Diversity of woody species in traditional agroforestry practices in Wondo district, south-central Ethiopia

Abstract

Woody species are very important components of agroforestry as they play multiple roles in the system. Therefore, this study was conducted to assess woody species diversity within households' farms. Stratified random sampling was employed for the study, where households were stratified via wealth ranking. Accordingly, the farm plots of 54 households were subjected to a complete on-farm woody species inventory and identification. Consequently, the diameter at breast height (DBH) of all woody species ≥5 cm was recorded. Therefore, important value and diversity indices, density, dominance, and frequency were computed and estimated. A total of 90 woody species belonging to 80 genera and 42 families were recorded in the area. Out of the total species recorded, 2 (2.22%), 32 (35.56%), and 56 (62.22%) were endemic, exotic, and indigenous, respectively. The family Fabaceae had the highest number of woody species represented by 16. The most frequent species were Cordia africana Lam., followed by Eucalyptus camadulensis Dehnh., Persia americana Mill., Mellitia ferruginea (Hochst.) Bak., and Croton macrostachyus Del. which occurred in 87.03%, 81.48%, 81.48%, 75.92%, 72.2% of sampled farms, respectively. Besides, the top five species which had the highest important value index were Eucalyptus camaldulensis (57.38), Cordia africana (30.45), Persea americana (27.36), Mellitia ferruginea (17.28), and Croton macrostachyus (14.59). Shannon Weiner index (H’) and Shannon evenness values of the study area were 2.17 and 0.80, respectively. Species richness and Shannon index values were statically significant (p < 0.05) among the three wealth categories. Besides, the Sorensen similarity index for studied villages ranged from 33.7% - to 77.5%. Generally, the current study showed that the agroforestry system plays a remarkable role in conserving woody species diversity. However, extension services on management practices for species and stands, increasing seedling accesses, and survival rates of species are very impotent to making agroforestry practices sustainable.

1. Introduction

Since the very beginnings of agriculture, many farmers retained or actively incorporated woody species as part of their agricultural landscapes [1,2]. Over 1 billion hectares (46%) of agricultural land worldwide has more than 10% tree cover [3,4]. Especially in the tropics, woody species are essential components of the farming system [1]. In Ethiopia, agroforestry is an old-age practice whereby farmers maintain and plant woody species in croplands for their multi-purpose uses [[5], [6], [7], [8]]. Agroforestry is practiced in different forms and the most common are homegardens and scattered trees in cropland as parkland agroforestry practices, trees in boundary fields, and grazing land [5]. A study conducted in the south-eastern Rift Valley escarpment of Ethiopia revealed that there are between 17 fruit tree systems and 429 plant species in different agroforestry practices grown within agroforestry systems in Ethiopia [9].

Woody species that are retained on farmlands provide multiple uses, such as shade, shelter, energy, food, fodder, lumber, and many other goods and services that enable the farmstead to thrive and assure food security for those who engage in this activity [10,11]. Because of this reliance on agricultural and forest products, the real challenge in tropical land management is to compromise the ever-growing population and its demand for these products [12,13]. This challenge is particularly severe in small-holder farming systems due to demographic, economic, and social pressures that lead to ecological degradation and the loss of traditional farming systems [14,15]. Similarly, with an increasing population, the size of landholdings decreases, and exploitation of woody species for firewood, fodder, and construction increases, resulting in losses of woody species diversity [16]. Intensification of agricultural practices and consequent simplification of an agricultural landscape is another cause of woody species diversity loss [17]. In spite of this challenge, the application of agroforestry is still a solution to meet farmers’ needs from the existing piece of land while supporting biodiversity conservation, the need for forest products, various goods and services, and income diversification [[2], [3], [4],7,10,18]. In this regard, agroforestry practices provide more multiple uses from their different components than mono-cropping systems [10]. Moreover, agroforestry has great potential for reducing deforestation and forest degradation, providing rural livelihoods and habitats for perennial woody species outside the forests, and alleviating resource-use pressure on conservation areas [19,20].

Recently, trends in plant species diversity conservation are not only focusing on protected areas of natural vegetation but also on the management of agricultural landscapes [15,19,20]. These landscapes are considered to be of vital importance in conserving woody species diversity through on-farm conservation in a way that conserving through utilization, in-situ conservation of woody species by reducing pressure on remaining forests, and protected areas [18,19,21]. Traditional agroforestry management, with less intensively managed systems using native woody species with perennial crops as an understory, and minimal external inputs, enhances conservation and sustainable use of biodiversity resources [6,10]. Farmers have a wealth of indigenous knowledge for growing and managing these massive woody species on their farms [7,22,23]. Woody species management practices are carried out in order to enhance and secure these species' functions now and in the future, and they are interdependent with the utilization of species [8,24].

One of the most difficult challenges is conserving biodiversity on agricultural land, particularly in the tropics where rapid population growth, unplanned settlement, and fragmentation destroy fragile habitats and reduce plant species richness, diversity, and abundance [2,10,15,19,25]. The current concerns to biological diversity necessitate research into the environmental aspects of resource conservation, not only in protected areas but also in ecosystems that are managed by humans and in the nearby agriculture system with effective management practices [26]. Researchers in agroforestry focused primarily on the sustainable production of agricultural products, particularly food, during the course of around two decades. However, over the past decade, scientists have also become interested in the biodiversity conservation and environmental services that agroforestry may provide to indigenous and even global society by maintaining watershed functions, retaining carbon in the plant-soil system, and biodiversity conservation [10]. Farmers in the study area (Wondo District) have been practicing different traditional agroforestry practices by integrating different woody perennials, crops, and livestock components into their lands. These traditional agroforestry practices institute perennial and herbaceous plants that may contributed to biodiversity conservation and socioeconomic alternatives for local communities. However, the contribution of these traditional agroforestry practices to biodiversity conservation has not been studied so far in Wondo District. Therefore, this study was aimed to assess woody species diversity in traditional agroforestry practices at in the Wondo district South-central Ethiopia.

2. Materials and methods

2.1. Description of study site

The study was conducted in Wondo district, West Arsi Zone, Oromia National Regional State, located on the western escarpment of the central rift valley of Ethiopia, about 267 km south of Addis Ababa (Fig. 1). According to the Wondo district agricultural office, the landscape of the study area varies with an altitude ranging between 1700 and 2300 m.a.s.l [27,28]. 90% of the Wondo district lies in the Woina Dega (mid-land) agro-ecological zone, while 10% of the district lies in the Dega (high-land) agro-ecological zone [29]. Accordingly, the present study was carried out in the Woina Dega (mid-land) agro-ecological zone of the district. Thus, the agro-climatic zone of the area is characterized by a ‘tropical highland monsoon’ [30]. The area has a bimodal rainfall pattern in which the short rainy season is between March and May, whereas a long rainy season occurs from July to October, accounting for more than 80% of the total rainfall [28]. The temperature of the area shows large diurnal but small seasonal changes, with an annual average of 20 °C [27]. The soils of Wondo district were classified as Virtic Andosols (Arenic), Leptic Nitisols (Aric), Leptic Vertisols (Aric), Leptic Luvisol (Arenic), and Cambic Phaeozems (Aric) [29].

Fig. 1.

Location map of the study area, south-central Ethiopia.

Remnant natural forest vegetation around the Wondo area can be categorized as dry evergreen Afromontane forest [28]. Trees have been often maintained and planted on homesteads, farmlands, and farm boundaries in the study area Figures (2a and 2b). A variety of fruit trees, shrubs, and cash tree crops like Persia americana, Catha edulis (Vahl) Endl., and Saccharum officinarum L. were dominant in homesteads [29]. Zea mays L., Eragrostis tef (Zucc.) Trotter, and Triticum species are the major grain crops grown in this area. Trees grown at the study site include Albizia gummifera (J. F. Gmel.) C. A., Cordia africana, Croton macrostachyus, Vernonia amygdalina Del., and Mellitia ferruginea [27]. The farmland of the study area is both rain-fed and irrigated. The major plants cultivated in the area are Catha edulis (Vahl) Forssk. ex Endl.), Coffea arabica L., Saccharum officinarum L., Musa paradisiaca L., Persea americana, Solanum lycopersicum L., Solanum tuberosum, L. Ensete ventricosum (Welw.) Cheesman, and Carica papaya L. [29]. These plants are used as a source of income and food. Cattle, sheep, goats, horses, and donkeys are some of the livestock animals commonly reared in the area [27].

Fig. 2.

Partial view of the studied farms (a = homegardens, b = landscape view of agricultural farms with settlement, c = discussion with key informants, and d = recording vegetation data, Photo by Tesfaye Molla, 2017) Wondo District, south-central Ethiopia.

2.2. Methods

2.2.1. Sampling frame and procedures

2.2.1.1. Study site selection

Due to the existence of agroforestry practices and the fragmentation of the land caused by a high population density, the Wondo District was purposefully selected [31]. The district is encompasses nine Kebele administrations, of which two Kebeles and three Villages from each Kebele were purposefully selected based on the existence of intensive agroforestry practices [6,32]. The smallest unit of government in Ethiopia is called a kebele, which is comparable to a ward, a peasant association, a neighborhood, or a confined and bound group of people. The selection was made through discussion with the District agricultural Office and field observation [20]. For the purpose of this study, households were defined as a basic unit of production and consumption, made up of a person whose farm shares common fields and lives under one central decision-maker, the household head [33]. According to the above definition of household, all polygamous families were considered as one household if they were under the same central decision-maker (husband) and farmed common fields. Contrarily, households were seen as independent if the polygamous families lived in different places and farmed on different farms since the household heads' power was partial and they were viewed as visiting husbands [33]. The household was taken as the unit of analysis and stratified random sampling was employed for the study [4,11,24]. Householders' wealth ranking was used to stratify farmers [6]. The list of households was obtained from the Kebele Administrative Office records. Moreover, key informants were requested to classify the households into wealth categories (poor, medium, and rich) in accordance with their local standards. Each key informant was asked his/her criteria for his/her selection (Fig. 2c). Therefore, following the wealth status category by the key informants; the average score was computed, and the wealth category was determined based on that score.

The sample size for this study was determined following the previously adopted formula (Eq. (1)) [34]. Accordingly, 54 households were taken for this study.

$$n=\frac{N}{1+\left(N*e^2\right)}$$ (1)

where n = sample size, N = total population, e = marginal error (10%).

2.2.2. Vegetation inventory

Vegetation sampling was conducted at the farm level and all woody species found on selected households’ farms were identified, counted (Fig. 2d), and subjected to analysis [35]. The total areas of farms were measured and different woody species growing on them were counted and listed [8,24,35]. Woody species along boundaries were inventoried first by determining the length of the boundary within a farm, and then the boundary length was sectioned into a series of 10 m. One section was selected for every 50 m of boundary length, but if the length of the boundary was less than 10 m, the actual length was taken and all woody species were counted and recorded on selected sections [36]. All woody species on each farm were identified. The basal area (dominance) was calculated using measures of diameter at breast height (DBH or at 1.3 m for trees and diameter at stump height (DSH or at 30 cm above the ground for shrubs)) 5 cm, which was then used to calculate the Important Value Index (IVI) [37]. Accordingly, DBH is related to IVI as IVI is driven by relative density, relative dominance, and relative frequency. Therefore, dominance can be computed based on DBH measurement. The diameter was measured using a caliper and diameter tape. In the case of multi-stemmed shrubs, each stem was measured and the diameter equivalent of the plant was calculated following Eq. (2) [37].

$$de=\sqrt{\sum _{i=1}^n{d}_i^2}$$ (2)

where de is the diameter equivalent of the entire stems at breast or stump height and d_i is the diameter of the ith stem at breast or stump height.

Woody species identification was done in the field with the help of local people familiar with flora. Species were given scientific names based on the published volumes of Flora of Ethiopia and Eritrea [[38], [39], [40], [41], [42]] and useful trees and shrubs in Ethiopia [43].

2.3. Important value index

The important value index (IVI) was used to compare the importance of individual species in the agroforestry practices. After combining the information for each species from each field, it was calculated for all woody species found in the sampled plots following (Eq. (3)) (in this case, the plot was equivalent to household farms) [44]. Likewise, relative density, relative dominance, relative frequency, and absolute frequency were computed following Equations, 4, 5, 6, and 7, respectively.

$$IVI=Relativedensity+Relativedominance+Relativefrequency$$ (3)

$$\mathrm{R}\mathrm{e}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{v}\mathrm{e}\mathrm{D}\mathrm{e}\mathrm{n}\mathrm{s}\mathrm{i}\mathrm{t}\mathrm{y}=\frac{Individualnumberofaspecies}{Individualnumberofallspecies}*100$$ (4)

$$Relativedominance=\frac{Dominanceofaspecies}{Dominanceofallspecies}*100$$ (5)

$$Relativefrequency=\frac{Frequencyofaspecies}{Frequencyofallspecies}*100$$ (6)

Frequency of woody species indicates the presence or absence of a given species within each farm of sample field. The absolute frequency for each woody species in agroforestry will be computed following [44].

$$AbsoluteFrequency=\frac{Frequencyofaspecies}{totalnumberofsampleplots}*100$$ (7)

2.4. Diversity indices

Species diversity indexes are mathematical functions that are commonly utilized in the landscape [44]. The measurement of diversity combines the evaluation of two distinct aspects of diversity, richness and evenness, into a single measure [45]. Species richness refers to the number of species per farm, while evenness refers to their relative abundance. To determine the species richness of each farm, the species index (S), which is simply the total number of species on-farm, was noted. However, the relative proportion of species will not be indicated in the species index. Hence, models that incorporate both richness and evenness were required. The Shannon-Wiener diversity index was applied to quantify the diversity of woody species. The Shannon-Weiner diversity index was calculated following Eq. (8) [46].

$$H^{\text{'}}=-\sum _{i=1}^{n}PilnPi$$ (8)

where H' = Shannon-Wiener diversity index, n = the number of species, ln = natural logarithm or log of base e, and Pi = the relative proportion of individuals of the ith species.

The values of the Shannon diversity index usually fall between 1.5 and 3.5 and only rarely surpass 4.5 [44]. Accordingly, the even existence or proportions of species resulted in a higher Shannon's diversity index and vice versa. Thus, the Shannon diversity index (H′) is high when the relative abundance of the different species in the sample is even and decreases when a few species are more abundant than the others.

To determine evenness, which measures the homogeneity of abundance in a farm, the number of species must be distributed as evenly as possible. It refers to the observed value of Shannon diversity divided by the maximum possible diversity with the same number of cover types (Eq. (9)) [47].

$$E=\frac{H^{\prime }}{H^{\prime }\mathit{max}}with{H}^{\prime }=lns$$ (9)

where E = Shannon evenness (equitability), ranging from 0 to 1, and with 1 representing a situation in which all species are equally abundant or perfect evenness, S = the number of species, and H′ max = is the natural logarithm of the total number of species.

2.5. Similarity index

The Sorensen similarity index (Ssi) measures the similarity of woody species composition across agroforestry practices. Similarity analysis was complemented by computing woody species similarities between kebeles, wealth status, and villages using Sorensen’s similarity index (Eq. (10)) [44].

$$Ssi=\frac{2a}{20+b+c}$$ (10)

where c is the number of species common to both sites; a = the number of species present on one of the sites; and b = the number of species present on the other site.

2.6. Data analysis

Diversity (richness and evenness) and similarity indexes were computed and presented. These parameters were compared between kebele, villages, and wealth classes following [6]. The frequency, density, basal area, and IVI of woody species in agroforestry were analyzed and presented. Analysis of variance (ANOVA) was used with SPSS version 20 to examine woody species richness, Shannon index, and evenness values between farms in various villages, wealth groups, and kebeles [48].

3. Results

3.1. Woody species diversity in farmlands

On various farms throughout the assessed households at the study site, a total of 90 woody species belonging to 80 genera and 42 families were recorded. (Appendix Table A1). Out of the total species recorded in the study area, 2 (2.22%), 32 (35.56%), and 56 (62.22%) were endemic, exotic, and indigenous, respectively. The family Fabaceae had the highest number of woody species (16), followed by Euphorbiaceae, Myrtaceae, Rutaceae, and Moraceae, which represent 7, 5, 4, and 4 woody species, respectively. The remaining 12 families each have two woody species, and the remaining three families each represent three woody species. The other 22 woody species were represented only by a single family. At the kebele level, a total of 74 and 57 woody species were recorded in Gotuanama and Entaye, respectively. Despite the presence of a higher number of species richness at Gotuanama kebele, the value of the Shannon diversity index and evenness were low (Table 1). The mean evenness value of the two studied kebele was (0.8). Table 1 shows that there were 16 woody species on average per farm, with 10 or more species present on 94.4% of farms. The minimum and maximum species per farm were 8 and 32, respectively.

Table 1.

Woody species diversity (Mean ± SE) in Farms of Gotuanama and Entaye, Wondo District, south-central Ethiopia.

Kebele	Number of species	Shannon index (H′)	Evenness index (E)
Entaye	15.93a ± 0.79	2.20a ± 0.07	0.81a ± 0.02
Gotuanama	16.00a ± 1.06	2.14a ± 0.08	0.79a ± 0.02
Overall mean	15.96 ± 0.93	2.17 ± 0.08	0.80 ± 0.02

The different letters following vertical mean values indicate significant difference (P < 0.05) at two study kebele.

Woody species richness recorded from farms of different wealth categories was variable. A higher number of woody species (74) was recorded in wealthy households, while the lowest (51) species were recorded in poor households. Woody species diversity (species richness and Shannon diversity index) was significantly (P < 0.05) higher on farms of rich households than in medium and poor wealth categories in Gotuanama kebele. However, there was no significant difference (P > 0.05) among the three wealth categories in Entaye kebele (Table 2). Medium households had high species richness at Entaye kebele as compared to the poor ones, but their evenness value was low.

Table 2.

Mean (±SE) number of species and Shannon diversity of woody species on farms belonging to three wealth categories at Gotuanama and Entaye Kebele, Wondo district, south-central Ethiopia.

Site	Wealth status	Number of species	Shannon (H′)	Evenness (E)
Entaye	Poor	14.56a ± 1.28	2.20a ± 0.09	0.83a ± 0.02
	Medium	15.56a ± 0.94	2.10a ± 0.19	0.77a ± 0.07
	Rich	17.67a ± 1.72	2.29a ± 0.09	0.81a ± 0.02
Gotuanama	Poor	11.22 b ± 1.18	1.89 b ± 0.13	0.80a ± 0.03
	Medium	14.33 b ± 0.96	2.08b ± 0.14	0.78a ± 0.04
	Rich	21.33a ± 1.72	2.46a ± 0.10	0.82a ± 0.04
Overall mean		15.96 ± 4.80	2.17 ± 0.08	0.80 ± 0.02

The Different letters following vertical mean values indicate significant difference among wealth categories (P < 0.05) at two study kebeles.

Table 3 shows the mean species richness and diversity of woody species in different villages. The Shutere shefama had the highest mean number of woody species (17.77), while the Giki Entaye contained the lowest mean number of species (14.55). On the other hand, Alkasa had the highest mean Shannon diversity index (2.22) and an evenness value of 0.85, whereas Ubdo had the lowest mean Shannon (2.08) and an evenness value of 0.76.

Table 3.

The mean (±SE) number of woody species and diversity in the six study villages of Gotuanama and Entaye Kebeles, Wondo district, south-central, Ethiopia.

Village	Number of species	Shannon index (H′)	Evenness (E)
Shutere shefama	17.77a ± 1.49	2.17a ± 0.19	0.77a ± 0.06
Alkasa	15.44a ± 1.06	2.22a ± 0.07	0.85a ± 0.02
Giki Entaye	14.55a ± 1.44	2.10a ± 0.09	0.80a ± 0.03
Toke	16.77a ± 1.88	2.19a ± 0.15	0.82a ± 0.02
Kombolcha	15.33a ± 1.30	2.16a ± 0.17	0.79a ± 0.05
Ubdo	15.88a ± 2.35	2.08a±0.13	0.76a ± 0.04
Overall mean	15.96 ± 0.65	2.17 ± 0.06	0.80 ± 0.02

3.2. Similarity in woody species composition

The similarity of woody species varied between kebeles and villages. The two kebeles under study had a comparable composition of woody species in about 72%. The Sorensen similarity index for the studied village showed that variation in woody species similarity ranged from 33.7% to 77.5%. The lowest similarity index value was revealed for the villages of Alkasa and Toke (33.7%), whereas the highest similarity index value was found in villages between Shutere Shefama and Alkasa (77.7%) (Table 4).

Table 4.

Sorensen's similarity index for woody species composition among villages of Gotuanama and Entaye Kebeles, Wondo district, south-central, Ethiopia.

Village	Shutere shefama	Alkasa	Giki Entaye	Toke	Kombolcha	Ubdo
Shutere shefama		0.775	0.557	0.527	0.617	0.523
Alkasa			0.389	0.337	0.556	0.512
Giki entaye				0.727	0.589	0.568
Toke					0.644	0.537
Kombolcha						0.63
Ubdo

3.3. Frequencies distribution of woody species

The occurrence of woody species across the assessed farm is variable. Cordia africana (87%) was the most frequent woody species, followed by Eucalyptus camadulensis (81.5%), Persia americana (81.5%), Mellitia ferruginea (76%), Croton macrostachyus (72.2%), Coffea arabica (64.8%), Casimiroa edulis La Llave (61%), Grevillea robusta R. Br. (50%), Calpurnia aurea (Ait.) Benth. (48%), and Psidium guajava L. which occurred in 44% of all the sampled farms (n = 54) (Fig. 3). On the other hand, 21 woody species were very rare, occurring only at a single sampled farm (Appendix Table 2).

Fig. 3.

Most frequent woody species with their corresponding percentage of frequency across assessed farms (n = 54) in Wondo district, south-central Ethiopia.

3.4. Density of woody species

The density of woody species with the top ten values across the assessed farm sites is presented in Fig. 4. The result shows that Eucalyptus camaldulensis has the highest density (21.68%), followed by Mellitia ferruginea (8.62%), Cordia africana (6.84%), Persea americana (6.27%), Croton macrostachyus (6.05%), Coffea arabica (5.09), Calpurnia aurea (4.78%), Grevilia robusta (3.67%), Ricinus communis L. (3.12%), and Cupressus lusitanica Mill., which account for 2.74% of the total individuals across the farm sites. These species accounted for 68.86% of the total density of woody species in the study area. About 31.14% of the total density was covered by the remaining 80 woody species. The study area's 41 recorded species accounted for less than 2% of the total density. Each of the 21 woody species in the study area has a density of 0.02401% (Appendix Table 3).

Fig. 4.

Woody species with the highest density values across assessed farms (n = 54), in Wondo district, south-central Ethiopia.

3.5. Basal area of woody species

The basal area of woody species with the top ten values across the assessed farm sites is presented in Fig. 5. The result shows that Eucalyptus camaldulensis has the highest basal area (30.03%), followed by Cordia africana (17.55%), Persea americana (15.42%), Grevilia robusta (4.26%), Podocarpus falcatus (Thunb.) Mirb. (3.96), Croton macrostachyus (3.52%), Mellitia ferruginea (3.37%), Ficus vasta Forssk (2.71%), Psidium guajava (2.27%), and Bersama abyssinica Fresen., which account for 2.10% of the total basal area across the farm sites. These species accounted for 85.18% of the total basal area of woody species in the study area. About 14.82% of the total basal area was covered by the remaining 66 woody species. The study area's 64 recorded species each accounted for less than 1% of the total basal area. Each of the five woody species in the study area has a basal area of 0.0053% (Appendix Table 3).

Fig. 5.

Woody species with the highest basal area values across assessed farms (n = 54), in Wondo district, south-central Ethiopia.

3.6. Important value index of woody species on study site

The Important Value Index (IVI) of woody species indicates the importance of individual species at the farm level and helps to evaluate the importance of species in the study area. Eucalyptus camaldulensis (57.38) has the highest mean IVI values in the study area, followed by Cordia africana (30.45), Persea americana (27.36), Mellitia ferruginea (17.28), and Croton macrostachyus (14.59), Grevillea robusta (11.41), Coffea arabica (9.69), Calpurnia aurea (8.75), Psidium guajava (7.06), and Casimiroa edulis (6.33) (Fig. 6). These species accounted for 190.34% of the total IVI value of woody species in the study area. About 109.66% of the total IVI was covered by the remaining 80 woody species. The study area's 47 recorded species accounted for 17.10% of the total IVI value, in which each species has less than 1% of the total IVI value (Appendix Table 3).

Fig. 6.

Woody species with the highest IVI values across assessed farms (n = 54), in Wondo district, south-central Ethiopia.

4. Discussion

4.1. Contribution of traditional agroforestry practices for plant diversity conservation

According to this study, agroforestry plays a significant role on the landscape's species diversity and evenness. Accordingly, the highest number of species recorded in Gotuanama kebele might be due to its location near Wondo Genet College of forestry and natural resources (WGCF and NR), as the college may serve as a source of seedlings and awareness creation about the importance of woody species in their farmlands. Some household members reported that they had received seedling support from WGCF and NR. Besides, the college has its own tree nursery and provides seedlings to the local farmers at a low cost. Furthermore, most of the households that dwell in this kebele have worked at WGCF and NR, which may help them to get awareness about the importance of woody species. The higher landholding size of the households at this kebele might also have contributed to the highest species richness compared to Entaye kebele.

The highest number of woody species recorded (90) in the present study puts farms in the study area among many agroforestry sites that are rich in woody species. The numbers of species recorded in the present study area are comparable with a total of 87 woody species reported in the Sidama traditional agroforestry land use [49]. However, the number of species reported in this study were higher than the number of woody species reported in south-central Ethiopian homegardens (64) and crop fields (32) [6]. Likewise, the numbers of woody species recorded in the present study were higher than the 32 species reported in the homegarden agroforestry systems in southern Tigray, Ethiopia [50], and 40 species in northern Ethiopian agroforestry practices [51]. It was also higher than 56 species reported in the Kachabira district of southern Ethiopia [32], the 55 species reported in the Dellomenna district of southeastern Ethiopia [52], the 75 species reported in the natural forest patches and adjacent enset-coffee based agroforestry in the Midlands of Sidama Zone [53], and the 77 woody species reported in the farmlands of Ethiopia’s east Shewa zone [54]. Conversely, the number of species found in this study was lower than the 120 species found in Sidama homegarden agroforestry systems [29], and the 108 species found in the Arbegona district of southern Ethiopia [32], and the 100 species reported in the agro-forestry practices of Yem special district, southern Ethiopia [55]. The possible differences in the number of species among those sites could be due to the variation in the management strategy, farmers' preference for woody species, landholding size, the habit of species' growing practices, and demographic factors [52]. Besides, this difference may be due to environmental variability, the difference in altitude, soils, climatic factors, and species adaptability.

On the other hand, the number of woody species recorded in the present study was higher than the number of species (41) reported at Mount Duro Natural Forest of Nagelle Arsi, south-central Ethiopia [56], 31 woody species in natural forests of the south-central highlands of Ethiopia [6], 11 species in the adjacent natural forest of Southern Tigray, northern Ethiopia [50], and 50 woody species in the Harego forest, northeastern Ethiopia [57]. Furthermore, the number of woody species recorded in the study area was also higher than that of 72 woody species reported in the Wondo Genet Afromontane forest of south central Ethiopia [58], with similar agro-ecology to the present study area. Likewise, the number of woody species recorded in the present study was greater than that of 32 species reported in the crop fields of south-central Ethiopia [6]. Therefore, traditional agroforestry practices might host a higher number of woody species than adjacent natural forests. Besides, preserving woody species in the cultivated landscape could help with productive farming, biodiversity preservation, and fulfilling farmers' demands for diverse wood products [6]. As a result, human-managed traditional agroforestry practices have the potential to conserve and improve biodiversity by reducing the pressure on remnant natural forests [59]. In contrast, the number of woody species recorded in the present study was lower than the 140 woody species recorded in the natural forests of Bonga, southern Ethiopia [60]. Moreover, the number of species recorded in this study was lower than the number of species reported at Berhane-Kontir (374), Harenna (289), Bonga (285), Yayu (217), and Maji (146), moist evergreen Afromontane forests of Ethiopia [61]. In this regard, natural forests had a greater number of woody species than traditional agroforestry practices due to the fact that unregulated agricultural activities on human-managed farmland might have a negative impact on the number of woody species.

Fabaceae and Euphorbiaceae have been reported as dominant families by other authors similar to the result of this study, such as in the homegardens of Arba Minch Town [62], in the urban vegetation of Dhaka City, Bangladesh [63], in the subtropical dry forests in St. Croix, U.S. Virgin Islands [64], in the habro district, Oromia Regional State, Ethiopia [65], and in the agroforestry systems around Jimma Town, Southwestern Ethiopia [66]. The Fabaceae family was also found to be dominant in other traditional agroforestry practice areas, including the Kachabira district in Southern Ethiopia [32], and Raya Alamata in southern Tigray, Northern Ethiopia [50]. Similarly, the dominance of the Euphorbiaceae family was reported in natural forest patches and adjacent enset-coffee-based agroforestry in the Midlands of Sidama Zone, Ethiopia [53]. The highest representation of species from the families Fabaceae and Euphorbaceae could be related to the fact that they are the second and third largest families in the vascular plants of Ethiopia and Eritrea [57,67]. This may also be linked to its capabilities and effective dissemination techniques, as well as its strong capacity for adaptation to the many ecologies of the nation [57]. However, most of the families in the traditional agroforestry systems under investigation consisted of just endangered few species [6,29,32]. Therefore, sound conservation and management should be provided for species that are exposed to destruction under traditional agroforestry systems [68].

The current study's significant difference in species richness and diversity among wealthy categories (at Gotuanama kebele) may be due to wealthy households' large landholding sizes, which allow them to plant and retain so many plants on their farms, and vice versa [31]. Besides, rich households can afford to buy seedlings [6,32]. They also conserve species without selling them because the number of trees they own on their farmlands is an indication of wealth in the study area. Similar findings on differences in diversity in wealthy versus medium and poor households have been reported, confirming the current study's findings [6,36]. Likewise, Abebe et al. [29] indicated that landholding size increases with increased wealth status, and this situation positively influences species diversity. However, a non-significant difference in Shannon’s diversity and evenness values across the wealthy category was reported in the Shashemene District, Ethiopia, similar to the results of this study (Entaye kebele) [31]. On the contrary, a significant difference in Shannon’s diversity index and evenness values among the wealth status of the households was reported in the south-central highlands of Ethiopia [6] and southeastern Ethiopia [52]. Similarly, Legesse and Negash [32] found variation in Shannon’s diversity and evenness values across wealth categories, with high values in the wealth categories.

The Shannon’s index of this study is comparable with the Shannon’s index reported by another study in the crop fields of south-central Ethiopia (2.22) [6]. However, it was higher than the Shannon index reported in Sidama zone homegardens (1.98) [6] and in the Kachabira district, southern Ethiopia [32]. Likewise, Shannon’s evenness value of this study is higher than reported in crop fields (0.64) and homegardens (0.48) [6]. Furthermore, the evenness value of the current study was comparable to studies in southwestern Ethiopian homegardens [69]. Furthermore, Shannon’s index of the present study is comparable with that computed in southern Cameroon [70]. However, the evenness values are lower than those reported by a similar study in southern Cameroon. The possible difference in species diversity and evenness could be due to the variation in the farm household landholding size, species preference, management, and the opportunity that affords the farmer to maintain the plant species on their farm [32].

46–60% similarity ranges of species among villages have been reported by Ref. [31], comparable to the results of the present study. Though the studied villages have similar agro-ecologies, the variations in the similarity of woody species among villages in the present study could be due to variations in management practices, planting preferences, wealth classes, and land size. Other researchers [6,31,32] confirmed similar findings. Furthermore, the variations in access to seedlings, family size, level of awareness of tree planting, and access to extension services might affect woody species similarity among villagers too [31]. Another study confirmed that plant diversity is influenced by culture, land shortage, available labor, economic status, farm size, extension services, types of species, socio-economic, biophysical features, and road accessibility [35,71].

The presence of a considerable number of native woody species (62.22%) in this study area indicates the potential of an agroforestry system for hosting many native woody species. Thus agroforestry is a means for biodiversity conservation. Similar to the present study, Jegora et al. [31] in the homegarden agroforestry of Shashemene District and Legesse and Negash [32] in the Kachabira district, Southern Ethiopia reported that 58% and 66% of the species recorded are native to Ethiopia, respectively. Besides, Endale et al. [54] in the farmlands of east Shewa, Ethiopia, and Eyasu et al. [50] in the Raya Alamata, southern Tigray, reported that more than 70% and 75% of the recorded species are native to Ethiopia. Furthermore, Kassa et al. [55] reported that about 89% of the recorded species are native to Ethiopia. As a result, agroforestry can be a solution to support biodiversity conservation in the current biodiversity loss, natural forest degradation, and species extinction and exploitation scenarios. Accordingly, when woody species diversity is higher in agroforestry, the pressure on the natural forests to get different forest resources decreases, which enables farmers to conserve woody species on their agricultural land [4]. Agroforestry might also serve as a seed source for ex-situ conservation [11,72]. In this regard, the conservation of biodiversity in agroforestry might be helpful by acting as a stepping stone for many migratory (birds), micro-organisms, and other little disturbance-tolerant species [2]. Therefore, though preserving biodiversity through nature reserves and other protected areas is an important short-term step, but it is not sufficient to solve the problem of biodiversity loss. Thus focusing on the conservation of the agricultural landscape is so worth [20]. Woody species in the agricultural landscape can also satisfy farmers’ need for wood products [4]. By doing so, agroforestry might indirectly contribute to the conservation of biodiversity by lessening the pressure on protected forests [15]. Moreover, for example, the existence of more than 24.5% edible plants such as Persea americana, Syzygium guineense (Wild.) DC., Mangifera indica L., and high-income value species (Coffea arabica), indicates agroforestry can be a sources of food and high income for households in addition to biodiversity conservation roles. Therefore, householders manage, conserve, and intentionally plant multipurpose plant species. Thus, sustainable management of homegardens could be helpful for income generation, job opportunities, and food security [73]. However, species selection, matching a species with a site, application of various management practices, provision of extension services, and planting materials might make agroforestry practices more successful [59].

The highest IVI values of Eucalyptus camaldulensis, Cordia africana, Persea americana, Mellitia ferruginea, and Croton macrostachyus in the present study might be because of the higher preference of the farmers for those species in their farms. The reasons for preference were multiple uses, such as fuel wood, construction, income, food, shade, bee keeping, and soil fertility improvement. According to Legesse and Negash [32], the IVI values of the species describe their importance to various uses for the farm household. The use values, source of seedling availability, the survival rate of species, and suitability of the climate for a particular species resulted in the difference in the IVI of woody species. Furthermore, farmers’ knowledge about the relative advantages of different woody species, such as the provision of balanced shade for crops and understory vegetation, the rapid rate of decomposition of leaf litter to improve soil fertility and additional values (cash and fodder), and the fast-growing ability of species may have been the major causes of the difference in the importance of the woody species in the study area [6].

Farmers in the study site use Eucalyptus species for fuelwood, construction wood, poles, and fencing materials. As a result of its rapid growth and high income potential, they incorporate this species into their grazing land and boundary. Cordia africana was also the species that used for timber production (construction work), fodder, soil fertility improvement, medicinal value, shade for animals and humans, and for fuelwood. Mellitia ferruginea is a species utilized by farmers for shade and soil fertility improvement. The species found with the highest IVI value in the study area are also reported in the agroforestry system of Kachabira district, southern Ethiopia [32]. Besides, Verma et al. [74] in the agroforestry practice of India found the highest important value index for Eucalyptus species and Cordia africana, in line with the results of this study. Generally, the most important woody species are those that are most commonly retained and planted in agroforestry systems [6,74].

Though a significant number of woody species are retained (conserved) via agroforestry practices in the present study area, providing extension services and training for householders on species selection and stand management practices are suggested. The commonly observed management practices in the study area include pruning, thinning, pollarding, lopping, coppicing, fencing to protect from animal browsing, and watering. Besides, increasing seedling access and survival rates of economically and socially important plant species might be very important to sustainably managing agroforestry practices in the study area. Moreover, further research on factors affecting woody species conservation, farmers’ planting preferences, goods and services provided by agroforestry, and the socio-economic benefits of agroforestry is suggested.

5. Conclusion

Scientific study on traditional agroforestry practices is important to understand the existing situation and status of plant diversity. Accordingly, the results of the present study confirmed that agricultural landscapes can play a significant role in the conservation of woody species, including endemic, indigenous, and exotic ones. Moreover, the presence of a significant number of woody species (90), 2.17 Shannon diversity, and 0.80 evenness values indicated that the landscapes in the present study area contributed to biodiversity conservation and favored the survival of other organisms belonging to the system. Likewise, there is a variation in woody species richness, occurrence, similarity of woody species, and IVI values across wealthy categories.

The presence of native woody species in the study area demonstrates how much the agroforestry system in the area can serve for woody species conservation. Thus, those species might have multiple uses for farmers for livelihood improvement. Besides, agroforestry has contributed a lot to conserving woody species. It could also reduce over exploitation of species in protected areas and natural forests by providing multiple uses and products for rural communities. So that, conservation of woody species depends on the value of individual species either in terms of productive or protective function. Therefore, a further detailed scientific study on examining socio-ecological factors determining plant species diversity and the contribution of different functional groups to livelihood is needed.

Author contribution statement

Melese Genete Muluneh, MSc; Belachew Bogale Worku, MSc: Analyzed and interpreted the data; Contributed reagents, materials, analysis tools or data; Wrote the paper.

Tesfaye Molla, MSc; Zebene Asfaw: Conceived and designed the experiments; Performed the experiments; Analyzed and interpreted the data; Contributed reagents, materials, analysis tools or data; Wrote the paper.

Funding statement

This study was supported by Hawassa University through the ministry of science and higher education of Ethiopia.

Data availability statement

The data that has been used is confidential.

Declaration of interest’s statement

The authors declare no competing interests.

Appendices.

Appendix Table A1.

Woody species identified in study area.

No	Scientific Name	Local Name	Family Name	Origin
1	Acacia abyssinica Hochst.	Bazra girar *	Fabaceae	I
2	Acacia brevispica Harms.	Kentefa **	Fabaceae	I
3	Acacia saligna (Labill.) Wendl	Akacha saligna **	Fabaceae	E
4	Acokanthera schimperi (A. DC.) Schweinf.	Mirenz *	Apocynaceae	I
5	Albizia gummifera (J. F. Gmel.) C. A. Sm.	Sesa *	Fabaceae	I
6	Albizia schimperiana Oliv.	Mukarba **	Fabaceae	I
7	Arundo donax L.	Shembeko *	Poaceae	I
8	Azadirachta indica A. Juss.	Kinin *	Meliaceae	E
9	Balanites aegyptiaca (L.) Del.	Bedeno **	Balanitaceae	I
10	Berchemia discolor (Klotzsch) Hemsl.	Jejeba **	Rhamnaceae	I
11	Bersama abyssinica Fresen.	Azamir *	Melianthaceae	I
12	Borassus aethiopum Mart.	Zenbaba *	Arecaceae	I
13	Bridelia micrantha (Hochst.) Baill.	Galalo **	Euphorbiaceae	I
14	Cajanus cajan (L.) Millsp	Yewof ater *	Fabaceae	E
15	Callistemon citrinus (Curtis) Skeels.	Bottle brush ***	Myrtaceae	E
16	Calpurnia aurea (Ait.) Benth.	Digta *	Fabaceae	I
17	Carica papaya L.	Papaye *	Caricaceae	E
18	Carissa spinarum L.	Agam *	Apocynaceae	I
19	Casimiroa edulis La Llave	Kazimir *	Rutaceae	E
20	Casuarina equisetifolia L.	Shewshewe *	Casurarinaceae	E
21	Catha edulis (Vahl) Forssk. ex Endl.	Chat *	Celastraceae	I
22	Celtis africana Burm.	Kewot *	Ulmaceae	I
23	Citrus aurantiifolia (Christm.) Swingle	Lomi *	Rutaceae	E
24	Coffea arabica L.	Buna *	Rubiaceae	I
25	Cordia africana Lam.	Wanza *	Boraginaceae	I
26	Croton macrostachyus Del.	Bisana *	Euphorbiaceae	I
27	Cupressus lusitanica Mill.	Yeferenji tsid *	Cupressaceae	E
28	Delonix regia (Boj.ex Hook.) Raf.	Yediredewa zaf *	Fabaceae	E
29	Dodonaea viscosa (L.) Jacq.	Kitkita *	Sapindaceae	I
30	Dovyalis abyssinica (A. Rich.) Warb.	Koshim *	Flacourtiaceae	I
31	Dracaena steudneri Engl.	Etse patos *	Dracaenaceae	I
32	Ehretia cymosa Thonn.	Wulaga *	Boraginaceae	I
33	Ekebergia capensis Sparrm.	Sombo **	Meliaceae	I
34	Entada abyssinica Steud. ex A. Rich.	Kontir *	Fabaceae	I
35	Embelia schimperi Vatke	Hanku **	Myrsinaceae	I
36	Erythrina brucei Schweinf.	Korch *	Fabaceae	Endemic
37	Eucalyptus camadulensis Dehnh.	Key bahrzaf *	Myrtaceae	E
38	Eucalyptus globulus Labill.	Nech bahrzaf *	Myrtaceae	E
39	Euphorbia candelabrum Kotschy	Kulkual *	Euphorbiaceae	I
40	Euphorbia pulcherrima Klotzsch.	Euphorbia *	Euphorbiaceae	E
41	Euphorbia tirucalli L.	Kinchib *	Euphorbiaceae	I
42	Ficus sur Forssk.	Shola *	Moraceae	I
43	Ficus sycomorus L.	Oda **	Moraceae	I
44	Ficus vasta Forssk	Warka *	Moraceae	I
45	Grevillea robusta R. Br.	Grevilia *	Proteaceae	E
46	Hibiscus rosa-sinensis L.	Yechina tsigereda *	Malvaceae	E
47	Jacaranda mimosifolia D. Don	Yetemenja zaf *	Bignoniaceae	E
48	Juniperus procera Hochst. ex Endl.	Yehabesha tsid *	Cupressaceae	I
49	Justicia schimperiana (Hochst. ex Nees) T. Anders.	Sensel *	Acanthaceaae	I
50	Lantana camara L.	Yewof kolo *	Verbenaceae	E
51	Leucaena leucocephala Lam.	Lukina *	Fabaceae	E
52	Maesa Lanceolata Forssk.	Abey **	Myrsinaceae	I
53	Mangifera indica L.	Mango *	Anacardiaceae	E
54	Manihot esculenta Crantz	Kazava *	Euphorbiaceae	E
55	Maytenus arbutifolia (A. Rich.) Wilczek	Atat *	Celastraceae	I
56	Melia azedarach L.	Nim *	Meliaceae	E
57	Millettia ferruginea (Hochst.) Bak.	Birbira *	Fabaceae	I
58	Moringa stenopetala (Bak. f.) Cuf.	Shiferaw *	Moringaceae	E
59	Morus alba L.	Yeferenji enjori *	Moraceae	E
60	Nuxia congesta R.Br. ex Fresen.	Atkuar *	Buddleiaceae	I
61	Ocotea kenyensis (Chiov.) Robyns & R.Wilczek	Gigicha **	Lauraceae	I
62	Olea europaea subsp. cuspidata (Wall. & G.Don) Cif.	Woira *	Oleaceae	I
63	Olinia rochetiana A. Juss.	Guna **	Oliniaceae	I
64	Oncoba spinosa Forssk.	Kokolfa **	Flacourtiaceae	I
65	Persea americana Mill.	Avocado *	Lauraceae	E
66	Phytolacca dodecandra L’Her.	Endod *	Phytolacaceaae	I
67	Pinus patula Schiede ex Schltdl.	Pachula *	Pinaceae	E
68	Plumeria alba L.	Plumeria *	Apocynaceae	E
69	Podocarpus falcatus (Thunb.) Mirb.	Zigba *	Podocarpaceae	I
70	Polyscias fulva (Hiern) Harms	Yezinjero wonber *	Araliaceae	I
71	Pouteria altissima (A.Chev.) Baehni	Kerero *	Sapotaceae	I
72	Prunus africana (Hook.f.) Kalkm.	Tikur enchet *	Rosaceae	I
73	Prunus persica L.	Kok *	Rosaceae	E
74	Psidium guajava L.	Zeytun *	Myrtaceae	E
75	Psydrax schimperiana (A.Rich.) Bridson	Galo **	Rubiaceae	I
76	Rhamnus prinoides L’Herit.	Gesho *	Rhamnaceae	I
77	Ricinus communis L.	Gulo *	Euphorbiaceae	I
78	Schefflera abyssinica (Hochst. ex A. Rich.) Harms	Harfetu **	Araliaceae	I
79	Schinus molle L.	Kundo berbere *	Anacardiaceae	E
80	Senna didymobotrya (Fresen.) Irwin & Barneby	Asene meka *	Fabaceae	E
81	Senna siamea (Lam.) Irwin & Barneby	Yeferenji digita *	Fabaceae	E
82	Sesbania sesban (L.) Merr.	Sesbania *	Fabaceae	I
83	Spathodea nilotica P. Beauv.	Yechaka nebelbal *	Bignoniaceae	E
84	Strychnos henningsii Gilg	Hadesa **	Loganiaceae	I
85	Syzygium guineense (Wild.) DC.	Dokma *	Myrtaceae	I
86	Teclea nobilis Del.	Adessa **	Rutaceae	I
87	Terminalia brownii Fresen.	Abalo *	Combretaceae	I
88	Vepris dainellii (Pichi-Serm.) Kokwaro	Medesa **	Rutaceae	Endemic
89	Vernonia amygdalina Del.	Girawa *	Asteraceae	I
90	Vernonia auriculifera Hiern.	Reji **	Asteraceae	I

Note: E = exotic I = indigenous, * = Amharic name, ** = Oromgna name, *** = English name.

Appendix Table A2.

Frequency distribution of woody species in entire site (n = 54).

No	Woody species	Frequency (%)
1	Cordia africana	87.03
2	Persea americana	81.48
3	Eucalyptus camaldulensis	81.48
4	Mellitia ferruginea	75.92
5	Croton macrostachyus	72.22
6	Coffea arabica	64.81
7	Casimiroa edulis	61.11
8	Grevilia robusta	50
9	Calpurnia aurea	48.14
10	Psidium guajava	44.44
11	Entada abyssinica	42.59
12	Chata edulis	42.59
13	Justicia schimperiana	40.74
14	Lantana camara	38.88
15	Euphorbia candelabrum	38.88
16	Vernonia amygdalina	35.18
17	Vernonia auriculifera	33.33
18	Cupressus lusitanica	24.07
19	Ricinus communis	22.22
20	Acacia abyssinica	22.22
21	Azardirachata indica	20.37
22	Callistemon citrinus	20.37
23	Carica papaya	16.66
24	Bersama abyssinica	16.66
25	Cajanus cajan	16.66
26	Olea africana	14.81
27	Schinus molle	14.81
28	Jacaranda mimosifolia	12.96
29	Albizia gummifera	12.96
30	Sesbania sesban	12.96
31	Podocarpus falcatus	11.11
32	Spathodea nilotica	11.11
33	Mangifera indica	11.11
34	Eucalyptus globulus	9.25
35	Embelia schimperi	9.25
36	Celtis africana	9.25
37	Morus alba	9.25
38	Rhamnus prinoides	9.25
39	Dovyalis abyssinica	9.25
40	Delonix regia	7.4
41	Strychonos henningsii	7.4
42	Ehretia cymosa	7.4
43	Erythrina brucei	7.4
44	Balanites aegyptiaca	7.4
45	Polyscais fulva	7.4
46	Maytenus arbutifolia	7.4
47	Ficus vasta	5.55
48	Ficus sycomorus	5.55
49	Dracaena steudneri	5.55
50	Vepris dainelli	5.55
51	Maesa lanceolata	5.55
52	Euphorbia tirucalli	5.55
53	Borassus aethiopum	5.55
54	Hibiscus rosa-sinensis	5.55
55	Juniperus procera	3.7
56	Casuarina equisetifolia	3.7
57	Senna siamea	3.7
58	Phytolacca dodecandra	3.7
59	Moringa stenopetala	3.7
60	Prunus africana	3.7
61	Schefflera abyssinica	3.7
62	Terminalia brownii	3.7
63	Citrus aurantifolia	3.7
64	Leucaena leucocephala	3.7
65	Manihot esculenta	3.7
66	Berchemia discolor	3.7
67	Arundo donax	3.7
68	Acokanthera schimperi	1.85
69	Acacia brevispica	1.85
70	Bridelia micrantha	1.85
71	Plumeria alba	1.85
72	Euphorbia pulcherrima	1.85
73	Prunus persica	1.85
74	Senna didymobotrya	1.85
75	Ocotea kenyensis	1.85
76	Nuxia congesta	1.85
77	Olinia rochetiana	1.85
78	Syzygium guineense	1.85
79	Dodonea viscosa	1.85
80	Carissa spinarum	1.85
81	Psydrax schimperiana	1.85
82	Oncoba spinosa	1.85
83	Albizia schimperiana	1.85
84	Pinus patula	1.85
86	Ekebergia capensis	1.85
87	Acacia saligna	1.85
88	Teclea nobilis	1.85
89	Pouteria altissima	1.85
90	Ficus sur	1.85

Appendix Table A3.

Importance value index of Woody species in entire assessed farms (n = 54).

No	Woody species	RF%	RDe%	RDo%	IVI
1	Eucalyptus camaldulensis	5.68	21.68	30.03	57.39
2	Cordia africana	6.06	6.84	17.55	30.46
3	Persea americana	5.68	6.27	15.42	27.36
4	Mellitia ferruginea	5.29	8.62	3.37	17.28
5	Croton macrostachyus	5.03	6.05	3.52	14.60
6	Grevilia robusta	3.48	3.67	4.25	11.41
7	Coffea arabica	4.52	5.09	0.08	9.69
8	Calpurnia aurea	3.35	4.78	0.62	8.75
9	Psidium guajava	2.97	1.82	2.27	7.06
10	Casimiroa edulis	4.26	1.34	0.73	6.33
11	Cupressus lusitanica	1.68	2.74	1.42	5.84
12	Vernonia amygdalina	2.45	2.50	0.77	5.71
13	Catha edulis	2.97	2.14	0.21	5.31
14	Podocarpus falcatus	0.77	0.50	3.96	5.24
15	Entada abyssinica	3.10	1.82	0.00	4.92
16	Justicia schimperiana	2.84	2.09	0.00	4.93
17	Ricinus communis	1.55	3.12	0.11	4.78
18	Vernonia auriculifera	2.32	1.87	0.00	4.20
19	Lantana camara	2.71	1.30	l0	4.01
20	Bersama abyssinica	1.16	0.55	2.10	3.81
21	Sesbania sesban	0.90	2.52	0.12	3.54
22	Euphorbia candelabrum	2.71	0.77	0.07	3.55
23	Ficus vasta	0.39	0.07	2.71	3.17
24	Azerdarach indica	1.42	0.84	0.38	2.64
25	Senna siamea	1.55	1.08	0.00	2.63
26	Spathodea nilotica	0.77	0.24	1.44	2.45
27	Callistemon citrinus	1.42	0.72	0.17	2.30
28	Eucalyptus globulus	0.65	0.91	0.63	2.18
29	Jacaranda mimosifolia	0.90	0.36	0.67	1.93
30	Carica papaya	1.16	0.41	0.14	1.71
31	Senna didymobotrya	1.16	0.55	0.00	1.71
32	Albizia gummifera	0.90	0.26	0.54	1.70
33	Olea africana	1.03	0.31	0.26	1.60
34	Erythrina brucei	0.52	0.12	0.94	1.57
35	Schinus molle	1.03	0.34	0.18	1.55
36	Celtis africana	0.65	0.12	0.74	1.51
37	Mangifera indica	0.77	0.38	0.13	1.29
38	Embelia schimperi	0.65	0.55	0.03	1.23
39	Ficus sycomorus	0.39	0.07	0.69	1.15
40	Dovyalis abyssinica	0.52	0.60	0.03	1.15
41	Acacia abyssinica	0.26	0.29	0.58	1.13
42	Delonix regia	0.52	0.17	0.44	1.12
43	Morus alba	0.65	0.29	0.06	1.00
44	Ehretia cymosa	0.52	0.31	0.12	0.95
45	Rhamnus prinoides	0.65	0.17	0.00	0.81
46	Strychonos henningsii	0.52	0.22	0.04	0.77
47	Balanites aegyptiaca	0.52	0.19	0.02	0.73
48	Dracaena steudneri	0.39	0.10	0.21	0.69
49	Prunus africana	0.26	0.05	0.38	0.69
50	Maytenus arbutifolia	0.52	0.12	0.00	0.64
51	Polyscais fulva	0.39	0.10	0.08	0.56
52	Phytolacca dodecandra	0.26	0.05	0.22	0.53
53	Hibiscus rosa-sinensis	0.39	0.14	0.00	0.53
54	Euphorbia tirucalli	0.39	0.10	0.01	0.49
55	Borassus aethiopum	0.39	0.07	0.01	0.47
56	Terminalia brownii	0.26	0.12	0.05	0.43
57	Pouteria altissima	0.13	0.07	0.22	0.43
58	Melia azerdarach	0.13	0.10	0.19	0.42
59	Casuarina equisetifolia	0.26	0.07	0.08	0.41
60	Manihot esculenta	0.26	0.14	0.00	0.40
61	Moringa stenopetala	0.26	0.10	0.05	0.41
62	Juniperus procera	0.26	0.10	0.03	0.38
63	Schefflera abyssinica	0.26	0.05	0.07	0.38
64	Arundo donax	0.26	0.10	0.00	0.35
65	Teclea nobilis	0.13	0.02	0.19	0.34
66	Measa lanceolata	0.26	0.07	0.01	0.34
67	Berchemia discolor	0.26	0.05	0.01	0.31
68	Cajanus cajan	0.26	0.05	0.01	0.31
69	Citrus aurantifolia	0.26	0.05	0.01	0.31
70	Leucaena leucocephala	0.26	0.05	0.00	0.31
71	Ekebergia capensis	0.13	0.02	0.11	0.27
72	Albizia schimperiana	0.13	0.02	0.11	0.27
73	Vepris dainellii	0.13	0.02	0.10	0.26
74	Pinus patula	0.13	0.02	0.08	0.23
75	Plumeria alba	0.13	0.02	0.02	0.17
76	ocotea kenyensis	0.13	0.02	0.04	0.19
77	Psydrax schimperiana	0.13	0.02	0.04	0.19
78	Nuxia congesta	0.13	0.02	0.03	0.18
79	Oncoba spinosa	0.13	0.02	0.03	0.18
80	Acacia saligna	0.13	0.02	0.03	0.18
81	Syzygium guineense	0.13	0.02	0.01	0.17
82	Olinia rochetiana	0.13	0.02	0.01	0.16
83	Prunus persica	0.13	0.02	0.01	0.16
84	Dodonea viscosa	0.13	0.02	0.01	0.16
85	Carissa spinarum	0.13	0.02	0.01	0.16
86	Ficus sur	0.13	0.02	0.01	0.16
87	Bridelia micrantha	0.13	0.02	0.01	0.16
88	Acokanthera schimperi	0.13	0.02	0.01	0.16
89	Acacia brevispica	0.13	0.02	0.00	0.15
90	Euphorbia pulcherrima	0.13	0.02	0.00	0.15
		100	100	100	300.00

Note: RF = Relative frequency, RDe = Relative density, RDo = Relative dominance.