4.1 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).
“ཨོ་པེ་སེ་ཏང་” (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 . Traditionally, Hani ethnicity took the tuber root of the species in decoction to treat stomachache in south Yunnan, China .
“སྲི་ཝ་པ་” (Arisaema utile) was the most frequently cited substitude grain (CIGrain=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 flatulence and gastrointestinal discomfort in southern western Ghats, Tamil Nadu, India . 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 .
“ཕེ་མིང་འེན་རྡོ་” (Actinidia venosa) was the most mentioned wild edible fruit (UR = 46, CIFruit=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].
“སྐེང་ཀྲོ་” (Schisandra grandiflora, S. neglecta, S. sphaerandra) was another very important wild edible fruit that supplements nutrients seasonally, with 45 use-reports. The local name of “སྐེང་ཀྲོ་” has three plant taxa. Sometimes, locals collected a large bag of “སྐེང་ཀྲོ་” 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 [53-55].
“སྲི་ཝ་པ་” (Urtica membranifolia) was the most mentioned wild edible vegetable (UR = 45, CIVegetable=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.
4.2 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 . 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 . 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 .
In the past, the Sherpa in Chenthang lived on hunting, and on this basis, they formed a “hunting culture” suitable for their economic life . 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 . 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 specific time periods (Fig. 3).
4.2.1 Carbohydrate supplement
WEPs played an important role in supplementing staple food under normal circumstances . 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 ‘ཕིས་ཆིན་’ (Cyclobalanopsis gambleana) to be processed into flour for consumption. From August to November, we collected ‘ཨོ་པེ་སེ་ཏང་’ (Arisaema utile) to be processed into flour 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 fills 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% . 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 . 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% . 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 flour 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 first recorded as edible. All of these substitude grain plants provide an important starch supplement to help them survive food shortages.
4.2.2 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 . In remote areas with inconvenient transportation, wild vegetables were the main source of vitamins for local people, especially women and children .
Wild vegetables, regarded as healthy and beneficial foods, were rich in trace elements, cellulose, flavonoids, saponins and vitamins . 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 fiber, 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 . 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 . 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 . Kiwifruit was rich in minerals and vitamins, which could enhance human immunity, digestion, and metabolism, and improve nutritional status .
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 . 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 . The further scientific utilization and development of WEPs would help provide protection for human nutrition, especially people in remote areas.
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-inflammatory, anti-oxidant and anti-diabetic effects through the study of 56 kinds of wild vegetables . 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.
4.3 Socio-economic supplement
Local people could earn extra income by selling some of the economic WEPs . And local people usually sold wild edible plants to urban residents and tourists in the market to increase their income . 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 profit of 150,000 yuan in 2016, which helped 15 poor households get rid of poverty . But while wild plants increase local income, excessive collection has caused a certain degree of damage to the local plant 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 . Unsustainable collection had also led to a decrease in the population of some edible plants with high market prices . 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.
4.4 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 . 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 . The utensils used in their homes, such as fruit baskets, and fruit plates, were all made of bamboo . 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 . The rhizome of Equisetum hyemale were found to be eaten for the first 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 influence the use of wild plants in different areas . 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.
4.5 Detoxification 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 , 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 .
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 .
སྲི་ཝ་པ་ (Arisaema utile) is a multifunctional plant, and its tuber detoxification 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 flowing out and the sourness can be smelled, and the detoxification 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 .
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 scientific methods to detect and monitor the toxicity of these edible plants and raising public awareness of food safety based on scientific research can fundamentally solve the problem. Future research could pay more attention to the local knowledge of food safety.