Traditional knowledge and cultural importance of Gardenia erubescens Stapf & Hutch. in Sudanian savanna of Burkina Faso

The study was conducted in 15 villages bordering three protected areas (PAs) located in the Cascades, Eastern, and West central Regions of Burkina Faso, namely Boulon, Tapoa-Boopo, and Tiogo (Fig. 1; Table 1). The description of the socio-political, governance, or biophysical contexts of the three forests areas are presented in Table 1. Boulon and Tiogo forests were classified by the colonial administration in 1955 and 1940, while that of Tapoa-Boopo was classified in the 80s [24]. In terms of climate, the forest of Boulon is located in the Sudanian zone while that of Tapoa-Boopo and Tiogo are located in the Sudano-Sahelian zone [23] as illustrated in Fig. 1. The subdivision of climatic zones in Burkina Faso is based on the annually rainfall amounts and the thermal regime. The Sahelian zone in the north of the country is characterized by an average annual rainfall lower than 600 mm, a high rate of evapotranspiration as well as high temperatures (> 30 °C), and a short rainy season (2 to 3 months) [8]. In the Sudano-Sahelian zone, the annual rainfall varies between 600 and 900 mm over 4- to 5-month period while the annual temperature ranges from 20 to 30 ° C. It comprises the most extensive climatic zone as it extends over all the central part of the country [8]. The Sudanian zone occupies the southern part of the country, where the rainy season lasts from 5 to 6 months with the level of rainfall attaining or even exceeding 1100 mm annually. This area is marked by low temperatures that range between 20 and 25 °C [8]. The current study is located in the last two climatic zones that experience a single rainy season that begins from the month of May to October with annual precipitation ranging between 600 and 1000 mm while the dry season occurs between the months of November and April. The mean annual temperature across the three sites is 35 °C; temperatures above 35 °C occur during peak period in the month of April [25]. The vegetation is a mosaic of shrubs and trees, woodland savannas, and grasslands. The main ethnic groups in the case study areas include Dogossin, Goin, Gourmantche, Gourounsi, Karaboro, Dioula, Mossi, and Fulani.

Gardenia erubescens Stapf & Hutch is a shrub species with a maximum height of 3 m above the ground (Fig. 2). It belongs to the genus Gardenia of flowering plants in the coffee family called Rubiaceae. This species is widely spread in tropical Africa, from Senegal to Sudan and Uganda. In Burkina Faso, the species is dominantly found in Sudanian zone [8]. The wood of the species is yellow, hard, and compact. The plant is sometimes gathered from the wild for local use as food, medicine, and as construction materials. The fruits are yellow and are used in sauces and soups (Fig. 2). The pale yellow, ellipsoid fruit can be 3–5-cm long. The leaves are opposite or in whorls of three or four, 5–50-cm long and 3–25-cm broad. They are dark green and glossy with a leathery texture. The flowers are solitary or in small clusters, either white, or pale yellow, with a tubular-based corolla with 5–12 lobes (petals) from 5 to 12 cm diameter. In Burkina Faso, G. erubescens is found in all three climatic zones but with great differences regarding its distribution and abundance [8].

The village authorities and their representatives were contacted, and the aim of the research was explained to get their consent. A consent form was part of the questionnaire for informants to understand the aim of the research and give their consent before engaging in the interview process. A pilot study (pre-test) was conducted in June 2016 to test the clarity of the questionnaire, determine suitability of the participants, and to determine the time required to complete a survey. The pre-test was also used to determine the number of respondents and to achieve this objective, a random sample of 40 people were selected for the pre-test. In order for the sample size to be representative, the number of respondents was calculated using the following formula [26]:

Where N is the total number of people surveyed; U is the value of the random normal variable for a probability value of α; U = 1.96 if α = 0.05; p is the proportion of respondents who used or knew the species; and d is the margin error.

The pre-test revealed that 72, 80, and 78% of the respondents in Boulon, Tapoa-Boopo, and Tiogo, respectively, know and use G. erubescens (Fig. 2). A sample size of 159 (Boulon), 173 (Tapoa-Boopo), and 182 (Tiogo) people was determined for a 6% margin of error (d) which is acceptable in statistics.

Respondents were classified as young people (below 40 years) and old people (above 40 years) as described by Goudégnon et al. [9]. Both groups were considered to represent two generations and finally, the aspect of gender (men and women) and location was also considered. Ethnobotanical surveys were conducted in 15 villages across the three study sites in the PAs of Boulon, Tapoa-Boopo, and Tiogo using face-to-face individual interviews to assess the traditional knowledge and uses of G. erubescens based on 514 randomly selected informants. Direct field observation was used to complement information gathered from the informants (see Table 2). The surveys were conducted between the months of July to September 2016. Data collection included demographic information (age, gender, and ethnic groups), ethnobotanical knowledge of G. erubescens (vernacular name, specific use per plant part, categories of use), and the real use of the species. The real use of the species was determined by asking the informant to score the use-categories based on the importance of their actual uses. The score varied from 3 (high use) to 0 (not used) with score 2 for “moderate use” and score 1 for “low use” [2].

Specimens of G. erubescens, in our case the leaves and fruits of the plant, were presented to interviewees (Fig. 3) to ensure the presence of the species in that village. Interviews were conducted in four local languages (Dioula, Mooré, Gourounsi, and Goulmancéma) that are commonly spoken in the study areas. A research assistant who understood these languages acted as a translator and each interview session lasted between 1 and 2 h.

A total of 514 people belonging to eight ethnic groups were interviewed to evaluate their TK and uses of G. erubescens. This tree species was identified by nine different local names among the eight ethnic groups present in the three case study areas (Table 2). Despite differences in local names of G. erubescens from one ethnic group to another, all of these names referred to the same species. In terms of its uses, a total of seven use categories were identified by the informants of which the two most reported uses were for food and medicine corresponding to 58.97% and 17.22% respectively and a minuscule percentage (0.23%) for magical uses. Six plant parts of the species were used locally, and many recipes were recorded for 30 different uses in addition to the treatment of several diseases (Appendix). The roots and leaves are the plant parts that are mostly utilized for traditional medicine to treat different types of diseases and as such, the leaves and roots are commonly harvested in addition to debarking for decoration purposes.

Furthermore, the number of uses reported per plant part were as follows: leaves (ten uses), roots (nine uses), young twigs (seven uses), and fruits (seven uses). The bark of the plant was involved in four uses locally, whereas three uses were reported for the wood from the plant (Appendix). Some of the uses of the different parts were reported by more than 80% of the respondents (Appendix).

The overall use value (UV) of G. erubescens varied significantly only between the eight ethnic groups given that p < 0.05 (see Table 3). Considering the analysis at the level of use-category, the results of the GLM indicated that the UV of G. erubescens for food, fodder, and magical uses was similar among the study sites, ethnic groups, and generation (p > 0.05) while that for medicinal use varied greatly between the study sites, ethnic groups, and generation because p < 0.05 (Table 3). The UV for cultural purposes differed significantly only between ethnic groups and generation (p < 0.05), whereas there was a significant relationship between energy use of G. erubescens and study sites, ethnic groups, and gender given that p < 0.05 (Table 3). Construction use varied significantly only among the study sites. However, there was no significant interaction between these factors.

Among the ethnic groups considered in this study, the Gourounsi, Goin, Gourmantché, and Dioula represent the ethnic groups that use G. erubescens the most in the study area (Fig. 4a). As for the generations, the old persons (age ≥ 40 years) reported more uses than the young (Fig. 4b).

Knowledge on the use of G. erubescens varied greatly across the plant parts (Fig. 5). Irrespective of the examined factors, fruit was the most used, followed by wood, leaves, and young twigs (Fig. 5a, b). The least used parts of the plant are the bark and roots. It was found that all ethnic groups use the fruit. Furthermore, the leaves were commonly used by Gourmantché, Dioula, Gourounsi, and Fulani while the wood was mainly used by Gourounsi (Fig. 5b). Aside from the use of its fruits, respondents below 40 years have low use value for the leaves, bark, and roots (Fig. 5c). Knowledge on fruit use was similar across the three study areas—Tapoa-Boopa, Boulon, and Tiogo (Fig. 5a). Regarding the wood of G. erubescens, respondents in Tiogo, belonging to the ethnic group of Gourounsi with an age above 40 years, reported more uses than others (Fig. 5). Regarding gender, men reported more uses based on their traditional knowledge when compared to women irrespective of the plant parts used with the exception of the leaves indicating a relatively higher UV for women (Fig. 5d).

The cultural importance of G. erubescens varied significantly among ethnic groups and study sites (p < 0.05) in the following use categories: medicinal, construction, energy (use of wood as fuelwood), and cultural use (see Table 4). In addition, the cultural importance of other categories of use (food, fodder, and magic) was statistically similar between ethnic groups and sites (Table 4). Table 5 revealed that the importance of G. erubescens varied significantly among generation for the category for medicinal uses only while the importance of other categories of use was statistically similar between generations.

G. erubescens was more important (higher IP) in Tiogo (4.32 ± 0.39) than in Tapoa-Boopo (4.06 ± 0.40) and Boulon (3.75 ± 0.38); more important for Gourounsi (4.41 ± 0.39), Dioula (4.21 ± 0.42), Gourmantché (4.17 ± 0.41), Goin (4.11 ± 0.36), and Fulani (3.80 ± 0.41) than other ethnic groups; and slightly more important for older informants (4.14 ± 0.40) than younger informants (3.90 ± 0.38).

Irrespective of the predictors considered in this study (study site, ethnic group, and generation), food use value (2.89 ± 0.03) was the most important followed by medicine (0.63 ± 0.11), energy (0.29 ± 0.13), cultural (0.17 ± 0.07), construction (0.05 ± 0.02), magic (0.005 ± 0.006), and fodder (0.003 ± 0.00). With respect to the study sites, traditional knowledge revealed that food use values were more important in the three study sites (Fig. 6), while medicinal uses were important in Tapoa-Boopo, and energy (fuelwood) in Tiogo (Fig. 6a). Considering the ethnic groups, Gourmantché and Goin gave more importance to food use while the Gourounsi gave more importance to the energy use compared to other ethnic groups (Fig. 6b). In relation to generations based on their TK, food, medicinal, and cultural uses were more important for older informants than younger informants while the use of the species for construction was more important for younger informant than older informants (Fig. 6c, Table 5). With respect to gender, food, cultural, and magical uses were more important for men than women while energy and medicinal uses were more important for women than men (Fig. 6d).

The overall knowledge of G. erubescens uses varied greatly across ethnic groups due to the cultural heritage, knowledge being transmitted from generation to generation within the same ethnic group. In this regard, Gourounsi, Goin, and Gourmantchés’s knowledge was relatively higher than that of other ethnic groups, confirming that cultural differences determine plant use habits—a view expressed by other studies in West Africa [34‐36]. Furthermore, indigenous ethnic groups for example the Gourounsi had more knowledge on the use of the wood of G. erubescens compared to other ethnic groups. This is because this group has lived in these communities for centuries and closely interacting with their environment, which has contributed to a gradual accumulation of knowledge over time. Thus, ethnicity constitute an important factor on the uses and knowledge of plants between communities and our findings support the general trend that ethnicity influences traditional knowledge on plant use [2, 33, 34, 37]. Ethnicity according to Etongo et al. [2] goes beyond belonging to a cultural group or way of life, and includes cultural beliefs, taboos, rituals, and ideology of social groups. Therefore, groups that interact with the environment daily or more frequently such as cattle headers (Mossi) in search of fodder or traditional healers (Gourmantché) in search of herbs have relatively more knowledge on the use of different plant parts of G. erubescens.

Additionally, this study showed that the elderly generation had more local knowledge on the use of G. erubescens than the younger generation. This could be explained, on the one hand, by the fact that older people have more uses than the younger ones and secondly by the fact that it is the result of the transmission of knowledge across generations [9]. According to Geng et al. [38], the transmission of knowledge from the older to the younger generation is nowadays confronted with a gradual disappearance of these knowledge systems partly due to migration from rural to urban areas. Several other studies including those of Lougbégnon et al. [39] and Salako et al. [15] have shown that individual characteristics such as age, for example, can influence knowledge of resources and their use within a community. The difference observed in medicinal use of the plant can be explained by the fact that such uses are often specific and are mostly reserved for the elderly. Besides, the collection of medicinal plants is particularly accompanied by certain religious, ethnic, empirical, and magico-religious rules [40]. Therefore, elderly have more knowledge in this category of use than young people given that these restrictions that are culturally motivated are applicable only to the latter group. However, traditional knowledge on plant uses does not accumulate by default and even those in the older age category (> 40 years), needed to have interacted with the natural environment in their respective communities—a pre-condition for them to gain more knowledge than the than younger informants. These results are similar to those of Goudégnon et al. [9] who reported significant difference between generations and ethnic groups on Lannea microcarpa Engl. & K. Krause in Benin.

The most common medicinal uses are the treatment of gastric diseases and syphilis, the treatment of sexual asthenia and female infertility. The variation in food use could be explained by the fact that the local populations of the three study sites do not use the plant in the same way. For instance, according to the Non-Timber Forest Products Promotion Agency (NFPA), in some areas of Burkina Faso, including the province of Nayala, the fruit would be prepared in paste form such as Tô (local name of maize or millet paste) or in association with couscous (a North African dish of steamed semolina usually served with meat or vegetables). In other localities, the fruits are eaten raw or cooked [8].

The knowledge on food uses was similar among the study sites, ethnic groups, generation, and gender. Our finding can be justified by the fact that food uses are common among the socio-demographic attributes as reported by Goudégnon et al. [9], suggesting a consensus for G. erubescens food uses.

The results also showed that fruits were the most used plant part for food by the local populations. Several studies have reported the use of fruits in the food and medicinal uses in West Africa [3, 13, 18]. In addition to its fruits, leaves, roots, and young twigs were also used for medicinal purposes which give a considerable value to the species since most of these plant parts are used in several areas. This represents an asset to valorize the plant and its parts for income, food, and nutrition. The fact that fruits was the most important plant part is an evidence that G. erubescens is an indigenous food tree species.

A study by Etongo et al. [2] stressed that understanding the cultural importance of plant resource is crucial for an informed management. The current study revealed differences in form of uses across the study sites, ethnic groups, and generation. Food and medicine were the most culturally important uses of G. erubescens in Burkina Faso. These use-categories are also the most important for Bombax costatum [41], Lannea microcarpa [9], and Borassus aethiopum [15]. Food and medicinal uses are basic needs for local population living in Boulon, Tapoa-Boopo, and Tiogo. These two use-categories are invaluable for local livelihoods especially with the relatively greater reliance of the rural communities on herbal/traditional medicine partly due to poverty and also due to the lack of health facilities that are of adequate standards to provide medical services to the rural population. The fact that food and medicinal uses were more important for women compared to men is an indication that women are responsible for kitchen and most often engaged in the marketing of food and medicinal products in the markets. Men on the other hand are often responsible for constructions, cultural, and magic care of the household members.