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

Abstract

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.

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

“…The afore-cited studies were conducted in limited locations and the results cannot be fully translated to the context of CRV due to differences in biophysical and socioeconomic differences. This was supported by a recent metaanalysis study on the influence of exclosures on improving soil properties (Yakob et al, 2022). This study suggested that such impacts of exclosures vary with site characteristics and exclosure age.…”

“…The major contribution of exclosures to restoring soil carbon could be attributed to increasing organic input from litterfall and root decomposition (Manaye et al, 2019), protecting the constructed soil and water conservation measures from destruction by free grazing reducing soil erosion, and improving soil moisture content (Mekuria et al, 2011). Increased inputs of decomposable organic matter (e.g., herbaceous plants, litterfalls and grasses) enhanced soil nutrient content, contributed to continuous nutrient cycling in the exclosures over years (Mekuria et al, 2007), and improved soil physicochemical properties and the local environment (Yakob et al, 2022). Consequently, SOC and soil total nitrogen stocks in the older exclosure (Abine Germama‐Gallo Hiraphe) improved significantly as compared to its adjacent grazing land.…”

Climate change and land-use change impacts on future availability of forage grass species for Ethiopian dairy systems

“…The Amhara region is topographically divided into the northern and eastern highlands at > 1500 m asl and the western and southern lowlands between 500-1500 m asl. Areas above 2300 m asl fall within the Dega climatic zone, those between 1500-2300 m asl within the Woina Dega climatic zone, and areas below 1500 m asl fall within the Kolla or hot climatic zones 45 . The annual mean temperature for most parts of the region is 15-21 °C; average rainfall ranges from 850 to 1485 mm with the highest rainfall occurring during the summer season (mid-June and ends in early September) but rains also occur from March-May 47 .…”

“…The region has two altitude extremes: the Tekeze Gorge, 550 m asl and the Kisad Gudo peak at 3, 935 m asl. The climate is characterized as Kolla (semi-arid) 39%; Woina dega (subtropical) 49% and Dega (temperate) 12% 45 ; the average rainfall is between 450-980 mm. The dominant soil texture type is sandy loam, and all areas are in the moderate runoff hydrological zone 46 (Suppl.…”

“…SNNP has an elevation of 367-4207 m above sea level. About 56% of the total area of the region is found < 1500 m elevation, and is mostly classed as very hot lowland (Kolla) while the remaining 44% is found in the temperate climatic zone 45 . The annual rainfall of the region ranges from 500 to 2200 mm, with intensity, duration and amount all increasing from south to northeast and northwest; mean annual temperature of the region ranges from 15 to 30 °C.…”