An ethnobotanical study of medicinal plants in Wonago Woreda, SNNPR, Ethiopia

Background Medicinal plants are the integral part of the variety of cultures in Ethiopia and have been used over many centuries. Hence, the aim of this study is to document the medicinal plants in the natural vegetation and home gardens in Wonago Woreda, Gedeo Zone, Southern Nations, Nationalities and Peoples Regional State (SNNPR). Materials and methods Thirty healers were selected to collect data on management of medicinal plants using semi-structured interview, group discussion, and field observation. The distribution of plant species in the study areas was surveyed, and preference ranking, direct matrix ranking, priority ranking of factors and Informant consensus factor (ICF) were calculated. Results The informants categorized the vegetation into five community types based on plant density and associated landform: 'Raqqa', 'Hakka cadanaba', 'Mancchha', 'Bullukko', and 'Wodae gido'. 155 plant species were collected from the natural vegetation and 65 plant species from the home gardens ('Gattae Oduma'). Seventy-two plant species were documented as having medicinal value: Sixty-five (71%) from natural vegetation and 27 (29%) from home gardens. Forty-five (62%) were used for humans, 15(21%) for livestock and 13(18%) for treating both human and livestock ailments: 35 (43.2%) were Shrubs, 28(34.5%) herbs, 17 (20.9%) trees and 1(1.2%) climbers. The root (35.8%) was the most commonly used plant part. The category: malaria, fever and headache had the highest 0.82 ICF. Agricultural expansion (24.4%) in the area was found to be the main threat for medicinal plants followed by fire wood collection (18.8%). Peoples' culture and spiritual beliefs somehow helped in the conservation of medicinal plants. Conclusion Traditional healers still depend largely on naturally growing plant species and the important medicinal plants are under threat. The documented medicinal plants can serve as a basis for further studies on the regions medicinal plants knowledge and for future phytochemical and pharmacological studies.


Introduction
Ethiopians have used traditional medicines for many centuries, the use of which has become an integral part of the different cultures in Ethiopia. The indigenous peoples of different localities in the country have developed their own specific knowledge of plant resource uses, management and conservation [1].
Traditional remedies are sometimes the only source of therapeutics for nearly 80% of human population and 90% of livestock in Ethiopia of which 95% are plant origin [2]. The majority of the population that lives in the rural and the poor people in urban areas rely mainly on traditional medicines to meet their primary health care needs.
In most scenarios, the traditional knowledge in Ethiopia is passed verbally from generation to generation and valuable information can be lost whenever a traditional medical practitioner passes without conveying his traditional medicinal plants knowledge. In addition, the loss of valuable medicinal plants due to population pressure, agricultural expansion and deforestation is widely reported by different workers [3,4]. As a result, the need to perform ethnobotanical researches and to document the medicinal plants and the associated indigenous knowledge must be an urgent task [5,6].
The studies conducted on the traditional medicinal plants in Ethiopia are limited when compared with the multiethnic cultural diversity and the diverse flora of Ethiopia. Thus, this study was initiated to document the medicinal plants in the natural vegetation and home gardens in Wonago Woreda, which assume that the data could be used as a basis for further studies on medicinal plants in Wonago Woreda and for future phytochemical and pharmacological studies.

Study sites
Wonago Woreda (N 6° 20' and E 38° 19') is located 380 km from Addis Ababa in Gedeo Zone, Southern Nations, Nationalities and Peoples Regional State (SNNPR) and bordering with Oromia to the west and northwest, Yirgachefee to the south and southeast, Dilla to the north and Bule to the east. It is approximately 248 sq. km (24,790 ha) and comprises of 19 Kebeles (Fig. 1).
The 2005 census indicates that Wonago Woreda has a total population of 162,663 of which 78,649 (48.3%) are males and 84,014 (51.6%) are females. The population density of the Woreda is 702 persons per km 2 at a national growth rate of 1.07 percent. Seventy four percent of the population in the Woreda are the Gedeo people.
As the agricultural sector is the dominant means of livelihood for the majority of Wonago Woreda people, out of the total of 24,790 hectares of land in the Woreda, 22,871 hectares are known to have potential for agriculture. Annual crops cover 5.03 percent; perennial crops 84.77 percent, uncultivable land 0.65 percent and others are 3.52 percent. It has three main agro-climatic zones with the topography ranging from wide flat valley bottoms to steep mountain slopes. The rainfall distribution of the study area is bimodal. The main rainy season is from June to September ('Kiremt' or Mahar') and the short rainy season is from February to April ('Belg'). The average annual rainfall is 107.72 mm and, the mean annual average temperature of the Woreda is 20°C (Fig. 2) The study was conducted in ten kebeles (farmers' associations) in Wonago Woreda, SNNPR from November 1, 2006 to December 3, 2006. Prior to ethnobotanical data collection, discussions were made with elders and local authorities to select the kebeles where traditional healers were found. The kebeles were selected based on availability of traditional healers, and on the recommendations of elders and local authorities in the Wonago Woreda: 'Bankookoto', 'Balebukisa', 'Deko', 'Halemo', 'Haseharo', 'Karasodity', 'Mokonisa', 'Sokicha', 'Sugale', and 'Tumata cherecha' (Fig. 1).

Ethnobotanical data collection
Thirty traditional healers (22 males and 8 females) were selected from Gedeo people in the Wonago Woreda based on the recommendation from elders and local authorities (Development Agents and Kebele administration leaders). The ages of the healers were between 35 years and 75 years. A brief group discussion was made with the informants at each kebele prior to ethnobotanical data collection to get their consent and to explain to them that their cooperation is a valuable contribution to the documentation of the traditional medicinal plants of the Wonago Woreda. Semi-structured interview, group discussion, and field observation were employed to collect data on knowledge and management of medicinal plants [7][8][9]. The group discussions were conducted to elaborate the methods of preparation, administration and conservation of the medicinal plants. Interviews were conducted in "Gedeoffa" language with the help of local translator. During the study period, each informant was visited two to three times in order to confirm the reliability of the ethnobotanical information. The responses that were not in harmony with each other were rejected.

Plant specimens' collections and identifications
The reported medicinal plants were collected from natural vegetation and home gardens during the field walks and trees, shrubs, herbs and climbers were listed. Voucher specimens were collected, pressed and deposited in the National Herbarium of Addis Ababa University (AAU). The plants identification was performed both in the field, and at the National Herbarium of AAU [10][11][12][13][14][15][16].

Data analysis
A descriptive statistical methods, percentage and frequency were used to analyze the ethnobotanical data on Location of Wonago Woreda in Gedeo zone; Southern Nations, Nationalities and Peoples Regional State (SNNPR) Figure 1 Location of Wonago Woreda in Gedeo zone; Southern Nations, Nationalities and Peoples Regional State (SNNPR).
reported medicinal plants and associated indigenious knowledge.
Preference ranking was computed to assess the degree of effectiveness of certain medicinal plants against most prevalent diseases in the area. Priority ranking of factors perceived as threats to medicinal plants based on their level of destructive effects (values 1-6 were given: 1 is the least destructive threat, and 6 is the most destructive threat) and Direct matrix ranking on uses perceived as threats to medicinal plants were conducted for multipurpose medicinal plants that were commonly reported by healers [7,9].
The Informant consensus factor (ICF) was calculated for each category to identify the agreements of the informants on the reported cures for the group of diseases. The ICF was calculated as follows: number of use citations in each category (n ur ) minus the number of species used (n t ), and divided by the numbers of use citations in each category minus one [17].

Local categories of vegetation
The local communities categorized the vegetation of the study area into five types based on plant density and associated landform. I. 'Raqqa' refers to densely forested land. Currently, this type of vegetation has declined in the study area because of degradation by human activities, over grazing, and climate changes.
II. 'Hakka Cadanaba' refers to vegetation growing in marshy or water logged areas often characterized by salty soil. Plant species such as Phoenix reclinata and Cyperus spp. were more frequent.
III. 'Mancchha' refers to a bare or with poor vegetation with some types of herbs and grasses appearing only during the rainy season.
IV. 'Bullukko' refers to the heterogeneous mixture of shrubs and grass communities not suitable for agriculture. V. 'Wodae Gido' refers to wooded and under-growing herbaceous vegetation growing along riversides. Plant species like Spatodea nilotica, Erythrina brucei, Ficus spp. and Arundo donax were common.

Plant species in the natural vegetation of the study area
155 plant species were collected from the natural vegetation, which were distributed among 63 families and 136 genera. The leading family was Asteraceae with 18 species, followed by Fabaceae with 12 species, Euphorbiaceae with 9 species, Poaceae, Solanaceae and Rosaceae each with 6 species and Myrtaceae with 5 species. Fifty-seven (37%) were herbs, 53 (34%) were shrubs, 39 (25%) were trees, 5 (3%) were climbers, and one (1%) was epiphyte [see Additional file 1].

Plant diversity of the 'Gattae Oduma' (Home garden)
In the 'Gattae Oduma' (Home garden), the farmers grew diverse plant species with known uses. The number of plants recorded represents 65 species that belong to 33 families and 57 genera. In terms of species composition, Solanaceae had 6 species followed by Poaceae with 5 species, Asteraceae, Fabaceae, Lamiaceae and Rosaceae each with 4 species and Brassicaceae, Euphorbiaceae and Rutaceae each with 3 species (Table 1).

Medicinal plants Medicinal plants used to treat human and livestock diseases
The highest medicinal plant knowledge acquisition by the healers in this study site was from parents or close relatives (91%) followed by self trial and error method (9%). The healers have a very high intention to keep their traditional knowledge secrete and less than 2% of them were ready to transfer their knowledge on incentive bases.
Seventy-two plant species distributed into 48 families and 70 genera were documented as having medicinal value in the study area. Sixty-five (71%) of the medicinal plants were collected from natural vegetation and 27 (29%) from home gardens. Of these 45(62%) were used as human medicines (Table 3), 15(21%) as livestock medicines (Table 4) and 13(18%) were used for treating both human and livestock diseases ( Table 5).
The highest number of plant species was found in Asteraceae with 10 plant species followed by Solanaceae with 6 plant species, Euphorbiaceae and Fabaceae each with 5 plant species, Celastraceae and Cucurbitaceae with 3 plant species each (Table 3, 4, 5).
Remedies were mainly prepared in the form of powder, concoction and decoction (Table 6). Healers used various units of measurement such as fingered length (e.g. for root, root bark, and stem), pinch (e.g. for powdered plant parts) and numbers (e.g. for leaves, seeds, fruits and flowers) were used to estimate and fix the dosage of the medicine. The methods of administration of herbal medicines were 48(59.2%) internal, particularly oral, followed by 22(27.1%) dermal and 10(12.3%) nasal.

Ranking of medicinal plants on their uses
Malaria and diarrhea were the most common diseases for which large number of patients visits the traditional medicinal practitioners. Vernonia amygdalina was the most preferred as effective treatment against malaria (Table 7) and Croton macrostachyus was preferred among the medicinal plants that were reported by more informants as a remedy to diarrhea (Table 8).

Informant consensus factor (ICF)
Diseases that were found to be prevalent in the area were treated by variety of medicinal plants. The category: malaria, fever and headache have the highest 0.82 ICF followed by ascariasis and diarrhea, and intestinal parasite and stomachache each with 0.78 ICF (Table 9).

Multiple uses of plants and effect on the conservation of the medicinal plants
The people in the Woreda relied on naturally growing plant species for various purposes such as construction, firewood, washing, cash income and charcoal. Croton macrostachyus was used for variety of services by the community followed by Millettia ferruginea; however, each plant species was used for a given specific service such as Phytolacca dodecandra was used for washing more often than the other plants (Table 10).
The medicinal plants in Wonago Woreda were threatened by natural and human made factors. Agricultural expansion was found to be the main threat followed by fire wood collection (Table 11).          Hunde [18], Mohammed [19], Tollosa [20] and Awas and Asfaw [21] used similar approaches to identify sites of collection of medicinal plants.

Natural vegetation and home garden diversity
In this study, the number of medicinal plants collected from the natural vegetation is more than home gardens. This is also true to the studies conducted in different parts of the country.  [25] are obtained from the natural vegetation. Asfaw [26] reported that only 6% of the plants maintained in home gardens in Ethiopia are primarily cultivated for their medicinal value. Some of the medicinal plants cultivated provided a number of services to the local people because the primary function of these home gardens was to produce foodstuffs. This might be because of high population density and shortage of land for cultivation in the area [27].

Medicinal plants
The medicinal plant species recorded in Wonago are also used as remedies in other parts of Ethiopia and Africa. Among the total of Seventy-two medicinal plant species investigated in this study, 22 species are mentioned in Taddese [28]; 20 species in Wondimu et al. [23]; 11 species in Taddese and Demissew [29]; 23 species in Tamene [30]; 21 species in Hunde [18]; 11 species in Balemie et al. [31]; 39 species in Lulekal et al. [22]; 21 species in Teklehaymanot and Giday [32] and 17 species in Teklehaymanot et al. [33]. In Africa, 13 medicinal plant species are documented by Anokbongo [34] and 16 by Iwn [35].  [37], and Calpurnia aurea (Alt.) Benth. and Phytolacca dodecandra L'Herit in Ethiopia [38] are used for treatment of skin disorders. Parts of medicinal plants used as remedy in the study area, Wonago Woreda Figure 3 Parts of medicinal plants used as remedy in the study area, Wonago Woreda.  [39].
The medicinal plants that were presumed to be effective in treating a certain disease had higher ICF values, which indicated that these diseases were more common than those with low ICF: malaria and headache (82.3%), ascariasis and diarrhea (78.2%), and intestinal parasite and stomachache (77.7%).
The most widely used plant remedies by people of Wonago were obtained from shrubs (43.2%) followed by herbs (34.5%). The documented data showed that the majority of medicinal plants from natural vegetation were shrubs and herbs; they were relatively common in the study area compared to medicinal tree species. This finding agrees with the findings of Tamene [30], Hunde [18] Yineger and Yewhalaw [25], Giday and Amani [40] and Lulekal et al. [22]. However, the finding of Birhanu [41]; Mohammed [19]; Gebre [42] and Teklehaymanot and Giday [32] shows that herbs are the primary habit form.
The informants' responses indicated that there were variations in dosages of remedies, unit of measurement of remedies, duration and time that were prescribed for the same kind of health problems. The major factors that determine the amount to be given were age, physical fitness, stage of illness, pregnancy and presence or absence of any disease other than the disease to be treated. Getahun [46], Sofowara [47] and Abebe [2] have also discussed lack of precision and standardization as a drawback of the traditional health care system.

Conservation and threats of medicinal plants
Some traditional practitioners had started to conserve medicinal plants by growing them in home gardens. Such as Ruta chalepensis, Rhus vulgaris, Ocimum lamiifolium, Artemisia abyssinica and Artemisia afra similar to the observation made by Kansheiae [27]. In most scenarios, the home gardens are fenced and protect the medicinal plants from grazing and unwise harvesting [48].
The main threat for medicinal plants in the natural vegetation was agricultural expansion (24.4%). Most of the respondents perceived urbanization and construction as the least destructive factors contributing to 11.8% and 10.2% of the total score, respectively. The rise in Coffea arabica and Catha edulis price on the market were some of the contributing factors for the expansion of agriculture. The other factor was the number of young farmers who were anxious to have their own agricultural land; hence, clearing of natural vegetation and expanding agricultural land was almost a daily activity in the study area. Nevertheless, during the field study, it was observed that large number of big trees of Macaranga capensis, Olea europaea, Pouteria adolfi-friederici, and Syzygium guineense were removed by the local people to prepare the forestlands for agricultural purpose. These factors combined with the natural vulnerability of the area may lead to further reduction in natural habitats of the medicinal plants. Pressure from agricultural expansion, wide spread cutting for fuel wood combined with seasonal drought is also reported in Balemie et al [31], Lulekal et al. [22], Nanyingi et al., [48], Kelbessa et al. [49] and Yineger et al. [50] as main factor for environmental degradation.
The conservation of medical plants in the study area was limited except in Juniperous-Eucalyptus dominated plantation, which was the only protected natural vegetation areas. Rather, the peoples' culture and spiritual beliefs somehow had helped in the conservation of medicinal plants. For instance, the claim of the traditional healers that medicinal plants will be effective only if cut and administered by the healers or healers' reletives had helped in the conservation of the medicinal plants. Also, the collection of medicinal plants in specific season, for example, at the end of the Ethiopian calendar year in 'Pagume' enabled the plants to regenerate and complete their life cycle. This is true mostly for annuals, those whose leaves, fruits and seeds are used, if other destructive pressures are kept at low level.

Conclusion
Traditional medicinal plants were harvested mostly from natural vegetation area followed by home gardens. They were also obtained from roadsides, farmlands and live fences. The medicinal plants in the natural vegetation were under threat and to tackle these problems traditional healers had turned their face towards home gardens. However, traditional healers still depend largely on naturally growing species because of their belief that those species in the natural vegetation are more effective in the prevention and treatment of diseases and health prob-

Declaration of competing interests
The authors declare that they have no competing interests.