Local background concentrations of trace elements in soils: a case study in the Grand Duchy of Luxembourg

Background concentration values of trace elements were determined for soils in the southern part of the Grand Duchy of Luxembourg, which are developed on the Bituminous shale (BS), the so-called “Bifrons” shale, and the “Minette” (M) Fe-oolitic sandstone substrates. Sampling sites with minimal anthropogenic influence were selected, and soil profile samples were analysed for major and trace element contents. A clear distinction is seen between the trace element content of the soils developed on the Minette sandstone on the one hand and those developed on shales on the other hand. For the Minette soil samples, most elements are present in concentrations exceeding those reported in literature for soils developed upon sandstones, with, for example, values of up to 278 mg kg⁻¹ As (median value 123 mg kg⁻¹), 287 mg kg⁻¹ Cr (median value 126 mg kg⁻¹), and 95 mg kg⁻¹ Co (median value 33 mg kg⁻¹). In the shale soil samples, concentrations are generally lower except for Cu and Mo. These elements reach maxima of up to 66 mg kg⁻¹ Cu (median value 41 mg kg⁻¹) and 59 mg kg⁻¹ Mo (median value 26 mg kg⁻¹). The results confirm the importance of determining background concentrations locally.Bivariate analysis shows a linear relationship between Fe content and elements such as As, Co, and Ni for the Minette soils. No relationship is found between trace element concentrations and clay or organic carbon (OC) content, but this could be due to the limited variation of these factors among the studied soils. A reconnaissance study with regard to the availability of the trace elements in the Minette soil samples shows that these elements are quite immobile and hence of minimal threat to the ecosystem.     

Surface runoff and seed trapping efficiency of shrubs in a regenerating semiarid woodland in northern Ethiopia

In forest restoration areas in northern Ethiopia, natural regeneration of Olea europaea ssp. cuspidata only occurs under pioneer shrubs. To assess the impact of erosion on the spatial distribution of Olea recruits, secondary dispersal of olive seeds by surface runoff was determined in and near the micro-environment of two important pioneers (Acacia etbaica and Euclea racemosa). We hypothesized that (1) Olea seeds deposited under the protective crowns of shrubs are less likely to be lost by surface wash than seeds in the bare inter-plant areas and (2) that seeds in the latter are more prone to be translocated by runoff to microsites under shrubs than to open areas.     

Buffering capacity of cashew soils in South Eastern Tanzania

Abstract. Cashew soils of South Eastern Tanzania become acidified due to sulphur used for controlling powdery mildew disease ( Oidium anacardii Noack). The buffering capacity of surface and subsurface horizons of 35 soil profiles of major cashew growing areas –- the Makonde plateau, its piedmont and inland plains –- was studied. The buffering capacity of surface and subsurface horizons was strongly correlated with clay content and weakly with organic carbon content. In addition, it was only weakly correlated with total exchangeable bases and available P of the surface horizon, but strongly with soil pH, base saturation and cation exchange capacity of the clay fraction of the subsurface horizon. Highly weathered sandy soils, dominant on the Makonde plateau and common on the Piedmont, had the lowest buffering capacity. Soils from the inland plains had better buffering capacities as they are generally more clayey or are less weathered. The risk of severe acidification and of a decline in productivity of cashew and of food crops is highest on the Makonde plateau. Further development and dissemination of methods which can reduce the use of sulphur are required.     

Emerging food-borne parasites

Parasitic food-borne diseases are generally underrecognised, however they are becoming more common. Globalization of the food supply, increased international travel, increase of the population of highly susceptible persons, change in culinary habits, but also improved diagnostic tools and communication are some factors associated with the increased diagnosis of food-borne parasitic diseases worldwide. This paper reviews the most important emerging food-borne parasites, with emphasis on transmission routes. In a first part, waterborne parasites transmitted by contaminated food such as Cyclospora cayetanensis, Cryptosporidium and Giardia are discussed. Also human fasciolosis, of which the importance has only been recognised in the last decades, with total numbers of reported cases increasing from less than 3000 to 17 million, is looked at. Furthermore, fasciolopsiosis, an intestinal trematode of humans and pigs belongs to the waterborne parasites as well. A few parasites that may be transmitted through faecal contamination of foods and that have received renewed attention, such as Toxoplasma gondii, or that are (re-)emerging, such as Trypanosoma cruzi and Echinococcus spp., are briefly reviewed. In a second part, meat-borne parasite infections are reviewed. Humans get infected by eating raw or undercooked meat infected with cyst stages of these parasites. Meat inspection is the principal method applied in the control of Taenia spp. and Trichinella spp. However, it is often not very sensitive, frequently not practised, and not done for T. gondii and Sarcocystis spp. Meat of reptiles, amphibians and fish can be infected with a variety of parasites, including trematodes (Opisthorchis spp., Clonorchis sinensis, minute intestinal flukes), cestodes (Diphyllobothrium spp., Spirometra), nematodes (Gnathostoma, spp., anisakine parasites), and pentastomids that can cause zoonotic infections in humans when consumed raw or not properly cooked. Another important zoonotic food-borne trematode is the lungfluke (Paragonimus spp.). Traditionally, these parasitic zoonoses are most common in Asia because of the particular food practices and the importance of aquaculture. However, some of these parasites may emerge in other continents through aquaculture and improved transportation and distribution systems. Because of inadequate systems for routine diagnosis and monitoring or reporting for many of the zoonotic parasites, the incidence of human disease and parasite occurrence in food is underestimated. Of particular concern in industrialised countries are the highly resistant waterborne protozoal infections as well as the increased travel and immigration, which increase the exposure to exotic diseases. The increased demand for animal proteins in developing countries will lead to an intensification of the production systems in which the risk of zoonotic infections needs to be assessed. Overall, there is an urgent need for better monitoring and control of food-borne parasites using new technologies.     

Contour furrows for in situ soil and water conservation, Tigray, Northern Ethiopia

In Tigray (Northern Ethiopia), soil moisture has been identified as the most limiting factor in agricultural production; on the other hand, loss of rain water through runoff as well as the induced soil loss has been determined as a critical problem in the region in the last two to three decades. To alleviate the above paradox, the government has mobilized communities and resources for the construction of physical soil and water conservation structures (stone bunds, terraces) in almost all land uses. However, yield improvement was mainly concentrated within the vicinity of the structures and runoff continued to overtop the structures, as no measures for in situ soil conservation were taken. The terwah system, consisting of traditional ploughing followed by making every 1.5–2 m contour furrows, and permanent raised beds with contour furrows at 60–70 cm interval treatments, were considered and evaluated as practices that could increase the efficiency of in situ water utilization and soil conservation. An experiment was started in Gum Selasa, which is one of the drought prone areas in Tigray, whereby runoff volume and sediment load were measured after every rain event. Permanent raised beds with contour furrows at 60–70 cm interval significantly (P < 0.05) reduced runoff volume, runoff coefficient and soil loss as compared to traditional ploughing: 255, 381 and 653 m³ ha⁻¹ runoff was recorded from permanent bed, terwah and traditional ploughing, respectively during the whole cropping season. The above runoff induced 4.7 t ha⁻¹ soil loss from permanent bed, 7.6 t ha⁻¹ from terwah and 19.5 t ha⁻¹ from traditional ploughing. Overall, contour furrows and permanent raised beds can be part of the ongoing intensification process which includes physical soil and water conservation, slope reforestation, irrigation development and agro forestry in crop lands. Moreover, the use of permanent raised beds if combined with crop mulching and crop diversification is an important component for the development of sustainable conservation agriculture practices in the region.     

The effect of short-term socio-economic and demographic change on landuse dynamics and its corresponding geomorphic response with relation to water erosion in a tropical mountainous catchment,Ecuador

The analysis of aerial photographs over a 33-year period (1962–1995) shows that land use in the study catchment is highly dynamic as a response to the land reform programs of the 1960s and 1970s and a strong population increase. The secondary forest is increasingly replaced by grassland while old grasslands are now used as cultivated land. Despite the increased pressure on the land, the upward movement of agricultural activity and the concurrent deforestation, the overall forest cover did not decline. The deforestation in the uplands is compensated for by a regeneration of secondary forest on abandoned rangelands and afforestation with Eucalyptus trees in the low-lying areas. The land use changes resulted in a strong decrease of the areas subject to intense soil degradation: afforestation with Eucalyptus trees on degraded lands was successful in controlling soil erosion in the lower parts of the catchment. The relationship between land use and sediment load in the river system is not straightforward. Statistical analysis of a time series of suspended sediment concentrations, which were measured at the outlet of three distinctive sub-catchments for a six-year period (1994 – 2000), revealed that the geomorphic response of the river system is not only dependent on the land use and the area affected by water erosion, but also on the spatial connectivity between sediment producing areas and the river network.This revised version was published online in May 2005 with corrections to the Cover Date.     

Household livelihood strategies and forest dependence in the highlands of Tigray,Northern Ethiopia

Forest environmental resources provide substantial contributions to the wellbeing of many rural dwellers. However, the level of forest use and the degree of reliance on forest environmental products differ across households. The factors that condition a household’s economic reliance on a particular economic activity in general and on forest environmental resources in particular may vary depending on the resource endowment of the household, the household’s demographic and economic characteristics, and exogenous factors such as markets, prices and technologies. This paper identifies the factors that condition a household’s livelihood strategy choice with a particular focus on forest products. For this, we use the livelihood approach as a framework of analysis. Environmentally augmented household income data were collected from 360 sample households in Tigray, Northern Ethiopia. On the basis of the share of forest environmental income in total household income, sample households were clustered into distinct livelihood strategies. Student’s t-test and ANOVA were used to test income differences among the clusters. Multinomial logit (MNL) regression on asset-based explanatory variables was run to identify the main factors that determine households’ livelihood strategy choice and forest dependence. The analyses indicate that differential access to, or endowment of, livelihood assets determines the choice of a household’s strategy. Asset-poor households should be encouraged to engage in activities with higher economic return.     

Estimation of soil weathering stage and acid neutralizing capacity in a toposequence Luvisol–Cambisol on loess under deciduous forest in Belgium

Soils derived from loess are extensive in Europe and are well suited for forestry. They are suspected to be poor acid buffers, however. We have estimated the weathering stage and acid neutralizing capacity of acid soils under forest in a toposequence on loess in the Belgian silt belt. The soils vary distinctly in morphology and physico‐chemical properties according to their topographic position. Dystric Cambisols have developed in colluvial deposits in the dry valley floors, whereas Dystric Luvisols have formed on the slopes in a rejuvenated material. The Cambisols are more acid and less saturated in bases than are Luvisols. They are strongly depleted of clay and contain less weatherable minerals. Easily weatherable minerals are concentrated mainly in the clay fraction of both soil types. Clay minerals of size < 2 μm therefore act as major sinks for protons in these soils. A simplified expression taking into account the total reserve in bases, total aluminium and iron occluded in silicates is used to estimate acid neutralizing capacity. Our estimates confirm that these acid loessic soils are indeed poor acid buffers. They show that the Dystric Cambisols depleted of clay are sensitive to potential acidification, whether natural or man‐made.     

The economic contribution of forest resource use to rural livelihoods in Tigray,Northern Ethiopia

By explicitly incorporating forest environmental products (FEPs) in household income accounting, this paper examines the role and significance of FEPs in household income and in rural poverty and inequality. As most conventional household surveys do not incorporate income from environmental sources, substantial gaps exist in our understanding of the actual functioning of rural economies and the extent of rural poverty and inequality. Using data from 360 randomly sampled rural households from 12 villages in Tigray (northern Ethiopia), we measure forest environmental resource use with a monetary yardstick and compares the value of FEPs with other household economic activities. We found that products from environmental sources represent an important component in rural livelihoods. Our analyses indicate that in the study area income from forest environmental sources occupies the second largest share in average total household income next to crop income. Poverty and inequality analyses show that incorporating forest environmental incomes in household accounts significantly reduces measured rural poverty and income inequality. Therefore, we suggest that sustainable forest management schemes should be adopted to maintain and enhance the flow of economic benefits to the surrounding communities without damaging the natural resource system.     

The effect of rainfall on spatio‐temporal variability in cropping systems and duration of crop cover in the Northern Ethiopian Highlands

In the Northern Ethiopian Highlands, ca. 33% of the land is cropland, which is mainly cultivated by smallholders who based on indigenous knowledge plan their cropping system on the basis of spatio‐temporal variability in rainfall. To understand the relationships between rainfall variability and cropping systems, a field campaign was undertaken in the rainy season of 2009 when 118 farmers were interviewed at different locations with different environmental characteristics. Five cropping systems were identified, each having a distinct cropping season length and crop association. Cropping systems with shorter cropping seasons were generally on the valleysides, whereas longer cycles occurred in the valley bottoms. The length of cropping season also increased from north–northeast to south–southwest. Crop associations within cropping systems also varied with altitude. Cropping systems changed in response to variation in annual rainfall. This resulted in shifts of cropping systems at catchment and regional scales, with cropping systems having longer cropping seasons where there was greater annual precipitation. The results were scaled up to the whole region by modelling the spatial distribution of cropping systems at a 8 × 8 km² resolution over the period 1996–2009. The results indicate that indigenous knowledge is important when assessing the impact of climatic variability on agricultural production and that large inter‐annual variability in the duration of crop cover in Northern Ethiopia might be an important, although generally overlooked, explanatory factor for explaining previous land degradation cycles.