Sustainable Use and Management of Wild Edible Fruit Plants: A Case Study in the Ulu Masen Protected Forest, West Aceh, Indonesia

ABSTRACT Wild edible fruit plant species (WEFs) are species that are not cultivated or domesticated but are available in their natural habitat, providing a readily available source of food, medicine, and economic value to the local people. In recent times, WEFs have been threatened by over-exploitation, land-use changes, and biodiversity loss. This study aims to (1) identify and document wild edible fruit plant species, (2) investigate the patterns of knowledge, use, and management of WEFs in the Ulu Masen protected area; and (3) assess threats to wild edible fruit plant species and recommend possible management scenarios for their conservation. The study was conducted in six villages of Pantai Ceuremen subdistrict, Southeast Aceh, Indonesia, namely Sikundo, Jambak, Canggai, Lawet, Pulo Tungoh, and Keutambang. The plant materials were randomly collected from the study area, while local knowledge was gathered through a semi-structured survey and in-depth interviews involving 209 respondents that were selected using random sampling. A total of 53 wild edible fruit plants from 30 genera and 21 families were found to be commonly used. Syzygium pycnanthum, Syzygium littorale, Syzygium polyanthum, Garcinia xanthochymus, Baccaurea polyneura, Flacourtia rukam, Sandoricum koetjape, and Baccaurea racemosa were the most important species for local communities in the study area. The WEFs in the study area is influenced by a variety of factors, primarily agricultural expansion, which means that conservation practices need to be improved through the implementation of management strategies, prioritizing species currently used by local communities. Management strategies based on traditional knowledge, such as community-based forest management systems (CBFMS) are being considered for future conservation, and they are also being implemented in other developing countries with similar circumstances.


Introduction
Wild edible fruit plant species (WEFs) refer to species that are not cultivated or domesticated but are available in their natural habitat (Beluhan & Ranogajec, 2011;Kidane & Kejela, 2021). Wild food plants, including WEFs, play an important role in rural communities' livelihoods as an integral part of people's subsistence strategies in many developing countries (Jadhav et al., 2015;Ojelel et al., 2019), providing a readily available source of food (Vinceti et al., 2018) and medicine (Biswas et al., 2018;Navia et al., 2021a;Suwardi et al., 2021.;Tarigan NS Elfrida et al., 2021), particularly for vulnerable social groups (Dejene et al., 2020). Furthermore, the use of specific WEFs is also influenced by culture and location, as well as being maintained by cultural mores and traditional practices (Dejene et al., 2020). Several studies show wild food plants, including WEFs, to be a potential source of nutrition, as they are often more nutritious than conventionally consumed crops (Ojelel et al., 2019;Suwardi et al., 2022). WEFs are a potential source of income for households (Mishra et al., 2021;Suwardi et al., 2020a;Thakur et al., 2017), and these activities also contribute to improved dietary and nutrition quality (Vansant et al., 2022). However, the commercialization of WEFs faces several challenges, such as low (re)production rates (Zardo & Henriques, 2011), limited trade (Sardeshpande & Shackleton, 2019), and market factors, particularly fruit quality grades (Smanalieva et al., 2019).
The Ulu Masen Ecosystem (UME) is a protected forest area with a total area of 13,174.49 km 2 managed by the Aceh Provincial Forestry Service as a wildlife reserve for 300 bird species, 87 reptile and amphibian species, and various endangered species, including the Sumatran tiger (Panthera tigris sumatrae), Sumatran elephant (Elephas maximus sumatrensis), and Sumatran orangutan (Pongo abelii; Radinal et al., 2019). In addition, this area has been designated as a pilot area for the implementation of Reducing Emissions from Deforestation and Forest Degradation (REDD), a mitigation scheme to reduce emissions from deforestation and forest degradation (Fash & Pakpahan, 2016). However, as human density has raised near and within forested areas, the pressure on plant populations has increased, resulting in forest degradation and biodiversity loss. UME, such as other protected areas around the world, plays a critical role as a site for the conservation of ecosystems and the species that comprise them, and it necessarily requires a comprehensive study to figure out the best conservation strategies.
Given the fact that several studies on protected forests have been conducted in various regions of Indonesia (Karim & Ahmad, 2019;Lestari & Christie, 2020;Naisumu et al., 2018;Nugroho et al., 2015;Tudjuka et al., 2014), the focus remains on identifying and listing threatened species, conservation actions for endangered species, storing threatened species germplasm ex-situ, and developing a protected area system. Most studies on wild plants have focused on harvest impacts or management at the population or species level, primarily on commercially important species. In fact, there is little descriptive information available about the role of traditional botanical knowledge and the indigenous community in the conservation of the protected area. Local communities have a particular concept of nature that could contribute to the development of sustainable management practices, promoting biological and socio-cultural diversity. According to several studies in Aceh province, many rural people have extensive knowledge of how to use plant resources (Mubarak A Elfrida et al., 2020;Navia et al., 2021aNavia et al., , 2020aRahimah, Hasanuddin, 2018;Suwardi et al., 2020aSuwardi et al., , 2020bWidyastuti et al., 2019). The use of plants for various purposes by local communities constitutes traditional ethnobotanical knowledge, which is not well documented but has been orally and vertically transmitted from generation to generation (Jadid et al., 2020;Sujarwo et al., 2014). Several studies showed that there is a widespread decrease in knowledge concerning wild food plants due to the acculturation of indigenous communities and their cultural backgrounds, as well as plant biodiversity loss. Promoting studies on wild food plants is critical in order to preserve this information for future communities (Asfaw, 2009).
Several studies have shown that social-economic factors, particularly age, gender, and level of education, influence the use of wild plants. Cruz et al. (2013) discovered that older people have a better understanding of wild edible plants than younger people. Mashile et al. (2019) discovered significant gender differences in attitudes; women prefer more fruit plants than men. Ekué et al. (2010) discovered that management practices to increase the number of ackee (Blighia sapida) plants varied by gender, with women being more commonly in possession of this activity.
The aim of this study was to (1) identify and document wild edible fruit plant species; (2) investigate the patterns of knowledge, use, and management of WEFs in the Ulu Masen protected area; and (3) assess threats to wild edible fruit plant species and recommend possible management scenarios for their conservation, with the following hypothesis: local people's knowledge, use, and management of WEFs are influenced by socioeconomic factors. To test our hypothesis, we investigated the relationships between socioeconomic factors and knowledge indicators, as well as the use and management of WEFs.

Description of the study area
Pantai Ceuremen subdistrict, West Aceh district, Indonesia Aceh district is geographically located between 4°51ʹ42" N and 96°38ʹ83" E, with an altitude range from 20 to 80 m asl. The area is located adjacent to the ecosystem of Ulu Masen, with an approximate land area of 6,250 ha, a topography of hills and valleys as well as settlements located along the river bank. These areas have a tropical humid climate with a dry season that lasts from March to August and a rainy season that lasts from September to December. The monthly averages rainfall is 394.8 mm, with an average of 16.4 rainy days, while the average annual temperature is around 23.4°C, with 86.8% humidity. The Pantai Ceuremen subdistrict has a population of 11,133 people, which consists of 5,624 men and 5,509 women, whereby the majority of them work as farmers, primarily producing rice (Oryza sativa L.) and vegetables as well as patchouli (Pogostemon cablin (Blanco) Benth.) which is grown together with various crop plants in the cultivated lands (The Central Bureau of Statistics of West Aceh District, 2020). The study was conducted in six villages of Pantai Ceuremen subdistrict, Southeast Aceh, Indonesia, namely Sikundo, Jambak, Canggai, Lawet, Pulo Tungoh, and Keutambang ( Figure 1).

Field survey and data collection
Field visits were conducted between 2019 and 2020 with prior informed consent which was obtained from villages where the study was conducted. Also, the local people granted verbal consent for the dissemination of their traditional knowledge. Data were collected using semi-structured interviews and field observations, whereby the questionnaires were divided into five sections: identities of the respondents, methods of usage, the local preference, economic value, and local conservation of wild edible fruit plants. A total of 209 respondents aged 15 to 68 were selected using random sampling methods (Table 1). This sample size was calculated using the Yamane formula for sample size at a 95% confidence level (Adam, 2020;Taro, 1967). Subsequently, a checklist of different categories of WEFs use such as food, medicine, agricultural tools, fodder, fuelwood, and construction was developed to determine the kind of species and their uses, whereby the respondents were asked if the species were used for additional purposes. The Chi-square (χ2) test was used to test the difference in the use of WEFs across the study villages.

Plant specimen collection and identification
Based on the ethnobotanical information obtained from respondents, samples were collected and additional information such as vernacular names were obtained, numbered, pressed, and dried for identification, and this was performed at the Herbarium of Andalas University, Padang, West Sumatra. The botanical names were updated according to the Plants of the World Online (http://www.plantsoftheworldonline.org), while all voucher specimens of the WEFs labeled with scientific and vernacular names were stored in ANDA herbarium of the University of Andalas.

Data analysis
Descriptive statistics, relative frequency citation, use-value, preference ranking, paired comparison, direct matrix ranking, and informant consensus were used to analyze the data. Ethnobotanical data were analyzed, both qualitatively and quantitatively using SPSS version 20 and an excel spreadsheet. The frequently used species were clustered based on the category of use by local communities, and the statistical significance of the age and education group differences, as well as differences in WEFs use between villages, was determined using a chi-square test and SPSS v.20. The spreadsheet data filter facility was employed to determine multipurpose uses, proportions of different variables like growth forms (habits), plant families, plant parts used, and methods of food preparation.

Relative frequency citation (RFC)
The ethnomedicinal information collected was analyzed quantitatively using the following relative frequency citation index (RFC) This index shows the local importance of each species and results from the frequency of citation (FC, the number of informants mentioning the use of the species) divided by the total number of informants participating in the survey (N), without considering the use categories (Vitalini et al., 2013).

Use value (UV)
The Use Value (UV) shows the relative importance of locally known plants, and it was calculated using the following formula (Tardio & Pardo-de-Santayana, 2008).
Where Ui is the number of uses mentioned by each informant for a given species and N is the total number of informants.

Preference ranking
The wild edible fruit plant preference ranking activities were carried out following Martin (1995). All respondents were asked to rank the top ten preferred WEFs in terms of taste quality. The most preferred value was five, and the least preferred value was one. Finally, the total scores were added and ranked to determine the most preferred WEFs.

Ranking of threatening factors
Priority ranking was used to determine threats of wild edible plants based on their level of destructive effects to determine the most threatening factors in the study area.
Respondents were asked to evaluate the impact of each threat on WEFs on a scale of 0 to 4, based on their knowledge and experience (Dejene et al., 2020), and a spider chart was used to interpret the mean risk value for each threat as categorized by respondents. Table 2 displays the socio-demographic characteristics of respondents. The majority of respondents (58.9%) were women, while (41.1%) were men. More than 80% of those respondents were married. All respondents professed Islam as their religion. The majority of respondents (29.2%) had only completed elementary school, with only 12% attending university. All respondents were native to the area.

Diversity of WEFs
The results show that the flora of the study area is rich in useful species, which includes a total of 53 WEFs belonging to 30 genera and 21 families (Suppl. 1). The Phyllantaceae is the most represented family with nine species, followed by Moraceae (8 species), Clusiaceae and Fagaceae (4 species each), as well Myrtaceae (3 species each). The average number of species identified by each age group of the respondent ranged from 47.4 ± 3.73 (15-25 years) to 53.1 ± 1.63 (> 65 years). In addition, the average number of species identified by each educational status of the respondent ranged from 45.1 ± 5.47 (University) to 53.0 ± 1.71 (Elementary School). The statistical analysis revealed that there was a significant difference between age (χ2 = 97.578; df = 55; α = 0.05; P < .05) and education level (χ2 = 1.476; df = 44; α = 0.05; P < .05) with the number of WEFs cited by the respondents. The most cited species by a majority of the respondents (RFC ≥ 0.85) are seven

Growth form, parts used, and mode of consumption of WEFs
The plant species had varied life/growth forms, and various plant parts were used. The large numbers of the species (86.8%) were trees, followed by shrubs (9.4%) and climbers (3.8%). In terms of the plant used, a total of six edible parts were recorded, of which 81% were fruits, 4% seeds, 4% young shoots, 6% fruits and leave, 2% fruits and seeds, 2% leaves and young shoots, and 2% fruits and stems ( Figure 3). The fruits (81%) are the plants part that is regularly utilized by the local community of the study area. Approximately 80% of the fruit is consumed fresh; however, several species, such as Garcinia xanthochymus, are dried in the sun for 2-3 days before being stored or used for spices.
The local community in the study area has traditional knowledge of selecting, harvesting, and managing the availability of WEFs. Approximately 60% of respondents stated that they would only harvest the fruit with certain characteristics, such as fruit that is not brightly colored, ripe, has less sap, and is consumed by animals. Fruits harvesting by hand was the preferred method with 80% of total respondents, followed by harvesting with a stalk (12%) and cutting the branch tree (8%). In addition, harvesting with a knife is common (100%) for collecting leaves and bark for medicinal purposes. Approximately 40% of respondents admitted that WEF harvesting locations were limited to forest edges and that they generally left a certain amount of fruit on the mother tree for animals and the regeneration process. Moreover, 12% of respondents said they frequently pruned tree branches to allow WEFs regeneration in order to increase WEFs population. They also keep fruitbearing trees from being felled or killed while agricultural land is being cleared. Indeed, 8% of respondents have planted WEFs such as Garcinia xanthochymus, Sandoricum koetjape, and Syzygium polyantum in their home garden or farmland.

Multipurpose use of WEFs
In addition to being used as food, the reported WEFs are used also for other purposes. 13 (24.5%) WEFs have been reported to be used as traditional medicine by local communities in the study area (Suppl. 2).
The 53 WEFs reported by respondents were generally classified into four groups based on their use categories (Figure 4), whereby the first main group consisted of 32 species that were primarily used for food and medicine. The second main group was comprised of 11 species that were categorized based on their use in food, fuelwood, and fodder, the third included six species that were primarily used in food, construction, and fuelwood, while the fourth included four species that were primarily used for food, agricultural tool, and fodder. However, respondents indicated that the branch of Vitex pinnata and Litsea cubeba were also used as agricultural tools by local communities.
Fifty-three species were reported to be used by communities in Sikundo village, followed by 50 species in Canggai, 48 species in Jambak, 47 species in Lawet, 44 species in Pulo Tengoh, and 42 species in Keutambang. The Chi-square (χ2) test (χ2 = 94.837; df = 25; α = 0.05; p < .05) revealed that the number of species reported to be used by the people of the six study villages differs significantly (Table 3), indicating that there is a diversity of traditional knowledge on the use of WEFs among local communities in different villages.

The economic value of WEFs
Local communities in the study area collect WEFs for sale in the traditional market, roadsides, or neighborhoods. Species, traded parts, average quantity, and the market price of WEFs that were sold by local communities in the study area are shown in Suppl. 3.
Approximately 65% of respondents reported to sell WEFs. The highest quantity of fruits sold was Garcinia xanthochymus (200 ± 12.93 kg) followed by Sandoricum koetjape (150 ± 12.84 kg), Musa balbisiana (100 ± 2.33 kg), and Baccaurea lanceolata (50 ± 1.05 kg). Among fruit species, Baccaurea polyneura and Garcinia xanthochymus have high market prices of around IDR 10,000-12,000 per kg. The mean income earned through the selling of WEFs by the households is IDR 8,000,000 per year, with the mean income of each respondent being IDR 2,000,000 per month. Of all households selling WEFs, 82% earned less than 20,000,000 Indonesian Rupiah (IDR) annually, while 14% earned more than 20,000,000 IDR. The mean total annual contribution to the household income from selling of WEFs was around 25.31%.

Preference ranking of WEFs by taste
The species preferences are comparable across the village, with no significant differences between the six villages (χ2 = 48.663; df = 55; α = 0.05; P = .714). This could be due to ethnic similarities, sharing the same culture of WEFs usage, and living in the same district. Baccaurea polyneura is the most popular WEFs, cited by the majority of respondents across all villages. Due to their pleasant taste, the fruits of Baccaurea polyneura were the most popular WEFs (preference ranking; Table 4).

Threats to WEFs and their habitats
Several factors, including land use, habitat destruction, and overharvesting, were identified as threats to WEFs in all villages. Agriculture expansion, timber harvesting, forest fire, leaf harvesting, fruit harvesting, and fuelwood collection were severely depleting WEFs in the study area. Among these problems, most respondents perceived that agricultural expansion was the main factor that threaten WEFs ( Figure 5).  Pawera et al. (2020), and 15 edible fruit plants in Bulumario village, North Sumatra by Silalahi et al. (2020). However, Rike et al. (2018) in West Kalimantan, Indonesia and Ong et al. (2012b) in Perak, Malaysia were reported higher diversity of WEFs than the current study. Trees were the dominant growth form of WEFs in the study area. The findings of Mengistu and Hager (2009) in the Amhara region and Kidane and Kejela (2021) in the Berek Natural Forest, Oromia special zone, Ethiopia were consistent with the current finding that trees were the most important growth form. On the other hand, Ong et al. (2012b) reported that in Perak, Malaysia, herbs were the dominant growth forms, followed by trees, shrubs, and climbers. WEFs contributed significantly to the dietary needs of the households in the study area. Fruits are plant parts that are commonly used by the local community. Approximately 80% of the edible plants recorded were consumed fresh, without further processing, and the majority of them are fruits. This study is consistent with those reported by Kidane and Kejela (2021) in the Berek Natural Forest, Oromia special zone, Ethiopia and Navia et al. (2021b) in North Aceh, Indonesia.
Baccaurea polyneura and Garcinia xanthochymus are the most popular fruit consumed by local communities in the study area. These fruits have a high economic value. Respondent state that before being stored or marketed, Garcinia xanthochymus fruit is sundried. Garcinia xanthochymus fruit is commonly used as a spice. In addition, local communities prioritized Garcinia xanthochymus, one of the ten medicinal plant species mentioned, to treat a variety of diseases such as sore tongue, fever, coughs, breast cancer, stomach problems, skin diseases, and preventing obesity. Garcinia xanthochymus fruit contains a bioactive compound that helps to reduce cholesterol and plays an important role in preventing obesity (Chen et al., 2019). Therefore, this is in line with the result of Navia et al. (2020b) and Sutrisno et al. (2021) which shows that Acehnese uses various plant species as spices and condiments to enhance the flavor of their cuisines. Local communities Table 4. Results of preference ranking of top ten WEFs by their taste quality (1 = least, 2 = less, 3 = good, 4 = very good, and 5 = excellent). in the study area use a variety of indigenous management strategies to conserve and manage their natural resources. These include planting in the home garden and farmland, as well as preventing the cutting of several WEFs in the establishment of new agricultural land, such as Ficus species, which they used for a variety of purposes in their daily lives. WEFs sales account for approximately 25% of total annual household income in the study area, which is less than the 43% reported for total annual household income in Central Aceh, Indonesia . Processing, drying, and grading have the potential to increase the economic value of these WEFs. Several studies have shown that semiprocessing, drying, and grading of wild foods can significantly increase the economic value of food products and the income of local people (Alijanpour, 2017;Ghanbari et al., 2017Ghanbari et al., , 2022. Improving market information and market connections are also important for the development of value-added activities and value chains for WEFs. Increase value addition through post-harvest processing activities and, as a result, the creation of new market opportunities (Heubach et al., 2011). The establishment of small-scale processing industries and cooperatives, with a focus on high-abundance species, will have a positive impact on rural household income (Ghanbari et al., 2022). However, rising prices and demand for these products may lead to an increase in WEFs collection in the future. As a result, WEFs may be vulnerable to overexploitation in the future (Sunderlin et al., 2005). As a consequence, a regulation that controls the overharvesting of WEFs is required to ensure their future availability.
This study reveals that identifying and utilizing WEFs varied across the six study villages. This variation is considered to be influenced by lifestyle change and respondent characteristics (age and education). In Sikundo and Canggai villages, for example, many parents prefer to bring their children with them when they go to the fields or the forest to collect forest products, wood, and other items. As a result, the children visit the forest regularly, allowing them to closely observe the forest as well as interact with their parents or other family members. As a consequence, the children gained a lot of knowledge about the forest and plants. In contrast, we discovered that children in the other four villages interacted less with the forest. Field observations support the information provided by several informants that the majority of children, particularly those aged 15 and over, are away from their homes for education in school and college and spend the majority of their time in the city. These children have less contact with their families, fewer opportunities to spend time in the village, and very few opportunities to visit the forest. Even though they are not in school, they prefer to engage in other forms of entertainment, such as watching television or surfing the internet, rather than participating in forest activities. Moreover, they dislike the taste of WEFs and prefer commercial fruit, such as apple or grape, implying a loss of interest in WEFs. In general, this study reveals that older people have better knowledge than younger people, and higher levels of education decrease preference and knowledge of WEFs. The lifestyle changes are a major factor addressing why younger generations are less interested in WEFs. These findings support other studies that show that lifestyle changes lead to a decrease in the consumption of wild food plants (Shumsky et al., 2014).
Field observations and discussions with respondents revealed that natural vegetation in the area has declined in recent decades as a result of natural and anthropogenic factors. The expansion of agriculture is the greatest threat to WEFs in the UME area. According to the respondents, the main reason for the loss of various WEFs is the agricultural expansion for cultivation, which is primarily due to increasing population pressure in recent decades. As a result of these activities, all respondents stated that forest cover has changed and the density of the WEFs has significantly decreased. The establishment of cultivation on land that was previously occupied by a natural forest will result in significant changes in the plant community (Freedman, 2009). The second greatest threat to the survival of a variety of useful plant species, including WEFs, is timber harvesting. According to respondents, timber sales provided up to 30-50% of their total annual income, and this was lower than the report by Campbell (2018) in Pakistan. Timber forest products have been regarded to have large economic impacts on the rural population across the world (Kawarty et al., 2020). Furthermore, timber harvesting boosts the rural economy by significantly increasing self-sufficiency, family income, and employment opportunities (Kidane et al., 2018). However, overharvesting of WEFs, such as Durio griffithii, Lithocarpus echinulatus, Lithocarpus indutus, and Lithocarpus wallichianus for house construction purposes, is aggravating the degradation status of these species. The ecological effects of selective logging are linked to the intensity of the harvest, which largely determines the level of collateral risk posed during and after timber harvest (Asner et al., 2009).
Pressure on forest ecosystems has increased in recent years as a result of increasing human needs, resulting in the extinction of a variety of useful plant species. Local communities in the study area, on the other hand, have made commendable attempts to maintain the availability of WEFs by incorporating traditional knowledge into WEFs management. These traditional knowledge include (1) implementing nondestructive harvesting methods to avoid the death of fruit trees; (2) extracting small quantities of WEFs from each location and each plant individually to ensure WEF availability, feed animals such as monkeys and birds, and regenerate WEFs; (3) pruning tree branches to allow WEFs regeneration in order to improve WEFs population; and (4) preventing the felling or killing of mother trees during land preparation for agricultural production. Several studies, therefore, suggest the conservation and protection of wild plants, as well as the enhancement and incorporation of traditional knowledge into management strategies (Ca´mara-Leret et al., 2014;Reyes-Garcı´a et al., 2011;Sosnowska et al., 2015).
WEFs play a critical role in the biodiversity of forest ecosystems. Besides creating a microclimate and placing an ecological niche, the fruit of these plants is a major food source for a variety of animals, including birds and monkeys which eat a variety of fruits and seeds as a source of nutrition (Nugroho et al., 2015). Thus, the existence and preservation of a diverse range of fruiting plants are critical to the survival of various animal species. Planting WEFs, including species preferred by local communities, can contribute to increasing the diversity of WEFs in forests, including UME-protected areas. Plant diversity, including WEFs, has increased as a result of natural regeneration processes (Malik & Bhatt, 2016); however, there may be opportunities to assist natural regeneration interventions such as site preparation and tree planting (Chazdon et al., 2020;Holl & Aide, 2011;Holl et al., 2018). Planting native trees is an effective way to promote natural regeneration (Holl, 2017;Levy-Tacher et al., 2019). In this way, they can also make a significant contribution to environmental conservation by halting uncontrolled harvesting from the wild and assisting in the conservation of various species in their native habitats, where they are most effective. Moreover, domestication of WEFs through the concept of agroforestry by combining WEFs with crops on orchards, home gardens, or farmland can be accomplished to reduce WEFs overharvesting in nature. This concept has also been used in other parts of Indonesia, such as forest management in Banyuasin district, South Sumatra (Undri, 2016), and management of Tembawang in Kapuas Hulu district, West Kalimantan (Aini et al., 2016).
Local community leaders, various local governments, academic institutions, and nongovernmental organizations (NGOs) play an important role in the management of UME. Community-based forest management systems (CBFMS) that integrate conservationthrough-use and bioeconomy-based approaches are one of the alternative forest management models that could be used in UME management. This concept has been widely used in several Asian countries, including Nepal, Bhutan, India, and Myanmar (Maraseni et al., 2019). The regulations for UME management, on the other hand, must be developed with the participation of forest communities. Inadequate regulation or poor implementation can result in overharvesting or conflict with other land-use activities (Willem et al., 2019). Local ecological knowledge must be considered and fully integrated into management and conservation plans (Ca´mara-Leret et al., 2014;Sosnowska et al., 2015). Documenting traditional knowledge, on the other hand, is absolutely necessary, in response to a decrease in traditional knowledge among the younger generation. Integrating traditional knowledge into formal education curricula can be a good alternative for preserving the traditional knowledge of local communities. In addition, traditional knowledge documentation can take many shapes and forms -through written registries and files, video, images, and audio. For example, writing down medicinal preparations by Shipibo communities (Peru), taking notes on Tuareg herding traditions in the Sahel (Africa), or digitizing ancient manuscripts such as Ayurvedic medical texts (India; WIPO, 2017).
Finally, while this study successfully demonstrates how traditional knowledge of local communities residing close to the Ulu Masen protected area can be used as part of forest inventories to identify WEFs and how they are used for provisioning and supporting ecosystem services, they are limited to specific areas and only include the Acehnese population who live around the protected forest. This does not imply that these interventions will be equally effective in other countries or cultures. Similar interventions, relevant to the particular forest and cultural conditions, would help to clarify methods even further.

Conclusion
This study provides basic information on WEFs in the Ulu Masen protected forest that is possibly used as part of a management strategy for the sustainable use of natural resources. The results are based on the social perception of the local communities who reported the current use of the species identified in the study area. A total of 53 WEFs belonging to 30 genera and 21 families were discovered in the study area. Syzygium pycnanthum, Syzygium littorale, Syzygium polyanthum, Garcinia xanthochymus, Baccaurea polyneura, Flacourtia rukam, Sandoricum koetjape, and Baccaurea racemosa were the most important species for local communities in the study area. We were able to highlight the existence of WEFs in the ecosystem area of Ulu Masen. The study also shows that WEFs play an important role as a source of food and medicine and contribute to their livelihood through a variety of uses. This indicates that the inhabitants of this region have a close relationship with their biological resources. However, WEFs in the study area are threatened by a variety of factors, including agricultural expansion, which means that conservation practices need to be improved through the implementation of management strategies, prioritizing species currently used by local communities. Therefore, the traditional knowledge of the inhabitants must be documented as it is vital for the future development and maintenance of important WEFs.

Disclosure statement
No potential conflict of interest was reported by the author(s).