Establishment Of Exclosures Research Articles

Effects of exclosures on mountain grassland floristic composition in Sidama, Ethiopia

This study was conducted to assess the effects of exclosure on mountain grassland’s species composition, richness, diversity and dominance in Sidama, Southern Ethiopia. Locally established exclosures aged between 10 and 12 years old were compared against adjacent open-grazed areas in Mollona-Meno Kebele for this study. The study was replicated at four sites. An exclosure was paired with adjacent open-grazed lands having a similar land area and slope. Both in the exclosures and adjacent open-grazed lands, 87 and 86 plant species were recorded, representing 20 families, respectively. A significantly higher difference was observed between exclosures and adjacent open-grazed lands in terms of herbaceous species abundance, diversity, evenness and density. Higher herbaceous species’ important value index (IVI) was recorded inside exclosures than in the open-grazed lands. The results suggested that the establishment of exclosures on degraded lands could support the restoration of degraded native herbaceous species which consequently enhanced ecosystem services.

Seasonal breeding in three sympatric rodent species in semi-arid Tigray, northern Ethiopia

Abstract We investigated the breeding activity of three sympatric rodent species: Stenocephalemys albipes, Mastomys awashensis, and Acomys cahirinus, in the semi-arid region of Tigray in northern Ethiopia, using mark-recapture data, to determine the influence of rainfall on their breeding patterns within exclosure (i.e., protected area from livestock grazing). Breeding activities of S. albipes and M. awashensis commenced during the wet season, continued into the early dry season, and ceased during the subsequent dry season. The proportion of breeding females reached its peak during the wet season, gradually declining until the dry season. In contrast, A. cahirinus exhibited a different breeding strategy, with year-round breeding, including during the dry season, a period characterized by limited resources. A significant difference in the proportion of breeding females among the three species was observed across seasons. Furthermore, all species shared a common trend of heightened breeding activity, particularly at the conclusion of the wet season and the onset of the early dry season. These findings enhance our understanding of the interplay between rainfall and seasonal breeding within exclosures, while other variables remain constant. Moreover, the region’s future plans for managing rodents and the establishment of exclosures must take this information into account.

Implications of changes in land use for ecosystem service values of two highly eroded watersheds in Lake Abaya Chamo sub-basin, Ethiopia

Ecosystems provide a variety of ecosystem services and functions for mankind, and their sustainable use plays an important role in livelihoods. However, the resulting land degradation due to land use and land cover changes leads to loss of valuable ecosystems and associated ecosystem functions and services. This study takes two highly degraded watersheds, Aba-Bora and Guder, in Ethiopia and uses the value transfer valuation method to estimate changes in ecosystem service values. The study shows how loss of cropland and grazing lands can significantly affect ecosystem services even when plantations and shrubland increase. The results suggest that over a period of 41 years, the ecosystem service value of exclosures/shrublands and plantations increased, whereas that of crop and grazing lands decreased. The loss of ecosystem service values due to the decrease in cropland and grazing lands outweigh the gains due to the expansion of plantations and exclosures and resulted in a total loss of ecosystem service values of US$ 1.6 million in Aba-Bora watershed and US$ 24.4 million in Guder. In both watersheds, the greatest contributor to ecosystem service loss was a decline in supporting services, while the increase in plantation and shrublands (mainly through establishment of exclosures) meant that regulating ecosystem services suffered the smallest loss. Given their importance to livelihoods in these areas, the loss in crop and grazing lands significantly increase the vulnerability to shocks and narrow future livelihood options for many households. Given that severe gully erosion is the major contributor to the reduction in crop and grazing lands, catchment management that integrates the conservation of upstream areas using diverse sustainable land management practices, and gully rehabilitation measures in downstream areas could be an important option to reducing the expansion of big gullies, and conserving crop and grazing lands and ecosystem service values. However, the results suggest that the risks to livelihoods may be underestimated while the effectiveness of current actions to address land degradation over-estimated by communities.

Effects of exclosures on woody species composition and carbon stocks: Lessons drawn from the Central Rift Valley, Ethiopia

AbstractEffects of exclosures on restoring degraded lands may vary with soil type, exclosure age, and conditions before the establishment of exclosures. Yet, studies investigating the effectiveness of exclosures in restoring degraded lands under different environmental conditions are lacking. This study aims at investigating the changes in woody species richness and diversity, and ecosystem carbon stocks after implementing exclosures in the Central Rift Valley, Ethiopia. Vegetation and soil data were gathered from 120 nested plots established in exclosures of eight and 30‐years‐old and adjacent grazing lands. Results showed that exclosures contained a higher number of economically important woody species compared to their respective adjacent grazing lands. However, the exclosures and respective adjacent grazing lands did not differ significantly in the diversity of tree and shrub species, and both the exclosures and adjacent grazing lands were dominated by few tree and shrub species. The older exclosure (30 years old) displayed significantly (p < 0.01) higher soil organic carbon and soil total nitrogen content and stocks than the adjacent grazing land, whereas the youngest exclosure (8 years old) did not show a significant difference in these variables. The results suggest that a longer time (e.g., ≥10 years) is needed to detect significant differences in soil organic carbon and total soil nitrogen. However, exclosures could bring considerable changes in woody species density in a relatively shorter period (e.g., ≤10 years) and support to restore degraded native woody species.

Restoration of diversity and regeneration of woody species through area exclosure: the case of Maun International Airport in northern Botswana

Background and objectives: Deforested and degraded areas can be cheaply and conveniently restored through establishment of exclosures. An area exclosure excludes animals and humans from accessing an area to promote natural regeneration of plants and rehabilitate ecological condition of the area. The study was aimed at: (1) determining the diversity (species richness, diversity and evenness); (2) assessing the stand structure (densities); and (3) assessing regeneration status of woody species inside and outside exclosed Maun International Airport, northern Botswana. Methods: Vegetation sampling was conducted from April to May 2018. A total of 48 and 37 quadrats of 20 × 20 m were laid down at 50 m intervals along transect lines inside and outside Maun International Airport, respectively. Identity, number of all live individuals and height of all woody species were recorded in all the quadrats. The diversity of all woody species was analysed by using the Shannon Diversity Index (H’) and regeneration status of each woody species was assessed using frequency distribution of height class. Results: The diversity, evenness and species richness were significantly higher inside than outside Maun International Airport. Colophospermum mopane was the most abundant species both inside (75% of all woody species) and outside (96% of all woody species) Maun International Airport. More species showed more regeneration inside than outside Maun International Airport. The inside of Maun International Airport recorded more alien invasive woody species compared with the outside, owing to its original use as a residential area. The local communities might have introduced these species as ornamental trees. Conclusion: This study, while limited in scale, contributes to understanding of the role of exclosures in enhancing woody species richness, diversity and evenness as well as facilitating regeneration of woody species. Degraded woodlands and other similar ecosystems could be cheaply and conveniently restored through establishment of exclosures, but more research and monitoring are required to fully understand the processes and impacts.

From runoff contributor to runoff absorber: Spate irrigation on exclosures in Tigray's semi‐arid environment (Ethiopia)

AbstractDespite many years of establishment of exclosures in the semi‐arid environments of north Ethiopia for rehabilitation of degraded areas, its effectiveness is constrained by water deficit. There is lack of empirical data on the response of vegetation to additional water (spate irrigation) application. This study aimed to evaluate the effects of spate irrigation using storm runoff on the growth of trees in exclosures. Two exclosures (May Ba'ati and Adi Kolakol), in Dogu'a Temben district, Tigray, north Ethiopia, were used for this study. Each exclosure was divided in two blocks (irrigated and non‐irrigated) to allow comparison of change of vegetation using several diversity indices as well as contrasts in tree ring widths. The amount of spate irrigation water diverted onto the exclosures (762 mm) was in the same order of magnitude as the direct rainfall on the sites (645 mm). The results show that the irrigated exclosures have larger species richness, Shannon–Weaver diversity index, tree density, abundance, evenness and basal area than the non‐irrigated areas. Following low rainfall (353 mm) in 2015, these indices decreased in the non‐irrigated area, whereas most indices remained much higher in the irrigated area. The findings indicate that diverting runoff to exclosures results in an average 15% increase in ring width as compared to non‐irrigated trees. In addition, there is strong abstraction of storm runoff in gullies in the study area. Besides the promotion of forestry in washout semi‐arid areas of existing spate irrigation systems, we suggest to apply spate irrigation to exclosures in order to improve their productivity.

Changes in Soil Properties Following the Establishment of Exclosures in Ethiopia: A Meta-Analysis

Community-led watershed development activities, including the establishment of exclosures (areas where both livestock and farming activities are excluded) on degraded communal grazing land, have become a common practice in Ethiopia since the 1990s. However, it is not yet fully understood how these exclosures change soil organic carbon and total soil nitrogen in different soil types and under different agroecologies. A meta-analysis using data gathered from the most relevant peer reviewed articles from Ethiopian exclosure systems was conducted to assess the variation in the effects of exclosures on soil carbon and nitrogen and to investigate the factors controlling change. The results demonstrate that after 16 years, exclosures can increase soil organic carbon and total soil nitrogen up to an effect size greater than two. This is moderated by soil type, exclosure age, landscape position and agroecology. More effective restoration of soil carbon was observed in less developed Leptosols and Cambisols than in more developed Luvisols, and in drier than more humid agroecologies. The results suggest that soil type and agroecology should be taken into consideration when planning and implementing exclosures on degraded communal grazing land. The findings of this study provide base line information for the future expansion of exclosures, and guide where to focus implementation. They also provide criteria to be used when planning and establishing exclosures to restore soil carbon and nitrogen. In addition, the results generated through this meta-analysis provide better understanding of the spatial and temporal variation of the effectiveness of exclosures to restore soil carbon and nitrogen.

Impact of exclosure on the vegetation composition and structure of Northern Ethiopia

Land rehabilitation by area exclosure was the fastest and moderate approach of recovering degraded sites. The objective of the study is to investigate the impact of exclosure establishment on the vegetation ecology of the Northern Ethiopia.A stratified preferential sampling design technique with flexible systematic model was used for data collection. Data on vegetation and environmental parameters were gathered from 120 quadrants (90 from restorations or exclosures of different ages and 30 from adjacent free grazing lands), of 20 m x 20 m (400 m2) size. Species richness and the presence or absence of herbaceous plants were recorded like soil samples in a 2 m x 2 m (4 m2) subplot inside each main quadrant from five points, one at each corner and one at the center. A total of 142 plant species belonging to 118 genera and 52 families were identified. All exclosures displayed higher plant species richness, diversity, and aboveground standing biomass compared to the adjacent free grazing lands. Consideration of edaphic (e.g. soil total nitrogen, available phosphorus, CEC, exchangeable bases, soil pH and soil texture) and site (e.g. Stoniness, Grazing) variables will help to optimize the selection of areas for the establishment of future exclosures. Moreover, our study suggests that with time exclosures may increasingly obtain an important role as refugees and species pool similar to church forests and should be protected and managed in a sustainable manner. Substantial numbers of forest species were found to have irregular population structure and are in reduced regeneration status. To prevent local extinction of these species, present efforts of nursery establishment and plantation of indigenous species in the exclosures should be strengthened and extended.

Stochastic simulation of restoration outcomes for a dry afromontane forest landscape in northern Ethiopia

Forest and Landscape Restoration (FLR) is carried out with the objective of regaining ecological functions and enhancing human well-being through intervention in degrading ecosystems. However, uncertainties and risks related to FLR make it difficult to predict long-term outcomes and inform investment plans. We applied a Stochastic Impact Evaluation framework (SIE) to simulate returns on investment in the case of FLR interventions in a degraded dry Afromontane forest while accounting for uncertainties. We ran 10,000 iterations of a Monte Carlo simulation that projected FLR outcomes over a period of 25 years. Our simulations show that investments in assisted natural regeneration, enrichment planting, exclosure establishment and soil-water conservation structures all have a greater than 77% chance of positive returns. Sensitivity analysis of these outcomes indicated that the greatest threat to positive cashflows is the time required to achieve the targeted ecological outcomes. Value of Information (VOI) analysis indicated that the biggest priority for further measurement in this case is the maturity age of exclosures at which maximum biomass accumulation is achieved. The SIE framework was effective in providing forecasts of the distribution of outcomes and highlighting critical uncertainties where further measurements can help support decision-making. This approach can be useful for informing the management and planning of similar FLR interventions.

Classification of riparian woody plant communities along the Thamalakane River in northwestern Botswana.

There is still paucity of information on the species composition of woody species along the Thamalakane River, northern Botswana, which may limit efforts aimed at conserving riparian woodland species. The current study was aimed at classifying the vegetation, and determining the species composition and diversity of the riparian woodland plant communities along the Thamalakane River. It was hypothesized that there will be no different woodland communities along the Thamalakane River. The 71 sampling plots measured 1000m2 (20m × 50m). In each plot,the percentage cover for each species was estimated following the Braun-Blanquet scale. Different woodland communities were determined through Hierarchical Cluster Analysis followed by Indicator Species Analysis. Multi-Response Permutation Procedures (MRPPs) were used to determine whether or not there was a significant separation between the groups. The Kruskal-Wallis test was used to statistically compare the diversity between woodland communities. Five major woodland communities were identified along the Thamalakane River, namely Vachellia tortilis-Gardenia volkensii, Combretum imberbe-Gymnosporia senegalensis, Philenoptera violacea-Garcinia livingstonei, Dichrostachys cinerea-Flueggea virosa and Croton megalobotrys-Colophospermum mopane. There was significant (p <0.05) separation between the plant groups. Species diversity was highest in Dichrostachys cinerea-Flueggea virosa community and lowest in Vachellia tortilis-Gardenia volkensii community. The distribution of woodland species in along Thamalakane river could be influenced by human disturbance, which may override abiotic environmental conditions such as flooding in influencing the composition and distribution of plant species. This calls for proper management initiatives of the riparian vegetation in the study area. Such initiatives may include establishment of exclosures to promote the germination and propagation of the woodland species. Other strategies may include education and awareness creation of the local communities to promote their co-existence with the riparian vegetation.

Assessing the sustainability of land use management of northern Ethiopian drylands by various indicators for soil health

Abstract Land use change and agricultural intensification in developing countries affect terrestrial carbon (C) stocks, CO2 efflux, microbial communities and overall soil health. This study assesses the effects of four land use types typical for northern Ethiopia (forests, exclosures, grazing lands and intensively cultivated croplands) on various soil health indicators. We quantified and compared microbial biomass carbon (MBC), water extractable organic carbon (WOC), metabolic quotient (qCO2), substrate use efficiency (SUE) and dynamics of 14C-labelled glucose added to soil. Irrespective of the land use, MBC but not SUE decreased 2- to 8-fold with increasing depth, demonstrating the C limitation of subsoil microbial communities under all land use forms. Sandy soils, however, which permit seepage and leaching of WOC into lower layers and promote subsoil microbial communities, adapted to frequent input of easily accessible C substrates. Significantly higher qCO2 were recorded in subsoils compared to topsoils, especially in croplands with low MBC. In croplands, high glucose-14C incorporation (≈20%) into their low microbial biomass indicates a high SUE and reflects a better nutrient supply of these microbial communities. Mineralization of up to 95% of 14C-labeled glucose in topsoils of forest and grazing lands was higher than in croplands, and exclosures never reached the level of natural ecosystems. This demonstrates that 6–10 years of exclosure establishment does not result in soil microbial communities and soil C dynamics resembling those of natural forests. Our study demonstrates that land use can negatively affect the ecological performance of microbial communities and that these impacts are more severe in sandy than in clayey soils. Mitigation strategies such as minimum tillage or residue retention in intensively cultivated croplands can increase microbial abundance and activity and help ensure environmental sustainability and mitigation of climate change. Nonetheless, such measures need to be carefully accompanied by monitoring indicators of soil health to confirm the sustainability of the chosen mitigation strategies.

Restoration of degraded landscapes for ecosystem services in North-Western Ethiopia

Establishing exclosures has become common in Ethiopia, especially in the central and northern highlands, where they serve as a response to persistent forest degradation, affecting forest resources and ecosystem services. We investigated changes in vegetation composition, aboveground biomass and soil properties after establishing an exclosure on degraded communal grazing land in Aba-Gerima watershed, North-Western Ethiopia. We selected 4-yr-old exclosure and paired the selected exclosure with an adjacent communal grazing land. In the exclosure, we recorded 46 plant species representing 32 families, whereas we recorded 18 plant species representing 13 families in the adjacent communal grazing lands. Most of the identified woody species are economically important. We observed significant differences between the exclosure and adjacent grazing land in woody species richness, diversity and evenness. Exclosure displayed higher woody species density, basal area and aboveground woody biomass compared to the adjacent grazing land. Landscape position influenced vegetation composition, richness and diversity in the exclosure and adjacent grazing land. Significant differences between the exclosure and adjacent grazing land in soil properties were detected. The influence of landscape positions on soil properties was not consistent. At foot slope position, in the 0- to 15-cm and 15- to 30-cm depths, soil organic carbon and nitrogen content detected in exclosure were significantly higher when compared to the values observed in the adjacent grazing land. However, differences at mid and upper slope positions were not significant. The results support that the establishment of exclosures on degraded lands could support the restoration of degraded native vegetation and soil properties, which consequently enhance the ecosystem services that can be obtained from degraded lands.

Evaluating Success of Alternative Restoration Methods for Riparian Willows: Seeding and Ungulate Exclosures

Riparian willows provide important ecosystem functions, however, in some locations they have been degraded due to over-browsing by wild and domestic ungulates. Fires can also have a detrimental effect on riparian vegetation, but have positive effects by creating bare soil necessary for willow seed germination. Both active and passive methods of restoration are common, but questions related to willow seed production are not well studied. We examined two questions: 1) Are bare soil patches created by wildfire suitable for willow seedling establishment? and 2) How has aerial seed rain changed since the establishment of exclosures to limit access of ungulates to willow stands? Working in montane riparian areas in Rocky Mountain National Park (USA), we seeded 1 m2 plots on bare soil patches created by a wildfire and monitored germination and survival. Seeds germinated in 46% of the plots and the number of seedlings ranged from 1 to 591. Plots with higher average growing season soil moisture had greater numbers of seedlings and seedling survival rates. In a nearby unburned valley, we assessed aerial seed rain biweekly using traps established at the same locations as a previous study in 2000. Five years after the establishment of exclosures, aerial seed rain was lower than in the pre-fence year 2000. We conclude that fire could trigger willow seeding establishment and controlled burns used as a viable option for restoration. In addition, five years of fencing is insufficient to reestablish willow seed rain after a period of heavy browsing.

Impact of exclosures on wood biomass production and fuelwood supply in northern Ethiopia

In the Ethiopian highlands, communal grazing lands are one of the major land uses, and are source of livelihood for the rural people. Free and uncontrolled grazing in the communal grazing lands is the dominant grazing system. The traditional uncontrolled and free grazing system has caused severe degradation of the grazing lands. As a result, communities have started to establish exclosures and support the restoration of degraded communal grazing lands. Studies have shown that exclosures are effective to restoring degraded communal grazing lands and improving ecosystem services. However, studies that investigate the changes in aboveground biomass following the establishment of exclosures and compare it with fuelwood demand of the beneficiaries in our study area is lacking. Therefore, our study aimed at: (1) quantifying yearly biomass accumulation in exclosures and compare it to fuelwood demand of households that manage the exclosures; (2) assessing household energy sources and their consumption levels. To monitor changes in biomass production with over time, replicated (n = 3) 5 and 10 year-old exclosures were sampled. To investigate fuelwood sources and consumption patterns, household surveys, key informant interviews and focus group discussion were conducted. Our results demonstrated that total biomass production increased with exclosure age. In both exclosure, biomass production from Vachellia etbaica was significantly (p < 0.05) greater than that from Euclea. racemosa. Average daily fuelwood consumption per person was (0.63 ± 0.2) kg day−1. This means that the total biomass (27.5 Mg year−1) obtained from 114.6 ha of exclosures covers only 9.4% of yearly fuelwood demand of the residents who manage the sampled exclosures. Nearly all respondents (95%) confirmed that they travel more than 10 km day−1 to gather fuelwood from surrounding degraded forest patches. We recommend plantings of fast growing native tree species within exclosures and around homesteads to provide a sustainable fuelwood supply and using improved stoves to address the problem of fuelwood shortage. District agricultural offices could provide seedlings of native plant species, while communities provide unpaid labour for planting and managing plantations.

Enhancement of diversity, stand structure and regeneration of woody species through area exclosure: the case of a mopane woodland in northern Botswana

IntroductionAn area exclosure is the practice of land management that involves the exclusion of livestock and humans from openly accessing an area that is characterized by severe degradation. Area exclosures have been employed as cheap and convenient means of rehabilitating degraded forests/woodlands. A study was carried out to (i) assess the species richness, diversity and evenness; (ii) determine the densities, frequencies, dominance and importance value index; and (iii) assess the population structure and regeneration status of woody species inside and outside the fence (area exclosure) of Okavango Research Institute (ORI) located in Maun, northern Botswana.ResultsThirty-five woody species were recorded inside (32 spp.) and outside (24 spp.) the ORI compound, and the population structure and regeneration status of the woody species were better inside than outside the ORI compound. The exclosure had seven times higher mean density of woody species than outside ORI, and an exceptional regeneration of seedlings was observed inside than outside the ORI compound, suggesting the process of recovery of the degraded woodland. The frequencies of more than half of the woody species also showed increment inside than outside the exclosure. The results suggest that the exclosed area is still in an initial recovery stage since it had been an open grazing area prior to the establishment of the exclosure. Most of the woody species encountered outside ORI showed hampered recruitment and regeneration, owing to different anthropogenic impacts and overgrazing by animals.ConclusionsDespite the relatively short period (10 years) of exclosure establishment, results from the present study have further provided empirical evidences on the actual crucial roles played by area exclosures to increase woody species richness, diversity, evenness, density, frequency, dominance and important value index as well as enhance the population structure and regeneration of the woody species in northern Botswana. Future research is recommended focusing on comparative studies on herbaceous species richness, diversity and density, horizontal and vertical distribution of soil seed banks, species richness of soil microorganisms, plant and soil biomass, plant and soil carbon pools (above and below ground) as well as soil contents and properties inside and outside the ORI compound.

Effect of Exclosure Age on Carbon Sequestration Potential of Restorations in Tigray Region, N. Ethiopia

Conversion of degraded free grazing lands into exclosures is one option to promote natural regeneration of plants and to restore degraded ecosystems in Ethiopia. The present study investigated the change in ecosystem carbon stocks (ECS) and the enhancement of plant species richness and diversity following the establishment of exclosures on free grazing lands in Tigray, Ethiopia. Exclosures of 10, 15, and 20 years old were selected and each exclosure was paired with an adjacent free grazing land. A total of 120 quadrants were sampled using a stratified preferential sampling design technique with flexible systematic model. The differences in carbon stocks and vegetation composition between an exclosure and free grazing lands were assessed using a paired t-test. Data analyses also included descriptive statistics, inferential statistics using one way ANOVA, t-test and Chi-square test. All exclosures displayed higher ECS, and plant species richness, diversity and aboveground standing biomass than the free grazing lands. Differences in ECS between exclosures and free grazing lands varied between 32.96 and 61.0 t. ha^-1 increasing with exclosure age. Over a period of 20 years, the carbon dioxide sequestered in the investigated exclosures was 223.88 t. ha^-1. Differences in plant species richness and aboveground standing biomass between exclosures and free grazing lands also increased with exclosure age. The results of the present study confirm that establishment of exclosures on degraded free grazing lands in the Northern Highlands of Ethiopian is a viable option to restore ECS. The study showed that ECS in exclosures, in free grazing lands and the change in ECS following the establishment of exclosures on free grazing lands can be predicted using easily measurable biophysical and management-related indicators. Such information is necessary for the establishment of baseline information for carbon sequestration projects, for evaluation of whether exclosure establishment should be expanded, and for policymakers to take into account the value of exclosures in their management decisions. Although the study showed that exclosures are effective to restore ECS, expansion of exclosures would increase grazing pressure on the remaining free grazing area. Therefore, the decision to establish additional exclosures should also include an economical analysis and an evaluation of the social consequences of such a decision.

Dynamics of Soil Erosion as Influenced by Watershed Management Practices: A Case Study of the Agula Watershed in the Semi-Arid Highlands of Northern Ethiopia.

Since the past two decades, watershed management practices such as construction of stone bunds and establishment of exclosures have been widely implemented in the semi-arid highlands of northern Ethiopia to curb land degradation by soil erosion. This study assessed changes in soil erosion for the years 1990, 2000 and 2012 as a result of such watershed management practices in Agula watershed using the Revised Universal Soil Loss Equation. The Revised Universal Soil Loss Equation factors were computed in a geographic information system for 30 × 30 m raster layers using spatial data obtained from different sources. The results revealed significant reduction in soil loss rates by about 55 % from about 28 to 12 t ha-1 per year in 1990-2000 and an overall 64 % reduction from 28 to 10 t ha-1 per year in 1990-2012. This change in soil loss is attributed to improvement in surface cover and stone bund practices, which resulted in the decrease in mean C and P-factors, respectively, by about 19 % and 34 % in 1990-2000 and an overall decrease in C-factor by 29 % in 1990-2012. Considerable reductions in soil loss were observed from bare land (89 %), followed by cultivated land (56 %) and shrub land (49 %). Furthermore, the reduction in soil loss was more pronounced in steeper slopes where very steep slope and steep slope classes experienced over 70 % reduction. Validation of soil erosion estimations using field observed points showed an overall accuracy of 69 %, which is fairly satisfactory. This study demonstrated the potential of watershed management efforts to bring remarkable restoration of degraded semi-arid lands that could serve as a basis for sustainable planning of future developments of areas experiencing severe land degradation due to water erosion.

Soil Restoration after seven Years of Exclosure Management in Northwestern Ethiopia

AbstractEcological restoration through exclosure establishment has become an increasingly important approach to reversing degraded ecosystems in rangelands worldwide. The present study was conducted in northwestern Ethiopia where policy programs are aiming to restore degraded lands. Changes in soil properties following establishing exclosures on communal grazing lands were investigated. A space‐for‐time substitution approach was used to monitor changes in soil properties after conversion of communal grazing lands to exclosures with ages of establishment ranging from 1 to 7 years. Significant differences in soil pH, exchangeable cations, cation exchange capacity, soil moisture content and bulk density were observed within exclosures and between exclosures and communal grazing land. Communal grazing land displayed significantly higher soil total nitrogen, phosphorus and potassium compared with exclosures. Exclosures did not display significantly higher soil organic matter content when compared with the communal grazing land. The results confirm that more than 7 years after the establishment of exclosures is required to detect significant improvements in most of the investigated soil properties. Prohibition of the practice of grass harvesting during the first 3 to 5 years following the establishment of exclosure, and decreasing the amount of grass harvest with exclosure age could support to increase easily decomposable organic inputs to the soil and improve soil properties in relatively short period of time. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Restoring aboveground carbon and biodiversity: a case study from the Nile basin, Ethiopia

In Ethiopia, exclosures in landscapes have become increasingly important to improving ecosystem services and reversing biodiversity losses. The present study was conducted in Gomit watershed, northern Ethiopia, to: (i) investigate the changes in vegetation composition, diversity and aboveground biomass and carbon following the establishment of exclosures; and (ii) analyse the economic returns of aboveground carbon sequestration and assess the perception of local communities on land degradation and exclosures. A space-for-time substitution approach was used to detect the changes in aboveground carbon, species composition, and diversity. Exclosures of 1-, 2-, 3-, 4-, 5-, and 7-years-old and a communal grazing land were selected. Household surveys, key informant interviews, and a financial analysis were used to assess the perception of local communities and the value of exclosure impacts, respectively. Significant (P = 0.049) differences in species diversity and considerable increases in aboveground carbon (ranged from 0.6 to 4.2 t C ha−1), CO2 storage (varied between 2.1 and 15.3 t CO2 ha−1), woody species composition, and richness (ranged from five to 28) were observed following the establishment of exclosures. Exclosures generated temporary certified emission reductions (tCER) of 3.4, 2.1, 7.5, 12.6, 12.5, and 15.3 Mg CO2 ha−1 after 1, 2, 3, 4, 5, and 7 years, respectively. The net present value (NPV) of the aboveground carbon sequestered in exclosures ranged from US$6.6 to US$37.0 per hectare and increased with exclosure duration. At a watershed level, 51.4 Mg C ha−1 can be sequestered, which represents 188.6 Mg CO2 ha−1, resulting in tCER of 139.4 Mg CO2 ha−1 and NPV of US$478.3 per hectare. This result would suggest that exclosures can potentially improve local communities’ livelihoods beyond rehabilitating degraded lands if carbon stored in exclosures is traded. Communities in the watershed demonstrated that exclosures are effective in restoring degraded lands and they are benefiting from increased fodder production and reduced impacts of soil erosion. However, the respondents are also concerned over the sustainability of exclosure land management, as further expansion of exclosures aggravates degradation of remaining communal grazing lands and causes fuel wood shortages. This suggests that the sustainability of exclosure land management can be attained only if these critical concerns are addressed by a joint effort among government agencies, nongovernmental organizations, and communities.

Conversion of Communal Grazing Lands into Exclosures Restored Soil Properties in the Semi-Arid Lowlands of Northern Ethiopia

In the semi-arid tropics, communal grazing lands provide a livelihood for millions of people. However, it is highly threatened by overgrazing and continuous land degradation and, as a result, proper management is important to improve the livelihood of the people. This study investigated the effectiveness of exclosures established on communal grazing lands to restore soil properties and identified the relationship among soil properties, site and vegetation characteristics, and exclosure age. A space-for-time substitution approach to detect changes in soil properties following the establishment of exclosures on communal grazing lands was used. Replicated (n = 3) 5-, 10-, and 15-year-old exclosures were selected and paired, each exclosure with an adjacent communal grazing land. All exclosures showed higher soil organic matter (OM), total soil nitrogen (N), available phosphorus (P), and cation exchange capacity (CEC) than the adjacent grazing lands. The increases in soil properties between exclosures and grazing lands in the 0- to 0.2-m depth varied between 58 and 101% for OM, from 54 to 108% for N, from 26 to 128% for P, and from 18 to 28% for CEC over the grazing lands. Soil properties in exclosures and grazing lands showed significant (p < 0.05) correlations with biomass and vegetation cover indicating that vegetation restoration is a key to restore degraded soils through exclosure establishment. Establishing exclosures on communal grazing lands can be effective in restoring the degraded soils in the semi-arid lowlands of Ethiopia. However, further studies are required on the ecological and economic benefits of future exclosures, as expansion of exclosure could cause grazing pressure on the remaining communal grazing lands.