Abstract
Ethiopia has a diverse topography with higher plant species composition and estimated to the higher proportion of endemic plant species. Currently, several factors drive natural forest destruction in the country, extensive agricultural land expansion triggered by increasing human population is probably the dominant force. The Dilla University Botanical and Ecotourism Garden was established targeting to rescue threatened flora from extinction, contribute towards conservation, and research on biodiversity and sustainable education as well as ecotourism development. The study was aimed to generate basic scientific information by identifying and documenting the formerly available plant species in to the garden and provide information for farther plant collection planning and research. Systematic sampling method was used to collect the vegetation data from 52 plots of 20 m × 20 m (400 m2) quadrats. To collect data for herbaceous plants, five 1 m × 1 m subplots were laid in each of the main plot, where four were at the corners and one at the centre. Vegetation classification was performed using R-programme version 3.6.1 software packages. Shannon–Wiener Diversity Index was used to calculate species diversity, richness, and evenness. A total of 408 plant species, including trees (30%), shrubs (25%), herb (30%), grass (6%), and 9% of other species, were collected. The identified species belong to 287 genera and 105 families. Out of this, 27 species of plants are endemic to Ethiopia and 72 plant species were screened as a medicinal plant used for the treatment of human diseases. Based on IUCN Red Data List, among the endemic plant species nineteen species were least concern; two were near threatened; two were endangered while four were vulnerable. Three vegetation community types were identified from the hierarchical clustering analysis. The result designates that Dilla University Botanical and Ecotourism Garden has high plant species composition and diversity with a good distribution. The higher composition of this ecologically, economically, and socially important plant species at its early stage makes the garden a unique garden in the country and realize to be a centre for research, education, and tourist destination.
1. Introduction
Ethiopia has a diverse topography with higher plant species composition, where 6,000–7,000 species of higher plants exist in the country of which about 780–840 (12-13%) plant species are estimated to be endemic [1, 2]. However, these biologically rich resources of Ethiopia are vanishing at an alarming rate due to monocropping and expansions of road construction through vegetation are becoming other causes of deforestation. Currently, increasing rate of drought, desertification, and shortage of food for both humans and animals are becoming serious problems that need attentions [3]. Although several factors drive natural forest destruction in Ethiopia, extensive agricultural land expansion triggered by increasing human population is probably the dominant force [4, 5]. The indigenous agroforestry systems in the southeastern Rift Valley escarpment of Ethiopia were shown to maintain a high proportion of native tree species (86%). This is considerably higher than reported for traditional tree-crop and Enset-coffee agroforestry systems in the eastern and southern parts of Ethiopia [6–8].
Today the forest cover in Ethiopia is less than 3% compared with an average of 20% for sub-Saharan Africa [9]. The need for fuel wood, Forest conversion to farmland, seasonally set forest fires, and over grazing areas have been indicated as the main causes of forest degradation; frequently leading to loss of forest cover and biodiversity, erosion, desertification, and reduced water resources [10].
The destruction of vegetation and environmental degradation has become issues of national and global concern in recent years. This is because of the fact that declining vegetation cover and depletion of natural resources are closely associated with drought and food shortages that have become major threat affecting the life of millions of people. The depletion of the natural vegetation in many parts of the country has also led to the threat and decline in number and distribution of many plant species [11].
According to Kelbessa et al. [12], 120 threatened endemic plant species are known from Ethiopia. Thirty-five of these species were from the Dry Afromontane forests of the country. Therefore, there is a need to conserve the natural vegetation. This could be achieved by appropriate management and use plans that include ecologically sound restoration or rehabilitation measures. There are diverse approaches and techniques to restore land and vegetation. Maintaining the Floristic composition, natural regeneration species, and conservation of the forest are among the approaches which closely linked with low cost in the form of in-situ conservation system.
Thus, establishing Botanic Gardens have significant role to save plant resources of special value from the looming destruction and eventual extinction. Botanic Gardens play major roles in strengthening conservation and care for plant species, particularly rare, economically important, and endangered species under threat by natural and manmade factors, including ex-situ conservation and appropriate scientific protection and care. It is accepted worldwide that Botanic Gardens are institutions working on conservation, care and research, and education services. Moreover, it also provides ecotourism services of natural attractions and aesthetic value from flower, seedling shops, and restaurant services.
Botanic gardens are delineated as a living museum that holds individual specimens or collections of plants for scientific, educative, conservation and aesthetic purposes. So that it defined, “Botanic gardens are institutions holding documented collections of living plants for the purposes of scientific research, conservation, display, and education.” [13]. The botanic gardens have worked to prioritise the plants facing threat, take conservation action both in situ and ex situ, tackle overexploitation of individual species, inform and educate visitors and the wider public, and champion plants. The recently established Dilla University Botanical and Ecotourism Garden is located in southern part of Ethiopia, Gedeo zone, which is located on the escarpments of the south eastern Ethiopian highlands overlooking the Rift Valley. The site has geographical, archaeological, biological, cultural, and political values. Geographically, the site has different types of rocks and very attractive landscape, archeologically it has different engravings and cave, and biologically it is rich both in plants and animals biodiversity. So, the significance of the garden for conservation of Ethiopian biodiversity especially for low land and mid land plant biodiversity is unquestionable. The aim of this study was to generate basic scientific information on plants by identifying and documenting the formerly available and introduced plant species and vegetation structures of the garden. It will be important for the future plant collection planning for conservation, research, and education activities.
2. Methods
2.1. Site Descriptions
Dilla University Botanical and Ecotourism Garden (DUBEG) is the conservation initiative established since 2017 G.C. on 130 hectares in Gedeo zone at the west corner of Dilla town, Sesa sub-City, Odaya Kebele between main and Odaya campus of Dilla University. The vision of the garden is to achieve internationally renowned botanic garden, witnessing Ethiopia’s floral richness and its centre of origin for many economic plants. The mission of the garden is to rescue threatened flora from extinction, contribute towards conservation, and research on biodiversity and sustainable education as well as ecotourism development. The geographical co-ordinates of the garden lies between latitude 6°25′55.66″ N and 6°26′ 44.6″N and longitudes 38°16′05.12″ E and 38°17′25.56″ E (Figure 1). The garden is located 1 km northeast of Dilla town and 1.5 km north to Dilla University main campus. The site is bordering with Laga Dara River (Sidama zone) to North, Don Bosco pig production to South, Mejege River (Abaya woreda) to Weast and Saron log and Odaya campus of Dilla University to East.
The site has geographical, archaeological, biological, cultural, and political values. Geographically, the site has different type of rocks and very attractive landscape, archeologically it has different engravings and cave, and biologically it is rich both in plants and animals biodiversity. Culturally, the local people were using the site for different ceremony like wedding and different concerts. Politically the site is also the borderline of three administrates zones (Gujje, Geodo, and Sidama). Therefore, the area gives great opportunity to strengthen the relationship between the three zones with Dilla University, the university with other stakeholders.
In addition, DUBEG is a potential area for education, conservation, research, and recreation. It also has an access for infrastructure, water (3 rivers), road, relatively fertile soil, geographically it is attractive (ranging from sheltered gullies and streams, rivers, valley, gorge, caves, escarpment, to steep hillsides, and exposed hilltops), and it is near to the Dilla university. Other than these the area has rich source of indigenous crops, wild animals, cultural heritages (engravings of wild animals expected to the age of antiquity), and cave.
The garden activities have currently started on land about 20.7 hectares at the subsite locally called Waleme. Don Bosco Catholic Church protected this area for the last 30 years. At this site, the garden has two separate parts nursery site (2.6 hectares) and the main garden (18.1 hectare). The internal parts of the main garden also have different components, which are uses for various activities of the garden. Each of the garden components has a particular function. It has seven main components, such as Child Garden, Scientific Garden, Recreation site, Nursery site, Science Cafe, research and staff office, and Infrastructure which includes roads, irrigation system, store room, composite site, and compound (fence). The nature of these different components determines the primary opportunities for teaching and visiting.
2.2. Climatic Conditions
The analysis of Metrological data of monthly maximum and minimum temperature and monthly rain fall were taken from Addis Ababa National metrological Agency for the period 1988–2018. It showed that the mean annual temperature of the study area is ranging from a mean minimum of 8°c to mean maximum of 25.4°c. The mean annual rainfall of the area is 1,267 mm per year. The region indicates concentration of a bimodal pattern type of rain in the zone when long rain (mid-February to mid-may) and short rain (September to November) with in tiny and fine rain showers in June (Figure 2). The lowest mean temperature over 30 years was 8°c recorded in metrological data of Dilla station.
2.3. Data Collection and Analysis
2.3.1. Sampling Methods
The vegetation data were collected from 52 plots of 20 m × 20 m (400 m2) quadrats laid at every 50 meters along seven transect lines from south-north direction using compass. The distance between each transect line was 70 m laid in a zigzag form of starting point of laying plot. To collect data for herbaceous plants, five 1 m × 1 m subplots were laid in each of the main plot, where four were at the corners and one at the center. Plant species in each plot was counted and recorded at individual level; voucher specimens were collected, numbered, and pressed for further identification by using checklists and flora Ethiopia and Eretria [14]. Additional plant species occurring outside the quadrats, but inside the forest within 10 m distance, were also recorded only as “present” for floristic composition, but they were not used in the subsequent vegetation data analysis [15, 16]. The vernacular (local) names were used when available. Finally, socioeconomically important plant species and their status were screened based on the previous literatures.
2.3.2. Plant Community Determination
The vegetation data analysis was made based on species absence presence data. The diversity of voucher plant species were estimated by using the Shannon–Wiener index (H′) and Simpson’s dominance index (1-D) [17]. The computer R-programme version 3.6.1 Vegan package was used to analyze the vegetation data through Agglomerative Hierarchical Classification technique. The Euclidean distance and Ward’s method were used for clustering the vegetation data. Its classification was made using cover abundance values as class labels. The clusters were assigned in number to indicate the individual communities’ number.
3. Results
3.1. Floristic Composition
A total of 408 specimens of plants (herbs, shrubs, trees, shrubs/trees, climbers, and tree/climbers) were identified and documented from Dilla University Botanical and Ecotourism Garden. Oof them, 131 were introduced from a different area for the purposes of conservation and garden beautfication. Three species, Ziziphus spina-christi, Ilex mitis, Eucalyptus citriodora, and Opuntia ficus indica, and some annual plant species were collected outside the sampling plots for the purpose of documentation of available plant species. Those plant species was not incorporated in statistical data analysis. The collected species were composed of 32% trees, 32% herbs, 24% shrubs, 4% grass, 4% climbers, 1% liana, and 1% Fern and Epiphytes species (Figure 3).
The identified species belong to 287 genera and 105 families. The major families were Fabaceae represented by 44 species (10.81%), Poaceae and Euphorbiaceae each with 22 species (5.41% each), Asteraceae by 20 species (4.91%), and the remaining (48%) families were represented by one species (Table 1).
3.2. Plant Community Classification
The abundance data of a species were used for the analysis. R program Version 4.2.2 software (Vegan and labdsv package) was used to perform a hierarchical cluster dendrogram, which depicted the vegetation community of plant species. Three communities (clusters) were identified as a result of grouping of quadrates and designated as communities 1, 2, and 3 shown in the dendrogram (Figure 4).
The results of Sorensen’s Similarity Index indicate the vegetative community similarity in species composition is slightly varied among communities. The highest similarity was observed between communities II and I (27.7%). The least similarity was observed between community II and III (18.1%) and relatively shares less species within the community. Overall similarity coefficient ranges from 18 to 28% among all the communities. Thus, species composition dissimilarities account for 72% for the most similar communities and 82% for those that share least similarity (community II and III).
Generally, the clusters represent the actual DUBEG components, community number one represents the nursery site and the protected forests along the river, community number two represents scientific garden and child garden sites, community number three represents recreation site and science cafe.
3.3. Species Diversity
The Shannon–wiener index (H) for the communities reflect the deference in their species richness and evenness. Species diversity among the Community types is categorised from highest to lowest as Community-II > Community-I > Community-III and species evenness Community-II > Community-I > Community-III has the highest species richness and highest H’max. Community III has the least even distribution, the least diversity, the least species richness, and the least equitability. Generally, the three communities have almost the same species distribution (equitability or evenness) but comparatively community III has the least species evenness (Table 2).
Among the identified plants of the study area, 27 species (6.61%) were endemic plant species to Ethiopia. According to the IUCN Red Data List, one species was categorized as Nearly Threatened (Maytenus addat (Loes.) Sebsebe), one species as Vulnerable (Echinops kebericho Mesfin), and the others 25 of them are Least Concern (Table 3). These endemic species were composed of herbs, shrubs, trees, liana, and grass constitute 33.33%, 25.93%, 18.51%, 11.11%, and 3.70%, respectively.
Following a desk study to review the literature on ethnobotanical uses of plants, it was found that 72 plant species belonging to 38 families were screened as a medicinal plant used for the treatment of human diseases (Table 4). Accordingly, the life forms of medicinal plants reviewed belongs to 28 trees (38.89%), 17 shrubs (23.61), 21 herbs (29.17%), two climbers (3.81%), two liana (2.78%), and one grass (1.39%). As the referenced authers indicated, the traditional healers have harvested these medicinal plant leaves, roots, barks, seeds, fruits, stems, flowers, barks, seeds, or latex for treatment of human diseases.
For the documentation purpose, 408 plant species are listed by their botanical name following the Flora of Ethiopia and Eritrea Volume 1–8 and Natural Database for Africa (NDA). On CD-ROM Version 2 (Table 5). The higher plant species composition at its early stage rank Dilla University Botanical and Ecotourism Garden at the second level among the botanic garden (Gullale botanic garden) and other protected field Gen banks and make it a unique garden to the country.
3.4. Discussions
3.4.1. Floristic Compostion
In this study, a total of 408 plant species, including shrubs, trees, shrubs/trees, herbs, epiphyte, liana, and grass, were recorded. Out of this, 27 species of plants are endemic to Ethiopia and 72 of plant species also have a medicinal value that is used for the treatment of human diseases. According to IUCN [24] Red Data List, 19 species were least concern, two were near threatened, and two were endangered, while four were vulnerable. Overall diversity and evenness were 1.79 and 0.09, respectively. According to Kent M. et al. [25], the Shannon–Weiner diversity index normally varies between 1.5 and 3.5 and rarely exceeds 4.5. In our study area, however, there is high diversity and evenness showing more or less even representation of individuals of most plant species in the sampled quadrats.
Vegetation classification is a powerful tool employed for several purposes, including efficient communication, data reduction, and synthesis, interpretation, and land management and planning. It also provides one way of summarizing our knowledge of vegetation patterns [26]. Hence, three plant community types were identified at the Dilla University Botanical and Ecotourism Garden. These three communities also represents the actual garden compartments. Community number three represents the scientific garden and child garden areas of the garden. This area is where high plant collection and plantation have been engaged. That is why this community was represented only by two plots. Species richness (number of species) was determined by summing up the number of species identified [27]. The diversity index [28] was computed for the three communities from the study garden. The different values of H′ for the communities reflect the difference in their species richness and evenness. The minimum value of H′ is zero, which a value for a community with a single species and increases as species richness and evenness increases. The variation in species richness and diversity may be attributed to varation in altitude, latitude, and soil gradient and disturbance factors [29]. The relatively higher similarities between community types IV and I is probably due to the similar environmental conditions and their similar altitudinal range.
As reported by Dereje D. et al. [30], in addition to altitudinal gradient, other environmental factors such as aspect, slope, and soil physical and chemical properties have sound effects on patterns of vegetation in communities. The study conducted in a similar method at different areas of catchiment indicates 213 plant species were collected from Chilimo forest [31] and 80 woody species from Gamo Gofa Zone [32]. Although, a total of 155 socioeconomical important plant species were collected from natural forest and 65 plant species from home garden at Gedeo Zone, Wonago Woreda [33]. Comparatively, DUBEG is composed of higher ecologically and socioculturally important plant species. The accessible plantation of collected plant species from various areas for the purpose of conservation, research, and education in DUBEG at the site of scientific garden and child garden has a great role for the existed variation among the communities. The existence of higher plant species on these selected areas is also very important to make plant conservation awareness, education, and demonstration for peoples visiting the site. It is also important to enhance and increase awareness of cultural diversity as part of the conservation mission [34].
4. Conclusions
The result of the study indicates that the Dilla University Botanical and Ecotourism Garden has high plant species composition and diversity with a good distribution. A total of 408 plant species were recorded from the garden; out of this, 27 plant species are endemic to Ethiopia and 72 of plant species have also a medicinal value that is used for the treatment of human diseases. Based on IUCN Red Data List, nineteen species were least concern; two were near threatened; four were vulnerable, while two were endangered. Three plant community types (cluster) and sample plots distribution were identified at DUBEG. These three communities are also representing the actual garden compartments and reflect their representative plant composition. The composition of this highly useful plant species compared to the surrounding catchiment and some protected forest at its early stage makes the Dilla University Botanical and Ecotourism Garden unique to the country and center for research, education, and tourist destination.
Finally, further studies on soil properties and detailed ethnobotanical studies are required to explore the wealth of indigenous knowledge on the diversity of plants and their implications in conservation are also recommended.
Abbreviations
| A.A: | Addis Ababa |
| DUBEG: | Dilla University Botanical and Ecotourism Garden |
| sps: | Species. |
Data Availability
All data relating to plant species generated or analyzed during this study are included in this published article. The data that support the findings of this study are available from the author upon request.
Ethical Approval
Research and dissemination committee (RDC) of Dilla University Research and dissemination Office (RDO) approved the research work. Contacts to Dilla University Botanical and Ecotourism Garden Director’s office were also made to make the agreement on about the purpose of the study, possible result and benefits of the study, and lastly to labor workers of the garden for plant sps identification in their local name. Finally, after the agreement was achieved and positive attitudes were developed, data collection was started.
Conflicts of Interest
The authors declare that they have no conflicts of interest.
Authors’ Contributions
All authors have read and approved the manuscript.
Acknowledgments
The authors would like to gratefully acknowledge Dilla University Botanical and Ecotourism Garden workers for their willingness to provide us a necessary information and plants local name as well as for those who were kind enough to share their knowledge and experiences without reservations are highly acknowledged. The study received support from the Dilla University in the form of transport during data collection.