who provided us with 1,199 use-reports. These use-reports were classi ed into 6 usecategories. the most frequent use-category was "fruit", followed by "vegetable", "substitute grain", "healthcare food", "seasoning" and "beverage". According to the description of the Sherpa people, we drew a collecting calendar of WEPs. The Sherpa collect WEPs almost throughout the year, except for January and February.
In our research, WEPs have made a huge contribution to the Sherpa dietary in supplementing carbohydrate, nutrition, and healthcare during the seasonal food shortage. These products and services also showed that the Sherpa had a deep understanding and close connection with the environment in which they lived. Additionally, Sherpa people learned some medical knowledge from tourists and drug dealers with the opening of Chenthang. For some poisonous plants, local people have developed unique detoxi cation methods, but from the public health perspective it is not enough to rely solely on local knowledge to treat the food healthy of edible plants. Future research could pay more attention to the local knowledge of food safety.
In general, the diversity and products and services of WEPs based on local knowledge enhance the resistance and resilience of local food supply system to treat food shortage which might be the answer to why the locals choose these plants.

Declarations Acknowledgements
We are very grateful to the informants for sharing their knowledge with us. We also are very glad to say " " (Sherpa language: thank you) to all of the local people who had helped us in the eld works. We

Availability of data and materials
Please contact the corresponding author for data requests.
Ethics approval and consent to participate