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In the Gilgel Gibe catchment in Ethiopia, local farmers intensify land use on Planosols by adjusting a traditional soil burning practice known as guie. The burning practice used to be applied in a cycle of shifting cultivation. However, more recently, farmers burn small plots to make fertile seedbeds for Eucalyptus seedlings in the first year before these trees are transplanted to larger plots. The purpose of this research was to assess the physico-chemical properties of Planosols that have been subjected to burning over the last 10 yrs and evaluate the contribution of guie to land-use intensification of these soils. Transect studies and interviews of local farmers, followed by chemical, physical and micromorphological analyses of samples from selected plots were used to compare the soil properties of recently (0-2 yrs) and formerly (3-10 yrs) burnt Planosols with those of unburnt Planosols. The analytical results show that the burning practice improved nutrient availability in the first 2 yrs after guie. Increased amounts of exchangeable aluminium (Al) were reported in the long term. Charge fingerprints illustrate that the nutrient-buffering capacity of the soil was high shortly after the practice but subsequently decreased with time. Given the population pressure on the formerly extensively used Planosols, it is argued that the current application of guie on small, localized plots for raising Eucalyptus seedlings is well adapted to the local socio-economic context and promotes land-use intensification on the Planosols. The increased exchangeable Al content of former Eucalyptus seedbeds merits further in-depth research into the biophysical sustainability of the burning practice. [ABSTRACT FROM AUTHOR]

Quantitative research on land use and land cover (LUC) in Africa usually addresses the second half of the twentieth century, by using remote sensing data. Terrestrial photographs, which are available since 1868 in Ethiopia, are seldom used in a quantitative way. This paper presents a methodology that allows to produce land use and land cover (LUC) maps on the basis of old terrestrial photographs. Therefore, land use and land cover was investigated on historical and present-day photographs, and these interpretations were warped to the horizontal plane of the map. The resulting maps allow to gain better insights into LUC changes over a period of 140 years. The results show that woody vegetation increased strongly, together with an increase in built-up area. This occurred especially at the expense of bushland. The study validates pervious findings and shows that improved land management strategies in one of the world's most degraded areas can lead to environmental rehabilitation. [ABSTRACT FROM AUTHOR]

ABSTRACT Compared with surface soil erosion by water, subsurface erosion (piping) is generally less studied and harder to quantify. However, wherever piping occurs, it is often a significant or even the main sediment source. In this study, the significance of soil loss due to piping is demonstrated through an estimation of soil volume lost from pipes and pipe collapses (n = 560) in 137 parcels under pasture on loess-derived soils in a temperate humid climate (Belgium). Assuming a period of 5 to 10 years for pipe collapse to occur, mean soil loss rates of 2.3 and 4.6 t ha−1 yr−1 are obtained, which are at least one order of magnitude higher than surface erosion rates (0.01-0.29 t ha−1 yr−1) by sheet and rill erosion under a similar land use. The results obtained for the study area in the Flemish Ardennes correspond well to other measurements in temperate environments; they are, however, considerably smaller than soil loss rates due to subsurface erosion in semi-arid environments. Although local slope gradient and drainage area largely control the location of collapsed pipes in the study area, these topographic parameters do not explain differences in eroded volumes by piping. Hence, incorporation of subsurface erosion in erosion models is not straightforward. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Soil erosion caused by low vegetation cover associated with agricultural land use in the catchment is blamed for the eutrophication of Lake Victoria. Above-ground biomass as an indicator of vegetation cover and biodiversity was assessed using the Normalized Difference Vegetation Index, estimation of tree density and biomass with the aim of assessing the extent to which vegetation covers the soil surface. Tree density is significantly different between agricultural and semi-natural systems with an average of 96 and 90 trees ha [ABSTRACT FROM AUTHOR]

The article presents a discussion about the use of land and soil at the Tigray Highlands in Dogu'a Tembien, Northern Ethiopia. The study focused on soil type, land use and crop production system. Type of soils found within the area are vertisols, vertic cambisols, cumulic regosols and calcaric regosols. The study found that population growth is affecting natural resources of the Ethiopian Highlands resulting land degradation. It is also noted that a decline in natural vegetation is also impacting sustainability of traditional agricultural systems.

Abstract: The high Andes region of south Ecuador is characterised by intense land use changes. These changes affect particularly the páramo, which is a collection of high altitudinal grassland ecosystems. In this region, the interaction between airborne volcanic ashes and the cold and wet climate results in very typical soils, with an elevated organic C contents. The physical soil properties are closely related to the high and reliable base flow in rivers descending from the páramo, which makes them important for the socio-economic development of the region. In this study, we analyse the regional variability of the soils in the south Ecuadorian rio Paute basin. In a first part of the study, data from soil profiles along north–south transects are used to determine the soil properties, and to relate the spatial variability of these properties to the major trends in parent material, volcanic ash deposits and climate. The profiles are Histic Andosols and Dystric Histosols devoid of allophane, with very high amounts of organic matter. Significant differences between the western and central mountain range are observed, as well as a general decrease in Andic properties from north to south, coinciding with the decrease in volcanic influence. Finally, the impact of human activities on the soil properties is assessed in a case study in the Machangara valley. Data from 5 profiles, located in an area with natural grass vegetation and a low degree of human impact are compared with 4 profiles in a heavily disturbed, intensively drained cultivated area. Despite the intensity of the land use, very few significant differences are found. [Copyright &y& Elsevier]

In contrast with the understanding of present-day soil erosion processes, knowledge on past soil erosion phenomena is still rather limited. Although some studies report on severe gully erosion phases during the fourteenth and eighteenth centuries, almost no evidence is available that documents earlier gully erosion phases. This study investigates the development and age of two old, permanent gullies that are conserved in the ancient Meerdaal forest in central Belgium. The development history of both gullies is very similar. In the first gully, archaeological evidence was found indicating an erosion phase during Roman times, followed by a partial infilling of the gully. In the second gully, radiocarbon dating provided evidence of the same Roman activity phase (cal. yr 46 BC–AD 78), but also of an earlier incision phase during the Middle Bronze Age (cal. yr 1743–1602, 1568–1533 BC). Also here, the erosion phase was followed by a partial infilling. This limited infilling indicates that the catchment of the gullies was reforested quite rapidly, hereby cutting off all runoff and sediment production. This has led to a unique situation in the Meerdaal forest, with the conservation of about 43 similar, large gullies in an area of about 17 km2. This area has a high geovalue, as the studied gullies are among the oldest and best conserved gullies in northwestern Europe. [ABSTRACT FROM AUTHOR]

Knowledge of past erosion events and their controlling factors is an important key to understanding the impacts of environmental change (climate–land use) on the landscape. In this study, knowledge about erosion processes on the development of present-day ephemeral gullies is used for reconstructing conditions leading to the formation of old, permanent gullies. Empirical relations between flow hydraulics and channel geometry have been recently established for gullies. Hence, using measured bottom width Wbottom of old gullies as input, peak flow discharges (Qp) of these gullies can be estimated. In two forested areas in central Belgium, 52 old gullies were mapped. The old gullies had an average Wbottom ranging between 1.1 and 1.5 m. Corresponding calculated Qp values ranged between 0.04 and 0.07 m3/s. Rainfall intensities (I) were also deduced from Qp using the rational formula. By simulating various land use scenarios and thus various runoff coefficient (C) values, I and concentration time (Tc) could be calculated for each land-use class. Using I, Tc and intensity–duration–frequency tables for the study area, the recurrence interval (RI) of the rain events, needed to erode the observed gully channels was assessed. Although analysis of historical documents indicates that both areas have probably been under forest since the Middle Ages, it is unlikely that the old gullies originated under forest vegetation or even degraded forest vegetation, since RI > 200 years were obtained for these land-use scenarios. Cropland is the only land use that provides acceptable values of RI (11–128 years). [ABSTRACT FROM AUTHOR]

After the reunion of North and South Vietnam in 1975, the area under small-holder, irrigated cultivation of Robusta coffee increased by a factor of 10 in the Central Highlands. The actual coffee acreage in Dak Lak province is estimated to be over 260,000 ha, representing 60% of the national production, with 405,000 t year-1 for the world market. Vietnam is presently the second largest exporter worldwide and expansion is still going on. In cooperation with the National Institute for Agricultural Planning and Projection (NIAPP), a 5-year development project “Land Evaluation for Land Use Planning and Development of Sustainable Agriculture in the Central Highlands of South Vietnam” was set up, with a goal of diagnosing the sustainability of the rapidly expanding Robusta coffee sector in Central Vietnam. This paper describes the reasons for this quick expansion and investigates the consequences in ecological and social terms. This is done based on a large-scale natural resources inventory, land suitability analysis for Robusta coffee and participatory rural appraisal combined with secondary statistical records from Dak Gan commune. It is representative of the Central Highlands in terms of geomorphological and pedological variability, ethnic identity and with regard to trade-offs between forest conservation and coffee expansion at the cost of available water stocks. Local institutional reforms in the eighties have accelerated coffee expansion in three ways: demographic resettlement, socio-economic liberalization and legislation towards land ownership. Interaction between these three factors has induced a second spontaneous migration flow towards the Highlands in the nineties. Forest area declined by 19% and was converted to coffee plantations, encouraged by the high economic return of this cash crop. The results indicate that this has happened in an haphazard manner and led to a mismatch between the present land use pattern and the natural resource base. Unsustainable land use manifests itself at four levels. (i) The areal limits for sustainable coffee production have been exceeded. (ii) As a consequence over 74% of the present coffee stand is situated on sub-optimal land units. (iii) An excessive coffee area in combination with over-irrigation is likely to deplete groundwater resources. (iv) And paradoxically 24.3% of suitable soils for coffee production is still under forest in Dak Gan. In turn this leads to large-scale environmental and socio-economic decline: soil erosion, water scarcity and social inequity resulting in conflicts between migrants and the indigenous tribes. Besides local reforms, world trade liberalization changed the global coffee market in the late nineties from a regulated system to a free trade market. This fostered global oversupply, which in combination with a stagnant coffee demand suppressed the world market price. Since Vietnam became the second world producer of Robusta, prices have declined by a factor of 3, not only affecting the local sector but households worldwide. [Copyright &y& Elsevier]

Studies the effect of land use on the water retention capacity of Umbric Andosols in south Ecuador. Objective was to acquire a better insight into the hydrological processes of the ecosystem and the role of the soil, in order to assess the impact of changing soil properties due to land use change on the hydrology of the high Andes region. Field data on the water retention capacity at wilting point of Umbric Andosols were collected for both cultivated field conditions and original bush vegetation. The pH in water and in NaF, texture, organic matter content and dry bulk density were measured to show which physicochemical soil characteristics are responsible for the water retention of the Umbric Andosols and for the irreversible loss in water retention due to air drying. Organic matter content appears to be very important and certainly more important than allophane clay content. Water retention of the organic litter layer was calculated to be 16 mm, this would be lost when vegetation was cleared and the land cultivated.

Closed depressions (CDs) are lower lying areas where the sediment eroded from the sur- rounding soil surfaces draining towards the CD is trapped in the system. CDs have been reported in several regions of the European loess belt and are attributed either to natural processes (e.g. dissolution of subsurface horizons) or to human intervention (e.g. quarrying). Previous studies focussed mainly on cropland areas where, however, only few and largely filled in CDs remain. The objectives of this study were to i) assess the spatial distribution of CDs under forest and cropland, ii) to determine and compare the morphology of CDs under forest and under cropland, and iii) to determine the origin and age of these CDs under forest. In a study area located partly in ancient forest (13 km2) and partly in cropland (29 km2), a systematic survey revealed the presence of 71 CDs under forest (5·3 CD.km-2) and 30 CDs under cropland (1 CD.km-2). Comparison of their morphology showed that CDs under forest were significantly deeper, with steeper sidewalls and a smaller surface area because of the erosion and deposition processes acting on the CDs under cropland. By comparing CDs that had been under cropland for different time intervals, the rate of this morphological evolution could be reconstructed. [ABSTRACT FROM AUTHOR]

During the past decades, land use change in the Lake Victoria basin has significantly increased the sediment fluxes to the lake. These sediments as well as their associated nutrients and pollutants affect the food and water security of millions of people in one of Africa's most densely populated regions. Adequate catchment management strategies, based on a thorough understanding of the factors controlling runoff and sediment discharge are therefore crucial. Nonetheless, studies on the magnitude and dynamics of runoff and sediment discharge are very scarce for the Lake Victoria basin and the African Rift region. We therefore conducted runoff discharge and sediment export measurements in the Upper Rwizi, a catchment in Southwest Uganda, which is representative for the Lake Victoria basin. Land use in this catchment is characterized by grazing area on the high plateaus, banana cropping on the slopes and Cyperus papyrus L. wetlands in the valley bottoms. Due to an increasing population pressure, these papyrus wetlands are currently encroached and transformed into pasture and cropland. Seven subcatchments (358 km 2 –2120 km 2 ), with different degrees of wetland encroachment, were monitored during the hydrological year June 2009–May 2010. Our results indicate that, due to their strong buffering capacity, papyrus wetlands have a first-order control on runoff and sediment discharge. Subcatchments with intact wetlands have a slower rainfall–runoff response, smaller peak runoff discharges, lower rainfall–runoff ratios and significantly smaller suspended sediment concentrations. This is also reflected in the measured annual area-specific suspended sediment yields (SYs): subcatchments with encroached papyrus swamps have SY values that are about three times larger compared to catchments with intact papyrus vegetation (respectively 106–137 ton km − 2 y − 1 versus 34–37 ton km − 2 y − 1 ). We therefore argue that protecting and (where possible) rehabilitating these papyrus wetlands should be a corner stone of catchment management strategies in the Lake Victoria basin. [ABSTRACT FROM AUTHOR]

Abstract: This study investigates the role of soil characteristics and land use in the development of soil pipes in the loess belt of Belgium. First, we tested the hypothesis that discontinuities in the soil profile enhance lateral flow and piping by impeding vertical infiltration. We focus on discontinuities in soil characteristics that can vary with soil depth, including texture, saturated hydraulic conductivity, penetration resistance, and bulk density. These characteristics as well as soil biological activity were studied in detail on 12 representative soil profiles for different land use types. Twelve sites were selected in the Flemish Ardennes (Belgium): four pastures with collapsed pipes (CP), four pastures without CP, two sites under arable land without CP and two sites under forest without CP. Secondly, this study aimed at evaluating the interaction of groundwater table positions (through soil augerings) and CP in a larger area, with a focus on pastures. Pasture is the land use where almost all CP in the study area are observed. Therefore, the position of the groundwater table was compared for 15 pastures with CP and 14 pastures without CP, having comparable topographical characteristics in terms of slope gradient and contributing area. Finally, the effect of land use history on the occurrence of pipe collapse was evaluated for a database of 84 parcels with CP and 84 parcels without CP, currently under pasture. As to the first hypothesis, no clear discontinuities for abiotic soil characteristics in soil profiles were observed at the depth where pipes occur, but pastures with CP had significantly more earthworm channels and mole burrows at larger depths (>120cm: mean of >200 earthworm channels per m2) than pastures without CP, arable land or forest (>120cm depth, a few or no earthworm channels left). The land use history appeared to be similar for the pastures with and without CP. Combining all results from soil profiles and soil augering indicates that intense biological activity (especially by earthworms and moles), in combination with a sufficiently high groundwater table, favours the development of soil pipes in the study area. [Copyright &y& Elsevier]

Abstract: Collapsible loess-derived soils are prone to soil piping erosion, where enlargement of macropores may lead to a subsurface pipe network and eventually to soil collapse and gully development. This study aims at understanding the main factors controlling spatial patterns of piping in loess-derived soils under a temperate climate. To map the spatial distribution of piping and identify the environmental controls on its distribution, a regional survey was carried out in a 236km2 study area in the Flemish Ardennes (Belgium). Orthophotos taken at optimal field conditions (winter) were analyzed to detect piping in open landscapes and ground thruthing was systematically done through field surveys. In total, 137 parcels having 560 collapsed pipes were mapped. Dimensions of the sinkholes and local slope gradient were measured in the field and topographical variables were derived from LiDAR data. Land use plays an important role as 97% of the sites with piping are found under pasture. The probability of piping increases rapidly on hillslopes with gradients exceeding 8% and with a concave profile and plan curvature, enhancing subsurface flow concentration. The zones with soil profiles on shallow loess over a relatively thin layer of homogeneous blue massive clays (Aalbeke Member) are most prone to piping. Soil characteristics are of less importance to explain piping occurrence. Furthermore, the topographical threshold line indicating the critical slope gradient for a given contributing drainage area was determined. This threshold line (negative power relation) is similar to the threshold line for shallow gully initiation. [Copyright &y& Elsevier]

Abstract: Analysis of contemporary and past gully erosion and infilling processes allowed to reconstruct the long-term evolution of a permanent gully system under cropland. An active and a buried gully under cropland were investigated. The recent sediment deposits within the active gully, adjacent to the buried gully, showed that the recent gully was filling in at a mean rate of 6.4 cm a−1. In the buried gully, several erosion and deposition phases could be identified and the type of deposited sediments revealed a complex infilling history. Charcoal, pottery and brick fragments of different sizes were found at all depths of the gully infilling. Their age indicates that the first gully incised after the midst of the 17th century, most probably in the second half of the 18th century or the early 19th century. Gully morphology and analogy with the processes in the recent gully indicate that the buried gully filled in rapidly. Overall, five cycles of cut and fill occurred in 350 years or less and four cycles even within little less than a few decades, indicating that gully development and infilling under cropland can be very rapid processes. [Copyright &y& Elsevier]

In many forests of Northwestern Europe old gullies can be found, but few studies have reported their genesis and characteristics. This study investigates these old gullies under forest in the large case-study area of Meerdaal Forest, in the Central Belgian loess belt. The objectives are (1) to determine the spatial distribution of these gullies, (2) to measure their morphological and topographical characteristics and (3) to reconstruct the factors that led to their development. In the 1329-ha study area, 252 channel-like incisions were mapped. Different types of incisions could be distinguished. Besides small and large gullies, many incisions were sunken lanes or road gullies. These road gullies are aligned along north–south oriented lines, whereas the concentration of old gullies is strongly related to the distribution of archaeological sites. Out of the 252 mapped incisions, 43 large gullies and 21 representative road gullies were selected for detailed morphological and topographical measurements. The characteristics of these two types of incisions were compared with ephemeral gullies formed under nearby cropland. Significant differences in morphology between the three types could be demonstrated. Ephemeral gullies under cropland and large gullies under forest differ significantly in all measured parameters, except bottom width. Both the old gullies and road gullies under forest have a significantly larger cross section and total eroded volume compared with the ephemeral gullies observed under cropland. This indicates that once formed, the old gullies were not ploughed in nor were they filled by sediment originating in their drainage areas, because of limited sediment production. Comparing topographical characteristics (i.e. slope at the gully head and runoff contributing area) of forest gullies and ephemeral gullies that formed under cropland yields important indications about their formation. The larger sedimentation slope of forest gullies, compared with ephemeral gullies and road gullies, suggests that the forest gullies incised on vegetated slopes as a consequence of runoff from the adjacent plateau, where the forest cover was disturbed. For the old gullies under forest, no relation between slope at the gully head and runoff contributing area is observed, probably because most gullies occur on very steep slopes. When simulating arable land-use in the study area, zones where ephemeral gullies are expected to develop can be predicted using published topographical threshold relationships. Comparing the zones where ephemeral gullies are predicted with the position of old gullies under forest leads to the conclusion that gully incision was most probably not triggered by extreme rainfall events and that they are not of periglacial origin. The observed gully pattern can best be explained by local, anthropogenically determined land-use changes. [Copyright &y& Elsevier]