Nutrient composition and short-term release from <Emphasis Type="Italic">Croton macrostachyus</Emphasis> Del. and <Emphasis Type="Italic">Millettia ferruginea</Emphasis> (Hochst.) Baker leaves

A field study was conducted to investigate the nutrient content of green and abscised leaves of Croton macrostachyus Del. and Millettia ferruginea (Hochst.) Baker and their decomposition to return these nutrients to the soil in the short-term. Green and abscised leaves were collected from trees of comparable size in Wondo Genet, Ethiopia, and were incorporated into litterbags to decompose for a period of 12 weeks. Green leaves of C. macrostachyus had significantly higher nutrient concentrations than those of M. ferruginea. In both species, green leaves had significantly higher (P<0.05) C, N and P and significantly lower (P<0.05) lignin and polyphenol concentrations than abscised leaves. Fifty percent of the biomass applied was lost during the first 7 weeks in C. macrostachyus, which was about 3 times faster than that of M. ferruginea. The half-lives of N and P were 5–8 weeks and 4–6 weeks, respectively, in C. macrostachyus; the corresponding values for M. ferruginea were 6–8 and about 22 weeks, respectively. Only 15.7% and 26.8% of green and abscised leaves of C. macrostachyus, respectively, were recovered after the 12 weeks of decomposition. The corresponding values were about 3.5-fold and 2.5-fold higher for M. ferruginea. Generally, leaves with higher initial lignin, polyphenol, lignin:N and C:N ratios had lower decomposition and mineralization rates. In both species, removal of leaf biomass before abscission (e.g. by pruning) could enhance both the quantity and rate of nutrient return to the soil.     

Growth of juvenile tilapia, Oreochromis niloticus L. from Lakes Zwai, Langeno and Chamo (Ethiopian rift valley) based on otolith microincrement analysis

Abstract – Age and growth of juvenile tilapia, Oreochromis niloticus , from Lakes Zwai, Langeno and Chamo (Ethiopia) were studied from microincrements in otoliths. Growth in length was best described by the Gompertz model. Average growth rate of the fish was most rapid in Lake Chamo (0.39 mm  ·  day⁻¹, 1.14%  ·  day⁻¹), intermediate in Lake Zwai (0.20 mm  ·  day⁻¹, 0.72%  ·  day⁻¹) and slowest in Lake Langeno (0.16 mm  ·  day⁻¹, 0.62%  ·  day⁻¹). Similarly, back-calculation from otolith increment widths gave growth rates of 0.28 to 0.43 mm  ·  day⁻¹, 0.15 to 0.32 mm  ·  day⁻¹ and 0.11 to 0.28 mm  ·  day⁻¹ for Chamo, Zwai and Langeno fish, respectively. In addition, Fulton's condition factor was largest for Chamo tilapia and smallest for Langeno tilapia; the difference between fish from Langeno and Zwai was small. Rapid growth of juvenile O. niloticus in Lake Chamo was attributed to warm temperature and better food quality. ^Note     

The characterization of Salmonella serovars isolated from apparently healthy slaughtered pigs at Addis Ababa abattoir, Ethiopia

We looked for Salmonella in all 278 apparently healthy pigs slaughtered between September 2004 and May 2005 at the only pig-slaughtering slaughterhouse in Addis Ababa, Ethiopia. We used standard methods and tested caecal contents, mesenteric lymph nodes, and carcass swabs from each pig (missing only one carcass swab). Of the 278 pigs, 120 (43%) were positive; of the 833 samples 173 (21%) were positive. Thirty-three percent of the isolates were multi-resistant (including 46/48 isolates of S. Hadar, but none of the 39 isolates of S. Eastbourne or of the 37 of S. Saintpaul). Resistance to streptomycin (32.4%), tetracycline (31.8%) and nitrofurantoin (27.2%) was relatively high. The most common pattern of MDR observed was to nitrofurantoin, streptomycin and tetracycline (Resistance type NitStrTet). Our results indicate that salmonellae are prevalent in pigs slaughtered at Addis Ababa abattoir and a large proportion of the isolates were multi-drug resistant.     

Village-based indigenous chicken production system in north-west Ethiopia

Surveys using both purposive and random sampling methods was carried out in four zones of north-west Ethiopia to describe the village-based poultry production systems and constraints in order to design future improvement and conservation strategies. The majority of the respondents were female (74.16%). This indicated that most of the time the women, whether in male-headed or female-headed households, are responsible for chicken rearing while the men are responsible for crop cultivation and other off-farm activities. About 99% of the respondents gave supplementary feeds to their chickens. Almost all farmers provided night shelter for their chickens, in part of the kitchen (1.36%), in the main house (39.07%), in hand-woven baskets (7.29%), in bamboo cages (1.51%) or in a separate shed purpose-made for chickens (50.77%). The major causes of death of chickens during the study were seasonal outbreaks of Newcastle disease (locally known as fengele) and predation. It is important to collect and conserve local poultry breeds before they are fully replaced by the so-called improved breeds. As most of the poultry production is managed by women, focusing on training and education of women will enable not only the improvement of poultry production but also family planning and the overall living standards of the family and the community.     

Historical landscape photographs for calibration of Landsat land use/cover in the northern Ethiopian highlands

The combined effects of erosive rains, steep slopes and human land use have caused severe land degradation in the Ethiopian Highlands for several thousand years, but since the 1970s, however, land rehabilitation programmes have been established to try to reverse deterioration. In order to characterize and quantify the transformations in the north Ethiopian Highlands, a study was carried out over 8884 km² of the Tigray Highlands of northern Ethiopia. Using Landsat Multispectral Scanner and later Thematic Mapper imagery (1972, 1984/1986 and 2000), historical terrestrial photographs (1974–1975) and fieldwork (2008), we prepared land use and cover maps. For assessing the use of the historical terrestrial photographs, Landsat images from 1972 were classified using two different methods, namely conventional change detection (image differencing) and ground truthing (using the historical photographs of 1974–1975). Results show that the use of terrestrial photographs is promising, as the classification accuracy based on this method (Kappa coefficient 0·54) is better than the classification accuracy of the method based on image differencing (Kappa coefficient 0·46). Major land use and cover changes indicate the following: (1) a gradual but significant decline in bare ground (32 per cent in 1972 to 8 per cent in 2000); (2) a significant increase of bushland (25 to 43 per cent) and total forest area (including eucalypt plantations, 2·6 to 6·3 per cent); and (3) creation of numerous lakes and ponds. The dominant change trajectory (27 per cent of the study area) indicates a gradual or recent vegetation increase. These changes can be linked to the population growth and the introduction of land rehabilitation initiatives, complemented by growing awareness of land holders. Copyright © 2012 John Wiley & Sons, Ltd.     

Variation of leaf esterases in some Ethiopian tetraploid wheat landraces

Summary Esterase isozymes of tetraploid wheat landraces originating from four localities in the central highlands of Ethiopia were studied using the horizontal starch gel electrophoresis. The landraces studied consisted of 60 Triticum turgidum L., one T. dicoccon Schrank, one T. polonicum L. and an improved local cultivar. One introduced durum cultivar was also included for comparison.A total of 12 esterase zymograms were detected in the landraces. Among these, the types C, A and G were found to be the most prevalent. The esterase isozymes exhibited high variation in the landraces. The esterase zymograms of the introduced durum cultivar and T. dicoccon differed from those of the landraces while the patterns attained in T. polonicum and the improved local cultivar were identical to those of the other landraces.The total number of bands detected was 10, of which 2 were rare, being displayed by only 1 pattern each. The band content of zymograms was in the range of 3–6 and the average was 4. The unique bands were observed in zymograms with both high and low prevalences in the landraces. Two zymograms, including zymogram C which had the highest frequency, occurred in all the localities. The high yielding landraces displayed 4 of the zymograms, one of which belonged to two of the zymograms with widest distribution.     

Soil property changes following conversion of acacia woodland into grazing and farmlands in the Rift Valley area of Ethiopia

Continued conversion of woodlands into grazing and farmland is seriously undermining the natural ecosystem of the dry and fragile Rift Valley areas of Ethiopia. This study investigated the effects of land‐use change on soil organic carbon (SOC), total nitrogen (N), pH, exchangeable bases, cation exchange capacity (CEC) and base saturation (per cent) in three adjacent land‐use types: controlled grazing, open‐grazing and farmland. A total of 81 soil samples were collected and analysed. Contents of SOC and total N decreased drastically in open‐grazing and farmland (p < 0·001), and were significantly higher in the top 0·2 m than in the subsurface soil layer. Compared with the controlled grazing, reductions in the contents of SOC and total N in the top 1 m soil layer were 22–30 and 19 per cent, respectively, due possibly to the decrease in plant biomass input into the soil and the fast decomposition of organic materials. Long‐term cultivation had significantly increased the concentration of exchangeable K. Exchangeable Na was high in the lower layers, while Mg was higher in the top surface soil. CEC also varied with soil depth (p = 0·016); it was higher in the topsoil than in the subsurface soil, which may be, among others, due to the differences in soil organic matter distribution with depth. Although these semi‐arid soils are known to have low organic carbon and CEC levels, the values from the current study area are critically low, and may indicate the further impoverishment of the soils under high agricultural and grazing pressures. Copyright © 2010 John Wiley & Sons, Ltd.     

EXCLOSURE LAND MANAGEMENT FOR RESTORATION OF THE SOILS IN DEGRADED COMMUNAL GRAZING LANDS IN NORTHERN ETHIOPIA

In the northern highlands of Ethiopia, establishment of exclosures to restore degraded communal grazing lands has been practiced for the past three decades. However, empirical data on the effectiveness of exclosures in restoring degraded soils are lacking. We investigated the influence of exclosure age on degree of restoration of degraded soil and identified easily measurable biophysical and management‐related factors that can be used to predict soil nutrient restoration. We selected replicated (n = 3) 5‐, 10‐, 15‐, and 20‐year‐old exclosures and paired each exclosure with samples from adjacent communal grazing lands. All exclosures showed higher total soil nitrogen (N), available phosphorus (P), and cation exchange capacity than the communal grazing lands. The differences varied between 2·4 (±0·61) and 6·9 (±1·85) Mg ha⁻¹ for the total N stock and from 17 (±3) to 39 (±7) kg ha⁻¹ for the available P stock. The differences in N and P increased with exclosure age. In exclosures, much of the variability in soil N (R² = 0·64) and P (R² = 0·71) stocks were explained by a combination of annual average precipitation, woody biomass, and exclosure age. Precipitation and vegetation canopy cover also explained much of the variability in soil N (R² = 0·74) and P (R² = 0·52) stocks in communal grazing lands. Converting degraded communal grazing lands into exclosures is a viable option to restore degraded soils. Our results also confirm that the possibility to predict the changes in soil nutrient content after exclosure establishment using regression models is based on field measurements. Copyright © 2011 John Wiley & Sons, Ltd.     

Valuing Natural Forest Resources: An Application of Contingent Valuation Method on Adaba-Dodola Forest Priority Area,Bale Mountains,Ethiopia

This research employs a contingent valuation method (CVM) to estimate the respondents' willingness to pay (WTP) to gain use and control rights to a natural forest resource at the Adaba-Dodola Forest Priority Area (ADFPA) in the Bale Mountains of Ethiopia. The analysis was based on data collected from 295 households residing in and around the forest resource. Both binary probit and ordered probit models were used to examine socioeconomic factors that determine the respondents' WTP to gain these rights. The estimated mean and median WTP were found to be ETB 24.41 (US$2.54) and ETB 22.14 (US$2.30) annually, respectively. Households with more members, have better exposure to education and training, perceive the need for forest conservation, are member of forest dwellers' association, and who are wealthier in terms of ownership of more cultivated land and livestock are willing to pay more; whereas those households characterized by earning better annual household income, those who got higher starting bid value, and those who live farther away from the prime forest resource are willing to pay less. This can be used to signal that there is a considerable non-market value attached to use and control rights to the natural forest. In particular, membership in official forest user groups has shown a strong and positive relationship with WTP in all the models employed. This implies the approach of participatory management using forest user groups is better both for the sustainability of the forest resource and the livelihoods of the people who depend upon it.     

New geoarchaeological investigations of the valley systems in the Aksum area of northern Ethiopia

Recent geoarchaeological investigations of the valley systems to the north and northeast of Aksum have revealed indications of a relatively recent alluvial sequence, probably within the last millennium. The implication is that both during and prior to the Aksumite Period, there was considerable landscape stability and resilience. This is reflected in the development of soils with vertic-like properties, which instead appear to be more like organic brown earths that gradually begin to aggrade through colluvial and alluvial additions. How much this is the result of sympathetic, long-term landscape management by the expanding population, and how much is related to underlying and longer-term climatic and vegetational trends is open to question at this stage. But in the last four to five centuries, the pace of alluvial aggradation appears to have increased markedly, and has deposited at least half of the sediment captured in the valley systems and lower slopes to the north of Aksum. This no doubt reflects a growing population and arable intensification.