•Agroforestry land topsoil and subsoil organic carbon and nitrogen stocks were equivalent with that of natural forest.•Cropland has much lower soil organic carbon and nitrogen stocks when compared to ...both forest and agroforestry.•Converting both forest and agroforestry to cropland have stimulated soil organic carbon and nitrogen loss from the soil.
The evergreen forests of southwest Ethiopia are important for soil fertility sustenance and climate change mitigation. However, the increasing human population and expansion of agricultural land have led to deforestation. We determine the effect of deforestation on soil fertility, soil carbon and nitrogen stocks and hypothesize that tropical forests and agroforestry have similar characteristics, in contrast to the deforested areas used as cropland. Hence, soil samples (n=360) have been taken from the natural forest, agroforestry and croplands at four depths (0–20cm, 20–40cm, 40–60cm and 60–80cm) in three altitudinal belts. The topsoil and subsoil physico-chemical characteristics, pH, organic carbon, total nitrogen, available phosphorus, exchangeable calcium, magnesium, cation exchange capacity and exchangeable base cations were significantly higher in both the forest and agroforestry than in croplands, at all elevation zones. Soil organic carbon and nitrogen stocks in soil under forest are similar to those under agroforestry at all elevation zones (0–20cm, 20–40cm, 40–60cm and 60–80cm soil depths). However, soil organic carbon and nitrogen stocks in soil under both forest and agroforestry were significantly different from cropland in all elevation zones at all depths except 60–80cm. The highest total soil organic carbon stocks were recorded in the forest (412Mgha−1 at the FH site and 320Mgha−1 at the FL site) and agroforestry (357Mgha−1 at the DM site, 397Mgha−1 at the ZH site and 363 Mg ha−1 at the ZM site). The total organic carbon loss due to the conversion of forest to cropland ranges from 3.3Mgha−1y−1 at the FL site to 8.0Mgha−1y−1 at the FH site. The soil organic carbon and nitrogen losses due to the conversion of forest to cropland are similar to the losses when converting agroforestry to cropland. The total carbon dioxide emission due to the conversion of forest to cropland ranges from 12Mgha−1y−1 at the FL site to 28Mgha−1y−1 at the FH site. Agroforestry has the potential to maintain soil fertility, and stores higher soil organic carbon and nitrogen in proportion to the natural forest. Therefore, it can be suggested that agroforestry has a similar capacity as Afromontane forests to sustain soil fertility as well as to regulate greenhouse gas emissions.
Soil erosion and conservation in Ethiopia Haregeweyn, Nigussie; Tsunekawa, Atsushi; Nyssen, Jan ...
Progress in physical geography,
12/2015, Letnik:
39, Številka:
6
Journal Article
Recenzirano
Odprti dostop
This paper reviews Ethiopia’s experience and research progress in past soil and water conservation (SWC) efforts and suggests possible solutions for improvement. Although indigenous SWC techniques ...date back to 400 BC, institutionalized SWC activity in Ethiopia became significant only after the 1970s. At least six national SWC-related programs have been initiated since the 1970s and their focus over time has shifted from food relief to land conservation and then to livelihoods. The overall current soil erosion rates are highly variable and large by international standards, and sheet, rill, and gully erosion are the dominant processes. The influence of human activities on the landscape has traditionally been deleterious, but this trend seems to have recently reversed in some parts of the country following the engagement of the communities in land management. The efficiency of SWC measures show mixed results that are influenced by the type of measures and the agro-ecology under which they were implemented; in general, the relative performance of the interventions is better in the drylands as compared with humid areas. Methodological limitations also occur when addressing the economic aspects related to benefits of ecosystem services and other externalities. Although farmers have shown an increased understanding of the soil erosion problem, SWC efforts face a host of barriers related to limited access to capital, limited benefits, land tenure insecurity, limited technology choices and technical support, and poor community participation. In general SWC research in Ethiopia is fragmented and not comprehensive, mainly because of a lack of participatory research, field observations, and adoptable methods to evaluate impacts. A potentially feasible approach to expand and sustain SWC programs is to attract benefits from global carbon markets. Moreover, a dedicated institution responsible for overseeing the research–extension linkage of SWC interventions of the country should be established.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, OILJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Due to overgrazing and agricultural intensification, gully erosion severely affects sub-Saharan countries; however, insufficient quantitative studies exist for this part of the world. This paper ...presents data on gully head retreat rates in Northern Ethiopia and relates these rates to gully and environmental characteristics. The monitoring of headcuts over one rainy season (2010) revealed that present-day retreat rates are low, with average annual linear (Rl), areal (Ra) and volumetric (Ve) retreat rates of 0.34my−1, 1.70m2y−1 and 5.2m3y−1, respectively. These results express the positive effects of recent soil and water conservation practices on gully stabilization. Significantly higher values of Rl (up to 1.93my−1) occurred in the Vertisol areas affected by soil piping. When considering the medium- to long time scale (1–47years) using archival terrestrial (and aerial) photographs, headcut retreat rates proved to be significantly higher than those in the short term. The averages for Rl, Ra and Ve are 3.8my−1, 31.5m2y−1 and 47.7m3y−1, respectively. Retreat rates are up to 10 times higher after road construction. For the medium to long term, headcut retreat rates were positively related to the catchment area (A). A power relationship that best describes the relation between Ve and A is Ve=0.53A0.31 (r2=0.27, n=18). Compared to other areas worldwide, regressive erosion has been rapid in Ethiopia as a result of the degraded and steep landscape combined with erosive rains and the occurrence of Vertisols. In Vertisols, headcut retreat is controlled by soil piping. Because no adequate techniques exist to control gully initiation and development in Vertisols, alternative techniques should be developed that deactivate soil pipes.
► Quantitative analysis of gully head retreat rates in sub-Saharan Africa. ► Power relation between catchment area and headcut retreat rates. ► High headcut retreat rates on the medium- to long-term. ► Soil piping (in Vertisols) increase headcut retreat rates. ► Recent soil and water conservation measures decrease headcut retreat rates.
The geographical configuration of northwest Ethiopia has changed often and significantly during the previous four centuries, according to a meta-analysis of historical maps. Boundary lines of ...languages in use and of territorial control were reported on the Main Map. Sixty-six coeval historical maps depict the territorial control of Western Tigray, also known as Welkait and its surrounding districts. The area is specifically recorded as part of Tigray from 1707 to 1794, 1831 to 1886, and 1939 to 1941. From 1891 to 1909 and 1944 to 1990, it is labelled as being a part of Amhara or Gondar. Welkait is shown in other eras as either being autonomous or a component of a broader Mezaga lowland territory. The agreement of 32 ethnolinguistic maps of northern Ethiopia from the twentieth century sustains the post-1991 extent of the Tigray region in the districts located between the Tekeze River and the Sudanese border.
In Ethiopia, the current regional organisation is determined by ethnolinguistic demographics rather than the historical dominance of a group over that land.
In Western Tigray (north Ethiopia), there have been challenges with identity and territorial conquest.
Based on ancient maps, we drew the successive positions of the border between the western portions of Tigray and Amhara.
Territorial organisation varied strongly throughout the centuries, with most maps showing borders positioned south of the current boundary of the two regions.
According to the near consensus of 20th C. language maps, the present size of the Tigray Region matches the extent of the Tigrinya language in Ethiopia.
This map supports an approach where the resolution of territorial disputes reflects the ethnolinguistic makeup.
We analyze whether private sustainability standards can improve the economic benefits from less intensified semi-forest coffee production in southwestern Ethiopia. We compare garden and semi-forest ...coffee systems, including non-certified and Rainforest Alliance certified semi-forest coffee, and evaluate yields, returns to land, returns to labor and profits. We use original household- and plot-level survey from 454 households and 758 coffee plots derived from a household survey and Geographic Information Systems, and ordinary least squares and fixed effects regression models. We find that more intensified garden coffee plots bring about higher yields and returns to land than less intensified semi-forest coffee plots; and that Rainforest Alliance certification of semi-forest coffee leads to higher returns to land and labor, and profits than non-certified semi-forest and garden coffee, mainly by guaranteeing farmers a better price and not by improving yields. Findings imply that in southwestern Ethiopia coffee certification can support farmers' incentives for land-sharing between coffee production and semi-natural forest conservation.
•Static comparison of garden coffee, and certified and non-certified semi-forest coffee•OLS and fixed effects models to control for observed and unobserved heterogeneity•Higher economic benefits for garden coffee than for less intensified semi-forest coffee•Rainforest Alliance certification of semi-forest coffee results in higher returns and profits.•Rainforest Alliance certification supports incentives for land-sharing.
Understanding historical and present gully development is essential when addressing the causes and consequences of land degradation, especially in vulnerable dryland environments. For Northern ...Ethiopia, several studies exist on the severity of gully erosion, yet few have quantified gully development. In this study, gully network and volume development were quantified over the period 1963–2010 for an area of 123km2, representing the regional variability in environmental characteristics. Gully networks were mapped from small-scale aerial photographs and high-resolution satellite images. For the latter, visualizing Google Earth images in 3D proved to be very suitable to investigate gully erosion. From the changes in networks and volumes over the period 1963–2010, the occurrence of one cut-and-fill cycle is apparent. From a largely low-dynamic gully system in the 1960s, network expansion and increased erosion rates in the 1980s and 1990s caused the drainage density and volume to peak in 1994. The average gully density (Dtotal) was then 2.52kmkm−2 and the area-specific gully volume (Va) 60×103m3km−2. This coincides with soil losses by gully erosion (SLg) of 17.6tha−1y−1 over the period 1963–1994. By 2010, improved land management and the region-wide implementation of soil and water conservation measures caused 25% of the gully network to stabilize, resulting in a net infilling of the gully channels over the period 1994–2010. The study validates previous findings that land degradation by gullying was indeed severe in Northern Ethiopia in the second half of the 20th century, but also shows that when proper land management is applied, a gully can be transformed into a linear oasis, which increases the resistance of gullies to further erosion.
•Quantifying gully networks and volumes since 1963 in Northern Ethiopia•Presenting long-term erosion rates by gullying•Assessment of the importance of gullying in dryland environments•Discussing the environmental factors controlling gully development•Using remote sensing methods (including of Google Earth imagery)
Extensive catchment degradation throughout the Ethiopian Highlands induced by long‐term intensified land use, erosion‐prone topography, and climate causes substantial soil erosion that limits ...agricultural productivity and results in lake sedimentation. However, before taking soil conservation measures, management of the soil loss problem essentially needs catchment‐level modelling to estimate the geographic distribution of erosion hotspots. With the increasing availability of sediment and spatial data and development of physically based models, this study aims multisite calibration of Soil and Water Assessment Tool (SWAT) to map erosion hotspot areas and to assess the effect of well‐known land management alternatives in sediment reduction in the Lake Tana Basin. The SWAT simulations indicated that the goodness of fit between predicted and observed data was satisfactory for all gauge stations except for one, and the model performance was within acceptable evaluation ratings. Simulated average sediment yield (SY) for the period 2001–2016 at subbasin level varies from negligible to about 169 Mg ha−1 yr−1 (basin average 32 Mg ha−1 yr−1). High potential SY (>50 Mg ha−1 yr−1) was simulated for 23% of the subbasins in Megech, upper Rib, upper Gumara, and Gilgel Abay catchments due to steep slope topography, aggressive rainfall, croplands dominance, and low rock fragment cover. The differences in level of erosion risk among subbasins help to prioritize and target specific areas of the basin that need urgent soil conservation activities. Scenario analysis also showed that implementing stone bunds, Acacia decurrens‐based crop rotation, reforestation, and grass contour strips reduces the existing SY by 51–61% at basin level. The potential sediment production could reach tolerable levels by implementing stone bunds, tree‐based crop rotation, reforestation in steep slope areas, and grass contour strips on gentle slopes. Overall, the multisite calibration of SWAT model using the measured run‐off and sediment data produces reasonable results that may support decision makers and planners to implement relevant land management measures and thereby reduce the alarming problems of soil loss in the basin and sedimentation of Lake Tana.
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