ASSESSMENT OF CARBON STOCK OF … · Web viewThe East cluster is primarily found in Ethiopian...

iH a r a m a y a U n i v e r s i t y

2014ASSESSMENT OF CARBON STOCK OF RANGELAND SYSTEMS IN SELECTED PASTORAL AREAS OF SOMALI,

AFAR AND OROMIA REGIONS

Kibebew Kibret (PhD) and Tesema Toru

PRIME Project

Assessment of Carbon Stock of Rangeland Systems in Selected Pastoral Areas of Somali,

Afar and Oromia Regions

A Draft Report

By

Kibebew Kibret (PhD) Tesema Toru

November 2014 Haramaya University

PRIME PROJECT HU

ACKNOWLEDGMENTS

The authors would like to express their sincere gratitude to all those who contributed, directly or indirectly, to the successful start and completion of this project. The technical, financial support and facilitation of all the field work by the PRIME project is highly acknowledged. The support provided, in every aspect, by the Haramaya University PRIME project management during the field work deserves special gratitude. The authors also express their indebtedness to the cluster level PRIME staff and staff members of the PRIME project partners who were actively involved in selection of the study sites, assignment of local staff as a guide and facilitation of the field work at the respective clusters. Without their true dedication and commitment, and also involvement in the actual field work, the difficult field work would not have been completed successfully.

The cooperation of the pastoral communities during the field work is also highly appreciated. Worth mentioning among these is the amazing hospitality the authors received during the field work at Harshin where the team’s vehicle was stuck in a mud and had to spend the night there. Long live to the Harshin community. The authors are also grateful to Mr. Kassaw Asfaw and Mr. Yitages Tamiru for their unreserved contribution in the collection of vegetation and soil samples, and laboratory analysis of the samples.

Last but not least by any means, the authors greatly acknowledge the support provided by pertinent local government offices by assigning staff members to facilitate the field work when needed.

EXECUTIVE SUMMARY

Pastoralism in Ethiopia is a direct source of livelihood to more than 7 million people who live in the vast lowlands and drought-prone areas. These areas make up about 40% of the total land area of the country. Despite living in the most fragile ecosystems, pastoralists and pastoralism make significant contribution to the national economy through livestock products. However, significant areas of these lands are affected by degradation. Climate change is predicted to have even a larger impact on these fragile ecosystems. On the other hand, the great potential of these lands for carbon sequestration has been highlighted. Their management can help in mitigating climate change. Different rangeland management practices have been tried over the years. Nevertheless, the impacts of these management practices on the rehabilitation of rangelands and their carbon stock have not been assessed to provide quantitative information to inform policy in these areas. PRIME project has started implementing participatory rangeland management scheme in pastoral areas of Somali and Afar regional states, and Borena and Guji zones of Oromia region. It is imperative to have baseline carbon stock information to evaluate the difference this management scheme might bring about after five years. This study was conducted to achieve this grand objective.

This study was conducted at three PRIME project target clusters, namely east cluster, Afar cluster, and south cluster with the objective of assessing carbon stock of grazing systems that are put under participatory rangeland management scheme. The East cluster encompasses the Somali Regional state, while the South cluster includes Borena and Guji zones of Oromia region. Harshin, Daketo, Mulu, and Afdem grazing systems were included from the East cluster; Mollale, Halydege, and Dudub grazing systems were selected from the Afar cluster; Malbe and Dire grazing systems from Borena zone, and Dida Dheda and Golba Genale grazing systems from Guji zone were selected from the South cluster. Both vegetation and soil samples were collected from field and analyzed for their carbon content. The results of the study reveal that the studied grazing lands in pastoral areas have immense potential to serve as carbon sinks both in soils and living vegetation. The results obtained in this study can help decision makers to guide their policy towards rangelands in pastoralist areas.

LIST OF ACRONYMS

ABTB Aboveground Tree BiomassAD Andido at HalydegeAD Arbala Dida at MalbeAGB Aboveground biomassAGWV Aboveground Woody VegetationBD Bulk DensityBGB Belowground biomassCSA Central Statistical AuthorityCV Coefficient of VariationDBH Diameter at Breast HeightDDH Dida Dheda in GujiDE Dire Ella in AfdemDH Dida Haya at MalbeDK Dubuluk at DireDM Dida Medhecho at DireEBL Elbahey Bush LandEGL Elbahey GrasslandFAO Food and Agriculture Organization of the United NationsGB Gointa BirkaGB Guduba Burure in Golba GenaleGDP Gross Domestic ProductGG Golba Genale in GujiHD Hudud at DudubHG Halydege villageHS Hussein SemaneHV Herbaceous VegetationIFPRI International Food Policy Research InstituteILRI International Livestock Research InstituteIPCC Intergovernmental Panel on Climate ChangeIR Irrebeto at DudubIRIN Integrated Regional Information NetworksJJ Jejeba in MuluKL Kulmeye in MuluLEAD Leadership for Environment and DevelopmentMC Mucho in Golba GonaleME Mecha in MuluMS Motor Sefer at DudubMSP Meesa Protected at Dida DhedaMSUP Meesa Unprotected at Dida DhedaNGO Non-governmental Organization

Acronyms (Continued)

OAU Organization of African UnityPRIME Pastoralist Areas Resilience Improvement through

Market ExpansionRC Rare Chebicha at DireSS Siselu in AfdemStD Standard DeviationSTP Siminto Protected at Dida DhedaSTUP Siminto Unprotected at Dida DhedaUNEP United Nations Environment ProgramWOCAT World Overview of Conservation Approaches and

TechnologiesWRI World Resources Institute

TABLE OF CONTENTS

ACKNOWLEDGMENTS iEXECUTIVE SUMMARY iiLIST OF ACRONYMS iiiLIST OF TABLES viiLIST OF FIGURES viiiLIST OF PLATES xABSTRACT xii1. INTRODUCTION 1

1.1. Background 1

1.2. Overall Objectives and Expected Result Linkage 4

2. METHODOLOGY 42.1. General Description of the Study Areas 4

2.2. Sampling Site Selection 5

2.3. Field layout for above ground vegetation sampling 8

2.4. Estimation of vegetation carbon stock 8

2.5. Soil Sampling and Preparation for Soil Carbon Stock Assessment 9

2.6. Estimation of Soil Carbon Stock 10

2.7. Estimation of Terrestrial Carbon Stock and Carbon Dioxide Equivalent11

3. KEY FINDINGS 123.1. East Cluster 12

3.1.1. Terrestrial Carbon Stock of Harshin Grazing System 12

3.1.1.1. Overview of the grazing system 12

3.1.1.2. Results and discussion 14

3.1.2. Terrestrial Carbon Stock at Daketo Grazing System 16



3.1.3. Terrestrial carbon stock of the Mulu grazing system 20



3.1.4. Terrestrial Carbon Stock of the Afdem Grazing System 23

3.1.4.1. Overview of the system 23


3.2. The Afar Cluster 27

3.2.1. Terrestrial carbon stock of Gewane Grazing System 28



3.2.2. Terrestrial carbon stock of Halaydege grazing system 31



3.2.3. Terrestrial carbon stock of the Dudub grazing system 34



3.3. South Cluster 38

3.3.1. Terrestrial carbon stock of Malbe Grazing System 38



3.3.2. Terrestrial carbon stock of Dire grazing system 42



3.3.3. Terrestrial carbon stock of the Dida Dheda grazing system 46



3.3.4. Terrestrial carbon stock of the Golba Genale grazing system 50



4. CONCLUSIONS 555. RECOMMENDATIONS 56REFERENCES 57

LIST OF TABLES

Table 1. Study sites selected for carbon stock assessment and their basis characteristics 6

Table 2. Terrestrial carbon stock and its carbon dioxide equivalent (t ha-1) at the Hussein Semane sub-grazing system in Harshin, Somali region 15

Table 3. Terrestrial carbon stock of the Elbahey grazing sub-system in Daketo grazing system of Somali region 19

Table 4. Terrestrial carbon stock at three grazing sub-systems in Mulu grazing system, Somali region 22

Table 5. The terrestrial carbon stock and its carbon dioxide equivalent at two grazing sub-systems in Afdem grazing system, Somali region 25

Table 6. Soil carbon stock and its carbon dioxide equivalent at Mollale grazing sub-system Gewane, Afar region 30

Table 7. Terrestrial carbon stock and its carbon dioxide equivalent at the Halydege grazing system in Afar region 33

Table 8. Terrestrial carbon stock and its carbon dioxide equivalent at the Dudub grazing system in Afar region36

Table 9. Terrestrial carbon stock and its equivalent carbon dioxide at Malbe grazing system, Borena zone of Oromia region 41

Table 10. Terrestrial carbon stock and its carbon dioxide variation with soil depth at three sites in Dire grazing system, Borena Zone 44

Table 11. Terrestrial carbon stock and its carbon dioxide equivalent at some grazing site in Dida Dheda grazing system, Guji zone of Oromia region 49

Table 12. Terrestrial carbon stock and its carbon dioxide equivalent at Golba Genale grazing system in Guji zone of Oromia region 52

LIST OF FIGURES

Figure 1. Location map of sampling sites at the different grazing systems in the three clusters. 5

Figure 2. Carbon stock and CO2e (t ha-1) variation with soil depth at the Hussein Semane grazing sites in Harshin grazing system, Somali region (HS = Hussein Semane). 16

Figure 3. Carbon stock and CO2e (t ha-1) variation with soil depth for selected grazing sites in Dakato grazing system (EBL = Elbahey bush land; EGL = Elbahey graa land). 19

Figure 4. Carbon stock and CO2e (t ha-1) variation with soil depth at selected grazing sites in Mulu grazing system (ME = Mecha; KL = Kulmeye; JJ = Jejeba). 22

Figure 5. Variation of soil carbon stock and the corresponding CO2e with soil depth at selected grazing sub-systems in Afdem, Somali region (DE = Dire Ella; SS = Siselu). 26

Figure 6. Mean terrestrial carbon stock and its carbon dioxide equivalent (t ha-1) at four pastoral area grazing systems in Somali region. 27

Figure 7. Soil carbon stock and its carbon dioxide equivalent distribution with soil depth at Mollale sub-grazing systems in Gewane, Afar region. 30

Figure 8. Soil carbon stock and its carbon dioxide equivalent variation with soil depth at selected sites in Halydege grazing system, Afar region (AD = Andido; HG = Halydege; GB = Gointa Birka). 33

Figure 9. Soil carbon stock variation with soil depth at selected sites in Dudub grazing system in Afar region (IR = Irrebeto; HD = Hudud; MS = Motor Sefer). 36

Figure 10. Mean terrestrial carbon stock and its CO2e (t ha-1) at selected grazing systems in Afar region. 37

Figure 11. Soil carbon stock and equivalent carbon dioxide variation with soil depth at the Malbe grazing system in Borena zone of Oromia region (AD = Arbala Dida; DH = Dida Haya; P = protected; up = unprotected). 41

Figure 12. Soil carbon stock and its carbon dioxide equivalent distribution with dept at selected site in Dire grazing system of Borena Zone, Oromia region (DK = Dubuluk; RC = Rare Chebicha; DM = Dida Medhecho). 45

LIST OF FIGURES (Continued)

Figure 13. Mean terrestrial carbon stock and its carbon dioxide equivalent for Malbe and Dire grazing systems in Borena Zone of Oromia region. 46

Figure 14. Soil carbon stock and the corresponding carbon dioxide equivalent variation with soil depth at selected sites in Dida Dheda grazing system, Guji zone of Oromia region (MSP = Meesa protected; MSUP = Meesa unprotected; STP = Siminto protected; STUP = Siminto unprotected).50

Figure 15. Soil carbon stock and its carbon dioxide equivalent distribution with soil depth at Golba Genale grazing system, Guji Zone of Oromia region (GB = Guduba Burure; MC = Mucho). 53

Figure 16. Mean terrestrial carbon stock and its carbon dioxide equivalent at two grazing systems in Guji Zone, Oromia region (DDH = Dida Dheda; GG = Golba Genale). 54

LIST OF PLATES

Plate 1. Partial view of the Hussein Semane sub-grazing system sampling sites, nature of vegetation cover, and stocking density in Harshin grazing system. 13

Plate 2. Partial view of the Elbahey sub-grazing system in Daketo; A and B show the upper smapling plot dominantly occupied by cactus and Lanthana camara, and B and C show the second sampling site in Daketo valley with annual herbaceous vegetation. 17

Plate 3. Nature of vegetation, vegetation data (measuring tree diameter and weighing fresh biomass of herbaceous vegetation), vegetation and soil sample collection activities at the three grazing sub-systems in Mulu grazing system. 21

Plate 4. Partial view of the highly degraded vegetation and soil in Afdem grazing system at Dire Ella and Siselu, and the livestock that are desperate to get some feed from these highly degraded grazing lands. 24

Plate 5. The partial view of the Mollale sub-grazing system in Gewane. Prosopis juliflora is being cleared from this field (bottom) and the soil was devoid of any other vegetation. 29

Plate 6. The extensive grazing lands located at the low lying areas in Halydege were devoid of grass vegetation at the time of sampling. However, Prosopis juliflora is still proliferating at some of the sites. 32

Plate 7. Some features of the grazing lands in Dudub grazing system. The soil is bare except the scattered bushy vegetation cover and is highly prone to wind erosion. 35

Plate 8. The nature of the extensive plain grass land at Arbala Dida (upper), soil and vegetation sampling activities (bottom left), and protected and adjacent unprotected grazing land (bottom last two) at Dida Haya at Elwaye sub-grazing system in Malbe. Note that the Arbala Dida grazing land is also home to some wild animals such as ostrich. 39

Plate 9. Partial view of the three sub-grazing systems and their status of vegetation cover at the Dire grazing system. Near the hills, the Dubluk sub-system is home to some wild animals like zebra. 43

LIST OF PLATES (Continued)

Plate 10. Partial view of the sampling sites at Meesa (upper) and Siminto (lower) sub-systems at Dida Dheda grazing system. The upper and bottom left photos indicate the protected kallos at both sub-systems, while the adjacent ones indicate the unprotected grazing lands. 47

Plate 11. Partial view of the sampled forest at Guduba Burure (upper), active participation of local partners in the study (bottom left), and nature of some trees at Mucho sampling site in Golba Genale grazing system. 51

ABSTRACT

A study on carbon stock assessment in pastoral PRIME target areas was conducted in Somali, Afar, and Oromia Regions. The baseline carbon stock was assessed based on measurements made on vegetation and soil samples collected from selected sites in grazing systems.The baseline mean terrestrial carbon stock and its carbon dioxide equivalent in Harshin grazing system was 73.924±26.426 and 271.301±96.984 t ha-1, respectively. The corresponding values for the Daketo system were 90.203±42.837 and 331.045±157.210 t ha-1, respectively. At Mulu grazing system, the baseline mean carbon stock and the corresponding baseline mean CO2e were 160.536±31.477 and 589.166±115.521 t ha-1. At Afdem the stock was relatively low (58.622±9.296 and 215.143±34.118 t ha-1 of carbon and equivalent carbon dioxide, respectively).At Mollale in Gewane, the carbon source was only the soil and it was 33.43 tha-1. The baseline mean value of the carbon stock and its carbon dioxide equivalent for the Halydege grazing system was 45.628±3.463 and 167.456±12.708 t ha-1, respectively. The corresponding values for Dubluk system were 29.519±17.771 t ha-1 carbon with equivalent carbon dioxide of 108.335±65.220 t ha-1. The mean terrestrial carbon stock and the corresponding carbon dioxide equivalent for the Malbe system were 60.962±14.110 and 223.729±51.785 t ha-1, respectively, while the corresponding values at Dire, Dida Dheda, and Golba Genale were, respectively, 81.697±20.248 and 303.498±74.312, 67.687±17.585 and 248.411±64.537, and 138.026±11.350 and 506.556±41.656 t ha-1.Comparison of the carbon stock in protected and unprotected grazing lands at Malbe and Dida Dheda grazing systems indicates that the contribution from herbaceous vegetation is higher in the protected than it is in the unprotected grazing lands. However, due to intensive grazing after protection and relatively short duration of the protected vegetation, this difference was not clearly reflected in the soil carbon stock. This clearly indicates that implementing participatory rangeland management practice in combination with controlled grazing and stocking could improve the contribution of both vegetation and soil to the total carbon stock of the grazing systems. This will in turn improve the productivity of the grazing systems through the favorable effects of organic carbon on soil properties, improve productivity of livestock through improving feed supply and eventually increase the resilience of the pastoral community to climate change impacts. Furthermore, the results obtained in this study suggest that management of grazing systems in pastoral areas could be among the options to mitigate climate change impacts as these areas are vast in their extent and have high potential to store carbon in live vegetation and soils.

1. INTRODUCTION1.1. Background

Livestock production, the main land use in pastoral areas and a source of livelihood for over 1 billion people (World Bank, 2007), can be found on two thirds of global drylands (Clay, 2004; Nori et al., 2005). About 60% of the 690,000 poor people living in sub-Saharan Africa rely on livestock for some part of their livelihood (Thornton et al., 2002). On the other hand, the report of IFPRI and ILRI (2000) indicate that 25 million pastoralists and 240 million agro-pastoralists living in sub-Saharan Africa depend on livestock as their primary source of income. The dedication of about 40% of Africa’s land to pastoralism highlights the importance of livestock to the livelihood of Africans (IRIN, 2007).

Livestock products, being the main outputs of grazing lands, have become among the fastest growing agricultural subsector globally. The World Bank (2007) report indicates that the contribution of the livestock sector accounts for 50-80% of some developing countries’ GDP, while the share in sub-Saharan Africa is estimated at 12.5%. This indicates the social and economic importance of livestock to rural livelihoods, and thus the sustainable management of the natural resources base that supports them should stand high on the agenda.

Estimates made by various studies (WRI, 2002; UNEP, 2006) indicate that drylands, which are predominantly used for livestock production, occupy a significant 41 per cent of the earth’s land area and are home to more than 2 billion people. Nevertheless, these expansive lands are particularly sensitive to land degradation, with 10–20 percent of them already degraded (Millennium Ecosystem Assessment, 2005). In connection with this, the report released by WOCAT (2009) indicates that an estimated 73 percent of the 3.4 billion ha of rangelands, most of which are located in drylands, worldwide are affected by soil degradation.

Climate change, through its effects on desertification that has resulted in the loss of 12-18 billion tons of carbon, is predicted to have even a more significant impact on these impoverished and vulnerable but important ecosystems (Muñoz-Rojas et al., 2012a; 2012b; 2013). It is feared that, if continued unabated, climate change and variability will continue to pose serious threats to the often vulnerable and impoverished people living in these hostile environments and their livelihood assets, the livestock. On the other hand, there are evidences (e.g. United Nations, 2011; FAO/LEAD, 2006; IPCC, 2007) that show that these areas might play a key role in mitigation of climate change effects through their great potential for sequestration of carbon in soils and living vegetation. Since carbon losses from drylands are associated with loss of vegetation cover and soil erosion, management interventions that slow or reverse these processes can simultaneously achieve carbon sequestration and, thus, help in climate change mitigation. Thus, reversing land degradation in extensive dryland areas through improved pasture and rangeland management would contribute to restoring the soil and vegetation carbon sink while also improving livestock-based livelihoods.

As a result, the potential of extensive areas of semi-arid and arid rangelands to sequester C has been receiving increasing attention because of the very large global extent of such environments (Glenn et al., 1993; Conant et al., 2001; Howden et al., 2001; Moore et al., 2001; Burrows et al., 2002; Dener et al., 2006; Harper et al., 2007). Efforts have been and are being made to estimate carbon sequestration potential of the drylands by several workers (Smith et al., 2008; Lal, 2001, 2003, 2004; Campbell et al., 2008; UNEP, 2008; IPCC, 2001; White et al., 2000; Grace et al., 2006; Squires et al., 1995; Keller and Goldstein, 1998).

Pastoralism in Ethiopia is a direct source of livelihood to more than 7 million people who inhabit the vast lowland and drought-prone territories, which make up about 40% of the total land area of the country (Helland, 2006). It produces 80% of the total annual milk supply (CAPE OAU/IBAR, 2014) and contributes 19% of the GDP with annual returns to capital from livestock (through the production of milk, meat, skin, hides, etc) estimated

at around 2.1-2.6 billion USD (Behnke, 2010). This makes the sector an important source of indigenous livestock for export markets and urban consumption.

Given the size of the C pool in grazing lands, it is important to improve understanding of the current and potential effects of grazing land management on soil carbon sequestration and storage (Schuman et al., 2002). There is, therefore, a growing interest in assessing the carbon sequestration potential of such strategies quantitatively. Real and accurate carbon data is scarce. Much of the available data is often based on limited assessment of carbon stocks in a specified range unit, which fails to capture the spatial and temporal heterogeneity that characterizes pastoral ecosystems (Dabasso et al., 2014).

Furthermore, limited data regarding soil carbon (C) sequestration potential and biosequestration potential in arid and semi-arid environments is an impediment to appropriate policy formulation directed at greenhouse gas abatement (Witt et al., 2011). Also, unavailability of such data has resulted in exclusion of carbon accumulation in grazing lands from existing international carbon trading mechanisms, such as the Clean Development Mechanism. Such carbon stock data can, therefore, provide baseline information to determine if pastoral grazing management can be engaged for carbon credit trading.

Nevertheless, the carbon stock and carbon sequestration potential of the extensive grazing areas in pastoral and agro-pastoral areas of Ethiopia has not been assessed in a comprehensive way. Furthermore, impacts of participatory rangeland management practices on carbon stock of grazing systems have not been evaluated. It is imperative to generate such quantitative information in order to provide evidence-based guide to policy decisions in pastoral areas.

1.2. Overall Objectives and Expected Result Linkage

The research was conducted with the following main objectives:

Assess the status of carbon stock of rangelands in PRIME intervention clusters and their contribution to climate change mitigation,

Compare the carbon stock of selected managed and unmanaged rangelands and its implication to climate change mitigation, and

Extract policy briefs that will direct policy makers on rangeland management in pastoralist areas for climate change mitigation

2. METHODOLOGY

2.1. General Description of the Study Areas

The study was conducted in selected PRIME intervention areas of East, Afar and South clusters during 2014. The East cluster is primarily found in Ethiopian Somali Region and Babile woreda of Oromia Region; the Afar cluster denotes the Afar Region and the South cluster encompasses pastoral areas of Borena and Guji zones of Oromia Region. From the East cluster four grazing systems (Harshin, Daketo, Mulu, and Afdem) were selected. From the Afar cluster, three grazing systems, namely Mollale (Gewane), Halydege, and Dudub were selected for the study. Similarly, from the South cluster Malbe and Dire from Borena zone, and Dida Dheda and Golba Genale grazing systems from Guji zone were considered. The selected grazing systems, the sub-systems within them, and important features of the specific sites from where samples were collected are discussed under each system. Figure 1 shows the location of sampling

sites at different grazing systems in the three clusters.

Figure 1 Location map of sampling sites at the different grazing systems in the three clusters.

2.2. Sampling Site Selection

Sites for collection of vegetation and soil samples were selected systematically in consultation with None Governmental Organizations (NGOs) operating in each grazing systems. To this end, the study sites in the East cluster were selected together with AVECO and ACPA. In Afar cluster, sites were selected in consultation with CARE Ethiopia. Grazing systems in South cluster were selected jointly with CARE and MERCY CORPS. As there was no information about the size of the grazing systems and sub systems, the sample plots were located randomly taking into account differences in topography and vegetation type within the selected sites in the systems.

Since there were no grazing systems that were put under protection before this study in East and Afar clusters, only three sites from Borena and Guji zones were used for comparison of carbon stock under protected and unprotected grazing lands. One of these (Dida Haya in Sarite from Malbe) was under traditional system of rangeland protection called the Kallo system, while the remaining two (Andereka in Meesa and Haro Areero in Siminto) were under participatory rangeland management scheme for the last 3 to 4 years. Table 1 describes some basic features of the sampling sites within the selected grazing systems.

Table 1. Study sites selected for carbon stock assessment and their basis characteristics

Cluster Grazing system

Sub-system Plot No. Special characteristics

East

Harshin Hussein Samane

1 Heavily degraded grazing land with patches of perennial grasses

2 Heavily degraded rangeland with patches of perennial grass and shrub

3 Forest land with no undergrowth

Daketo

Elbahi 4 Upper part of Daketo valley dominated by cactus and Lanthana camara

Elbahi 5 Lower part of Daketo valley and wetland covered by grass and annual herbaceous plants

Mulu

Jejeba 6 Mixed grazing land with acacia trees, cactus and perennial grasses

Kulmeye 7 Mixed grazing land with acacia trees, cactus, shrubs, and grass

Mencha 8 Mixed grazing land with Acacia and perennial grasses bordering Ethiopian Somali and Oromia regions

Afdem

Siselu 9-11 Open grazing land dominated by perennial grasses and patchy bushes

Dire Ella 12 Stony and heavily degraded with scattered acacia trees

Afar

Mollale Bonketto

Mollale 13 Newly cleared from Prosopis juliflora

Halydege Gonita Birka 14 An open grazing land with encroaching prosopis and perennial grass production potential

Halydege Village

15 Degraded grazing land with patches of perennial grasses and scattered prosopis plants

Cluster Grazing system

Sub-system Plot No. Special characteristics

Andido 16 Vast grazing sub system devoid of vegetation with cracking soil type

Dudub

Motor Sefer 17 Degraded, stony and scattered Acacia trees

Irribeto 18 An area newly cleared from Prosopis and have scattered bushes

Hudud 19 Have sparsely distributed bush

Sout

h

Malbe

Elwaye (Dida Arbela)

18-19 Vast grazing system with perennial and annual grasses and wildlife potential

Elwaye (Dida Haya)

20-21 Protected and unprotected grazing land

Dire

Soda 22 Mixture of grass and woody perennials with wildlife potential

Dida Medhicho 23 Protected area with good regeneration of grass and other vegetation

Dubluk 24 Heavily grazed area with wildlife potential

Siminto Miessa (two plots)

25-27 Rangeland passing through several phases (protection, Damage and again protection)

Siminto (two plots)

28-29 Rangeland composed of both protected and unprotected areas

Golba Genale

Muche 30 Rangeland with dense vegetation

Guduba Bururie

31 Rangeland with vegetation

2.3. Field layout for above ground vegetation sampling

A ‘nested’ sampling approach (Hairiah et al., 2011) was followed, assessing large diameter trees (with a stem diameter above >30 cm) in rectangular plots of 100 m x 20 m, and trees and shrubs with DBH 2.5- 30 cm in subplots of 40 m x 5 m. As there were no big trees with DBH > 30 cm, samples were taken from a rectangular plot of 40 m X 5 m. All trees and shrub with DBH and height of trees greater than 2.5 cm within the 40 m X 5m plot were recorded on pre-prepared registration sheet. A 1m X1m quadrat was laid at the four corners and center of the 40 m X 5 m plot for herbaceous plants, undergrowth vegetation and litter sample collection. All herbaceous plants and woody undergrowth vegetation with DBH < 2.5 cm were cut at the ground level and their fresh weight was measured

together with litter collected from the same plot using weighing balance. A sub-sample of 300 g fresh mass was taken from the composite sample for laboratory analysis. The samples were oven dried at 80 ⁰C for 24 hours until the mass of the sample remained constant. The diameter of trees was measured using caliper, while the height was measured using clinometer.

2.4. Estimation of vegetation carbon stock

The following allometeric equation was used to estimate the aboveground biomass and carbon stock of trees:

[1]

where: ABTB = aboveground tree biomass; D = diameter of tree

Then after, the carbon stock was calculated as:

[2]

Estimation of carbon stock of root biomass

Non-destructive (conservation) method was employed for calculation of carbon stock in the root system. As suggested by Santantonio et al. (1977) and MacDicken (1997), the below ground biomass (root) of a plant is close to 20 percent of the total aboveground biomass. Accordingly, the root biomass of trees was estimated using the following formula:

[3]

where BGB is below ground biomass, AGB is above ground biomass

Total carbon stock = Carbon stock of above ground biomass + Carbon stock of below ground biomass

2.5. Soil Sampling and Preparation for Soil Carbon Stock Assessment

Soil samples were collected from the four corners and center of the 40 m X 5 m plots from 0-10, 10-20, and 20-30 cm depths and mixed thoroughly on an aluminum tray to make one composite sample per depth per plot. Accordingly, three composite samples were collected per plot for laboratory analysis of soil organic carbon. The collected samples were properly labeled and transported to Haramaya University Soil Science laboratory. The samples were then air-dried by spreading them on paper in a ventilated soil sample preparation room. The total mass of the air-dried samples was recorded before crushing the samples to pass them through a 2 mm sieve diameter. Visible coarse fragments, such as gravel, were separated before crushing the samples. Following this, the samples were gently crushed with mortar and sieved. The mass of the coarse fragments that did not pass through the 2 mm sieve and those that were separated before grinding were recorded for each sample. Undisturbed soil samples were also collected from the respective depths using soil cores that were inserted into a metallic cylindrical core that is prepared for this purpose. For all the plots, the undisturbed samples were collected from centers of the plots only.The soil organic carbon content was determined following the Walkley-Black oxidation method (Walkley and Black, 1934). The dry bulk density of the soils was determined using the core method as described in Blake and Hartge (1986) in which case the core samples were dried in an oven set at a temperature of 105 C to a constant weight. The dry bulk density was calculated using the following equation:

[4]

where:MODS = mass of the oven-dry soil (g)Vt = total volume of the soil core calculated from:

r is the internal radius of the cores measured using a caliber (cm), and h is height of the cores measured using a hand tape. After oven drying the core samples, any coarse fragment that did not pass through the 2 mm sieve diameter was separated and the fine earth (< 2 mm) weighed and used as mass of the oven dry soil. is a constant which is equal to 22/7.

2.6. Estimation of Soil Carbon StockThe organic carbon content of soils obtained from laboratory analysis was used to calculate carbon stock per unit area of land. The carbon stock for each layer per hectare was calculated as:

[5]where:BDi = bulk density of the ith layer (i =1-3) (kg/m3)CFi = coarse fragment content of the ith layer (fraction)di = thickness of the ith layer (m)OCi = organic matter content of the ith layer (fraction)10 = conversion factor from kg/ha to ton/ha

The total carbon stock for the 0-30 cm depth was calculated as:

[6]

2.7. Estimation of Terrestrial Carbon Stock and Carbon Dioxide Equivalent

Finally, the terrestrial (total) carbon stock (ton/ha) of a given site was obtained from:

[7]where:

Csoil = soil carbon stock

CAGWV = carbon stock of above-ground woody vegetationCHV = carbon stock of herbaceous vegetationCBGB = carbon stock of below ground biomass

As 1 tone of soil OC = 3.67 (44/12-ratio of molecular weight of CO2 to carbon) tons of CO2 (sequestered or emitted) (Pearson et al., 2007; Craig et al., 2010), the equivalent CO2 sink (tons/ha) in a given site was estimated from:

[8]

3. KEY FINDINGS

The results obtained from field measurement and laboratory analysis are discussed on grazing system basis. Furthermore, comparisons among carbon stock of sub-systems within a grazing system is made. The detailed discussions are presented here under.

3.1. East Cluster

3.1.1. Terrestrial Carbon Stock of Harshin Grazing System

3.1.1.1. Overview of the grazing system

Harshin grazing system is found in Harshin Woreda of the Somali Regional State of Ethiopia. Harshin is bordered on the south by the Degehabur zone, on the west by Kebri Beyah, and on the northeast by Somalia. According to the 2007 census, the total population of the Woreda was 80,244 of which about 49% were pastoralists (CSA, 2007). The Woreda is inhabited by the Arap and Habar Awal subclans of the Somali Isaac clan.

The Hussein Semane sub-system was selected as it was believed to be representative of the whole grazing system and has high potential for rehabilitation and/or change. The sub-grazing system comprises of grassland, grass land mixed with patches of herbaceous shrub locally called Gahadi, and woody vegetation dominated by acacia species of different types. The dominant livestock in the area are sheep, goats, and camel. The grassland is highly degraded due to overgrazing. As a result, there are places with only bare soil. The woody vegetation is also devoid of any undergrowth. The understory is completely bare soil with no other vegetation type of any sort. Plate 1 indicates the partial view of the three sampling sites, the nature of their vegetation cover, and the intensity of grazing.

Plate 1. Partial view of the Hussein Semane sub-grazing system sampling sites, nature of vegetation cover, and stocking density in Harshin grazing system.

The soils are mainly sandy loam to sandy clay loam in texture with relatively high surface bulk density (1.85-1.90 g cm-3) that shows the existence of compaction. This compaction is the result of repeated animal trampling. The disadvantage of this high bulk density is its effect on infiltration of rain water into the soil system. It results in low infiltration rate and high runoff generation from a given rainfall event. This, in turn, results in low water storage in the soil system for plants. Furthermore, the soils are strongly alkaline (Tekalign, 1991) in reaction with pH that ranged from 8.75 to 8.92. Soils with such a high pH are likely to contain excess amount of sodium on the exchange complex. This cation has unfavorable effect on soil structure resulting in dispersion of soil aggregates. The high bulk density could be related to this dispersion in addition to the effect of repeated animal trampling.

Three sample plots were laid in the sub-grazing system based on differences in vegetation and topography. The first plot was laid on a heavily degraded grazing land with patches of perennial grasses. The

second plot was on a heavily grazed but with patches of perennial grasses and a shrub locally called Gahadi, which is browsed mostly by camel. The third plot was laid within the woody forest of the sub-grazing system. Unlike most woody forest based grazing systems, the Hussein Semane sub-grazing system is devoid of undergrowth vegetation and grasses.

The sample collection was done during April, 2014, which was a rainy season for almost large part of the Somali region.

3.1.1.2. Results and discussion

The terrestrial carbon stock of the Hussein Semane sub-system is indicated in Table 2. In the first two sites with mainly degraded grassland, significant proportion of the carbon stock (99.99%) was contributed by the soil. On the other hand, at the site with woody forest, the vegetation contributed for 44.15% (46.08 t ha-1) of the terrestrial carbon stock, while the soil carbon stock accounted for 55.85% (58.29 t ha-1) of the total carbon stock for the sub-system. The carbon dioxide equivalent (CO2e), which indicates the carbon dioxide emitted or sequestered, ranged from 208.951 at the second site with degraded grass and patches of herbaceous bush to 383.038 t ha-1 at the woody forest site.

Since it was not possible to find the total area of the Harshin grazing system, it was not possible to estimate the total terrestrial carbon stock and its CO2e for the whole system. However, it is possible to put an average value for the whole system based on the results obtained from this baseline assessment. Accordingly, the baseline mean terrestrial carbon stock of the Harshin grazing system can be taken as 73.924±26.426 t ha-1 with coefficient of variation of 35.75%, which actually indicates the existence of high variability within the system. Similarly, the corresponding mean CO2e of the system can be taken as 271.301±96.984 t ha-1.

The results obtained clearly indicate the contribution of the soil and vegetation sinks and their relative importance. As it has always been true,

combined management of both soil and vegetation would contribute for better carbon sequestration and, thus, climate change mitigation.

Table 2. Terrestrial carbon stock and its carbon dioxide equivalent (t ha-1) at the Hussein Semane sub-grazing system in Harshin, Somali region

Plot Carbon stock (t ha-1) inCO2e (t ha-1)AGW

VHV BGB Soil Total

1 - 0.004 0.003 60.46 60.467 221.9142 - 0.003 0.002 56.93 56.935 208.9513 38.4 - 7.68 58.29 104.37 383.038Mean ±StD 58.56±1.78 73.924±26.426 271.301±96.984

AGWV = above-ground woody vegetation; HV = herbaceous vegetation; BGB = below-ground biomass; StD = standard deviation

The contribution of the soil varied with soil depth (Figure 2). At all the three sites, the carbon stock consistently decreased with soil depth. Nevertheless, the difference was the highest at site 1 compared with the other two. This could be attributed to the fact that, in grasslands, most of the contribution is limited to the upper few centimeters of the soil. The CO2e also varied in accordance with the variation in soil organic carbon stock. Nevertheless, the variability in soil carbon stock among the three sites was relatively low with a coefficient of variation of 3.04%.

The results indicate that management of grazing systems in pastoral areas could enhance the carbon sequestration potential of both soil and vegetation. The improvement will help in mitigating climate change impacts through directly reducing the amount of CO2 emitted from these systems

and indirectly improving the productivity of both vegetation and soil.

Figure 2. Carbon stock and CO2e (t ha-1) variation with soil depth at the Hussein Semane grazing sites in Harshin grazing system, Somali region (HS = Hussein Semane).

3.1.2. Terrestrial Carbon Stock at Daketo Grazing System


The Daketo grazing system is located within Babile woreda of Ethiopian Somali Region and Babile woreda of Oromiya region, thus connecting two regional states. Babile woreda, which is part of the Jijiga zone, is bordered on the west by the Oromia region, on the north by Gursum, and on the east and south by Fiq zone. Census conducted in 2007 indicates that the Woreda has a total population of 77,317, of 22.68% are pastoralists. The Woreda is inhabited by the Karanle Hawiye clan of the Somali people, as well as the Babille Oromo.

However, this study was conducted in Babile woreda of Ethiopian Somali region in the Daketo valley and its surrounding called Elbahey. The upper part of the valley is covered with cactus and Lanthana camara vegetation with poorly growing annual grass. The valley bottom, on the other hand, is a marshy area covered with perennial grasses and herbaceous vegetation of different types. Samples were collected from two separate plots one each at the upper and

lower (valley) parts of the Elbahey sub-system. Plate 2 shows the nature of vegetation at the two

sampling sites.

Plate 2. Partial view of the Elbahey sub-grazing system in Daketo; A and B show the upper smapling plot dominantly occupied by cactus and Lanthana camara, and B and C show the second sampling site in Daketo valley with annual herbaceous vegetation.

The soils of the area had high bulk density values, which ranged from 1.90-1.93 g cm-3 at the surface 0-10 cm soil depth to 1.95-2.01 g cm-3 in the subsurface layers, which indicate the presence of high compaction. As already stated, this high compaction, caused presumably by repeated animal trampling, is likely to affect the water economy of the root zone by increasing runoff and reducing infiltration into the soil system. This is a disadvantage in pastoral areas where rainfall is most of the time torrential and erratic in its distribution. The textural class of the soils ranges between loamy fine sand and sandy clay, which also indicates the inherently low water holding capacity of the soils. On the other hand, the pH of the soils (8.23-8.35) indicates the strongly alkaline nature of the soils (Tekalign, 1991).

The main livestock kept are a mixture of camel, goats, sheep, and cattle. Furthermore, significant area of this system is under crop production. In this system, therefore, both pastoralism and agro-pastoralism are being practiced.


A

C D

B

At both sites, there were no woody vegetation to be sampled. The results indicate that the contribution of the herbaceous vegetation, as compared to that of the soil, was almost insignificant. Accordingly, at the upper part where cactus and Lanthana camara are the dominant vegetation cover, 99.998% (120.49 t ha-1) of the carbon stock was from the soil sink. This clearly indicates the importance of the soil as a carbon sink in this degraded grazing system. At the valley where the second site is, the trend is almost the same in that 99.997% (59.91 t ha-1) of the organic carbon is stored in the soil (Table 3). Comparing the two sites, the site dominantly covered by cactus and Lanthana camara had by far the largest carbon stock than that covered by herbaceous vegetation and grass. This might be attributed to the intensive grazing, particularly by cattle, of the herbaceous vegetation and grass, which leaves very little organic input into the soil system. Furthermore, the Daketo valley is a grazing system that most pastoralists in the area use during the dry season.

The corresponding CO2e ranged from 219.881 t ha-1 in the valley to 442.209 t ha-1 in the upper part of the sub-grazing system. The Daketo grazing system is a very extensive system dominated mainly by sparsely populated trees of acacia species, cactus and Lanthan camara. The topography of the system is also characterized by hills and valleys with extensive rock outcrops covering the hills. The two plots are assumed to represent majority of the grazing system, though.

The variation of the carbon stock followed almost consistent trend with soil depth at the upper part of the grazing system, while it remained equal in all the depths in case of the grazing system in the valley (Figure 3). The top 10 cm of the soil layer seems to store most of the organic carbon stock. This might be attributed to the distribution of organic matter sources in the soil system. Furthermore, there was high variability in organic carbon stock between the two soils with a coefficient of variation of 47.49%. This indicates that the relatively high terrestrial carbon stock variability within the Daketo system is mainly due to differences in soil carbon stock.

On the basis of this assumption, therefore, the baseline carbon stock of the system was taken as 90.203±42.837 t ha-1 with coefficient of variation of 47.49%, which also shows the high variability within the system. The corresponding baseline mean CO2e of the system was 331.045±157.210 t ha-1.

Table 3. Terrestrial carbon stock of the Elbahey grazing sub-system in Daketo grazing system of Somali region

Plot Carbon stock (t ha-1) inCO2e (t ha-1)AGWV HV BGB Soil Total

1 - 0.002 0.001 120.49 120.493 442.2092 - 0.002 0.001 59.91 59.913 219.881Mean±StD 90.20±42.837 90.203±42.837 331.045±157.210


The results indicate that even the highly degraded grazing lands in pastoral areas have significant

carbon stock in them. Rehabilitation of such grazing systems through, for instance, participatory

rangeland management approach could enhance their carbon sequestration potential further. This

will help create climate change resilient ecosystems that support the livestock better and improve

the livelihood of the pastoral and agro-pastoral community in the area.

Figure 3. Carbon stock and CO2e (t ha-1) variation with soil depth for selected grazing sites in Dakato grazing system (EBL = Elbahey bush land; EGL = Elbahey graa land).

3.1.3. Terrestrial carbon stock of the Mulu grazing system


The Mulu grazing system is located in Meiso Woreda, which is located at the westernmost point of the former Shinile zone, now Ayisha zone. The Woreda shares boundaries with Oromia region on the south, Afar region on the northwest, and Afdem woreda on the east. Based on figures published by the CSA in 2005, this woreda has an estimated total population of 53,665. This Woreda is primarily inhabited by the Issa clans

of the Somali people. Although the exact figure is not known, both pastoralism and agro-pastoralism are being practiced in the Woreda.

The Mulu grazing system comprises of Jejeba, Kulmeye and Mencha sub-grazing systems. All the sub-systems are characterized by the presence of a mixture of trees dominantly of acacia, shrubs, cactus, grasses and other herbaceous vegetation. The system supports cattle, shoats and camel. Limited large-scale crop production is also being practiced. However, in terms of vegetation cover, it

is in a better condition with relatively well protected vegetation cover. Plate 3 shows nature of the

vegetation cover, data and sample collection activities at the three sub-grazing systems in Mulu

grazing system.

Plate 3. Nature of vegetation, vegetation data (measuring tree diameter and weighing fresh biomass of herbaceous vegetation), vegetation and soil sample collection activities at the three grazing sub-systems in Mulu grazing system.

The textural classes of the soils within the system are between sandy clay loam and clay loam with relatively better clay content. The bulk density values in the grazing system ranged from 1.86-1.88 g cm-3 at the top 10 cm layers to 1.86-1.98 g cm-3 at the subsurface layers. Similar to the bulk density values discussed above, these bulk density values are also in the

range that shows the existence of soil compaction in these grazing systems. The pH values (8.42-8.62) indicate the saline nature of the soils in all the three grazing sub-systems. Only plants that are tolerant to such extremes can thrive better. Salinity management seems relevant for adapting wide range of grass species in those grazing systems if artificial seeding is envisaged.

3.1.3.2. Results and discussionAt Mulu grazing system, both vegetation and soil contributed to the terrestrial carbon stock of the system. On the basis of this, 18.875, 20.895, and 23.605% of the terrestrial carbon stock at Jejeba, Mencha, and Kulmeye, respectively, is stored in the vegetation cover, while the corresponding carbon stock in the soil was 81.125, 79.105, and 76.395%. Because of the significant contribution from the vegetation cover, the terrestrial carbon stock was relatively high. The corresponding CO2e ranged from 455.898 t ha-1 at Kulmeye to 660.791 t ha-1 at Mencha.

Table 4. Terrestrial carbon stock at three grazing sub-systems in Mulu grazing system, Somali region

Site Carbon stock (t ha-1) inCO2e (t ha-1)AGWV HV BGB Soil Total

Jejeba 27.89 0.002 5.58 143.86 177.332 650.808Mencha 31.35 0.002 6.27 142.43 180.052 660.791Kulmeye 24.43 0.003 4.89 94.90 124.223 455.898Mean±StD

127.063±27.863 160.536±31.477 589.166±115.521


The results obtained here also indicate the existence of high potential for carbon sequestration in pastoral areas if proper management scenario is put in place.

Depth-wise distribution of the soil carbon stock indicates that, at all the three sub-systems, the

organic carbon stock of the soils decreased consistently with soil depth (Figure 4). At system level,

the mean soil carbon stock was 127.063±27.863 with a coefficient of variation of 21.93% which

indicates the presence of moderate variability among soils within the grazing system.

Figure 4. Carbon stock and CO2e (t ha-1) variation with soil depth at selected grazing sites in Mulu grazing system (ME = Mecha; KL = Kulmeye; JJ = Jejeba).

Similar to the other grazing systems in the East cluster, it was not possible to get the total area covered by the Mulu grazing system. As a result, it was not possible to estimate the baseline carbon stock of the system. However, it is possible to derive a mean value for the system based on measurements made in these three representative sub-grazing systems. Accordingly, the mean baseline terrestrial carbon stock of the system can be taken as 160.536±31.477 t ha-1 with coefficient of variation of 19.61%, which indicates the existence of relatively low variability in the system. Similarly, the corresponding baseline mean CO2e of the system can be taken as 589.166±115.521 t ha-1.

3.1.4. Terrestrial Carbon Stock of the Afdem Grazing System

3.1.4.1. Overview of the system

Afdem is located in the former Shinile Zone, now Ayisha Zone, of Somali region of Ethiopia. It is bordered by Mieso on the southwest, Afar region on the north, Erer on the east, and Oromia region on the south. There are some high peaks (e.g. Mount Afdem about 2000 meters above sea level) in the Woreda. According the results of the 2007 Census, the total population of the Woreda is around 65,031. Out of this total population, 76.54% are pastoralists. The Woreda is inhabited by the Issa clan of the Somali people.

The Afdem grazing system, particularly the Dire Ella around the Afdem town, is more degraded compared to the adjacent Mulu grazing system in terms of its woody perennial composition. Dire Ella sub-systems is highly degraded with sparsely distributed Acacia bush and open grassland. The

understory is highly degraded with almost no vegetation cover. On the other hand, the Siselu sub-

system is a very extensive grass land with sparsely distributed herbaceous bushes and woody

vegetations of different species. The common livestock in the system are shoats, camel, and cattle.

Plate 4 below shows the degraded nature of both vegetation and soil at Dire Ella (upper) and,

degraded grass land and the heavy overgrazing at Siselu (bottom) in Afdem grazing system.

Plate 4. Partial view of the highly degraded vegetation and soil in Afdem grazing system at Dire Ella and Siselu, and the livestock that are desperate to get some feed from these highly degraded grazing lands.

The textural class at Dire Ella is loamy fine sand with high proportion of sand. This high proportion of sand indicates the likely poor water holding capacity of the soils, and, thus, more vulnerability to moisture deficit stress. Nevertheless, the textural class at the Siselu site is sandy loam at all the three sites and depths, indicating the uniformity of the soil in the sub-system. The bulk density values, unlike those recorded in the other grazing systems, ranged from 1.30 g cm-3 at Siselu to 1.78 g cm-3 at the surface layers, and 1.29 g cm-3 at Siselu to 1.97 g cm-3 at Dire Ella in the subsurface layers. The bulk density values at Siselu are within acceptable bulk density ranges for mineral soils, while those at Dire Ella, particularly those in the subsurface layers, indicate the existence of some degree of

compaction. The pH of the soils at Dire Ella, like the other systems, was high (> 8.5), which indicates the strongly alkaline nature of the soils. The pH ranges indicate the possible dominance of exchangeable sodium on the exchange complex of soils in Dire Ella sub-system. On the other hand, the pH values at Siselu ranged from 7.2-7.9 at the surface layers, and 7.4 to 7.8 in the subsurface layers, which fall in the range of neutral to moderately alkaline (Tekalign, 1991).


The terrestrial carbon stock in the Afdem grazing system varied from 50.210 t ha-1 at grass dominated Siselu 1 sub-system to 67.855 t ha-1 at Dire Ella (Table 5). Similar to the trends observed in the other grazing systems, the proportion of the total carbon stock stored in the soils was generally higher than that in the vegetation. The equivalent carbon dioxide sequestered ranged from 184.271 t ha-1 at Siselu 1 to 249.028 t ha-1 at Dire Ella.

Table 5. The terrestrial carbon stock and its carbon dioxide equivalent at two grazing sub-systems in Afdem grazing system, Somali region

SiteCarbon stock (t ha-1) in

CO2e (t ha-1)AGWV HV BGB Soil TotalDire Ella 15.46 0.005 3.09 49.30 67.855 249.028Siselu 1 - - - 50.21 50.210 184.271Siselu 2 - 0.003 0.002 65.38 65.385 239.963Siselu 3 - 0.005 0.003 51.03 51.038 187.309Mean±StD 53.98±7.633 58.622±9.296 215.143±34.118

AGWV = above-ground woody vegetation; HV = herbaceous vegetation; BGB = below-ground biomass

The carbon stock increased with soil depth consistently at both the grazing sub-systems (Figure 5). The results obtained so far indicate the relative importance of the upper 10 cm of the soil layer as carbon sink. At system level, the mean soil carbon stock was 53.980±7.633 which shows relatively narrow variation as was also indicated by the low coefficient of variation (14.14%).

The results obtained in this system also clearly revealed the carbon sequestration potential of even the relatively degraded grazing systems such as the Afdem system. The mean carbon stock for this system can be taken as 58.622±9.296 with relatively low variability as indicated by the coefficient of variation (15.86%). The corresponding baseline mean carbon dioxide equivalent is 215.143±34.118 t ha-1.

Figure 5. Variation of soil carbon stock and the corresponding CO2e with soil depth at selected grazing sub-systems in Afdem, Somali region (DE = Dire Ella; SS = Siselu).

Comparison of the four grazing systems selected in the East cluster indicates that the status of terrestrial carbon stock and the corresponding CO2e was relatively high at Mulu grazing system followed by Daketo and Harshin systems (Figure 6). The Afdem system, being relatively the drier system, was found to be low in its terrestrial carbon stock and the corresponding carbon dioxide equivalent. Nevertheless, the variability of the terrestrial carbon stock was the highest in the Daketo grazing system followed by the Harshin grazing system. This may imply that the number of sampling sites need to be increased in order to get representative value of carbon stock. On the other hand, the variability of the terrestrial carbon stock was relatively low at Mulu and Afdem grazing systems.

Figure 6. Mean terrestrial carbon stock and its carbon dioxide equivalent (t ha-1) at four pastoral area grazing systems in Somali region.

In addition to helping in mitigating climate change effects through carbon sequestration, the pastoral areas can also be sources of income from the carbon finance. Using the rate used by Ethiopian Wildlife Authority (Daan et al., 2012), which suggests a currency value of $4/tCO2e, the monetary value of the mean carbon dioxide sequestered in each of the grazing systems will be 1085.18, 1324.16, 2356.67, and 905.88 US$ ha -1 for Harshin, Daketo, Mulu, and Afdem grazing systems, respectively. This is a huge amount of money which can be used for infrastructure and other livelihood improvement interventions in those pastoral areas. The management of these grazing systems, following participatory approach, will undoubtedly improve the carbon sequestration, productivity of the grazing systems and livestock, and eventually increase the resilience of the pastoral community to climate change and variability impacts.

3.2. The Afar Cluster

The pastoralist community in Afar region makes up about 90% of the total population with remaining 10% being agro-pastoralists. This clearly indicates the importance of pastoralism in the region. In the Afar cluster, three grazing systems were selected based on discussion held with the local partners and government offices. These systems were Gewane, Halydege, and Dubdub grazing systems. Brief background of each of these systems is presented below together with the results.

3.2.1. Terrestrial carbon stock of Gewane Grazing System


Gewane is among the woredas in Afar region and forms part of the Zone 3. It shares boundaries with Amibara in the south, Bure Mudaytu and Zone 5 in the west, and Somali region in the east. This Woreda is where Mount Ayalu (2145 meters above sea level) and Mount Yangudi are found. It also includes water bodies such as Lake Kadabassa which lies in the swampy lowlands that stretch alongside the Awash River and serve as an important pasture for pastoralists. The Yangudi Rassa National Park is also found in the northeastern part of the Woreda. The Woreda has a total population of 31,318 (CSA, 2007) with no reliable estimate of the pastoralist community.

The Mollale sub-system was selected from the Mollale Erribeto garzing system in this Woreda. At the time of sampling, the area was recently cleared from Prosopis juliflora, the major vegetation cover in the area, hence there was no undergrowth vegetation and trees to be measured. The surface was covered by a bare soil that contains no remains of herbaceous vegetation cover. The measured carbon stock was, therefore, only that present in the soil. There were extensive wide and deep cracks that are closely spaced. Plate 5 clearly shows these features.

Plate 5. The partial view of the Mollale sub-grazing system in Gewane. Prosopis juliflora is being cleared from this field (bottom) and the soil was devoid of any other vegetation.

The textural class of the soil ranges from clay loam to clay. This fine textured nature of the soil could be good quality since it results in high water retention. The bulk density of the soil ranged from 1.14 g cm-3 at the surface layer to 1.36 g cm-3 at the subsurface layers. These bulk density values are below critical values of bulk density for plant growth at which root penetration is likely to be severely restricted (Jones, 1983). This might be attributed to shrinking and swelling nature of the soil, which results in healing the compaction naturally. The major problem of the soil, however, is the extremely high pH (8.83-9.79) which may limit the number of adaptable species. Only those species that have the natural ability to overcome this high pH can survive in this environment. If artificial seeding is planned, consideration of this problem is important in adaptable species selection.

3.2.1.2. Results and discussionAs described above, there was no vegetation sample of any kind collected due to complete coverage by Prosopis juliflora, which was being cleared. There was also no other herbaceous vegetation due to overgrazing and dry season of the time. As indicated in Table 6, the carbon stock of the sub-system was relatively low due to its degraded nature and absence of vegetation cover. However, the area has an immense potential for rehabilitation if proper management practices can be put in place. The issue related to Prosopis juliflora, however, should receive a more serious attention than ever, for it has completely replaced the native vegetation cover.

Table 6. Soil carbon stock and its carbon dioxide equivalent at Mollale grazing sub-system Gewane, Afar region

Site Carbon stock (t ha-1) inCO2e (t ha-1)AGWV HV BGB Soil Total

Molale - - - 33.43 33.43 122.688

The depth-wise distribution of the organic carbon stock followed a consistent trend with soil depth

(Figure 7). This indicates the relative importance of the top 10 cm of soil in carbon stock

management.

Figure 7. Soil carbon stock and its carbon dioxide equivalent distribution with soil depth at Mollale sub-grazing systems in Gewane, Afar region.

3.2.2. Terrestrial carbon stock of Halaydege grazing system


The Halydege Grazing System is found in Amibara woreda to the eastern side of the main road to Djibouti and stretches to mount Assebot. Amibara is bordered by Awash Fentale Woreda on the south, the Awash River on the west, Zone 5 on northeast, Gewane woreda in the north, Somali region on the east, and by Oromia region on the southeast.

Based on the 2007 Census conducted by the Central Statistical Agency of Ethiopia (CSA), this woreda has a total population of 63,378, of which 10.34% are pastoralists.

Three sub-grazing systems were considered from the Halydege grazing system namely Gonita Birka, Andido and Halydege near the village. The Andido sub-system is characterized by extensive area of grazing land that did not contain any vegetation cover at the time of sampling (dry season). It looks like a ploughed land. Gointa Birka and Halydege sub-systems, on the other hand, are covered by mixed grass, herbaceous vegetation and non-woody bushes. In these systems also, the area covered by Prosopis juliflora is quite significant. The dominant native woody vegetation is mainly acacia of different

species. Plate 6 shows some of the features of the grazing system.

Plate 6. The extensive grazing lands located at the low lying areas in Halydege were devoid of grass vegetation at the time of sampling. However, Prosopis juliflora is still proliferating at some of the sites.

The bulk density values recorded indicate that the soils are not affected by compaction. The values ranged from 1.28 to 1.40 gcm-3 at Andido, 1.14 to 1.25 gcm-3 at Halydege village, and 1.14 to 1.35 gcm-3 at Gointa Birka. The textural class, on the other hand, varies between loam, sandy clay loam, and sandy clay, which indicate the presence of appreciable clay content. This can be taken as a good quality for quick rehabilitation of the degraded vegetation, for it results in good water holding capacity. However, the major limitation to these soils is the strongly alkaline nature of the soil reaction with pH that ranged between 8.71 and 9.51. This limits the number of adaptable species in those systems, particularly if artificial seeding is to be considered.


As described above, the woody vegetation was scant in the system. As a result most of the carbon stock (99.99% at Halydege village and Gointa Birka, and 100% at Andido) was stored in the upper 0-30 cm depth of the

soils. Owing to the poor vegetation cover, the carbon stock was relatively low and ranged from 42.160 t ha-1 at Halydege village to 49.095 t ha-1 at Gointa Birka. The corresponding carbon dioxide equivalent varied from 154.764 t ha-1 at Halydege to 180.179 t ha-1 at Gointa Birka (Table 7).

Table 7. Terrestrial carbon stock and its carbon dioxide equivalent at the Halydege grazing system in Afar region


CO2e (t ha-1)AGWV HV BGB Soil TotalHalydege village

- 0.006 0.004 42.16 42.170 154.764

Gointa Birka - 0.003 0.002 49.09 49.095 180.179Andido - - - 45.62 45.62 167.425Mean±StD 45.623±3.465 45.628±3.463 167.456±12.708


The distribution of the carbon stock with soil depth indicates that, at all the sites, the relatively

better contribution was from 10-20 cm depth of the soils (Figure 8). Except at Andido, the high

carbon stock in this layer was due to the high bulk density value rather than high organic carbon

content. Furthermore, the variability of the soil carbon stock at system level was relatively low as

indicated by the coefficient of variability (7.59%). The mean value obtained from the three sites can,

therefore, represent the soil carbon stock of the entire system reasonably well.

Figure 8. Soil carbon stock and its carbon dioxide equivalent variation with soil depth at selected sites in Halydege grazing system, Afar region (AD = Andido; HG = Halydege; GB = Gointa Birka).

The baseline mean value of the carbon stock and its carbon dioxide equivalent for the Halydege grazing system can be taken as 45.628±3.463 and 167.456±12.708 t ha-1, respectively, with coefficient of variation of 7.59%. This low coefficient of variation indicates that the variability in carbon stock within the system is relatively low and can be represented by the mean value reasonably well.

3.2.3. Terrestrial carbon stock of the Dudub grazing system


The Dudub grazing system is located in Awash Fentale woreda. This Woreda is part of Administrative Zone 3 in Afar region. It shares boundaries with Oromia region in the south, Amhara region in the west, Dulecha in the north, and by Amibara in the eastern direction. The Awash River and its tributary Germama cross this Woreda, which indicate the potential for practicing irrigation. Nevertheless, significant area of this Woreda is occupied by the Awash National Park.

According to the 2007 Census, the total population of the Woreda was 29,780 of which only 5.69% were pastoralists (CSA, 2007). More than 55%, according to this Census, were urban inhabitants. In addition to pastoralism, agriculture is also being practiced in the Woreda.

The carbon stock assessment was conducted in three sub systems namely Motor Sefer, Irribeto and Hudud. The three sub systems do not have woody trees. As a result, measurements were made for grass, non-woody undergrowth vegetation, and soil. Plate 7 shows the nature of vegetation cover in this

grazing system.

Plate 7. Some features of the grazing lands in Dudub grazing system. The soil is bare except the scattered bushy vegetation cover and is highly prone to wind erosion.

The bulk density values of the soils were below the critical bulk density values that are quoted as causing root penetration problems due to excessive compaction (Jones, 1983) and ranged between 1.25 to 1.33 g cm-3 at the surface layers and 1.39 to 1.51 g cm-3 at the subsurface layers. Nonetheless, the soils are dominated by the sand fraction in which the textural class varied from loamy sand to sandy clay. Such soils are highly prone to drought due to their poor water holding capacity and high permeability. The pH of the soils ranged from 8.02 to 8.99, which falls in the range of strongly alkaline (Tekalign, 1991).


Similar to the previous grazing systems, about 99.99% of the terrestrial carbon stock was in the soil system at all the three systems. The herbaceous vegetation was highly degraded and over grazed at the time of sampling, which was during the dry season. That is why the contribution from the vegetation was extremely small. Except at the Motor Sefer sub-system, the carbon stock was very low as compared to what is recorded in the other systems. The values varied between 16.884 t ha -1 at Irrebeto to 49.836 t ha-1 at Motor Sefer (Table 8). The corresponding carbon dioxide ranged from 61.942 to 182.898 t ha-1. As compared to the Gewane and Halydege systems, this is more degraded rangeland.

Table 8. Terrestrial carbon stock and its carbon dioxide equivalent at the Dudub grazing system in Afar region


CO2e (t ha-1)AGWV HV BGB Soil TotalMotor Sefer

- 0.006 0.004 49.83 49.840 182.913

Irrebeto - 0.004 0.003 16.88 16.887 61.976Hudud - 0.006 0.004 21.82 21.830 80.116Mean±StD 29.51±17.77 29.519±17.771 108.335±65.220


The soil carbon stock did not follow any consistent trend with soil depth at the Motor Sefer site (Figure 9). At Irrebeto, soil sample collection was limited to the upper 10 cm depth only due to shallow depth of the soil. At the Dudub grazing system, there was high variability of the soil carbon stock as revealed by the high coefficient of variation (60.22%). This implies, for future studies, the number of sampling sites/grazing sub-systems has to be increased in order get a mean value for the system

Figure 9. Soil carbon stock variation with soil depth at selected sites in Dudub grazing system in Afar region (IR = Irrebeto; HD = Hudud; MS = Motor Sefer).

The baseline mean terrestrial carbon stock and its carbon dioxide equivalent for this system can be taken as 29.519±17.771 t ha-1 with equivalent carbon dioxide of 108.335±65.220 t ha-1 and coefficient of variation of 60.20%.

Comparison at system level indicates that the baseline mean terrestrial carbon stock was better at Halydege followed by Gewane grazing system, while it was the lowest at Dudub grazing system (Figure 10). In terms of management, therefore, the Dudub grazing system requires more attention in order to rehabilitate the severely degraded grazing system. The variability of the terrestrial carbon stock was the highest at the Dudub grazing system as compared to the Halydege system.

Figure 10. Mean terrestrial carbon stock and its CO2e (t ha-1) at selected grazing systems in Afar region.

If the carbon dioxide sequestered is changed into monetary value using the Ethiopian Wildlife Authority rate of US $4/t CO2e, the amount of money that can be generated from the carbon finance scheme will be 490.75, 669.79, and 433.28 USD per ha of grazing land for Gewane, Halydege, and Dudub grazing systems, respectively. If the carbon sequestration capacity of these grazing systems is improved through management, the amount of money generated from the carbon finance will obviously increase by many folds. This will help in improving the livelihood of the pastoral community in many ways.

3.3. South Cluster

The South Cluster is one of the clusters under PRIME project which is operating in Borona and Guji Zones of Oromiya Regional government. From this cluster, a total of four grazing systems were considered for this study. The systems were Malbe and Dire from Borena zone, and Dida Dheda and Golba Genale from Guji zone. Brief description of the Woredas in which the grazing systems are found is presented under discussions of each grazing system.

3.3.1. Terrestrial carbon stock of Malbe Grazing System


The Malbe grazing system is found in Teltele woreda. It is characterized by hilly and gently sloping topography, and extensive plains. The vegetation in the system varies depending on the topographic position. In general, the plain land is mainly dominated by grasses with some brushes and shrubs, the hills by woody vegetation composed of different species including Juniperous procera, while the gentle slopes are composed mainly of acacia of different species. The major grazing areas are the plains that are dominantly covered by grass. Due to this, the sampling sites were chosen to be on these plain lands.

Teltele is located in the southwest corner of the Borena zone. It shares borders with Kenya in the southwest, Sagan River in the west and north, Yabelo in the northeast, and Dire in the southeast. As stated above, the altitude of the Woreda ranges from 710 to 1460 meters above sea level; the landscape consists mainly of lowlands and isolated hills. About 45% of the land in the Woreda is pastureland, while some 25% is arable. As a result both pastoralism and crop production are practiced in the Woreda. The total population of this Woreda, as per the 2007 Census, was 70,501 and the dominant ethnic gropus in the Woreda are the Borena Oromos. Other ethnic groups residing in the Woreda include the Konso, Arbore, and Hamer.

From the Malbe grazing system, the Elwaye sub-system was selected in consultation with local partners and its great potential for rehabilitation. Samples were collected from Arbala Dida, and Dida Haya in Sarite. Both sites are grasslands. At Dida Haya, samples were collected from traditionally protected grassland called Kalo and the adjacent unprotected land,

whereas at Arbala Dida samples were collected from two sites representing the entire extensive

grassland. Vegetation samples collected were grasses at both the sites. The major livestock in the

area are cattle, shoats and camel. Plate 8 illustrates the status of the grazing sites and some

sampling activities.

Plate 8. The nature of the extensive plain grass land at Arbala Dida (upper), soil and vegetation sampling activities (bottom left), and protected and adjacent unprotected grazing land (bottom last two) at Dida Haya at Elwaye sub-grazing system in Malbe. Note that the Arbala Dida grazing land is also home to some wild animals such as ostrich.

The textural classes of the soils range from sandy loam to sandy clay loam. The bulk density values measured were 1.15-1.20 gcm-3 at the surface layers, and 1.22-1.37 g cm-3 at the subsurface layers of the Arbala Dida site. The values recorded indicate that the soils of the grazing land are not yet affected by compaction or have the ability to heal themselves from compaction naturally. The soils, as observed during sample collection, are characterized by shrinking (wide and deep cracks) when dry and swelling when wet. At the Dida Haya site, the values ranged from 1.32 to 1.42 g cm-3 at the surface layers, and 1.12-1.40 g cm-3 at the subsurface layers. The higher bulk density values were recorded on the unprotected land. The soils generally have high pH values. Accordingly, the pH values at the surface layer varied from 8.65 to 9.88. The subsurface layers also had very high pH (8.14-9.96) across the grazing system. In general, the pH of the soils within the Malbe grazing system falls within the range of strongly alkaline pH (Tekalign, 1991). These high pH values could be detrimental to sensitive plants and limit the number of adaptable species in the grazing system.


Similar to most other systems discussed so far, the major sink of carbon in this sub-system (Elwaye) was the soil (Table 9). About 99.99% of the carbon stock at all the sites was stored in the soil. Moreover, spatial difference in carbon stock was also observed at the Arbala Dida grazing site. On the other hand, there was very little difference in carbon stock of protected and unprotected grass land at Dida Haya. In general, the terrestrial carbon stock at the Elwaye subsystem, representing the Malbe grazing system, ranged from 43.564 to 72.446 t ha-1 with a corresponding carbon dioxide equivalent of 159.880 and 265.877 t ha-1, respectively.

Table 9. Terrestrial carbon stock and its equivalent carbon dioxide at Malbe grazing system, Borena zone of Oromia region


CO2e (t ha-1)AGWV HV BGB Soil TotalArbala Dida 1

- 0.004 0.0002 43.56 43.564 159.880

Arbala Dida 2

- 0.006 0.0001 55.39 55.396 203.303

Dida Haya P*

- 0.006 0.0025 72.44 72.446 265.877

Dida Haya Up

- - 0.0001 72.44 72.44 265.855

Mean±StD

60.958±14.111 60.962±14.110 223.729±51.785

AGWV = above-ground woody vegetation; HV = herbaceous vegetation; BGB = below-ground biomass; StD = standard deviation; P = protected; Up = unprotected.

The depth-wise variation of the soil carbon stock indicated that its variation was not consistent with soil depth (Figure 11). This indicates the importance of all the three layers in storing carbon in the soil system. Furthermore, there was considerable variability in soil carbon stock within the system with a coefficient of variation of 23.15%. This variability was almost the major source of the terrestrial carbon stock within the system as well.

Figure 11. Soil carbon stock and equivalent carbon dioxide variation with soil depth at the Malbe grazing system in Borena zone of Oromia region (AD = Arbala Dida; DH = Dida Haya; P = protected; up = unprotected).

As can be observed from the values in Table 9, there exists a huge difference in carbon stock between the two different sites within the Malbe grazing system. However, as baseline information the mean terrestrial carbon stock and the corresponding carbon dioxide equivalent for the Malbe system can be taken as 60.962±14.110 and 223.729±51.785 t ha-1, respectively, with coefficient of variation of 23.15%.

Both the sites from where samples were collected have very good potential for fast improvement. Particularly the extensive grazing land at Dida Haya, can support large number of livestock for long period if allowed to fully attain its potential through participatory management. The huge difference in grass cover between the enclosed and intensively grazed adjacent land at Sarite is a clear indication of the potential the grazing land has for fast rehabilitation. Nevertheless, grazing of the protected land should also be taken with caution if some organic carbon has to be returned to the soil system. If intensive and uncontrolled grazing is allowed, nothing may return to the soil, thus playing no role in improving the carbon stock of the soil. Therefore, controlled grazing has to be practiced. Identical values of soil carbon stock recorded in both protected and unprotected lands at Sarite are typical evidences of the effects of intensive and uncontrolled grazing on protected lands.

3.3.2. Terrestrial carbon stock of Dire grazing system


The Dire grazing system is found within Dire Woreda, which is located in the southern part of the Borena Zone. This Woreda shares borders with Kenya in the south, Teltele in the west, Yabelo in the north, Moyale in the east, and Arero in the northeast. The altitude of this Woreda ranges from 750 to over 2400 meters above sea level. A survey of the land use shows that, of the total area of the Woreda, 14.3% is arable, 47.5% pasture, 17.5% forest, and the remaining 20.7% is considered swampy, degraded or otherwise unusable. In the Woreda, therefore, both pure pastoralism and agro-pastoralism are being practiced. The 2007 national census reported a total population for this Woreda of 73,401 (CSA, 2007).

For the carbon stock study, three sites were selected. These were Dubuluk grazing sub-system, Rare

Chebicha, and Dida Medhecho within the Soda grazing sub-system. The Dubuluk site is dominantly

occupied by scattered shrubs, bushes, and grass. The Rare Chibicha is also composed of scattered

woody vegetation, dominantly of acacia species, while the Dida Medhecho is dominantly covered by

degraded grass and some noxious vegetation. Furthermore, the site at Dubuluk is a ‘protected ranch’

but animals were grazing at the time of sample collection. It is also home to wild animals such as

Zebra. The Rare Chebicha site was also traditionally protected from grazing during the season, while

the Dida Medhecho is open grazing land. The dominant livestock kept in those sites are cattle,

shoats, and camel. The dominance varies from site to site. Plate 9 below shows some of the features

of the sampling sites in Malbe grazing system.

Plate 9. Partial view of the three sub-grazing systems and their status of vegetation cover at the Dire grazing system. Near the hills, the Dubluk sub-system is home to some wild animals like zebra.

The textural classes are mainly sandy loam, indicating that these soils contain large proportion of the sand fraction. The bulk density values at the soil surface ranged from 1.32 g cm-3 at Rare Chebicha to 1.62 g cm-3

at Dubuluk, while the subsurface layer bulk density values varied from 1.37 g cm-3 at Rare Chebicha to 1.57 g cm-3 at Dubuluk. The soil at Dubuluk was extremely difficult to penetrate at the time of sample collection and this is reflected in the relatively high bulk density values recorded at this site. The pH of the soils was also high and ranged from moderately alkaline (7.4-8.0) to strongly alkaline (> 8.0) (Tekalign, 1991).


Except at Rare Chebicha, the major carbon sink at the Dire grazing system was the soil (Table 10). At Rare Chebicha, the vegetation cover contributed about 5.98% of the terrestrial carbon stock, whereas at the other two sites the soil accounted for 99.99% of the terrestrial carbon stock. The Dida Medhecho site, dominantly occupied by grass, had relatively the highest terrestrial carbon stock as compared to the other two sites. In general, the terrestrial carbon stock within the Dire grazing system ranged from 61.548 to 101.905 t ha-1. The corresponding carbon dioxide equivalent, on the other hand, varied between 225.881 t ha-1 at Dubuluk to 373.991 t ha-1 at Dida Medhecho.

Table 10. Terrestrial carbon stock and its carbon dioxide variation with soil depth at three sites in Dire grazing system, Borena Zone


CO2e (t ha-1)AGWV HV BGB Soil Total

Dubuluk - 0.005 0.003 61.54 61.548 225.881Rare Chebicha

4.22 0.005 0.843 79.57 84.638 310.621

Dida Medhecho

- 0.003 0.002 101.90 101.905 373.991

Mean±StD

81.003±20.218 81.697±20.248 303.498±74.312


Furthermore, the carbon stock and the corresponding carbon dioxide equivalent in the major carbon

sink, the soil, showed spatial variation with soil depth at a given site (Figure 12). Accordingly, the soil

carbon stock decreased consistently with soil depth at Dubuluk site, while it showed irregular

pattern with depth at Rare Chebicha and Dida Medhecho. At system level, the mean value can be

taken as 81.003±20.218 with coefficient of variation of 24.96%. This indicates the existence of some

notable variability in carbon stock of soils in the grazing system.

Figure 12. Soil carbon stock and its carbon dioxide equivalent distribution with dept at selected site in Dire grazing system of Borena Zone, Oromia region (DK = Dubuluk; RC = Rare Chebicha; DM = Dida Medhecho).

As baseline information, mean terrestrial carbon stock and its carbon dioxide equivalent for the Dire grazing system can be taken as 81.697±20.248 and 303.498±74.312 t ha-1, respectively, with coefficient of variation of 24.49%. From the foregoing, it can be seen that there exists spatial variation in terrestrial carbon stock within the same grazing system. This highlights the need for increasing the intensity of sampling in future studies to obtain a more representative value for the system.

Comparison of the two sub-systems indicates that the Dire grazing system is better in its terrestrial carbon stock than the Malbe grazing system (Figure 13). However, the variability was slightly higher at Dire than it was at the Malbe grazing system.

If the carbon dioxide sequestered is converted into carbon finance using the Ethiopian Wildlife Authority rate of $4/tCO2e, the amount of money generated will be US$ 894.916 and 1213.952 per ha of grazing land, respectively, for Malbe and Dire grazing systems. This clearly highlights the importance of carbon sequestration as potential source of income for the pastoral community in addition to its direct role in improving productivity of the grazing systems and mitigating climate change by reducing the CO2 emission from grazing systems.

Figure 13. Mean terrestrial carbon stock and its carbon dioxide equivalent for Malbe and Dire grazing systems in Borena Zone of Oromia region.

3.3.3. Terrestrial carbon stock of the Dida Dheda grazing system


This grazing system is located in Liben Woreda of the Guji Zone, Oromia National regional state. The Woreda is bordered on the south by the Dawa River, which separates it from the Borena Zone, on the west by Odo Shakiso, on the northwest by Adolana Wadera, on the north by the Genale Dorya River, which separates it from the Bale Zone, and on the east by the Somali Regional state. The altitude of this Woreda ranges from 1120 to 1600 meters above sea level. According to the 2007 Census made in the country, the population of the Woreda was 138,813. Both pastoralism

and agro-pastoralism are being practiced in the Woreda. Some of the farms are even large scale farms that involve mechanization. The main livestock kept in the area are dominantly cattle mixed with shoats and to some extent camel.

Two well established sub-grazing systems, Miessa and Siminto, that were under the participatory rangeland management scheme were selected for this baseline carbon stock study. At Miessa alone the community protected 1200 ha as communal Kallo, while no concrete information was obtained from concerned offices about the size of the Siminto communal Kallo. These sites are characterized by extensive grazing lands covered mainly by grasses with scattered acacia and some noxious species. The specific sampling site was Andereka in Meesa, and Haro Areero in Siminto. Samples were collected from protected kallos and adjacent unprotected grazing

lands. This is shown in Plate 10 below.

Plate 10. Partial view of the sampling sites at Meesa (upper) and Siminto (lower) sub-systems at Dida Dheda grazing system. The upper and bottom left photos indicate the protected kallos at both sub-systems, while the adjacent ones indicate the unprotected grazing lands.

The textural classes of the soils are dominantly sandy loam and sandy clay loam indicating the relatively large proportion of the sand fraction. The bulk density values ranged from 0.98 to 1.52 g cm-3 at the soil surface, and 1.13 to 1.42 g cm-3 at the subsurface layers. Furthermore, the bulk density of the protected lands was lower than the unprotected

lands at Siminto sub-system. The pH values ranged from 7.21 to 7.78 at the soil surface, and 6.83 to 7.66 at the subsurface layers. In general, the pH values in the grazing system were in the range of neutral to moderately alkaline (Tekalign, 1991). This pH range is suitable for most plants and indicates that the system has high potential for further improvement.


At the Dida Dheda grazing system, both vegetation cover and the soil contributed considerably to the terrestrial carbon stock (Table 11). Consequently, the vegetation accounted for 34.16% (23.705 t ha -1) and 23.27% (21.174 t ha-1) at protected areas of Mieeso and Siminto, respectively. On the other hand, nearly 99.99% (49.28 and 61.09 t ha-1) of the terrestrial carbon stock at unprotected areas of Mieesa and Siminto, respectively, was stored in the soil system. This clearly shows the importance of protecting the grazing sites for improving their carbon sequestration potential and also productivity. The difference in carbon stock between protected and unprotected lands is largely due to difference in vegetation cover particularly the scattered trees found in the system. As can be seen from the data in Table 11, the difference in soil carbon stock between protected and unprotected lands is low. This has an important implication if improving the carbon stock in the soil system through such management practices is envisaged. The implication is that, in addition to relieving the grazing land from pressure through enclosure, controlled grazing has to be exercised when livestock are allowed to graze. Otherwise, nothing will return in to the soil system if intensive grazing is allowed.

The corresponding carbon dioxide equivalent across the system varied from a minimum of 180.880 t ha-1 at the unprotected grazing land of Mieesa to a maximum of 333.911 t ha-1 at the protected grazing land of Siminto (Table 11). Furthermore, it is important to note that, at both grazing sub-systems, the minimum carbon stock and its carbon dioxide equivalent was recorded at the adjacent unprotected grazing lands.

However, this was not reflected in the soil carbon stock at Mieesa. This might give an indication that the building up of the soil carbon stock through such management practices might require relatively longer period than usually anticipated. This in turn implies that the way the protected grazing lands are grazed after sometime of protection requires caution not to totally remove the vegetation cover, which is the source of organic carbon pool in the soil.

Table 11. Terrestrial carbon stock and its carbon dioxide equivalent at some grazing site in Dida Dheda grazing system, Guji zone of Oromia region


CO2e (t ha-1)AGWV HV BGB Soil TotalMeesa P 19.75 0.005 3.95 45.68 69.385 254.643Meeas Up**

- 0.006 49.28 49.286 180.880

Siminto P 17.64 0.004 3.53 69.81 90.984 333.911Siminto Up

- 0.003 61.09 61.093 224.211

Mean±StD

56.465±11.067 67.687±17.585 248.411±64.537

AGWV = above-ground woody vegetation; HV = herbaceous vegetation; BGB = below-ground biomass; StD = standard deviation; P* = protected; Up** = unprotected

Spatial variation in soil carbon stock with soil depth was observed (Figure 14). However, the variation was consistent with depth in the unprotected grazing lands only. The variation among the sampled sites within the system, as indicated by the coefficient of variation (19.60%), was relatively acceptable. The mean soil carbon stock for the system can be taken as 56.465±11.067 tha-1 with a corresponding carbon dioxide equivalent of 207.227±40.616 t ha-1.

Figure 14. Soil carbon stock and the corresponding carbon dioxide equivalent variation with soil depth at selected sites in Dida Dheda grazing system, Guji zone of Oromia region (MSP = Meesa protected; MSUP = Meesa unprotected; STP = Siminto protected; STUP = Siminto unprotected).

There was no information on the total area of the Dida Dheda grazing system. As a result, it was not possible to calculate the total terrestrial carbon stock and its carbon dioxide equivalent for the system. Its carbon stock and equivalent carbon dioxide were, therefore, represented by the mean values of the two systems, which were 67.687±17.585 and 248.411±64.537 t ha-1, respectively. The monetary value of the carbon dioxide sequestered, based on the Ethiopian Wildlife Authority rate of $4/tCO2e, amounts to US$ 993.644 per ha of grazing land.

3.3.4. Terrestrial carbon stock of the Golba Genale grazing system


This grazing system is found in Goro Dola Woreda of Guji zone in Oromia regional state. It is a new

Woreda. This grazing system is covered mainly by traditionally protected forest and is characterized

by undulating topography. It is dominated by agro-pastoralism with limited pastoralism in the

lowland areas of the system. Cattle are the dominant livestock kept in the system. Partial view of the

nature of forest at Golba Genale grazing system is illustrated in Plate 11.

Plate 11. Partial view of the sampled forest at Guduba Burure (upper), active participation of local partners in the study (bottom left), and nature of some trees at Mucho sampling site in Golba Genale grazing system.

The soils are highly variable in their textural class. Accordingly, sand to sandy clay loam textural classes are recorded across the Golba Genale grazing system. The bulk density of the surface layers ranged from 1.62 g cm-3 at Guduba Burure to 1.67 g cm-3 at Mucho, whereas at the subsurface layers it varied between 1.25 g cm-3 at Mucho to 1.68 g cm-3 at Guduba Burure. The pH of the soils, on the other hand, ranged between 7.02 and 7.35, which fall in the range of neutral to moderately alkaline, respectively (Tekalign, 1991).


Because the system is dominantly covered by forests of different species, the contribution of this forest cover to the terrestrial carbon stock of the system was significant. Therefore, the forest’s carbon stock accounted for 33.8% (43.940 t ha-1) and 28.72% (41.952 t ha-1) at Guduba Burure and Mucho sub-systems, respectively (Table 12). On the other hand, the soil system, even under forested environment, proved to be the major carbon sink in this grazing system. The results further indicate that combined management of vegetation cover and soil could result in high carbon sequestration and, thus, play a key role in climate change mitigation. This can be seen from the high carbon dioxide equivalent sequestered (477.10 to 536.011 t ha-1) in this grazing system.

Table 12. Terrestrial carbon stock and its carbon dioxide equivalent at Golba Genale grazing system in Guji zone of Oromia region


CO2e (t ha-1)AGWV HV BGB Soil TotalGuduba Burure

36.62 - 7.32 86.06 130.00 477.10

Mucho 34.96 0.002 6.99 104.10 146.052 536.011Mean±StD

95.080±12.756 138.026±11.350 506.556±41.656

AGWV = aboveground woody vegetation; HV = herbaceous vegetation; BGB = belowground biomass; StD = standard deviation

The depth-wise distribution of the soil carbon stock indicates that the upper 0-10 cm soil layer contributed the greatest share of the total soil carbon stock at both grazing sub-systems (Figure 15). This could be attributed to the relatively high contribution from the forest litter. Furthermore, the variability of the soil carbon stock within the system was relatively low with mean value of 95.080±12.756 tha-1 and coefficient of variation

of 13.42%.

Figure 15. Soil carbon stock and its carbon dioxide equivalent distribution with soil depth at Golba Genale grazing system, Guji Zone of Oromia region (GB = Guduba Burure; MC = Mucho).

Similar to what has been done for the other systems, the baseline mean carbon stock and its carbon dioxide equivalent of the Golba Genale grazing system were taken as the means of the two sub-systems, which were 138.026±11.350 and 506.556±41.656 t ha-1, respectively.

The monetary value of the carbon dioxide sequestered, using the Ethiopian Wildlife Authority rate of $4/t CO2e, will be US$ 1908.4 and 2144.044 per hectare of land, respectively, at Guduba Burure and Mucho. Again, these figures indicate the potential grazing lands in pastoral and

agro-pastoral areas have as sources of huge finance if carbon financing mechanisms are put in place. The impact of this financial income on improving the livelihood of the pastoral communities is immense. It is, therefore, imperative to recognize the potential these lands have to sequester significant amount of carbon within them and device management scenario that will protect them from degradation and help them achieve their potential.

Comparison of the two systems indicates that the terrestrial carbon stock of the Golba Genale system, which is covered by forest, was higher than that of the Dida Dheda system, which is dominated by annual grasses and scattered acacia trees and noxious shrubs (Figure 16). Furthermore, the variability of the terrestrial carbon stock was relatively high at the Dida Dheda system than it was at the Golba Genale system.

Figure 16. Mean terrestrial carbon stock and its carbon dioxide equivalent at two grazing systems in Guji Zone, Oromia region (DDH = Dida Dheda; GG = Golba Genale).

4. CONCLUSIONS

In this study carbon stock was measured in Ethiopian Somali, Afar and Oromia regions grazing systems as part of improved governance for climate smart natural resource restoration and enhancement activity of the PRIME project. The study clearly showed carbon stock differences within and among clusters, and between protected and unprotected rangeland systems. This variation is attributed to the observable differences in management, vegetation cover density, vegetation type, and soils in the study areas. Those systems with woody perennial composition had better carbon stock than the other systems which do not have woody perennials. In all the grazing systems studied, the soil system was found to be the major carbon sink. Unlike many other forest based grazing systems, the Hussien Semane sub grazing system in Harshin grazing system had no undergrowth vegetation, which further needs investigation on the soil characteristics, grazing system and soil seed bank.

The baseline carbon stock status indicates that pastoralists, through long existing customary system, have developed deep understanding of their grazing systems and have well established rangeland utilization mechanisms though it is now being eroded due to internal and external factors. Revitalization of the customary system and injecting modern knowledge into it is vital to sustain the rangeland systems and enhance their environmental and economic contribution to the pastoral community in particular and the nation at large. The results obtained disproof the usual belief that pastoral area grazing systems are degraded and have poor carbon stock and sequestration potential.

The difference in carbon stock between protected and unprotected rangelands is a clear indication of the contribution of participatory rangeland management practices and their potential in mitigating climate change besides improving the productivity of rangelands and livestock. The current community based natural resources management, particularly

the participatory rangeland management practice, should be strengthened as these activities are enhancing the carbon stock and sequestration potential of rangelands.

5. RECOMMENDATIONS

The following recommendations are suggested to fully utilize the potential of rangelands in climate change mitigation:

The study was conducted during the wet (East cluster) and dry (all other clusters) seasons. Therefore, results only reflect one season carbon stock of the respective study areas. Similar studies should be conducted during different seasons to get the full picture of the annual carbon stock dynamics of the rangeland systems.

Currently PRIME is using community maps which indicate location of resources, mobility roots and other important events but not the total area of the grazing systems that are going to be under participatory rangeland management scheme. Though rangeland systems covered hundred and thousands of hectares, it was difficult to obtain their areal coverage from any sources. The area coverage of the different grazing systems should be mapped.

The trade-offs between the government formal administrative system and PRIME rangeland system (following customary system) should be resolved and all parties should agree on the coverage of rangeland systems.

These preliminary results should be communicated to decision makers for guiding policies in pastoral area grazing systems.

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