Rift Valley Escarpment Research Articles

The Landslide Threat Evaluation and Zoning in The Birbir Mariam District, Gamo Highlands, Ethiopia Great Rift Valley Escarpment Using Slope Susceptibility Analysis and Geospatial Techniques

The current research focuses on landslide assessment and hazard zonation in the Birbir Mariam district of the Gamo Highlands. The study examined landslide causative factors and used the slope susceptibility evaluation parameter to create a landslide hazard zonation covering an area of 110 square kilometers. The landslide hazard zonation was classified using facet-wise observation. As a result, the intrinsic and external causal parameters of score schemes have been held responsible for slope instability. Inherent causative elements consist of slope geometry, slope material (rock or soil), structural discontinuities, land use or land cover, and groundwater conditions. Rainfall and human interest have seemed like external elements. The intrinsic and external triggering elements for every facet (a total of 106) were rated for their contribution to slope instability. Finally, an evaluated landslide hazard value was calculated and classified into three landslide hazard classes. According to the findings, the area has a high hazard zone of 18.87 percent (20.76 km2), a moderate hazard zone of 54.72 percent (60.19 km2), and a low hazard zone of 26.41 percent (29.05 km2). The methodology employed in this investigation, as well as the resulting landslip susceptibility zonation map, were both reliable and applicable to other places with similar geology and topographic circumstances. 
 Keywords: Landslide evaluation, Slope stability, Landslide, Hazard zonation, Ethiopia

Modeling and prediction of effects of land use change in an agroforestry dominated southeastern Rift-Valley escarpment of Ethiopia

Through the increased use of innovation, human population has been growing rapidly in its ability to derive resources from the environment. Predicting how land use/cover (LUC) changes affect regions and the society requires a good understanding of the dynamic human-environment interactions associated with land use change. This article addresses the future spatial distribution of land use and the impacts that ongoing LUC change have on the ecosystems of Gedeo-Abaya landscape. The actual LUC maps of 2000 and 2015 reference years together with natural and socioeconomic indicators were used in a combined Markov–CA model with GIS technology to simulate and forecast the changes in 2025 and 2035. Our prediction processes shows among the indicators used, distance to the nearest road and slope have more significant effects on the transition potential maps followed by elevation. Area based prediction change generally shows significant increase in agroforestry, cultivation land, and wetland/marshes LUC classes, while most natural vegetation classes, particularly woodland/shrubland (−29.8%), and grazing land (−5.7%) show significant reduction from 2015 to 2035. The present and forecasted trend of LUC changes has visible environmental and socioeconomic impacts, particularly on woodland ecosystems and on the well-being of (agro)pastoral communities in the downstream. Whilst, the betterment of the upstream study region strongly depends on the continuity with the current government landscape restoration policy as well as on the permanence of farmers current environmental friendly land management practices. Forecasting LUC changes in the study landscape offers the possibility that unwanted changes are prevented through proper and timely interventions.

REGREENING OF THE NORTHERN ETHIOPIAN MOUNTAINS: EFFECTS ON FLOODING AND ON WATER BALANCE


 
 
 The hydro-geomorphology of mountain catchments is mainly determined by vegetation cover. This study was carried out to analyse the impact of vegetation cover dynamics on flooding and water balance in 11 steep (0.27-0.65 m m-1) catchments of the western Rift Valley escarpment of Northern Ethiopia, an area that experienced severe deforestation and degradation until the first half of the 1980s and considerable reforestation thereafter. Land cover change analysis was carried out using aerial photos (1936,1965 and 1986) and Google Earth imaging (2005 and 2014). Peak discharge heights of 332 events and the median diameter of the 10 coarsest bedload particles (Max10) moved in each event in three rainy seasons (2012-2014) were monitored. The result indicates a strong reduction in flooding (R2 = 0.85, P<0.01) and bedload sediment supply (R2 = 0.58, P<0.05) with increasing vegetation cover. Overall, this study demonstrates that in reforesting steep tropical mountain catchments, magnitude of flooding, water balance and bedload movement is strongly determined by vegetation cover dynamics.
 KEY WORDS: HYDRO-GEOMORPHOLOGY, REFORESTATION, CREST STAGE, PEAK DISCHARGE, BEDLOAD
 
 

Regreening of The Northern Ethiopian Mountains: Effects on Flooding and on Water Balance

The hydro-geomorphology of mountain catchments is mainly determined by vegetation cover. This study was carried out to analyse the impact of vegetation cover dynamics on flooding and water balance in 11 steep (0.27-0.65 mm-1) catchments of the western Rift Valley escarpment of Northern Ethiopia, an area that experienced severe deforestation and degradation until the first half of the 1980s and considerable reforestation thereafter. Land cover change analysis was carried out using aerial photos (1936,1965 and 1986) and Google Earth imaging (2005 and 2014). Peak discharge heights of 332 events and the median diameter of the 10 coarsest bedload particles (Max10) moved in each event in three rainy seasons (2012-2014) were monitored. The result indicates a strong reduction in flooding (R2 = 0.85, P<0.01) and bedload sediment supply (R2 = 0.58, P<0.05) with increasing vegetation cover. Overall, this study demonstrates that in reforesting steep tropical mountain catchments, magnitude of flooding, water balance and bedload movement is strongly determined by vegetation cover dynamics.

Soil management and soil properties in a Kenyan smallholder irrigation system on naturally low-fertile soils

In this study we examine the impact of soil management practices on soil properties in a landscape with naturally relatively poor soils on and below the dry slopes of a Rift Valley escarpment in Kenya that have been dominated by extensive smallholder investments in canal irrigation over the last 300 years. We show that farmers in the area have been able to keep up agricultural production in the face of growing population. The actual practices of soil management at one moment in time appear to be of minor importance to soil improvement, as indicated by the low correlation between Soil Management Index (SMI) and soil chemical data. However, cultivation triggers a process of slow soil improvement manifested by a positive correlation between nutrient levels and duration of irrigated cultivation and soil management, which likely explains farmers' confidence in soil productivity. However, we also identify sodicity as a risk connected to intensified irrigation in the area. Finally, we stress the need for further studies integrating investigations of local irrigation and soil management with soil and water quality analyses. These will be crucial to shape sustainable place-based and farmer-led solutions for African agricultural growth.

Land cover changes as impacted by spatio-temporal rainfall variability along the Ethiopian Rift Valley escarpment

Magnitudes of land cover changes nowadays can be assessed properly, but their driving forces are subject to many discussions. Next to the accepted role of human influence, the impact of natural climate variability is often neglected. In this paper, the impact of rainfall variability on land cover changes (LCC) is investigated for the western escarpment of the Raya Graben along the northern Ethiopian Rift Valley. First, LCC between 2000 and 2014 were analysed at specific time steps using Landsat imagery. Based on the obtained LCC maps, the link was set with rainfall variability, obtained by means of the satellite-derived rainfall estimates (RFEs) from NOAA-CPC. After a correction by the incorporation of local meteorological station data, these estimates prove to be good estimators for the actual amount of precipitation (ρ RFE1.0 = 0.85, p = 0.00, n = 126; ρ RFE2.0 = 0.76, p = 0.00, n = 934). By performing several linear regression analyses, a significant positive relationship between the precipitation parameter DIFF 5Y (i.e. the at-RFE pixel scale difference in five-year average annual precipitation for the two periods preceding the land cover maps) and the changes in the woody vegetation cover was found (standardised regression coefficient β = 0.23, p = 0.02, n = 108). Despite the dominance of direct human impact, further greening of the study area can be expected for the future concomitantly to a wetter climate, if all other factors remain constant.

Sediment flux dynamics as fingerprints of catchment rehabilitation: The case of western Rift Valley escarpment of northern Ethiopia

Variability in supply and entrainment of stream bedload particles during storm events is an important hydrogeomorphologic response of steep mountain streams to land management in their catchments. Because of difficulties in its measurement and absence of accurate measuring equipment, bedload transport in mountain streams is, however, poorly understood. This study focuses on analyzing bedload supply and entrainment in 11 streams of sloping (27–65%) catchments (0.4–25km2) in northern Ethiopia, which have experienced severe deforestation and degradation processes until the first half of the 1980s and considerable rehabilitation thereafter. Field measurements of the median diameter of the 10 coarsest bedload particles (Max10) moved in each event (n=332) and stream bed particle sampling were carried out in three rainy seasons (2012–2014). Event peak discharges were calculated from daily measurements by 11 crest stage gauges using Manning's equation. Percentages of land cover classes in the catchments were detected from high resolution (0.6m) Google Earth imagery (1 February, 2014). Morphometric characteristics of the catchments were computed from an ASTER digital elevation model and topographic maps. Hydraulic competence analysis for entrainment of the average Max10 was carried out using peak discharge, stream power, and critical shear stress approaches. The supply of Max10 was positively related to scar density on the surrounding slopes (R2=0.50, p<0.05) and catchment area (R2=0.36, p<0.05) while negatively related with total forest cover (R2=0.63, p<0.05) or vegetation cover (R2=0.58, p<0.05). A multiple regression analysis showed that 98% of the variability in Max10 is explained by scar density and catchment area. Entrainment of Max10 was positively related to peak discharge (Qp) (R2=0.60, p<0.01), stream power (Ω) (R2=0.71, p<0.01), Strickler's roughness (Sn) (R2=0.86, p<0.01), and critical shear stress (τc) with reference to D50 (r50) (R2=0.96, p<0.01), and with reference to D84 (r84) (R2=0.93, p<0.01). The relationships between event Max10 and event Qp in each catchment were also used to extrapolate the peak discharges that would have prevailed in the first half of the 1980s, and the results showed huge reductions in peak discharges (p<0.01) as a result of the reforestation interventions. Overall, this study demonstrates that (i) the supply of bedload in steep tropical mountains is determined negatively by forest or vegetation cover and positively by the presence of scar networks in the sloping parts of the catchments and catchment size; (ii) entrainment of the coarsest bedload particles is determined positively by peak discharge, stream power, stream bed roughness, and most strongly by critical shear stress; and (iii) in steep mountain streams where direct measurement of bedload movement is difficult, yet simple in situ measurement of the coarsest bedload particles (Max10) supplied and entrained in each event helps for understanding the dynamics of sediment flux in relation to catchment rehabilitation.

Determinants of peak discharge in steep mountain catchments – Case of the Rift Valley escarpment of Northern Ethiopia

Peak discharge is an important hydrological parameter of mountain torrents. However, due to the flashy and destructive nature of their stream flows, it is usually difficult to understand the hydrological behavior of steep mountain catchments through direct measurements of discharges. In this study, 332 daily peak discharge events from 11 steep (0.27–0.65 m m−1) catchments (0.4–25 km2) were measured in three rainy seasons (2012–2014) with the objective of analyzing runoff response of steep mountain catchments in the western Rift Valley escarpment of Northern Ethiopia. Seven rain gauges were installed at different altitudes (1623–2851 m a.s.l.) in and nearby the catchments. Event peak discharges were calculated using the Manning’s equation from daily measurements of maximum discharge height at 11 crest stage gauges. Percentages of land cover classes were detected from high resolution (0.6 m) Google Earth Imagery (February 1, 2014). Morphometric characteristics of the catchments were computed both from ASTER digital elevation model (DEM) and topographic maps. Correlation analysis between average daily precipitation (Pd) and peak discharge (Qp) showed strong positive relation (R2 = 0.32–0.94, P < 0.05) in all the catchments. Catchment-specific peak discharge coefficient (Cp) showed a strong decreasing relation with vegetation cover (R2 = 0.85, P < 0.01), relative distance of vegetation cover from the thalweg (R2 = 0.55, P < 0.01), combined index of vegetation cover and its relative distance from the thalweg (R2 = 0.76, P < 0.01), catchment length (R2 = 0.37, P < 0.05) and time of concentration (R2 = 0.43, P < 0.05). It was correlated positively with catchment slope gradient (R2 = 0.37, P < 0.05) and index of vegetation distribution (R2 = 0.45, P < 0.05). A stepwise multiple regression analysis revealed that 99% (P < 0.01) of the variability of catchment-specific peak discharge coefficient in the catchments can be predicted by vegetation cover and infiltration number. Overall, this study demonstrates that in reforesting steep mountain catchments, where direct measurement of discharges using the conventional methods is difficult due to the flashy and destructive nature of the stream flows, hydrological variability can easily be understood using simple measurements of daily precipitation and peak discharges. Further, runoff response is determined by precipitation event and strongly by percentage of vegetation cover and its strategic location: farther from the thalweg in the sloping sides of the catchments.

Biomass and soil carbon stocks of indigenous agroforestry systems on the south-eastern Rift Valley escarpment, Ethiopia

Background and Aims Biomass carbon (C) and soil organic carbon (SOC) stocks in three indigenous agroforestry (AF) systems (Enset [Ensete ventricosum, Musaceae], Enset-Coffee and Fruit-Coffee) practiced on the Rift Valley escarpment of Ethiopia are presented and evaluated. These unique AF systems are characterised by a high proportion and diversity of trees.

Catchment Rehabilitation and Hydro‐geomorphic Characteristics of Mountain Streams in the Western Rift Valley Escarpment of Northern Ethiopia

AbstractThe catchments in the western Rift Valley escarpment of northern Ethiopia are highly responsive in terms of hydro‐geomorphic changes. With deforestation, dense gully and scar networks had developed by the 1980s on the escarpment between the towns of Alamata and Korem, transporting huge amounts of runoff and sediment down to the fertile and densely populated Raya Valley. To reverse this problem, catchment‐scale rehabilitation activities were initiated in the mid‐1980s. In this study, we examine the major hydro‐geomorphic response of streams after catchment rehabilitation. Scar networks in 20 adjacent catchments were mapped on Google Earth imagery of 2005, and their density was explained in terms of its corresponding Normalized Difference Vegetation Index and slope gradient. Soil and water conservation measures and vegetation recovery have reduced discharge and sediment flow which in turn resulted in various hydro‐geomorphic changes. In a multiple regression analysis, scar density was negatively related with Normalized Difference Vegetation Index and positively with average gradient of very steep slopes (r2 = 0·53, p &lt; 0·01, n = 20). The size and amount of sediment supply to streams decreased, and various channel adjustments occurred. Notably, previously braided streams have changed to single thread streams, lateral bars have been stabilized and stream channels are narrowing and incising. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Wildlife Conservation Leases are Considerable Conservation Options outside Protected Areas: The Kitengela - Nairobi National Park Wildlife Conservation Lease Program

. It is one of Kenya’s most visited Parks, located at the boundary of Nairobi, Kenya’s capital city. The NNP is fenced on the northern boundary to separate it from the Nairobi metropolis as well as to the eastern and western boundaries. The southern boundary which lies along the Empakasi River is open and adjoins the Kitengela, an area of 390 km 2 . Kitengela is one of the three triangles that comprise the larger wildlife dispersal area for NNP called the Athi-Kaputiei Plains (AKP), an area of 2200 km 2 . The rangelands of AKP are private land, majority of it owned by the pastoral Maasai, who have historically shared their land with wildlife [1]. The Nairobi National Park together with AKP comprise the AthiKaputiei Ecosystem (AKE) whose limits are bounded by the Rift Valley escarpment to the west, the Nairobi-Mombasa railway line to the east and the Konza-Magadi railway line to the south (Figure 1). The area is dry and the annual rainfall increases from 500 mm in the southeast to 800 mm in the northwest. The AKE ecosystem support 24 species of resident large mammals, but the park itself is too small to support viable populations of most of the large herbivores. Consequently, some herbivore species such as the wildebeest (ConnochaetestaurinusBurchell), zebra (EquusBurchelliGray) and eland (Taurotragusoryx) use the park as a dry season (June-November) refuge and disperse to the private land in the AKP in the wet season (MarchMay) for forage and calving. The AKP is the traditional home to the Kaputiei Maasai pastoralists, whose main livelihood is livestock production, keeping cattle, sheep and goats in the vast plains. When NNP was established in 1946, the Kitengela plains were declared but never formally gazzetted as a wildlife conservation area. In the mid-1970s, land in the AKP was privatized with the creation of the Kitengela Group Ranch covering an area of 18,292 ha (45,200 acres) and collectively owned by 215 members of the Maasai community. In 1988, the Kitengela Group Ranch was sub-divided into individual plots of roughly 215 acres allocated to each of the 250 members. The process of land privatization and sub-division followed in the entire Kajiado County as the Maasai landowners passed on plots to several inheritors, and increased land sales mostly to non-Maasai’s interested in agriculture [2]. The land sales, alongside rapid increase in

Litterfall production and associated carbon and nitrogen fluxes of seven woody species grown in indigenous agroforestry systems in the south-eastern Rift Valley escarpment of Ethiopia

We compared the litterfall production and associated carbon (C) and nitrogen (N) fluxes for seven woody species grown in three agroforestry systems practiced on the slopes of the south eastern Rift Valley escarpment of Ethiopia. Five of the species were native (Coffea arabica L., Cordia africana Lam., Croton macrostachyus Del., Erythrina brucei Schweinf. and Millettia ferruginea (Hochst.) Bak) and two were non-native fruit tree species (Mangifera indica L. and Persea americana Mill.). Together, these species accounted 85 % or more of the crown area of each agroforestry system: the Enset system (occurring at 2,100–2,400 m asl), the Enset-Coffee system (1,900–2,200 m asl), and the Fruit-Coffee system (1,500–1,900 m asl). Enset or false banana [Ensete ventricosum (Welw.) Cheesman] is a staple food crop in this region of Ethiopia and coffee and fruit trees are grown as cash crops. Monthly litterfall was collected from 4 to 6 trees of each species during 2010 and dry mass, carbon and nitrogen contents determined. The annual litterfall production per unit area of crown decreased in the order: C. macrostachyus (1,014 g m−2), E. brucei (929), C. africana (917), P. americana (809), M. indica (807), C. arabica (446) and M. ferruginea (362). The simple linear regression equation using breast height diameter explained 95 % of the variation in the litterfall production of M. ferruginea, but only 55 % for C. africana. The annual litterfall production of the seven species combined per unit area of land was the highest for the Fruit-Coffee system (average 12,938 kg ha−1), followed by the Enset-Coffee system (10,187) and the Enset system (7,430). The associated annual C fluxes (kg ha−1) were 5,145 (Fruit-Coffee system), 3,928 (Enset-Coffee system) and 2,803 (Enset system), and corresponding N fluxes 278 (kg ha−1), 257 and 190. The combined litterfall production of the seven species in our study was higher than has been reported for other agroforestry systems and tropical forests.

Erratum to: Allometric equations for estimating aboveground biomass of Coffea arabica L. grown in the Rift Valley escarpment of Ethiopia

Coffee, Coffea arabica L., which is native to Ethiopia, is the world’s most widely traded tropical agricultural commodity. While much is known about the productivity and management of coffee for coffee beans little attention has been given to the plants overall biomass production and carbon sequestration. The objective of this study was to develop and evaluate allometric equations for estimating the aboveground biomass of C. arabica plants growing in indigenous agroforestry system in the Rift Valley escarpment of south-eastern Ethiopia. Coffee plays an important role in providing income and in sustaining these productive systems. Biomass harvesting of 31 plants with 54 stems was carried out in a 40 km2 area varying in elevation from 1,500 to 1,900 m. The stem accounted for most (56 %) of plant biomass, followed by branches (39 %) and twigs plus foliage (5 %). Plant mean biomass was 22.9 ± 15.8 kg. Power equations using stem diameter measured at either 40 cm (d 40) or at breast height (d, 1.3 m) with and without stem height (h) were evaluated. The square power equation, $$ Y \; = \; b_{ 1} d_{ 40}^{ 2} $$ , was found to be the best (highest ranked using goodness-of-fit statistics) for predicting total and component biomass. The reliability of the prediction decreased in the order: stem > branches > twigs plus foliage. A cross-validation procedure showed that equation parameterization was stable and coefficients reliable. Our parameterized square power equation for total aboveground biomass was also found to be better than the equations parameterized by Hairiah et al. (Carbon stocks of tropical land use systems as part of the global C balance: effects of forest conversion and options for clean development activities, International Centre for Research in Agroforestry, Bogor, 2001) and Segura et al. (Agroforest Syst 68:143–150, 2006) for C. arabica grown in agroforestry systems, confirming the importance of parameterization of allometric equations with site specific data when possible.

Allometric equations for estimating aboveground biomass of Coffea arabica L. grown in the Rift Valley escarpment of Ethiopia

Allometric equations for estimating aboveground biomass of Coffea arabica L. grown in the Rift Valley escarpment of Ethiopia

Allometric equations for biomass estimation of Enset (Ensete ventricosum) grown in indigenous agroforestry systems in the Rift Valley escarpment of southern-eastern Ethiopia

Enset (Ensete ventricosum), commonly known as false banana, is a large thick, single-stemmed, perennial herbaceous banana-like plant growing in the wild of sub-Sahara Africa, Madagascar and parts of Asia. In Ethiopia it has been domesticated and serves as a food plant. While the productivity and management of enset for food (pseudostem and corm) has been studied, little attention has been given to total biomass production and associated carbon sequestration. The objective of this study was to develop and evaluate allometric models for estimating above and belowground biomass and organic matter contents of enset grown in indigenous agroforestry systems in Rift Valley escarpment of south-eastern Ethiopia. Biomass harvesting of 40 plants was carried out at altitudes from 1900 to 2400 m.a.s.l. The mean plant dry weight was 9.4 ± 0.84 kg and organic matter content 94 %. Pseudostem biomass accounted for highest (64 %) of total biomass, followed by corm (24 %) and foliage (12 %). Basal diameter (d 10) was the best predictor variable for total and all biomass components (Spearman r = 0.775–0.980, p < 0.01). The power model using d 10 and height (H) (Y = 0.0007d 10 2.571 H 0.101; R 2 = 0.91) was found to be the best performing model (highest ranking over six good-of-fit statistics) for predicting total biomass. Model performance decreased in the order pseudostem > corm > foliage biomass. The models presented can be used to accurately predict biomass and organic matter of enset in the agroforestry systems of Rift Valley escarpments Ethiopia.

Altitudinal variation and conservation priorities of vegetation along the Great Rift Valley escarpment, northern Ethiopia

Understanding plant species distribution patterns along environmental gradients is fundamental to managing ecosystems, particularly when habitats are fragmented due to intensive human land-use pressure. To assist management of the remaining vegetation of the Eastern Afromontane Biodiversity Hotspot, plant species richness and diversity patterns were analyzed along the main elevation gradient (1,000–2,760 m) of the Great Rift Valley escarpment in northern Ethiopia, using 29 plots established at 100-m elevation intervals. A total of 129 vascular plant species belonging to 59 families was recorded. Species richness and diversity showed a hump-shaped relationship with elevation, peaking at mid-elevation (1,900–2,200 m). Beta diversity values indicated medium species turnover along the elevation gradient and were lowest at mid-elevation. Elevation strongly partitioned the plant communities (r = 0.98; P < 0.001). Four plant communities were identified along the elevation gradient: Juniperus procera–Clutia lanceolata community (2,400–2,760 m), Abutilon longicuspe–Calpurnia aurea community (1,900–2,300 m), Dracaena ombet–Acacia etbaica community (1,400–1,800 m), and Acacia mellifera–Dobera glabra community (1,000–1,300 m). To optimize conservation of species and plant communities, it is recommended that a conservation corridor be established along the elevation gradient that includes all four plant communities. This strategy—in contrast to creating single isolated reserves in zones with high species richness—is necessary for the habitat protection of species with narrow elevational ranges, in particular the globally endangered Nubian dragon tree (Dracaena ombet).

Potential of indigenous multistrata agroforests for maintaining native floristic diversity in the south-eastern Rift Valley escarpment, Ethiopia

Most studies undertaken in the field of agroforestry have focussed on system design, soil fertility management, and system interactions. Less emphasis has been placed on biodiversity aspects. The aim of this study is to investigate the potential of indigenous, multistrata agroforests for maintaining native woody species diversity in the south-eastern Rift Valley escarpment, Ethiopia. A total of 60 farms, representing three agroforest types (enset-AF, enset-coffee-AF and fruit-coffee-AF), were randomly selected along altitudinal gradients. Enset (Ensete ventricosum) is a perennial, herbaceous monocarpic banana-like plant which serves as a food plant in Ethiopia. The three agroforests are results of the domestication of natural forests and intensification of the landuse systems centuries ago. Sample-based assessment protocols were employed to place sample quadrats and to measure all individuals in the quadrats. A total of 58 woody species, belonging to 49 genera and 30 families, was recorded. Of all woody species identified, 86% were native. The highest proportion of native woody species was recorded in enset-AF (92%), followed by enset-coffee-AF (89%) and fruit-coffee-AF (82%). Among native tree species, Millettia ferruginea and Cordia africana were the most widespread. In all, 22 native woody species were recorded as of interest for conservation, acccording to IUCN Red lists and local criteria. Among them, Pygeum africanum and Rhus glutinosa were categorised as vulnerable in the wild, and in need of conservation priority. The introduction of non-native fruit trees in agroforests can be a threat to maintenance of native woody species. Management strategies favoring enset and coffee will also put other native tree species at risk. A smaller number of native woody species was recorded in fruit-coffee-AF, but a higher mean basal area and stem number. The mean basal area and stem number ranged from 5.4 ± 0.5 to 11.7 ± 1.0 m2 ha−1 and 625 ± 84 to 1,505 ± 142 stems ha−1, respectively. Altitude explained 68 and 71% of the variation in species richness and abundance, respectively. Finally, it is concluded that recognition of the indigenous agroforestry system as an option for maintaining native woody species should be given more attention, to counteract the local threat of these species from the wild.

Taxonomic Changes and New Species of the Flightless GenusParepistaurusKarsch, 1896 (Orthoptera: Acrididae, Coptacridinae) from Mountainous East Africa

Two new species of the flightless genus Parepistaurus, occurring on high mountains of northern Tanzania, are described in this paper. P. hanangensis n. sp. is an inhabitant of the montane zone of Mt Hanang, a solitary volcano of northwestern Tanzania. P. uguenoensis n. sp, occurs in the North Pare Mts, a mountain range of the northern branch of the Eastern Arc chain. Both species have their closest relatives in species of adjacent situated mountain areas, as seen in their morphology and molecular phylogeny. Phylogenetic reconstructions were performed for three genes [16S rRNA gene, cytochrome oxidase subunit I (COI) and the histone gene H3], using different assumptions on sequence evolution. The closest relative of P. uguenoensis is P. deses from Mt Kilimanjaro, a geologically young volcano. The closest morphological and molecular relative of P. hanangensis is P. manyara, distributed along mountainous ranges of the rift-valley escarpment. The molecular relationship of the investigated taxa suggests that the subspecies of P. deses should receive species status.

Soils of the Main Ethiopian Rift Valley escarpment: A transect study

The mountainous environment of the Ethiopian highlands has a great variety of ecotopes and thus demands great flexibility in land management. Different climatic conditions and landscape positions induce different soil forming processes, leading to various soil types with specific risks and potentials. The present study portrays a soil sequence of the central section of the Main Ethiopian Rift Valley, from the footslopes of the eastern escarpment to the marginal volcano structures. Six profiles under natural vegetation are described for classification according to the USDA Soil Taxonomy and World Reference Base for Soil Resources classification systems, and special site characteristics are discussed. The Acacia savannah of the footslopes (1900 m a. s. l.) is characterized by Vertisols (Mazic Vertisols/Aridic Haplusterts), with often pronounced effects of seasonal waterlogging. All other soils are well-drained and reflect the general increase in rainfall with elevation and slope, causing a decline in topsoil pH and a change from cation-rich clay soils of the Podocarpus-dominated forest at 2300 m a. s. l. (Mollic Nitisols/Typic Palehumults) to strongly-leached Humic Umbrisols/Humic Dystrudepts of the Hagenia-dominated forest around 2600 m a. s. l. The highland savannah plain (2700 m a. s. l.) with a drier and cooler environment has typically Mollic Cambisols/Dystric Haplustepts, which are less leached and have a rather brownish colour. At 2900 m a. s. l., Niti-umbric Alisols/Andic Hapludalfs are found in the Hypericum forest at the midslopes of the marginal volcanoes receiving high rainfall, whereas soil development is at a more initial state in the Erica-dominated forest at 3200 m a. s. l. (Umbric Andosols/Alic Hapludands). Clay mineral composition is kaolinite-dominated for the upper five profiles, with a high proportion of poorly crystalline components in the upper savannah and the volcano upslopes. The lowermost profile probably has a polygenetic origin indicated by an abrupt change from a smectitic to a kaolinitic composition in the subsoil. Soil development on quite homogeneous bedrock appears essentially controlled by relief and climate, underlining the suitability of the region as a model area for in-depth gradient studies on ecosystem processes and land use.

A Bibliography of Karamoja, Uganda: Books and Articles Published in English

The Karamoja region of northeastern Uganda is bordered on the east by the Rift Valley escarpment that drops down into the Kenya territory of Turkana, on the north by the Sudan, on the south by the Mt. Elgon region, and on the west by the home territories of the Teso, Langi, and Acholi peoples. A large region of approximately 27,200 square kilometers, it is dominated by the huge semi-arid plains of its center, where rainfall is seasonal, unpredictable, and too often sparse. In the north and south and along the eastern escarpment the land becomes more forested and mountainous, and in the west the area of the Labwor people is better watered.