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Hailemariam Meaza Diress Tsegaye Jan Nyssen 《Norsk geografisk tidsskrift. Norwegian journal of geography》2016,70(1):1-12
In the northern highlands of Ethiopia degraded hillsides have been allocated to landless farmers for tree planting since the mid-1990s. The authors assessed the effect of hillside plantations on the livelihoods of landless farmers in the eastern part of the Tigray Region by using transect walks, focus group discussions, and pretested questionnaires. A matched-pairs design was used to compare crop yields, livestock holdings per household, and household incomes to test the differences before and eight years after the intervention. In addition, regression analysis was used to capture variables influencing hillside management. The findings revealed that the plantations significantly increased crop yields, livestock holdings, and the household incomes of all beneficiaries. In addition, tree planting on degraded hillsides had a positive impact on the livelihoods of formerly landless farmers. However, moisture stress and free-ranging livestock were crucial problems. The findings are highly relevant in a conservation context because many existing or planned hillside allocations to landless farmers are located on degraded steep slopes that are unsuitable for crop production. Thus, replicating the practice to other areas with similar environment and problems would be worthwhile, although the management should focus on careful planning to avoid conflicts of interest between beneficiaries and non-beneficiaries. 相似文献
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On Tenerife, one of the Canary Islands, a series of clastic dikes and tubular vents is attributed to liquefaction of sediments during a high-intensity paleoearthquake. Geotechnical, geological, tectonic, and mineralogical investigations have been carried out to identify the soil composition and structure, as well as the geological processes operating in the area. Geochronological analysis has indicated an age ranging from 10,081±933 to 3490±473 years BP for the liquefaction features. The area in which these liquefaction features are found has undergone tectonic uplift and is affected by two faults. One of these faults was responsible for displacing the Holocene materials. The paleoearthquake responsible for this liquefaction has been analysed in terms of its peak ground acceleration (pga) and magnitude by back calculation analysis based on the cyclic stress and Ishihara methods. A range of 0.22–0.35g was obtained for the pga, with the value of 0.30g being selected as most representative. From this, an earthquake-modified Mercalli intensity of IMM=IX was estimated for the liquefaction site. The magnitude-bound method and energy-based approaches were used to determine the magnitude of the paleoearthquake, providing a moment magnitude M in the range of 6.4–7.2; M=6.8 is taken as the representative figure. 相似文献
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Thermochemically induced transformations in Al-smectites: A Spanish natural analogue of the bentonite barrier behaviour in a radwaste disposal 总被引：1，自引：0，他引：1
L. Prez del Villar A. Delgado E. Reyes M. Pelayo J.M. Fernndez-Soler J.S. Czar M. Tsige A.J. Quejido 《Applied Geochemistry》2005,20(12):2252-2282
The thermal effect induced by the Morrón de Mateo volcanic dome (Cabo de Gata volcanic region, Spain) on the adjacent bentonitised tuffaceous beds has been studied as a natural analogue of the thermal behaviour of the bentonite-engineered barrier of a geological radwaste repository. These bentonites consist mainly of Fe-rich smectites and were formed in equilibrium with seawater at temperatures between 75 and 95 °C, according to the δ18O and δD values. In contrast, bentonites from other localities in the region consist mainly of Al-smectites, formed in equilibrium with meteoric water below 25 °C.This investigation is focussed on the detection of the chemical differences between smectites from proximal and distal zones to the dome, as well as to test whether the temperatures calculated based on the O and H isotopic values correspond to their formation or transformation. The initial hypothesis was that the chosen smectites could be formed under marine conditions, being later transformed and isotopically re-equilibrated as a result of the intrusion. To check this hypothesis, a detailed mineralogical, chemical, geochemical and isotopic study has been performed on the smectitised tuffaceous materials and the overlaying biocalcarenites outcropping near and far from the dome.The results show that distal smectites are dioctahedral Al-smectites, similar to those from other deposits in the region, while proximal smectites are Fe- and Mg-rich smectites, showing two evolutionary trends on a Fe–Mg–Al ternary diagram. Similar features are observed when their structural formulae are plotted on the muscovite–celadonite–pyrophylite diagram. Thus, they plot in the smectite domain with interlayer charge less than 1, which is mainly due to octahedral substitution for distal smectites, while for proximal ones it is caused by both octahedral and tetrahedral substitutions. In this ternary diagram, the domains of both proximal and distal smectites are partially overlapped. The coexistence of di- and trioctahedral smectites was only detected in one proximal sample. Further, proximal biocalcarenites are enriched in Fe-rich dolomite in relation to the distal ones.The 87Sr/86Sr and δ13C values in carbonates and δD in smectites indicate equilibrium with seawater. In contrast, δ18O values of carbonates and smectites indicate that they were transformed and re-equilibrated between 40 and 90 °C, and between 55 and 66 °C, respectively, independently of their location with respect to the dome.These data suggest that the transformation of calcite into Mg–Fe-carbonates and the occurrence of Fe- and Mg-rich smectites near to the dome resulted from a chemically induced process at similar temperatures. The compositional differences among samples suggests that Fe, Mg and minor Mn were supplied by a contaminant plume originated from the dome, migrating through the sediments and becoming more diluted away from the source. The absence of a well-defined thermal gradient in the system could be due to the small size, semi-closed and shallow character of the basin, as well as to its high underlying volcanic activity.Finally, the results are discussed in terms of analogue processes that can be expected in the bentonite barrier of a radwaste geological repository. 相似文献
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Impacts of artisanal gold mining systems on soil and woody vegetation in the semi‐arid environment of northern Ethiopia 
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下载免费PDF全文 Hailemariam Meaza Mushir Ali Zbelo Tesfamariam Niguse Abebe 《Singapore journal of tropical geography》2017,38(3):386-401
Gold mining is a tremendously important economic activity in rural districts of Ethiopia. We assessed the impacts of artisanal gold mining on soil and woody vegetation in northern Ethiopia. Estimation of soil loss, plant inventory, group discussions and transect studies were used to address the research questions. We employed t‐test to compare woody species and soil loss between mined and unmined sites. Moreover, we ran one‐way ANOVA to compare the average volume of soil loss among the mining sites. The study shows that gold mining removed colossal volumes of soil from the mining landscape with a significant difference among gold mining sites (P ≤ 0.05). Soil loss between the mined and unmined sites was also significant (P ≤ 0.05). Moreover, gold mining destroyed massive tracts of vegetation. Woody species encountered at plot level decreased from artisanal gold mined to unmined sites (P ≤ 0.05). Moreover, dead trees and exposed tree roots were higher in mined than the unmined areas (P ≤ 0.05). This discouraged regeneration and recruitment of woody vegetation. To conclude, gold mining system converted vegetated sites and farmlands into dysfunctional landscape. Therefore, we suggest that combined rehabilitation efforts are required to overcome the challenges of artisanal gold mining on sustainable land management in northern Ethiopia. 相似文献
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Hailemariam Meaza Amaury Frankl Jean Poesen Amanuel Zenebe Veerle Van Eetvelde Biadgilgn Demissie 《水文科学杂志》2018,63(6):957-977
Marginal grabens are major development corridors in Ethiopia, and need to be understood for proper assessment of the hydrological budget. This study investigates the water balance of the Aba’ala graben (553 km2) in the period 2015–2016 under the challenge of data scarcity. We measured the rainfall and river discharge in order to analyse the runoff components of the graben. The rainfall volume in the Aba’ala graben showed erratic behaviour, which led to rapid flood runoff of the major river into the graben bottom. The average annual inflow and outflow of the graben bottom for the period 2015–2016 amounted to 364 and 254 hm3, respectively. However, flood runoff and evapotranspiration had a marked effect on water availability. Water storage took 36% of the water inflow into the graben bottom. Sustainable water management could reduce the temporal variation of the water storage in Aba’ala graben. 相似文献
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