FLORISTIC COMPOSITION AND PLANT DIVERSITY ANALYSIS OF ANBESSA FOREST IN WESEREN ETHIOPIA AND ITS CONRTIBUTION TO BIODIVESRITY CONSERVATION

 

Tamene Yohannes ¹, Sebsebe Demissew ², Mekuria Argaw ³, Sutuma Edessa ⁴

 

¹ Crop and Horticulture Directorate, Ethiopian Biodiversity Institute, Addis Ababa, Ethiopia

² Plant Systematics and Biodiversity, Addis Ababa University, Addis Ababa, Ethiopia

³ Center for Environmental Science, Addis Ababa University, Addis Ababa, Ethiopia

⁴ College of Education and Behavioral studies, Addis Ababa University, Addis Ababa, Ethiopia

 

 

1. INTRODUCTION

With its geological history, broad latitudinal spread and immense altitudinal range, Ethiopia spans a remarkable number of the world’s broad ecological regions.  These range from the Dalol depressions in the Afar (120 meters below sea level (m.b.s.l)) to the spectacular mountaintops of Ras Dashen (4620 meters above sea level (m.a.s.l.)) in the north and the Bale Mountains such as Tullu Dimtu (4337 m and the second-highest peak in Ethiopia) and Batu (4307 m) in the southeast. These varieties of habitats also support rich variety of different species contributing to the biological diversity of the country Institute of Biodiversity Conservation (2005).

Biodiversity is a common factor that links agriculture, forestry, fisheries, and other sectors and provides the necessary materials for livelihood, sustenance, trade, medicines and industrial development. Ethiopia is endowed with plant diversity; the total number of vascular plants in Ethiopia is estimated to be about 6000 species Hedberg et al. (2009) out of which about 10% are endemic. The number of woody plants is said to be around 1000 and out of which about 300 are tree species Berhan (1991), Ethiopian Forestry Action Program (1994), Environmental Protection Authority (1997). According to Kent and Coker Kent and Coker (1992), over large parts of the globe, human populations have modified plant communities extensively. This is also true in Ethiopian condition. However, there is high deforestation and the annual rate of deforestation of the high forests in Ethiopia ranges from 150,000 to 200,000 ha Ethiopian Forestry Action Program (1994), Environmental Protection Authority (1997). The Ethiopian country report of the FAO, from the Global Forest Recourses Assessment (GFRA), also shows similar results of deforestation rate which is 1.25% for forests (156,241.96 ha of forest per year) Food and Agriculture Organization of the United Nations (2015). From the same report the deforestation rate for woodlands is even more serious which amounts 1.8% per year which is 731,363.13 ha of woodlands per year. 

Information on vegetation may be required to help to solve ecological problems such as biological degradation, as an input for environmental impact assessments, to monitor management practices or to provide the bases for prediction of possible future changes.

Eventhough some studies were conducted on Anbessa forest, it did not provide holistic information. Currently information on the status of plant diversity of Anbessa forest is not available. Factors suchas landscape change (changing forest to other type of land use), deforestation, agricultural expantion, climate change and others are affecting the forest. Therefore, this study was initiated to conduct plant diversity study and vegetation structure, in order to support the knowledge-based plant diversity conservation planning effort of the country, to support the sustainable development of the forest, as well as to supply current information of the forest for the scientific community.

 

2. MATERIALS AND METHODS

2.1. Description of the study area

·        Geographical location

Anbessa forest is located in Bambacy district (“Wereda”), Assosa zone of the Benshangul Gumuz National Regional State (BGNRS) in Western Ethiopia. It is located at 9^o 55′ 40.8′′ N Latitude in the north to 9^o 53′ 24.3′′ N Latitude in the south and around 34^o 50′ 55.3′′ to 34^o 39′ 09.0′′ E Longitude in the east and west, respectively. The forest is very narrow from north to south, while it is wide east - west ward, which reach near to Dabus River in the east. The main asphalt road from Addis Ababa (Bambacy) to Asossa crosses the forest around the western part.  Anbessa forest is found surounded by six Kebele administratives namely: Amba 16, Jematsa, Garabiche Welega, Sonka, Village 44, and Village 47 (Figure 1).  According to the information from the local communities, the forest is said to be stretched from Dabus River in the east, to Ethio-Sudan border in the west. The eastern part, which goes to Dabus River, is called Sissa, the middle part is called Anbessa, and the western part, which extends to Ethio-Sudan border, is called Penshuba forest. The total area of the Anbessa forest is estimated to be 15,072 hectares.                

Figure 1

Figure 1 Map of Anbessa Forest with Bordering Kebeles

 

·        Topography

The topography of Anbessa forest is very flat. Except for a few hills in the western part of the forest, near the main Addis Ababa-Asossa Road, the rest of the forest is flat wooded grass land with very small slope variation. The elevation ranges from 1292 to 1563 m.a.s.l. with the highest peak being to the western side, while the lowest area is to the eastern side around Selga River with a total elevation variation of only 271 meters.

·        Hydrology

Anbessa forest is found in the Blue Nile River basin. There are a number of big and small rives which are tributaries of Blue Nile, such as Dabus, Afa, Selga, Shosha, Mutsa, Nifiro, Abakidi, Eshama, Chilonya and many small streams which pass through or near by the forest. As described by Herrmann et al. (2007), the Assosa–Bambasi area has many small creeks and rivers forming an extensive network of permanent water courses. Lakes do not exist only in and around Anbessa forest, but also in the whole of BGNRS. However, there are wetlands in some parts and during the rainy season some depressions fill with precipitation water, forming temporary or even permanent pools Herrmann et al. (2007).

·        Climate

Anbessa forest is found in the western lowlands of the country. Climate data from the nearest meteorological stations Amba 16 (only rainfall, from 1988-2013) and Assosa (from 1981-2013), were extracted and presented in Figure 2 and Figure 3. Amba 16 is located at 9^o 57’ 12.4’’ N Latitude and 34 ^o 39′ 21.7′′ E Longitude, with an altitude of 1401 m.a.s.l. and is found around three kms Northwest of Anbessa forest. Assosa is located at 10^o 03’ 56.7’’ N Latitude and 34 ^o 32′ 34.5′′ E Longitude, with an altitude of 1554 m.a.s.l. and is found around 20 km Northwest of Anbessa forest. 

The average annual rainfall is 1381.42 mm and 1128.59 mm for Amba 16 and Assosa, respectively, while the mean annual maximum temperature is 28.37 °C for Assosa. The area is characterized by unimodal rainfall distribution with the rainy season extends from March to November and one distinct short dry season extending from December to February (Figure 2 and Figure 3). Typically, during the onset of the main rainy season, the first two months receive small amount and gradually reach to its peak in August. More than 55% of the mean annual rainfall falls from June to August.

The mean maximum monthly temperature is about 28.37 ^oC. Mean maximum monthly temperature reaches to its peak during March followed by April and February, with a temperature of 32.69oC, 32.05 ^oC and 31.96 ^oC, respectively, whereas the lowest mean minimum monthly temperature occurs during December with a temperature of 13.28 ^oC. 

 Figure 2

Figure 2 Climate Diagram of Asossa Data Source: National Meteorological Agency (2016) Personal Communication

 

Figure 3

Figure 3 Monthly Rainfall Pattern of Amba 16 (Data Source: ENMSA, 2015, Personal Communication)

 

·        Vegetation

The altitudinal variation in Anbessa forest is very low; there is no as much variability in the vegetation type. In general, the Anbessa forest can be characterized as Combretum-Terminalia woodland. The forest is dominated by Oxytenanthera abyssinica (lowland bamboo) stands with scattered Combretum – Terminalia Woodland vegetation.  Major characteristic species such as Albizia malacophylla, Combretum collinum, Combretum molle, Dombeya quinqueseta, Entada africana, Erythrina abyssinica, Gardenia ternifolia and Syzygium guineense subsp. macrocarpum and others present in the area.

 

2.2. Socioeconomic characteristics

According to the 2007 population and housing census of the Ethiopian Population Census Commission Ethiopian Population Census Commission (2007), the population of the BGNRS is ca. 784,345 of which 13.50% (105,926) are settled in the urban areas and the rest 86.50% (678,419) in the rural areas.

This shows that the rural urban population ratio of the region is a little bit higher than the national averages of the country which is 83.92%. The population of Bambasi district where the Anbessa forest is found is 48,694 of which 18.78% (9,146) lives in urban areas specifically in the Bambasi town and the rest 81.22% (39,548) lives in the rural area Ethiopian Population Census Commission (2007). On the contrary, Bambasi district has lower rural urban population ratio, which is lower than that of the regional as wells the national average. Among the population of the district 70.73% (34,491) are economically active and available to be engaged in the production of economic goods and services.

Concerning the energy source of the Bambasi town, which has direct relation to the natural resource of the Anbessa forest, among the total 2,171 house-holds, only 2.58% (56 house-holds) uses electricity as energy source for cooking. The great majority of the population which is 89.36% (1940 house-holds) and 52.97% (1151 house-holds) uses fire wood and charcoal, respectively as energy source for cooking Ethiopian Population Census Commission (2007).

 

2.3. Sampling Design and Data Collection

Systematic sampling design was used according to Mueller-Dombois and Ellenberg (1974) and Kent and Coker (1992) and 30 plots were systematically laid along 4 transect lines. The size of the sampling plots was 20 m x 20 m for trees, 5 m x 5 m for shrubs and 1 m x 1 m for herbs and laid along the transect at every 50 m altitudinal drop for hilly areas and at every 200 m for flat areas. 

All woody vascular plant species encountered in each sample plot were recorded and their cover abundance was recorded by visual estimation of the percentage foliage cover of each species in the sampling plot and recorded as percentage in order to do analysis related to plant community types. Then the percent cover was transformed to ordinal scale and assigned to one of the nine cover classes according to modified 1-9 Braun-Blanquet scale Van der Maarel (2004). Plant specimens were collected and brought to the National Herbarium (ETH) of Addis Ababa University for identification. The specimens were properly dried and identified using authenticated specimens, consulting experts, and referring the published volumes of Flora of Ethiopia and Eritrea. Nomenclature followed the publications of the Flora of Ethiopia and Eritrea. All the plant specimens were properly labelled and deposited in the National Herbarium (ETH) Addis Ababa University.

Species diversity, richness, and evenness

The diversity of woody species in Anbessa forest was determined according to Kent and Coker (1992), using the Shannon-Wiener diversity index (H′) and evenness or equitability index (E) based on cover/abundance value of the species as input data.

 

3. RESULTS AND DISCUSSION

3.1. Floristic composition

A total of 118 plant species were identified which belongs to 97 genera from 46 families (Table 1 and Appendix 1). Out of the 118 identified plant species, 39 species (33.05 %) were trees, 14 species (11.86 %) were shrubs, 14 species (11.86 %) were climbers, and the rest 51 species (43.22 %) were herbs. Table 1 below show the growth habit or life forms of collected plants and their percentage.

Table 1

Table 1 Number, percentage, and life forms of plant species collected from Anbessa forest
S. No	Life form	Number	Percentage
1	Trees	39	33.05
2	Shrubs	14	11.86
3	Climbers	14	11.86
4	Herbs	51	43.22
Total		118	100

 

As shown in Appendix 2, out of 97 identified genera and 46 families; 14.41 % were Fabaceae represented by 17 species, followed by Asteraceae 11.86 % represented by 14 species, Poaceae 8.47 % represented by 10 species and Lamiaceae 5.93 % represented by seven species. The rest 42 families have 3.39 % up to 0.85 % and represented by number of species ranging from four to one, among which eight families have been represented by two species and 26 families by only one species (Appendix 2).

 

3.2. Endemic plants and new records from Anbessa forest for Wellega (WG) Floristic Region of Ethiopia

The result also revealed that, Anbessa forest harbors nine endemic plant species of Ethiopia which belongs to seven Families (Table 2). Moreover 29 plant species collected from Anbessa forest were recorded as new records for WG Floristic Region of Ethiopia according to the published Flora of Ethiopian and Eritrea volumes and voucher specimens of the National Herbarium (ETH) (Table 3). This makes the forest, important alternative in situ conservation sites for such species as well as for others.

Table 2

Table 2 List of Endemic plant species of Ethiopia recorded from Anbessa forest
No.	Scientific Name	Family	Habit
1	Albizia malacophylla (A. Rich.) Walp. var. malacophylla	Fabaceae	Tree
2	Berkheya chiesiana Chiov.	Asteraceae	Herb
3	Crinipes abyssinicus (Hochst. ex A. Rich.) Hochst.	Poaceae	Herb /Grass
4	Dombeya aethiopica Gilli.	Sterculiaceae	Tree
5	Lippia adoënsis Hochst. ex Walp.	Verbenaceae	Shrub
6	Mucuna melanocarpa Hochst. ex A. Rich	Fabaceae	Climber
7	Pimpinella heywoodii Abebe	Apiaceae	Herb
8	Tragia abortiva M. Gilbert	Euphorbiaceae	Shrub
9	Tragia doryodes M. Gilbert	Euphorbiaceae	Climber

 

Table 3

Table 3 List of species recorded as new records for Welega floristic region
No	Scientific Name	Family	Habit
1	Acacia polyacantha subsp. campylacantha (Hochst. ex A. Rich.) Brenan	Fabaceae	Tree
2	Acacia robusta subsp. usambarensis (Taub.) Brenan	Fabaceae	Tree
3	Aframomum alboviolaceum (Ridl.) K. Schum.	Zingiberaceae	Herb
4	Ageratum conyzoides subsp. latifolium (Cav.) M.F. Johnson	Asteraceae	Herb
5	Albizia malacophylla (A. Rich.) Walp. var. malacophylla	Fabaceae	Tree
6	Asparagus scaberulus A. Rich.	Asparagaceae	Climber
7	Brachiaria lachnantha (Hochst.) Stapf	Poaceae	Herb/Grass
8	Citrullus colocynthis (L.) Schrad.	Cucurbitaceae	Climber
9	Clematis hirsuta Perr. & Guill.	Ranunculaceae	Climber
10	Crinipes abyssinicus (Hochst. ex A. Rich.) Hochst.	Poaceae	Herb/Grass
11	Crinipes longifolius C.E. Hubb.	Poaceae	Herb/Grass
12	Dombeya aethiopica Gilli.	Sterculiaceae	Tree
13	Entada africana Guill. & Perr.	Fabaceae	Tree
14	Faurea speciosa Welw.	Proteaceae	Tree
15	Ficus ingens (Miq.) Miq.	Moraceae	Tree
16	Ficus platyphylla Del.	Moraceae	Tree
17	Habenaria armatissima Rchb. f.	Orchidaceae	Herb
18	Hyparrhenia anthistiriodes (Hochst. ex A. Rich.) Stapf.	Poaceae	Herb/Grass
19	Lannea fruticosa (A. Rich.) Engl.	Anacardiaceae	Tree
20	Lepistemon owariense (Beauv.) Hall. f.	Convolvulaceae	Climber
21	Murdannia simplex (Vahl) Brenan	Commelinaceae	Herb
22	Ocimum spicatum Deflers	Lamiaceae	Small shrub
23	Oxalis obliquifolia A. Rich.	Oxalidaceae	Herb
24	Pennisetum trachyphyllum Pilg.	Poaceae	Herb/Grass
25	Reichardia tingitana (L.) Roth	Asteraceae	Herb
26	Sporobolus pyramidalis P. Beauv.	Poaceae	Grass
27	Tacca leontopetaloides (L.) O. Ktze.	Taccaceae	Herb
28	Tamarindus indica L.	Fabaceae	Tree
29	Terminalia laxiflora Engl. & Diels-	Combretaceae	Tree

 

3.3. Plant community classification

The vegetation data matrix was analyzed and classified to analyze pattern of variation in species composition. The data set consisting of 30 woody plant species in 30 relevés were used in plant community classification.  The species codes are explained in Appendix C. 

The woody vegetation of Anbessa forest was classified into four clusters using a simple ordination plot (Fig. 4). The first vertical axis separated the riverine vegetation which is found near River “Selga” with characteristic species of Pittosporum viridiflorum and Syzygium guineense subsp. afromontanum with that of the two non-riverine vegetation types dominated by lowland Bamboo (Oxytenanthera abyssinica) and that of the wooded grassland. The second horizontal axis separated the wooded grassland which has no O. abyssinica into two communities with Piliostigma thonningii and Terminalia macroptera as a characteristic species on the one side and Combretum collinum, Dombeya quinqueseta and Securidaca longepedunculata as characteristic species on the other side. Four associations were identified which represent the plant communities in Anbessa forest. These plant communities have been named as follows by two or three dominant species based on highest mean cover/abundance value that appears within a group. Even though, Oxytenanthera abyssinica, Terminalia laxiflora, Lannea welwitschii, Syzygium guineense subsp. macrocarpum, Entada africana, Dombeya quinqueseta, Albizia malacophylla, Piliostigma thonningii, Bridelia micrantha and Combretum collinum have a wide distribution, there is no single species that appeared in all plant communities.

 

 

 

Figure 4

Figure 4 Species, Scater Plot Diagram for 30 Species Arranged by DCA Axes 1 and 2. The x-axis is Axis 1 (Eigen value = 0.783), the y-axis is Axis 2 (Eigen value   = 0.422). The Axes are Scaled in S.D Units. The Circles and Bold Numbers Represent the Four Plant Communities of Anbessa Forest.

 

·        Pittosporum viridiflorum - Syzygium guineense subsp. afromontanum Community

This plant community occurs near River “Selga”.  Though this plant community contiunes following the river Selga, the transect crossed it at once and the community was recorded only in one plot which is the lowest place of all the plots with elevation of 1292 m.a.s.l. This community includes trees such as: Pittosporum viridiflorum, Syzygium guineense subsp. afromontanum, Albizia gummifera and Gardenia ternifolia. The ground layer is dominated by Aframomum alboviolaceum.

·        Oxytenanthera abyssinica - Combretum molle - Syzygium guineense subsp. macrocarpum Community

This plant community occurs within a larger part of Anbessa forest. It was recorded between 1413 to 1563 m.a.s.l. This community includes trees and shrubs such as: Oxytenanthera abyssinica, Combretum molle, Syzygium guineense subsp. macrocarpum, Annona senegalensis, Lannea welwitschii, Dombeya quinqueseta and others.

·        Piliostigma thonningii - Terminalia macroptera community

This plant community occurs relatively to the lower part of Anbessa forest. It was recorded around 1338 m.a.s.l. This community includes trees such as: Piliostigma thonningii, Lonchocarpus laxiflorus, Terminalia macroptera, Terminalia laxiflora, Entada africana, Albizia malacophylla, Combretum collinum and others.

 

·        Combretum collinum - Dombeya quinqueseta - Securidaca longepedunculata Community

This plant community occurs in intermediate elevation. It was recorded at an altitude of 1442 m.a.s.l. This community includes trees such as: Combretum collinum, Dombeya quinqueseta, Entada africana, Maytenus undata, Pterocarpus lucens, Securidaca longepedunculata, Steganotaenia araliacea, Stereospermum kunthianum,Terminalia laxiflora and Vitex doniana.

 

4. Ordination

4.1. Detrended correspondence analysis

Detrended Correspondence Analysis (DCA) ordination was done (Figure 5) by using computer program Canoco Version 4.55 (ter Braak and Smilauer, 2002).

 Figure 5

Figure 5 Detrended Correspondence Analysis (DCA) Ordination Diagram of 30 Plots, Arranged by DCA Axes 1 and 2. The x-axis is Axis 1 (Eigen value = 0.783), the y-axis is Axis 2 (Eigen value   = 0.422). The Axes Are Scaled in S.D Units. The Circles and Bold Numbers Represent the Four Plant Communities.

 

Similar grouping of sample plots was observed as that of species since both were computed using species cover and abundance in the sample plots. The total inertia of the ordination was 4.11547. The first axis had an Eigen value of 0.783, which represents the long gradient (5.109 S. D unit) explained 19% of the total variation (total inertia) in the dataset. This gradient separated communities 3 and 4 from the others which are 1 and 2.  The second axis had an Eigen value of 0.422 and 2.837 S. D units, which explained 10.3% of the remaining variation. This gradient has separated community 3 from community 4 which were not clearly separated by axis 1.  The third and fourth DCA axes are not presented here as they have low Eigen values.

 

4.2. Canonical correspondence analysis

Canonical Correspondence Analysis (CCA) ordination was done (Figure 6) by running a computer program Canoco Version 4.55 (ter Braak and Smilauer, 2002) for different environmental variables. CCA-biplot of plant community types and environmental variables shows the relationships of variation of the plant communities along the environmental gradients.

Figure 6

Figure 6 CCA Ordination Biplot Produced Using CANOCO, Axis 1 (horizontal) and Axis 2 (vertical). Arrows Represent Environmental Variables. Each Arrow Points Toward the Direction of the Steepest Increase in Environmental Gradients. The Angles Between Arrows Indicate Correlations Between Individual Environmental Variables. Relevé Numbers are Indicated. Overlapping Relevés were Slightly Moved. C = Carbon, N = Nitrogen, P = Phosphorus, K = Potassium, CEC = Cation Exchanging Capacity.

 

 As the CCA-biplot of plant community types and environmental variables indicates it is possible to visualize the correlation between plots or plant communities and environmental variables. Pittosporum viridiflorum-Syzygium guineense subsp. afromontanum Community (Community 1) and Piliostigma thonningii-Terminalia macroptera Community (Community 3) are negatively correlated with altitude and amount of Phosphorus in the soil, while they are positively correlated with Slope and Sand. Whereas the other two plant communities: Combretum collinum-Dombeya quinqueseta-Securidaca longepedunculata Community (Community 4) and Oxytenanthera abyssinica - Combretum molle - Syzygium guineense subsp. macrocarpum Community (Community 2) are positively correlated with Altitude and amount of Phosphorus in the soil and negatively correlated with that of Slope and sand as opposed to Communities 1 and 3.

Species diversity, richness, and evenness

Shannon-Wiener diversity indices, species evenness and richness were computed for the four-plant community of Anbessa forest (Table 4).

 

 

 

 

Table 4

Table 4 Shannon–Wiener Diversity Index, species richness and evenness of plant communities in Anbessa forest
Communities	Species richness	Diversity index (H′)	Evenness (J)
I	4	1.88	0.90
II	30	0.16	0.04
III	10	2.70	0.90
IV	12	2.90	0.91
Where: I = Pittosporum viridiflorum-Syzygium guineense subsp. afromontanum community II= Oxytenanthera abyssinica -Combretum molle-Syzygium guineense subsp. Macrocarpum community III= Piliostigma thonningii-Terminalia macroptera community IV= Combretum collinum-Dombeya quinqueseta-Securidaca longepedunculata community

 

The Shannon-Wiener diversity index was computed for the four plant communities in Anbessa forest (Table 4) and showed that Combretum collinum-Dombeya quinqueseta-Securidaca longepedunculata community is the most diverse with H′ 2.90, followed by Piliostigma thonningii-Terminalia macroptera and Pittosporum viridiflorum-Syzygium guineense subsp. afromontanum communities with H′ 2.70 and 1.88, respectively, whereas Oxytenanthera abyssinica-Combretum molle-Syzygium guineense subsp. macrocarpum community is the least diverse community with H′ 0.16. Regarding species richness, which is a measure of alpha diversity, Oxytenanthera abyssinica -Combretum molle-Syzygium guineense subsp. macrocarpum community is the most species rich with 30 species, whereas Pittosporum viridiflorum-Syzygium guineense subsp. afromontanum community is the least species rich with four species.

 

5. DISCUSSION

5.1. Floristic Composition, Diversity and Structure of Anbessa Forest                     

Floristic diversity

As the result in Table 4 shows, there is a high variation of species richness and evenness between the different plant communities in the Anbessa forest.  Regarding species richness, which is a measure of Alpha diversity, community 2 (Oxytenanthera abyssinica -Combretum molle-Syzygium guineense subsp. macrocarpum community) is the most species rich community, but on the contrary, it is the list diverse with the lowest Shannon-Wiener diversity index of 0.16518 and also the list even community with the evenness value J = 0.040344.  Evenness is a measure of equitability, and it attempts to quantify the unequal representation of species in a community against a hypothetical community in which all species are equally common. Therefore, Community 2 is more unevenly distributed species. This is mainly because of the high number of Bamboo stands (up to 12,000/ha) as compared to other species.   Low diversify index also shows that, there is a high natural and human disturbance in this community such as unsustainable Bamboo extraction, fire, and others.

On the other hand, community IV (Combretum collinum-Dombeya quinqueseta-Securidaca longepedunculata community) is the most evenly distributed community with J= 0.913903 and with relatively high Shannon–Wiener Diversity Index (H”) value of 2.90. This community is relatively with fewer disturbances as compared to community 2 (Oxytenanthera abyssinica -Combretum molle-Syzygium guineense subsp. macrocarpum community).

 

6. CONCLUSIONS and RECOMMENDATIONS

6.1. CONCLUSIONS

 

The Anbessa forest represents different vegetation types of the country such as Combretum-Terminalia woodland and wooded grassland and Riverine vegetations. Also, they harbor a number of endemic plant species. The high number of new plant species recorded for Wellega floristic region shows that, this floristic region was not adequately explored.

Several tree species such as Albizia gummifera, Entada africana, Erythrina abyssinica, Faurea speciosa, Lannea welwitschii, Oncoba spinosa, Pittosporum viridiflorum, Syzygium guineense subsp. Afromontanum, Syzygium guineense subsp. Macrocarpum and Vitex doniana are at higher risk, since they have no seedings and saplings recorded.

In addition to the invaluable ecosystem services such as flood damage control, water purification, source of foods and feeds, supply of goods and services and others, which they are being providing, the forest can play a significant role in the mitigation of climate change as a carbon sink, since it can store huge amount of carbon. Therefore, proper management of the forest and enabling the forest to continue such ecosystem services is very important.

 

6.2. RECOMMENDATIONS

·        The present study focused on plant diversity, while many aspects of the Anbessa forest are still untouched and needs further study. 

·        Since Anbessa forest harbors nine endemic plant species of Ethiopia, it is important to give conservation priority particularly for these endemic species. The forest can be used as in-situ conservation site for these endemic species.

·        The plant community “Pittosporum viridiflorum-Syzygium guineense subsp. Afromontanum” which represents the riverine vegetation also needs special conservation attention, since it is present in a small area near the “Selga” river.

·        In Anbessa forest it is important to have a well-planned and well managed extraction of the Bamboo resource which does not affect the regeneration capacity of the species.

 

CONFLICT OF INTERESTS

None. 

 

ACKNOWLEDGMENTS

None.

 

 

 

REFERENCES

Berhan, T. (1991). Diversity of the Ethiopian Flora. In J. Engels, J. Hawkes, & M. Worede (Eds.), Plant Genetic Resources of Ethiopia, 75-81. Cambridge : Cambridge University Press. https://doi.org/10.1017/CBO9780511551543.005.

Environmental Protection Authority (1997). Conservation Strategy of Ethiopia. Environmental Protection Authority, Addis Ababa.

Ethiopian Forestry Action Program (1994). Final Report Volume II - The Challenge for Development and Volume III - Issues and Action. Ministry of Natural Resources Development and Environmental Protection, EFAP Secretariat, Addis Ababa.

Ethiopian Population Census Commission (2007). The Third National Population and Housing Census. Central Statistical Agency, Addis Ababa.

Food and Agriculture Organization of the United Nations (2015). Global Forest Resources Assessment (GFRA), Country Report Ethiopia, Food and Agriculture Organization of the United Nations, Rome, Italy.

Hedberg I., Friis I. and Persson E. (2009). Flora of Ethiopian and Eritrea, Vol. 8. General Part and Index to vols 1-7. Addis Ababa, Ethiopia and Uppsala.

Herrmann, C., Cribb, P., & Demissew, S. (2007). The Orchid Flora of Benishangul-Gumuz (Western Ethiopia) : An Ecological and Phenological Study. Selbyana, 28(2), 123–136.

Institute of Biodiversity Conservation (2005). National Biodiversity Strategy and Action Plan. IBC, Addis Ababa, 103.

Kent M. and Coker P. (1992). Vegetation Description and Analysis : A practical approach. New York : John Wiley and Sons, 363.

Mueller-Dombois, D. and Ellenberg, H. (1974). Aims and Methods of Vegetation Ecology. New York : John Wiley and Sons.

Van der Maarel, E. (2004). Vegetation Ecology. Wiley–Blackwell.     

 

APPENDIX

Appendix 1

Appendix 1 List of Plant Species Recorded from Anbessa Forest, with their Family, Local Name, and Growth Habit
S. No.	Scientific Name	Family	Habit	Local Name	Language
1	Acacia polyacantha subsp. campylacantha (Hochst. ex A. Rich.) Brenan	Fabaceae	Tree	Qudu	Berta
2	Acacia robusta subsp. usambarensis (Taub.) Brenan	Fabaceae	Tree	Ashifudi/ Shibil	Berta
3	Acanthus polystachius Delile	Acanthaceae	Shrub	Yeqedo	Berta
4	Aframomum alboviolaceum (Ridl.) K. Schum.	Zingiberaceae	Herb	Penpe Amesimu	Berta
5	Ageratum conyzoides subsp. latifolium  (Cav.) M.F. Johnson	Asteraceae	Herb	Shekot	Berta
6	Albizia malacophylla (A. Rich.) Walp. var. malacophylla	Fabaceae	Tree	Kender /Gender	Berta
7	Ampelocissus schimperiana (Hochst. ex A. Rich.) Planch.	Vitaceae	Climber	Mangug	Berta
8	Andropogon gayanus Kunth.	Poaceae	Grass	Gnerbiru	Berta
9	Annona senegalensis Pers.	Annonaceae	Tree	Adegella	Berta
10	Asparagus scaberulus A. Rich.	Asparagaceae	Climber	Moro	Berta
11	Asplenium aethiopicum (Burm.f.) Bech.	Aspleniaceae	Herb
12	Becium obovatum E. Meyer. ex Benth. in E. Mey.	Lamiaceae	Herb
13	Berkheya chiesiana Chiov.	Asteraceae	Herb	Duduro	Berta
14	Bidens prestinaria (Sch. Bip.)  Cufod.	Asteraceae	Herb	Atsekatsia hudu	Berta
15	Brachiaria lachnantha (Hochst.) Stapf	Poaceae	Grass	Ashinshilo	Berta
16	Breonadia salicina (Vahl.) Hepper & Wood	Rubiaceae	Tree	Digil	Berta
17	Bridelia micrantha (Hochst.) Baill.	Euphorbiaceae	Shrub	Tentse / Tsende	Berta
18	Cayratia gracilis (Guill. & Perr.) Suesseng.	Vitaceae	Herbaceous climber
19	Citrullus colocynthis (L.) Schrad.	Cucurbitaceae	Climber	Embabayaquriyo	Berta
20	Clematis hirsuta Perr. & Guill.	Ranunculaceae	Climber	Ashiro Balu	Berta
21	Clerodendrum alatum  Gürke	Lamiaceae	Herb	Dudu Shigniru	Berta
22	Clerodendrum cephalanthum Oliv.	Verbenaceae	Shrub	Hallale	Berta
23	Clerodendrum umbellatum Poir.	Lamiaceae	Herb
24	Coccinia grandis (L.) Voigt	Cucurbitaceae	Climber	Fesh	Berta
25	Combretum collinum Fresen. (1837) subsp. elgonense (Engl.) Okafor	Combretaceae	Tree	Sistsia Begneni	Berta
26	Combretum molle R. Br. ex G. Don	Combretaceae	Tree	Kushmindari	Berta
27	Crinipes abyssinicus (Hochst. ex A. Rich.) Hochst.	Poaceae	Grass	Gnere Bello	Berta
28	Crinipes longifolius C.E. Hubb.	Poaceae	Grass	Fitti	Berta
29	Crotalaria sp.	Fabaceae	Herb		Berta
30	Cyphostemma adenocaule (Steud. ex A. Rich) Desc. ex Wild & Drummond	Vitaceae	Climber	Enqulenchi	Berta
31	Cyphostemma cyphopetalum (Fresen.) Desc. ex Wild & Drummond	Vitaceae	Climber	Wishibi	Berta
32	Dicoma sessiliflora Harv.	Asteraceae	Herb
33	Dioscorea abyssinica Hochst. ex Kunth	Dioscoreaceae	Climber	Qyesa	Berta
34	Dioscorea schimperiana Kunth	Dioscoreaceae	Climber	Awade	Berta
35	Diplolophium africanum Turcz.	Apiaceae	Herb	Feleqet	Berta
36	Dolichos kilimandscharicus Taub.	Fabaceae	Herb	Qembu	Berta
37	Dolichos sericeus E. Mey.	Fabaceae	Climber	Amermoto	Berta
38	Dombeya aethiopica Gilli.	Sterculiaceae	Tree	Fodok	Berta
39	Dombeya quinqueseta (Del.) Exell	Sterculiaceae	Tree	Fodok	Berta
40	Dorstenia benguellensis Welw.	Moraceae	Herb	Ashehu	Berta
41	Echinops amplexicaulis oliv.	Asteraceae	Shrub	Asholgeri	Berta
42	Ensete ventricosum (Welw.) Cheesman	Musaceae	Perennial herb
43	Entada africana Guill. & Perr.	Fabaceae	Tree	Dirtsign / Tsaba Regno	Berta
44	Erythrina abyssinica Lam. ex DC.	Fabaceae	Tree	Amblish	Berta
45	Faurea speciosa Welw.	Protiaceae	Tree	Atete	Berta
46	Ficus ingens (Miq.) Miq.	Moraceae	Tree	Babekel	Berta
47	Ficus platyphylla Del.	Moraceae	Tree	Dwe	Berta
48	Ficus sp.	Moraceae	Tree	Gansha / Gnansha	Berta
49	Gardenia ternifolia Schumach. & Thonn.	Rubiaceae	Tree	Aqenda	Berta
50	Gladiolus dalenii subsp. Dalenii van Geel	Iridaceae	Herb	Adebergella	Berta
51	Gladiolus sp.	Iridaceae	Herb/Shrub	Adebergella	Berta
52	Grewia mollis A. Juss.	Tiliaceae	Shrub	Hormotse/ Hornotse	Berta
53	Guizotia scabra (Vis.) Chiov.	Asteraceae	Herb	Duda Shiri	Berta
54	Habenaria armatissima Rchb. f.	Orchidaceae	Herb	Fefelu	Berta
55	Hibiscus cannabinus L.	Malvaceae	Herb	Shuri Mugu	Berta
56	Hibiscus corymbosus Hochst.  ex A. Rich.	Malvaceae	Herb	Merub	Berta
57	Hyparrhenia anthistiriodes (Hochst. ex A. Rich.) Stapf	Poaceae	Grass	Abendu	Berta
58	Hyparrhenia anthistiriodes (Hochst. ex A. Rich.) Stapf	Poaceae	Grass	Bundur	Berta
59	Hypoestes forskaolii (Vahl) R. Br.	Acanthaceae	Herb	Signdimitssera	Berta
60	Hypoxis villosa complex	Hypoxidaceae	Herb
61	Indigofera arrecta Hochst. ex A. Rich.	Fabaceae	Herb	Hinealalbelal	Berta
62	Lactuca inermis Forssk.	Asteraceae	Herb	Etseya Meir	Berta
63	Laggera crispata (Vahl) Hepper & Wood	Asteraceae	Herb	Aro	Berta
64	Lannea fruticosa (A. Rich.) Engl.	Anacardiaceae	Tree	Etsiya Urubo	Berta
65	Lannea welwitschii (Hiern) Engl.	Anacardiaceae	Tree	Qua	Berta
66	Lepistemon owariense (Beauv.) Hall. f.	Convolvulaceae	Climber	Adebera	Berta
67	Lippia adoënsis Hochst. ex Walp.  var. adoënsis	Verbenaceae	Shrub	Shinhorihudi	Berta
68	Lonchocarpus laxiflorus Guill. & Perr.	Fabaceae	Tree	Ahutse	Berta
69	Maytenus undata (Thunb.) Blakelock	Celastraceae	Tree	Telemiyo	Berta
70	Moraea schimperi (Hochst.) Pic. Serm.	Iridaceae	Herb	Dungefru	Berta
71	Mucuna melanocarpa Hochst. ex A. Rich	Fabaceae	Climber	Aguba	Berta
72	Mucuna stans Welw. ex Bak.	Fabaceae	Shrub	Dudu Melates	Berta
73	Murdannia simplex (Vahl) Brenan	Commelinaceae	Herb		Berta
74	Ochrocephala imatongensis (Philipson) Dittrich	Asteraceae	Shrub	Telenbey Fidi	Berta
75	Ocimum lamiifolium Hochst. ex Benth.	Lamiaceae	Herb	Beshikiri	Berta
76	Ocimum spicatum Deflers	Lamiaceae	Shrub
77	Oncoba spinosa Forssk.	Flacourtiaceae	Tree	Abubuqu/ Akuku	Berta
78	Oxalis obliquifolia A. Rich.	Oxalidaceae	Herb		Berta
79	Oxytenanthera abyssinica (A. Rich.) Munro	Poaceae	Tree	Kagu	Berta
80	Ozoroa insignis Del.	Anacardiaceae	Shrub	Ahulo	Berta
81	Pennisetum trachyphyllum Pilg.	Poaceae	Grass	Gnagnael Mushel	Berta
82	Phoenix reclinata Jacq.	Arecaceae	Palm tree
83	Piliostigma thonningii (Schumach.) Milne-Redh.	Fabaceae	Tree	Megel	Berta
84	Pittosporum viridiflorum Sims	Pittosporaceae	Tree
85	Plectranthus barbatus Andrews	Lamiaceae	Herb	Etsenebishu	Berta
86	Protea gaguedi J. F. Gmel.	Protiaceae	Tree	Chedeber	Berta
87	Pseudarthria hookeri Wight & Arn.	Fabaceae	Shrub	Dudu Lesedi	Berta
88	Pterocarpus lucens Guill. & Perr.	Fabaceae	Tree	Miroro	Berta
89	Reichardia tingitana (L.) Roth	Asteraceae	Herb
90	Rhus glutinosa A.Rich.	Anacardiaceae	Tree	Silkela	Berta
91	Rumex abyssinicus Jacq.	Polygonaceae	Herb	Mankuku	Berta
92	Scleria bulbifera Hochst. ex A. Rich.	Cyperaceae	Sedge	Qenqesh	Berta
93	Securidaca longepedunculata Fresen.	Polygalaceae	Tree	Sheqet	Berta
94	Sesamum orientale L.	Pedaliaceae	Herb	Heshe Fudi	Berta
95	Sida rhombifolia L.	Malvaceae	Shrub	Meshene	Berta
96	Snowdenia polystachya (Fresen.) Pilg.	Poaceae	Grass	Afamere	Berta
97	Solanecio tuberosus (Sch. Bip. ex.  A. Rich.) C. Jeffrey	Asteraceae	Herb	Alaberi	Berta
98	Solanum dasyphyllum Schumach.	Solanaceae	Herb	Atunturus	Berta
99	Sopubia ramosa (Hochst.) Hochst.	Scrophulariaceae	Herb
100	Sporobolus pyramidalis P. Beauv.	Poaceae	Grass	Awishu	Berta
101	Steganotaenia araliacea Hochst. ex A. Rich.	Apiaceae	Tree	Ashinshilo	Berta
102	Stereospermum kunthianum Cham.	Bignoniaceae	Tree	Agulqa / Aqolqa	Berta
103	Syzygium guineense subsp. afromontanum F. White	Myrtaceae	Tree	Bulmetse	Berta
104	Syzygium guineense subsp. macrocarpum (Engl.) F. White	Myrtaceae	Tree	Anzu	Berta
105	Tacca leontopetaloides (L.) O. Ktze.	Taccaceae	Herb
106	Tamarindus indica L.	Fabaceae	Tree	Mela	Berta
107	Terminalia laxiflora Engl. & Diels	Combretaceae	Tree	Hori	Berta
108	Terminalia macroptera Guill. & Perr.	Combretaceae	Tree	Kebugir	Berta
109	Tragia abortiva M. Gilbert	Euphorbiaceae	Shrub	Menegne Buqeshingi	Berta
110	Tragia doryodes M. Gilbert	Euphorbiaceae	Climber	Aponpolo	Berta
111	Vernonia galamensis (Cass.) Less.	Asteraceae	Shrub	Hesran	Berta
112	Vernonia perrottetii Sch. Bip. ex Walp.	Asteraceae	Herb	Alkamun Dudu	Berta
113	Vernonia purpurea Sch. Bip. ex Walp.	Asteraceae	Herb
114	Vigna membranacea A. Rich.	Fabaceae	Herb	Dheberimugu	Berta
115	Vitex doniana Sweet	Lamiaceae	Tree	Atsota / Chedo	Berta
116	Ximenia americana L.	Olacaceae	Tree	Babe	Berta
117	Zehneria scabra (Linn. f.) Sond.	Cucurbitaceae	Herb
118	Ziziphus abyssinica Hochst. ex A. Rich.	Rhamnaceae	Tree	Merqeqo	Berta

 

Appendix 2

Appendix 2 Plant Families, Number of Genera, Species and their Percentage Recorded from Anbessa Forest
S. No	Families	Number of General	Number of species	%
1	Fabaceae	14	17	14.41
2	Asteraceae	12	14	11.86
3	Poaceae	8	10	8.47
4	Lamiaceae	5	7	5.93
5	Anacardiaceae	3	4	3.39
6	Combretaceae	2	4	3.39
7	Moraceae	2	4	3.39
8	Vitaceae	3	4	3.39
9	Cucurbitaceae	3	3	2.54
10	Euphorbiaceae	2	3	2.54
11	Iridaceae	2	3	2.54
12	Malvaceae	2	3	2.54
13	Acanthaceae	2	2	1.69
14	Apiaceae	2	2	1.69
15	Dioscoreaceae	1	2	1.69
16	Myrtaceae	1	2	1.69
17	Protiaceae	2	2	1.69
18	Rubiaceae	2	2	1.69
19	Sterculiaceae	1	2	1.69
20	Verbenaceae	2	2	1.69
21	Annonaceae	1	1	0.85
22	Arecaceae	1	1	0.85
23	Asparagaceae	1	1	0.85
24	Aspleniaceae	1	1	0.85
25	Bignoniaceae	1	1	0.85
26	Celastraceae	1	1	0.85
27	Commelinaceae	1	1	0.85
28	Convolvulaceae	1	1	0.85
29	Cyperaceae	1	1	0.85
30	Flacourtiaceae	1	1	0.85
31	Hypoxidaceae	1	1	0.85
32	Musaceae	1	1	0.85
33	Olacaceae	1	1	0.85
34	Orchidaceae	1	1	0.85
35	Oxalidaceae	1	1	0.85
36	Pedaliaceae	1	1	0.85
37	Pittosporaceae	1	1	0.85
38	Polygalaceae	1	1	0.85
39	Polygonaceae	1	1	0.85
40	Ranunculaceae	1	1	0.85
41	Rhamnaceae	1	1	0.85
42	Scrophulariaceae	1	1	0.85
43	Solanaceae	1	1	0.85
44	Taccaceae	1	1	0.85
45	Tiliaceae	1	1	0.85
46	Zingiberaceae	1	1	0.85
Total		97	118	100

 

Appendix 3

Appendix 3 Species list for the codes used in the DCA analysis for Anbessa forest
S. No	Code	Species name	Family
1	Albi gumm	Albizia gummifera	Fabaceae
2	Albi mala	Albizia malacophylla	Fabaceae
3	Anno sene	Annona senegalensis	Annonaceae
4	Brid micr	Bridelia micrantha	Euphorbiaceae
5	Comb coel	Combretum collinum subsp. elgonense	Combretaceae
6	Comb coll	Combretum collinum	Combretaceae
7	Comb moll	Combretum molle	Combretaceae
8	Domb quin	Dombeya quinqueseta	Sterculiaceae
9	Enta afri	Entada Africana	Fabaceae
10	Eryt abys	Erythrina abyssinica	Fabaceae
11	Faur spec	Faurea speciosa	Protiaceae
12	Gard tern	Gardenia ternifolia	Rubiaceae
13	Grew moll	Grewia mollis	Tiliaceae
14	Lann welw	Lannea welwitschii	Anacardiaceae
15	Lonc laxi	Lonchocarpus laxiflorus	Fabaceae
16	Mayt unda	Maytenus undata	Celastraceae
17	Onco spin	Oncoba spinosa	Flacourtiaceae
18	Oxyt abys	Oxytenanthera abyssinica	Poaceae
19	Ozor insi	Ozoroa insignis	Anacardiaceae
20	Pili thon	Piliostigma thonningii	Fabaceae
21	Pitt viri	Pittosporum viridiflorum	Pittosporaceae
22	Pter luce	Pterocarpus lucens	Fabaceae
23	Secu long	Securidaca longepedunculata	Polygalaceae
24	Steg aral	Steganotaenia araliacea	Apiaceae
25	Ster kunt	Stereospermum kunthianum	Bignoniaceae
26	Syzy guaf	Syzygium guineense subsp. afromontanum	Myrtaceae
27	Syzy guin	Syzygium guineense subsp. macrocarpum	Myrtaceae
28	Term laxi	Terminalia laxiflora	Combretaceae
29	Term macr	Terminalia macroptera	Combretaceae
30	Vite doni	Vitex doniana	Lamiaceae