4.1 Diversity of WEF species and uses
The ethnobotanical survey recorded 52 species of WEFs from 35 botanical families in Trashigang and Trashiyangtse Dzongkhag, indicating a high number of species compared to other studies previously undertaken in Bhutan, in which 32 species of wild vegetables were reported from Tsirang Dzongkhag . However, the finding is less when compared to the studies conducted in Dagana and Trashiyangtse Dzongkhag, which reported 241 and 165 species of wild edibles [27,38]. Similarly, a study conducted by Matsushima et al.  identified 172 wild edible species in Bhutan. The possible explanation for these differences could be the inclusion of all wild edibles like wild vegetables, wild fruits, cane, mushroom, and orchid, while the present study focused only on the WEFs. The number of wild edibles recorded in the present study is similar to those found in other regions of Asia, such as Pakistan , Indonesia , Western Himalayas , and Ethiopian countries [43,44].
The present study showed that many WEFs were collected from the forest habitat compared to the surrounding field. A similar finding was also reported by Regassa et al.  in Ethiopia. This result aligns with the term “wild,” which is more generally associated with unmanaged environments. The majority of the WEFs were collected during summer and autumn compared to winter and spring due to favorable climatic conditions for fruit setting and maturity, which is similar to the findings reported in Nepal and Yunnan [21,46]. Similar uses of WEFs among different communities in the two Dzongkhags indicate the existence of common traditional uses across different cultures and geographical areas, which is consistent with the reports of past studies in Ethiopia and Nepal [4,21]. However, a higher citation for medicinal use of WEF in Trashigang Dzongkhag might be due to some of the respondents being local healers and lay monks who commonly use wild edibles to treat local people. Chauhan et al.  also reported that the local healers were the most knowledgeable about wild plants.
WEFs were mostly consumed as both raw and cooked/processed as most of them were used after drying or fermenting into wine. For example, fruits of Docynia indica and Pyrus pashia were consumed raw as well as dried for consumption. This result differs from the findings in Ethiopia where WEFs were mostly consumed raw [44,47,48]. Contrarily, species like Dioscorea bulbifera, Colocasia esculenta, and the flowers of Oroxylum indicum were consumed after cooking. WEF species such as Rubus ellipticus, Docynia indica, and Juglans regia were relatively common and familiar to the respondents and were widely collected and consumed by the local people. Hence, these species were extensively listed in both the Dzongkhags, which is similar to the findings of studies elsewhere where they found that the plant use probability is higher for the most commonly found species in the area [49,50]
The ethnobotanical information showed that WEFs have multiple uses in addition to food, with a higher citation for their use as a raw material for furniture and construction comparable with the report of Ethiopia , where the people highly exploited the species with multiple uses. The medicinal use of WEFs was mentioned generally for traditional remedies to treat common illnesses such as cough, dermal issues like skin irritation, pimples, and dandruff problem, which correspond to the study in Ethiopia . In this study, one plant species was cited for multiple health purposes. For example, Terminalia bellirica was cited concerning six health uses: to treat cough, sore throat, diarrhea, ingestion, constipation, and asthma. However, medicinal use of the species was one of the least cited uses by the respondents, probably due to the easy accessibility of modern health facilities such as BHU in each geog which is similar to the reports of Weckmüller et al. . Similarly, Zanthoxylum armatum was reported to be the most commonly collected and consumed spices, as was the case in Yunnan, China . Likewise, Yangtse geog is popular for its traditional paper made from the bark of Daphne bholua, which is used for painting and writing religious scripts. A similar finding was reported in Arunachal Pradesh, where the climatic condition and religion are alike in Bhutan .
4.2. WEF consumption
The present study demonstrated that the respondents mostly collected WEFs for self-consumption, with only a few species being sold in the local market for income generation, probably due to no or low market value for the WEFs . Barely 9% of the respondents sold the WEFs to the local market for income generation, including the fruits of Zanthoxylum armatum, Mangifera sylvatica, and Juglans regia. Despite 100% citations for the food use by the respondents, the consumption of WEF has decreased compared to the past. Our observation found that the primary reasons for decreased consumption of WEFs were: 1) the introduction of improved varieties, 2) easy access to improved varieties in the market, 3) less demand of WEF in the market, 4) change in food preferences and 5) lack of knowledge to identify WEF species. These reasons are interrelated, as the introduction of improved varieties may have improved the accessibility to improved fruit varieties in the market, leading to decreasing demand for WEFs in the market. Accordingly, Aryal et al.  also reported the negligence of traditional food due to changing food habits, taste, and availability of readymade foods in Western Himalaya. Generally, in addition to being easier to manage, the improved varieties are widely perceived as having better quality than WEFs. As WEFs grow in less ideal conditions, they are often smaller and produce fewer fruits that are less juicy and more seeded compared to the improved ones . Hence, it is understandable that the preference shifts from the wild to the improved varieties.
The present study found that middle-aged people between 41-50 years consumed more WEFs than the younger and elderly. These middle-aged people are generally energetic in the villages, working closely with nature. Moreover, this age group has more indigenous knowledge, resulting in higher consumption. However, the finding contrasts the reports of other studies where young boys involved in cattle herding in the forest consumed more WEFs [21,43]. Likewise, the Trashigang residents consumed more WEFs than the residents of Trashiyangtse. This unequal distribution in consumption might be because of the difference in accessibility and acceptability of WEFs in the two Dzongkhags, which is in line with the findings of Bvenura & Sivakumar . The locations of WEFs in Trashiyangtse may be situated extremely far away from the village where people have to walk very long distances affecting their consumption. Moreover, the result showed that only 26% of the respondents in Trashiyangtse have consumed WEFs in the last twelve months, indicating their dependence on improved varieties. Indigenous knowledge was significantly associated with WEF consumption which corresponds to the findings of Reyes-Garcia et al. . Generally, people consume WEFs when they know the fruit is edible or has some health benefits. Contrary to the studies in Ethiopia and Indonesia, there was no significant association of WEF consumption with gender and education level [44,59].
4.3 Indigenous knowledge pattern
In line with studies elsewhere [21,60], this study showed that indigenous knowledge of WEF differed significantly between Dzongkhags, with the respondents of Trashigang having more knowledge compared to those of Trashiyangtse. An average citation of 14.5 and 11.4 WEF species in Trashigang and Trashiyangtse justifies the predominance of high indigenous knowledge in Trashigang Dzongkhag. Local healers and lay monks would have contributed a higher level of indigenous knowledge in Trashigang Dzongkhag. Notably, age groups had a significant association with indigenous knowledge of WEF. In this regard, we found high indigenous knowledge for middle-aged people in their 40’s and 50’s compared to younger and older age groups which are in line with a study in Northwest Pakistan . However, it contradicts other studies in Nepal and Ethiopia [21,61], where younger people were more knowledgeable than the older, and some studies in China that the oldest generation has more traditional knowledge than others [54,62]. Based on our field observation, there are three possible explanations for this tendency: firstly, people in their 40’s and 50’s were more knowledgeable due to first-hand experience. Secondly, the low level of knowledge in younger generations, particularly between 20-30 years, would likely stem from their little interest in WEFs, and less exposure to the wild environment since the majority of the youngsters nowadays spend more time at schools or in town. Thirdly, the declining knowledge exhibited by the senior citizens could be because they have less direct involvement in the forest.
In line with previous studies [54,59], the association between gender and indigenous knowledge was not statistically significant since they work closely with nature irrespective of their gender. Nonetheless, the result contrasts with other studies in Ethiopia, Brazil, and Italy [44,45,63,64], where women reported more wild edibles than their male counterparts. On the contrary, Kang et al.  concluded that men were more knowledgeable in Central China. Similarly, this study also found no association between indigenous knowledge and the education level of the respondents. Generally, indigenous knowledge is transferred orally from parents to children requiring no qualification level, which is consistent with the findings of Mengistu &Hager . However, this result contrasts with the findings in Ethiopia, where literates had more indigenous knowledge [44,45]
4.4 Implications for promotion and conservation of WEF
The present study found that WEF consumption has decreased compared to the past, resulting in the extinction of wild food culture and its associated indigenous knowledge. Thus, it is important to focus on promoting these neglected species before the culture of wild food consumption disappears. With their high nutrient content and other uses, WEFs have a high potential to enhance food security and income generation in the remote areas of Bhutan. Hence, it is imperative to create awareness on the nutritional and other use diversities of the species in the region. Regardless of its inferior quality and taste, the value addition of WEF is reported to yield high returns to the farmers and increase the keeping quality . In the study area, people hardly processed or value-added the WEFs except for some conventional drying and pickle making for self-consumption owing to limited skills in agro-processing and value addition. Thus, training programs on agro-processing and value addition are essential to diversify products and increase profit to the farmers . At the same time, integrating wild plants related knowledge in the school curriculum would make the youths familiar with these important wild species and their associated indigenous knowledge.
This study found that 85% of the species were rarely and moderately found in the region, indicating the possible declining diversity of some species, which is perceived to be caused by deforestation, climate change, and overharvesting. Similar findings of decreasing availability of the species were reported in Nepal and Ethiopia [21,44]. Hence, the future agroforestry agenda should prioritize the conservation and domestication of these rarely available species. With their hardy nature and better adaptation to harsh climate than the improved varieties , and their resistance to drought and natural disasters such as fire , these wild species are suitable for planting in slide-prone areas. In addition, some WEF species like Ardisia macrocarpa, Cornus capitata, and other evergreen or deciduous trees with beautiful flowers and fruits also have an additional aesthetic value for landscape and highways.
One of the limitations of this study is the short time fieldwork, including only the individual survey. Consequently, a logical follow-up would be participatory and focus group discussions. Another limitation of this study is the lack of marketing surveys since the WEF species were hardly sold in the market for income generation. This study attempted to document species diversity and ethnobotanical uses of WEFs in eastern Bhutan. Although the survey was limited to only two Dzongkhags, we believe that the results sufficiently represent the species diversity and indigenous knowledge in the east but may not be necessarily pervasive to other regions in Bhutan. Therefore, replicating this research based on a case study in other regions is advisable to elucidate more comprehensive information on species diversity and indigenous knowledge associated with WEFs.