The study was carried out in Bale Mountains Eco-Region (BMER), southeastern Ethiopia. Geographically it is located between latitude 5°16ꞌ54ꞌꞌN and 7°52ꞌ55ꞌꞌN, and longitude 38°37ꞌ52ꞌꞌE and 41°13ꞌ0ꞌꞌE (Figure 1). The BMER is found within one of the Afromontane forests. The Afromontane rain forest is mainly distributed in two geographically different and wide apart regions namely South-west and South-East forests (Friis, 1992). Both areas are part of the Eastern Afromontane Biodiversity Hotspot. The two sites are known for their non-carbon resources among which Non-Timber
Forest Products (NTFP), where forest dependent communities practice their customary rights, such as collection of wild coffee, honey and spices, which are abundant. In the BMER there is Participatory Forest Management (PFM). There are more than 60 forest user groups who are responsible for the management of this forest area.
Sixteen districts (locally known as Woredas), namely Agarfa, Dinsho, Adaba, Dodolla, Goba, Sinana, Gololcha, Gasera, Delo Mena, Kokosa, Berbere, Harana Buluk, Nansebo, Mada Walabu, Goro and Guradhamole form the BMER. The forests in the BMER are mainly high forests composed of six forests formerly designated as “forest priority areas”, namely, Aloshe Batu, Goro Bale, Harana Kokosa, Kubayu, Menna Angetu and Adaba Dodolla (EFAP, 1994). According to FARM-Africa (FARM Africa, 2008), the total forest area of the BMER was 690,000 ha in 2011, of which 193,000 ha was covered by the Bale Mountain National Park (BMNP), which was not included in this study.
About 1,904,279 people live in the sixteen districts (CSA, 2013) of which BMER comprises 61.4%. BMNR receives almost eight months of precipitation (March-October). Temperature varies from the lowest less than 7.5°C at the Sannati Plateau to over 25°C in Dolo Mena (WBISPP, 2001).
The Bale Mountains, housing BMNP and surrounded by the priority forest areas, mountains, valleys, grasslands and agricultural land, represent the largest area of Afro-alpine habitat in the African continent (FARM Africa, 2008). It is home of not only the endangered Ethiopian Wolf (Canis simensis) but also diverse bird species, Mountain Nyala (Tragelaphus buxtoni), the entire population of the Giant Mole Rat (Trachyoryctes macrocephalus) and stocks of valuable genetic material, including wild coffee (Coffea arabica L.) (OFWE et al., 2014).
The BMER is considered as the water tower of south-eastern Ethiopia, Somalia and Northern Kenya. According to recent studies, the BMER supplies water for some 12 million people in the lowlands of southeast Ethiopia, Northern Kenya and Somalia (OFWE et al., 2014). A total of 40 rivers arise in the area, contributing to five major rivers, namely the Web, Wabi Shebele, Welmel, Dumal and Ganale (FARM Africa, 2008). These rivers are the only sources of perennial water for the arid lowlands of the eastern and southeastern Ethiopia, including the Ogaden and Somali agricultural belt (OFWE et al., 2014).
Despite its great significance, the BMER is under threat. Deforestation and forest degradation, resulting from immigration of people from other parts of Ethiopia and, hence, population increment, livestock pressure, fire and settlement, have affected the status and future of the forest resources. The projected deforestation for the period of 10 years exceeds 150,000 ha (FARM Africa, 2008), and it has been projected to continue unless proper incentives to the stakeholders in the area are provided. Failure to design attractive incentive system to the communities and the local government as well as restricting communities to access non-carbon benefits may lead to further loss of these invaluable resources. Temperature in BMER varies from the lowest, less than 7.5°C at Sannati Plateau to over 25°C at around Dolo Mena (WBISPP 2005).
The ecoregion consists of conifers and broadleaved species. The large Harenna forest of the Bale Mountains is floristically very closely related to South Western Ethiopian Afromontane forests (Friis 1992). The conifers are mainly Podocarpus falcatus and Juniperes procera.
Tree species in the area include Oleaa europea subsp. cuspidata, Acacia abyssinica, Acacia negri, Euphorbia abyssinica and Apodytes dimidiata, Allophylus abyssinicus, Myrsine melanophloeos and Olinia rochetiana. Epiphytes like orchids, mosses and lichens are also present. The shrub layer is primarily composed of Myrsine africana, Calpurnia aurea, Dovyalis abyssinica and Carissa spinarium. Climbers include Smilax aspera, Urera hypselodendron, Embelia schimperi, Jasminum abyssinicum and various species of the Cucurbitaceae family. The ground is usually covered with grasses, herbs, mosses and ferns.
Other trees that are grouped under broadleaved tree species include Apodytes dimidiate, Celtis africana, Croton macrostachyus, Ekebergia capensis, Milletia ferruginea, Polyscias fulva, Syzigium guineense, Cassipourea malosana, Elaeodendron buchananii and Schefflera abyssinica. The most frequent small tree species include Allophylus abyssinicus, Bersema abyssinica, Bridelia micrantha, Ehretia cymosa, Maesa lanceolata, Nuxia congesta, Oxyanthus speciosus, Rothmannia uncelliformis, Teclea noblis and Vepris daniellii. Wild coffee is one characteristic species in the understory between 1000 and 2000 masl.
Non-timber forest products (NTFPs) that are essential for the local economy include Arabica coffee, Gesho (Rhamnus stado) and medicinal plants. Grass for domestic animal is another significant NTFP especially during the dry season. Quite a lot of cattle are dwelling in the forest during the hot season.
The main soil types common in the area are Cambisols, Vertisols, Luvisols, Lithosols and Nitosols (FARM Africa, SOS Sahel and OFWE, 2014). The Bale Mountains form part of the Ethiopian highlands system and was formed during the Oligocene and Miocene geological periods, between 38 - 7 million years ago. The area consists of a vast lava plateau with at least six volcanic cones, each more than 4,200 m high, which have been considerably flattened by repeated glaciations (ibid). For this study, four districts are considered. These are Dodolla, Harena Buluk, Kokosa and Dolo Mena districts (hereafter referred to as by their names). The districts housed conifers, mixed conifers, broadleaved and high forests (Table 1).
In the selected districts, sample households were selected using simple random sampling (SRS) method (Moore and McCabe, 2002). Three kebeles (the smallest and lowest administrative unit in Ethiopia) from each representative district were chosen. The sample kebeles in a district were considered to be representative in terms of wealth status (poor, medium and rich), age (more than 50, less than 50), sex (female and male) and education background (read and write and illiterate) of the interviewees. Accordingly, Berisa, Deneba and Bura Chale kebeles in Dodolla, Huro Bero, Korema and Bulga kebeles in Nansebo, Sodu, Welmel, Angetu and Shawe kebeles in Harena Buluk and Cheri, Wabero and Irba kebeles in Dolo Mena were chosen (Table 1). The final analyses were, then, aggregated at the district level.
Methods
Various methods were employed to investigate the relationships between different woody species diversity indices and carbon stock as well as the non-carbon benefits obtained by the local communities from the natural forests in the study area.
Relationships between different woody species diversity indices and carbon stock
To investigate the relationships between different woody species diversity indices and carbon stock, the dataset collected during the forest inventory carried out by FARM Africa (with written permission to use the data from FARM Africa) in the study forest resources in 2013 was used.
To determine species richness, diversity, densities, frequencies, dominance and, hence, important value indices of woody species as well as their carbon stock, a total of 28 square quadrats measuring 100 x 100 m (10,000 m2) were laid down randomly. In each of the quadrats, the following parameters were recorded: identity of all woody species, number of all live individuals and diameter at breast height (DBH) of individuals with DBH > 2 cm of each woody species. A calliper and graduated measuring stick were used to measure DBH and height, respectively, of the woody species.
Non-carbon benefits
To investigate the types, quantities and values of non-carbon benefits obtained by the local communities from the forest resources, household surveys (HHSs) and focus group discussions (FGD) were undertaken.
Household survey: To determine the number of households for the HHSs, the coefficient of variation (CV) was calculated using data from a study carried out on maize production per household in the BMER in 2013. A total of 223 households were considered to estimate the coefficient of variation (CV) in production. The mean production was about 10 quintals per household. The standard deviation was approximately 11. Using these two figures, the CV was calculated as 91%. Accordingly, the numbers of sample households for this study were determined using the following formula (Moore and McCabe, 2002; Loetsch and Haller, 1973):
Where, n = number of sample households, CV = coefficient of variation, t = Student-t and the value of 2 is considered, e = allowable error (10% allowable error is considered). Using the above formula, the total number of sample households required for the HHSs was 331 (Table 1).
According to the Ethiopian Central Statistics Agency (undated publication), there are about 414 kebeles, including towns in the BMER, and the number of kebeles in each district varies. There are 67 kebeles in the four study districts of which 12 (18%) were considered as representative for the study. The 331 sample households were distributed randomly over the 12 kebeles proportional to the number of kebeles in the four districts (Table 1). However, during the actual visits, some households were found abandoned due to one or the other reason. Hence, the total number of households used in the survey was 321 rather than 331. Accordingly, 99, 77, 76 and 69 households were interviewed in Dodolla, Dolomena, Nansebo and Harena Buluk districts, respectively.
The HHSs were carried out by using a questionnaire developed for the purpose. The questionnaire covered issues pertaining to livelihood situation, annual income of households, their relation with forests, duration of households visit to forests to get products or non-carbon benefits, duration or number of days that livestock feeds in the forest within a year and other relevant information.
During the survey, two major research questions were addressed: (i) what are the most important forest products for local communities? (ii) What is the contribution of forests to the local economy? In this study, local economy refers to the sum of total income obtained by the households in the study area. Hence, the non-carbon benefits of the forests, such as water, watershed protection and other intangible non-carbon benefits were not considered. Values of forage obtained from the forests were estimated roughly.
The volume of forest products and kinds of non-carbon benefits obtained by each respondent household were assessed using semi structured questionnaires. Likewise, an attempt to assess revenue generated from crop production and livestock production was made. Each respondent was asked what non-carbon benefits he/she collects from the forest every day, every week or at any regular interval. The respondent also estimated the harvested or collected forest service and product into monetary value using the local market price.
Focus group discussion: The focus group discussion (FGD) was conducted in addition to the HHS. The FGD was conducted in each sample kebele. A FGD has particular advantage to get qualitative data or information. The discussion focused on various issues concerning the environment, REDD+, crop production, livestock production, tangible forest resources and intangible forest resources, for which a list of lead topics/questions were prepared well ahead of the discussions. The discussion on environment focused on situations of forest, land, air, water and wildlife in the study areas or their vicinity. Past and present situations were addressed and the understanding of REDD+ of members of the FGD was captured. The discussion on production of major crops and livestock focused on types of crops grown and animals reared, type of inputs used, costs of production and input as well as market value per unit measurement. The discussion on tangible and intangible forest resources focused on products and non-carbon benefits that the groups get from the forest. Information on the most important forest products for market was gathered.
Data analyses
Species richness, diversity and evenness
Species richnes of the study districts was determined from the total number of woody species recorded in each of the districts. It does not take into account the proportion and distribution of each species at the project sites (Neelo et al., 2013).
Diversity and evenness of all woody species in each district were determined using the Shannon-Wiener diversity index (H) and evenness (E) (Krebs, 1989; Magurran, 2004; Zerihun, 2012). The indices were computed using the following formulas:
Where H = Shannon-Wiener diversity index and Pi = the proportion of individuals found in the ith woody species:
Where E = evenness, Hmax is the maximum level of diversity possible within a given population, which equals ln (number of species);
Similarity in species composition
Jaccard’s similarity coefficient (J) (Krebs, 1989) was used to compute similarity in the composition of woody species between the study districts using the following formula:
Where, J = Jaccard’s similarity coefficient, C = the number of woody species common to both districts, A = the number of woody species present in one of the districts to be compared and B is the number of woody species present in the other district.
The values of J range between 0 and 1, 0 indicating complete dissimilarity and 1 indicating complete similarity in woody species composition (Krebs, 1989; Kent and Coker, 1992).
Density, frequency and dominance
Density was calculated by converting the total number of individuals of each species to equivalent numbers per hectare (absolute density), and as the percentage of the absolute density of each species divided by the total stem number of all species ha-1 (relative density). Frequency distribution of each species was determined from the number of plots in which the species was recorded (absolute frequency), and as a percentage (relative frequency) by dividing the absolute frequency of the species by the sum of the absolute frequencies of all the species. The absolute dominance of woody species with DBH > 2.5 cm was determined from summing the basal area (BA) of all individuals of a species. Relative dominance was calculated as the percentage of the BA of a species divided by the total BA of all species (Neelo et al., 2013, 2015).
Importance value index
The relative ecological importance of each woody species, commonly referred to as important value index (IVI), was determined by summing its relative frequency, relative density and relative dominance (Kent and Coker, 1992).
Carbon stock
Carbon stock is the quantity of carbon in a given pool or pools per unit area (Pearson et al., 2005). In this study, above ground biomass of woody species encountered in the plots was considered as the carbon pool. Carbon stock was estimated using the DBH of all individuals of all woody species having DBH of 2 cm and above. For the estimation of carbon stock, the following algorithms, which are applicable for tropical moist and dry deciduous forests were used (Chave et al., 2005):
To see if there were any statistical significant differences among the mean values of carbon stock of the woody species in the forests found in the four study districts of BMER, the data were subjected to analysis of variance (ANOVA). Also, regression analysis was undertaken to test the relationships between the Shannon diversity indices and carbon stocks of woody species. Microsoft excel was used to organize data and MINITAB and SPSS 20 were used to analyze the data.
Household survey
The number of livestock in the surveyed households that stay in the forest was estimated. The number was converted to tropical livestock unit (TLU). Then the TLU was multiplied by 6.25 kg to estimate the amount of forage consumed everyday by the livestock. Mean TLU per household was estimated and it varied from 0.678 to 3.011. This figure refers TLU relevant to forest grazing. Otherwise, Woody Biomass Inventory Strategic Planning Project (WBISPP, 2005) reported that TLU per farmer in Arsi and Bale Zones is 5.4 and 6.1, respectively.
The forest non-carbon benefits considered are fuelwood, construction material, forage, forest coffee and forest honey. Local economy in this context is the aggregated economy of each household in the BMER. Therefore, the contribution of forest non-carbon benefits to each household can be aggregated to the local economy. In each surveyed household, the forest products and non-carbon benefits harvested annually were estimated. The volume harvested was valued using local market price that was given by the respondent. Similarly, production and transport cost of the products and non-carbon benefits were estimated based on the information from the respondent. Then, the difference was considered as net income to the household.
Forage consumption depends on the number of days the cattle stay in the forest. Total forage consumed can be estimated from these numbers of days. Then, the contribution of forests to livestock can be estimated. The households reported the number of days their cattle stay in the forest per year. The dates are grouped into the four districts and, then, ANOVA was undertaken.
To estimate contribution of non-carbon benefits to each household, a rapid appraisal of each product collected from the forest was carried out based on local market prices. Similar accounting was also made to crop and livestock production in the study districts.
Household respondents were also asked to identify the most important forest services. The responses were grouped in to two-way table and the analysis was conducted accordingly. To test the presence of differences in the use of forest non-carbon benefits by the different respondent households in the study areas, a Chi-square test was conducted. Chi-square test was used to determine whether there was a significant difference between the expected frequencies and the observed frequencies in one or more categories (Moore and McCabe, 2002). The share of forest contribution to each household was calculated as:
Where a = income generated from forest, b = income generated from crop production, c = income generated from livestock. Mean contribution of forest in each household per district was estimated. Confidence interval at 95% for each district was estimated using bootstrap in SPSS 20.
Focus group discussion
Summaries from each FGD were compiled and synthesized to draw conclusions. To estimate the value of forage, getting recent data on price of forage from forest was not possible. Market price is available from 2007 studied by International Livestock Research Institute. This market price covers for teff [Eragrostis tef (Zucc.) Trotter] straw, barely/wheat straw, sorghum and hay. According to the study, the prices of one kilogram of teff straw, barley/wheat straw, sorghum and hay were Ethiopian Birr (ETB) 2.00, 0.6 to 1.00, 0.65 and 1.66, respectively in Sululta (Gebremedhin et al., 2009).