Natural and anthropogenic controls on soil erosion in the Internal Betic Cordillera (southeast Spain)

Soil erosion in southeast Spain is a complex process due to strong interactions between biophysical and human components. Significant progress has been achieved in the understanding of soil hydrological behavior, despite the fact that most investigations were focused on the experimental plot scale. Although experimental plots allow exploring the effect of multiple biophysical and anthropogenic factors, they provide limited insights in the combined effect of all factors acting together at the landscape scale. In this study, area-specific sediment yields (SSY) have been estimated based on the volume of sediment trapped behind 36 check dams in the southeast of Spain. Low SSY-values were reported (mean = 1.40 t ha⁻¹ year⁻¹: median = 0.61 t ha⁻¹ year⁻¹). SSY variability could be explained for 67% by catchment characteristics such as drainage area, soil characteristics, land cover, average catchment slope, and annual rainfall. The low SSY values are probably caused by the agricultural abandonment that occurred over the past decades and allowed the recovery of natural vegetation. Furthermore, our results suggest that the soils have eroded in the past to such an extent that nowadays not much sediment is detached by overland flow due to residual enrichment of clay and stones. Also, sediment is to a large extent trapped locally in the catchment, as indicated by the negative relationship between SSY and catchment area.     

Assessing the costs of land degradation: a case study for the Puentes catchment,southeast Spain

Whereas many studies point out the economic benefits of controlling land degradation through sustainable land management (SLM) approaches, there is often a lack of local adoption of SLM techniques. Analysis of the local impacts and costs of land degradation is critical for understanding farmers' responses to land degradation. The objective of this paper is to analyse the local costs of land degradation in the Puentes catchment in southeast Spain. This catchment has been identified as particularly vulnerable to erosion, yet farmers show a general lack of interest in applying erosion control techniques. The paper subsequently analyses land degradation processes in the Puentes catchment, the income derived from agriculture and several other ecosystem services, and the local costs of land degradation. Erosion is widespread in the catchment, comprising sheet and rill erosion as well as gulley erosion. Relatively high erosion rates are encountered in cropland. The most important source of local income is irrigated agriculture, with revenues of up to €1350/ha y⁻¹. Dryland agriculture, hunting and herding provide additional income. The costs of erosion on cropland, calculated with a replacement method, vary from around €5/ha y⁻¹ on slopes between five per cent and ten per cent, to around €50/ha y⁻¹ on slopes between 30 per cent and 50 per cent. Except on the steepest slopes, these costs are relatively low for the farmers, which explains the limited application of erosion control techniques in the catchment. Copyright © 2007 John Wiley & Sons, Ltd.     

Uncertainty and Sensitivity Analyses of the Modified Wind Erosion Equation for Application in Canada

The wind erosion equation (WEQ) was used for several decades for predicting soil loss by wind erosion, but few systematic studies on the uncertainty of predicting wind erosion have been conducted. Several researchers found that WEQ is not accurately representing soil erosion and under‐represents soil erodibility that consequently results in WEQ underestimations. WEQ was modified under Canadian conditions for the National Agri‐Environmental Health Analysis and Reporting Program, referred as (WEQ‐NAHARP). The model, input, and parameter uncertainties that control model efficiency were used to analyze the local and universal uncertainties for WEQ‐NAHARP. One and ninety‐nine percentiles were used as lower and upper boundaries of uncertainty bound when using general likelihood uncertainty estimation for estimating the uncertainty of WEQ‐NAHARP's prediction. The soil erodibility (I ), climate factor (C ), and soil surface roughness factor (K ) were found as the three most sensitive factors in predicting wind erosion in WEQ‐NAHARP. The vegetation cover factor (V ) was discovered not sensitive to the prediction model as it is less than 1,000 kg ha⁻¹ and became very sensitive as V ‐value is greater than 5,000 kg ha⁻¹ . Field length along the prevailing wind erosion direction (L ) and V have lower local sensitivity indexes than the other three factors. WEQ‐NAHARP underestimated wind erosion rate of Pampas, Argentina, and overestimated at Washington State, USA. This probably reflected the nature of WEQ‐NAHARP's behavior, which had a great uncertainty of its prediction. The model appears to underestimate total annual soil loss for coarse soil and overestimate annual soil loss for finer soil. Copyright © 2017 John Wiley & Sons, Ltd.     

Erosion quantification in the small marly experimental catchments of Draix (Alpes de Haute Provence, France). Calibration of the ETC rainfall–runoff–erosion model

Erosion rates measured for 15 years in the small (ranging from 0.13 ha to nearly 1 km²) and steep (30–75%) mountainous marly basins of Draix (South Alps, France) are over 100 tons/ha/year in a badland area devoid of vegetation. In a similar basin, reforested at the end of the 19th century, the sediment yield is considerably reduced (less than 3 tons/ha/year). The analysis of the sediment yield of these torrents reveals the importance of the erosion processes on slopes at the scale of the elementary gully, and the influence of deposition, transport and scouring processes as soon as the channel network of the basin is developed.These processes were modelled by a hydrosedimentologic model developed by Cemagref for flood torrent erosion and called ETC. ETC is an integrated, spatialized and global model, working at the event scale. The rainfall–runoff component and the solid transport component, which involves scouring, deposition and armouring, are well developed. On the other hand, the erosion component is not yet a physically based model as the knowledge on the elementary processes is not enough quantitative. The ETC model was used on a badland basin of 86 ha in area, the Laval, and has shown its ability to simulate both water and sediment flows in mountainous and steep basins. The erosion modelling highlighted the need for a better representation of the slope processes and for more information on the storing of sediments in the channel network. Observations carried out on the influence of the vegetation cover patterns and the links between slopes and channels should be taken into account to improve the model.     

The influence of land management on soil erosion in the Sneeuberg Mountains,Central Karoo,South Africa

Farm practices in the Sneeuberg Mountains, Karoo, South Africa are examined to assess their contribution to the development of the observed gullies and badlands. Data from the literature is augmented by interviews with local farmers and measurements in the field. Changes in stocking rates, grazing systems and technological advances are assessed for their impact on soil erosion, vegetation cover and species composition. The possibility of natural and managed rehabilitation of badland areas is discussed, as are future prospects for farm management in the Sneeuberg. The findings suggest that high stock numbers and less benign management practices in the 19th century and the early 20th century underlie much of the degradation seen today. Copyright © 2007 John Wiley & Sons, Ltd.     

Effects of Topography and Surface Soil Cover on Erosion for Mining Reclamation: The Experimental Spoil Heap at El Machorro Mine (Central Spain)

Mining reclamation tries to reduce environmental impacts, including accelerated runoff, erosion and sediment load in the nearby fluvial networks and their ecosystems. This study compares the effects of topography and surface soil cover on erosion on man‐made slopes coming from surface mining reclamation in Central Spain. Two topographic profiles, linear and concave, with two surface soil covers, subsoil and topsoil, were monitored for two hydrologic years. Sediment load, rill development and plant colonization from the four profiles were measured under field conditions. The results show that, in the case of this experiment, a thick and non‐compacted topsoil cover on a linear slope yielded less sediment than carbonate colluvium or topsoil cover on a concave slope. This study also shows that vegetation establishment, which plays an important role in erosion control, depends on topography. Plant cover was more widespread and more homogeneous on linear profiles with topsoil cover. On concave slopes, plant establishment was severely limited on the steepest upper part and favoured in the bottom. This study suggests that management of topography and surface soil cover should be approached systematically, taking three outcomes into consideration: (i) topsoil can lead to a successful mining reclamation regardless of topography, (ii) created concave slopes can lead to a successful mining reclamation and (iii) topography determines the vegetation colonization pattern. Copyright © 2013 John Wiley & Sons, Ltd.     

Rhetoric and reality of reforestation methods for soil and water conservation in Guadalajara (Spain)

Foresters have played an important part in the Spanish national strategy against land degradation. It might be expected that after the changes restored political democracy in Spain in the late 1970s, a reorganization of the way the planning and implementation of soil and water conservation projects through reforestation would be changed. This paper considers the case of Guadalajara province as an example of the way in which reforestation has been effected at national level, and the consequences for the ecosystem. It examines how, since the 1940s, the technical methods used by forestry technicians have changed from concerns with protection to those of wood production. Although reforestation methods for wood production have been recognized as detrimental to soil and water conservation, they continue to be used even in the face of considerable opposition by local people and environmental pressure groups. The paper concludes that claims for soil protection mask a policy of wood production, excluding affected people from the decision-making process. Copyright © 1999 John Wiley & Sons, Ltd.     

Modelling Post‐Tree‐Harvesting Soil Erosion and Sediment Deposition Potential in the Turano River Basin (Italian Central Apennine)

The overall aim of the paper is the assessment of human‐induced accelerated soil erosion processes due to forest harvesting in the Upper Turano River Basin. The spatio‐temporal pattern of soil erosion processes was investigated by means of a spatially distributed modelling approach. We used the Unit Stream Power Erosion and Deposition model. During the soil erosion‐modelling phase, the forest cover changes were mapped via remote sensing. According to this operation, the forest sectors exploited for timber production amounted to about 2781 ha or 9·9% of the wooded surface from March 2001 to August 2011. In this period, the average annual net soil erosion rate estimated by means of modelling operations totalled 0·83 Mg ha⁻¹ y⁻¹ for all the forest lands. The net soil erosion rate predicted for the disturbed forest lands is significantly higher than the average value for the entire forest (5·34 Mg ha⁻¹ y⁻¹). Estimates indicate a soil loss equal to 8521 Mg y⁻¹ (net soil erosion 0·34 Mg ha⁻¹ y⁻¹) in the undisturbed forest area (254 km²), whereas the 27·8 km² of disturbed forest area could potentially lose 14 846 Mg y⁻¹. The paper shows that a disturbed forest sector could produce about 74·2% more net erosion than a nine times larger, undisturbed forest sector. Copyright © 2013 John Wiley & Sons, Ltd.     

Assessment of soil degradation in the Canary Islands (Spain)

In the Canary Islands a number of factors, both natural and induced by human activity, act on the fragile ecosystems and agricultural land to cause increasing problems with desertification and progressive degradation of soil productivity. the results of an assessment of soil degradation in the Canary Islands, The processes, causes and impacts, are presented in this paper. Although several processes and factors contribute to soil degradation in the Canary Islands, two have been found to exert a greater qualitative influence: (a) accelerated erosion (water and aeolian); (b) salinization-sodification (natural and induced by agricultural use). Approximately 40 per cent of the Canary Islands' land is undergoing rapid erosion. the factors involved May, be grouped into: natural erosion—torrential rainfall, sparse vegetation, high soil erodibility, rugged relief; and erosion due to human activities—unsuitable management of arable soils on the steep slopes, overgrazing and deforestation. About 60 per cent of the surface of the archipelago, including areas given over to intensive agriculture, is affected by salinization.The main factors responsible are: natural—an arid climate and a regime of oceanic winds; and human activities—overexploitation of the aquifers, irrigation with water having a high salt and/or sodium content, intensive monoculture, and excessive and indiscriminate use of chemical fertilizers and other agrochemicals.     

Effectiveness and geomorphological impacts of check dams for soil erosion control in a semiarid Mediterranean catchment: El Cárcavo (Murcia, Spain)

The construction of transverse structures (check dams) is a widely used method in Spanish Mediterranean areas to stabilise gullies and ephemeral streams, to reduce channel incision and to prevent sediment deposition downstream. The effectiveness of check dams and their effects on the morphology of ephemeral channels (ramblas) were investigated in a semiarid, highly degraded catchment. In the study area, 36 dams were surveyed, of which 29 were filled up with sediments, 2 had been destroyed and only 5 had still not completely filled with sediments. The streams above the dams held sediments, which resulted in a decrease in the longitudinal gradient. Field observations of changes in the cross-sectional shape of the stream channel, the composition of channel bed material, and bankfull stage measurements indicated that the dams cause erosion downstream. The amount of sediments stored by the dams was found to be higher than the amount of eroded material in the downstream reaches of the dam.     

宁夏限制开发生态区生态敏感性综合评价与保护对策

以乡镇为基本研究单元,针对宁夏限制开发生态区存在的主要生态环境问题,选取土壤侵蚀、土地沙漠化作为评价因子,运用GIS技术在单因子评价的基础上,采用多因子综合评价的方法,对宁夏限制开发生态区生态敏感性进行综合评价。结果表明:（1）研究区内各乡镇均存在生态敏感性问题,生态敏感程度分为轻度敏感、中度敏感、高度敏感、极敏感4个等级,且94.34%的面积属于中度以上敏感性。（2）生态敏感性的空间分布特征为:位于中部干旱半干旱风沙区的各乡镇,主要的生态问题是土地沙漠化;位于南部黄土丘陵沟壑区的各乡镇,主要的生态环境问题是土壤侵蚀。（3）以市（县）为基本空间单元所得的评价结果,没有考虑县内各区域之间的差异性,研究结果可操作性较差,以乡镇为基本空间单元所得的评价结果因均质性较好,研究结果具有较强的针对性和可操作性。     

Landscape changes as visible indicators in the social,economic and political process of soil erosion: A case study of the municipality of puebla de valles (Guadalajara Province), Spain

This paper proposes a methodological approach to data gathering as a sound basis for understanding land degradation processes, breaking down barriers of distrust between Government officials and land users, and promoting participation in planning for soil and water conservation. It examines how landscape changes, of value as indicators of erosion, are perceived by land users and can be used in planning. It is proposed that the participation of land users in the construction of questionnaires, data gathering, analysis and writing up of the findings are examples of the participatory initial stages in planning.     

Multi‐temporal Digital Photogrammetric Analysis for Quantitative Assessment of Soil Erosion Rates in the Landola Catchment of the Upper Orcia Valley (Tuscany,Italy)

This paper focuses on the analysis of the slope and catchment erosion dynamics in a typical Mediterranean context and its sensitivity to recent climatic and socio‐economic changes. The main objective of the present study is to test the reliability of digital photogrammetric analysis to evaluate the time and space evolution of erosion processes mainly triggered by surface running waters and landslides for about the last 60 years. The selected test area is the Landola catchment, a minor tributary of the Upper Orcia River Valley (Southern Tuscany). The Upper Orcia valley is a key site for the comprehension of denudation processes typically acting in Mediterranean badland areas thanks to the following: (i) the availability of long‐lasting erosion monitoring datasets (20 years' long direct measurements at erosion ‘hot spots’); (ii) its representativeness as a sub‐humid Mediterranean badland area; and (iii) the rapidity of development of erosion processes, which makes it suitable as an open‐air laboratory for the study of badland dynamics. The outputs of this work highlight that the application of high‐resolution digital photogrammetric methodologies can represent a powerful and low‐cost tool to evaluate rates and spatial–temporal distribution of denudation processes, as confirmed by the validation through field point monitoring in areas close to the study area. The results obtained for the study area confirm that high erosion rates are a persistent environmental problem for the Upper Orcia Valley, which is not solved up to now, despite various land conservation interventions. The performed multi‐temporal analysis shows a slight decrease in the average water erosion rate during the last 60 years and a parallel increase in the frequency of mass wasting events. These variations are most likely related to a complex interplay between land use changes that have affected the study area during the studied period, revealing a very delicate equilibrium between farming activities and erosion processes. Copyright © 2014 John Wiley & Sons, Ltd.     

Contamination of Forest Soils in the Vicinity of the Sedimentation Pond after Zinc and Lead Ore Flotation (in the Region of Olkusz,Southern Poland)

In the technological processes of ore flotation in the non-ferrous metal industry flotation, tailings constitute up to 98% of the total of the processed material. They are stored in sedimentation ponds as fine-grained drift containing an excess of heavy metals, mainly zinc, cadmium, lead and copper. After the dehydration and drying up of the surface of sedimentation ponds, these metals are carried with dust by the wind and they are accumulated in the vicinity of the ponds in humus horizons of soils causing considerable degradation and even devastation. In this publication, we have presented the results of research on the negative influence of such a structure on the soils of an adjacent fragment of forest and its dependence on the distance from the sedimentation pond. The level of degradation of the soils under research has been assessed on the basis of changes and transformations of the morphological soil profiles, the level of alkalization and accumulation of heavy metals (Zn, Pb, Cd) in the topsoil layers and their translocation in the soil horizons. The following soils have been distinguished in the investigated area: Haplic Podzols distorted and degraded as well as Urbic Anthrosols. The acquired results have served to depict the spatial accumulation of these heavy metals in the topsoil layers. The highest accumulation of heavy metals and the degradation of the forest sites connected with it has occurred in the vicinity of a sedimentation pond drain channel. Soil remediation has been recommended in this area.     

Temporal Variations of Flow–sediment Relationships in a Highly Erodible Catchment of the Loess Plateau,China

The flow–sediment relationship is important to understand the soil erosion and land degradation processes in severe eroded areas. This study researches on variations of streamflow, sediment load, and flow–sediment relationship on multi‐temporal scales (annual, flood season and, monthly scales) in a highly erodible catchment of Chinese Loess Plateau. The results demonstrated that the streamflow, sediment load, sediment concentration, runoff coefficient, and sediment coefficient all experienced evident reductions, and the decrease in the middle and downstream stations was more significant compared with the upstream stations. The land use changes and implementation of soil and water conservation measures played major role for the streamflow and sediment load reductions with respect to precipitation change, and the runoff coefficient and sediment coefficient linearly decreased with the percentage of conservation measure area. The runoff‐sediment yield relationship on annual, flood season, and monthly scales could be generally characterized by the linear function, and the slopes during the post‐change period was lower than those during the pre‐change period of sediment load. The sediment concentration–streamflow discharge relationship represented consistent form over the entire study period, and the logarithmic function was appropriate to describe the relationships on the three timescales. The decrease of sediment concentration contributed greatest (60·7%) to sediment reduction compared with runoff productivity of rainfall (30·2%) and precipitation (9·1%). Copyright © 2015 John Wiley & Sons, Ltd.     

Upland Farming System Erosion Yields and Their Constraints to Change for Sustainable Agricultural Conservation Practices: A Case Study of Land Use and Land Cover (LULC) Change in Indonesia

In the upper catchments of Southeast Asia, land use change from forest to agricultural systems generated land degradation and conflicts between uplanders and lowlanders. More sustainable cropping systems are proposed to upper‐catchment farmers. Grass fodder strip (GFS) is an effective anti‐erosion practice, and it involves lower costs for farmers. However, labour and cash constraints are sometimes preventing farmers to implement it. To evaluate farms' current impact and adaptation capacities, we need a comprehensive understanding of farm and farm household characteristics that influence their activities. This paper proposes an approach that combines farm household surveys and modelling of farm erosion yield to help project planners and policy makers to identify such farmers in a data‐scarce environment. We developed two farm typologies—one based on both farm and farm household characteristics and one based on their erosion yield and constraints. We calculated erosion yields on plot level by using revised universal soil loss equation method and identified their constraints. We found that a typology based on farm constraints and calculated farm erosion was a good complement to identify farmers who are generating the highest erosion yields and would be able to change their production systems. This methodology is mainly useful at the beginning of conservation projects, when very few hard data are available. Copyright © 2016 John Wiley & Sons, Ltd.     

Overgrazing effects on vegetation cover and properties of volcanic ash soil in the páramo of Llangahua and La Esperanza (Tungurahua, Ecuador)

Abstract. The páramo is a high-altitude ecosystem of the northern Andes. The vegetation is continuous, with grasses as the dominant groundcover. Because of their high water retention, páramos play a fundamental role in water availability for all the population of the inter-Andean valleys. There are many studies of this specific ecosystem, but very few are focussed on overgrazing and its effect on vegetation and soil properties. Intensive grazing started less than 20 years ago and was studied in a representative area in the western Cordillera of central Ecuador covered by recent volcanic ash deposits. Intensive sheep grazing has led to a strong decline in the number of plant species, the replacement of the tussock grass vegetation by a short carpet grass vegetation, and an increase of bare land. In that area, the upper 50 cm of Andisols are deeply affected by a convergent decrease of Al and Fe oxalate and pyrophosphate in soil extracts, carbon contents decrease from 100 g kg^–1 to less than 50 g kg^–1 in the humid zone, from 70 to 40 g kg^–1 in the dry zone and a reduction of water-retention capacity at −33 kPa matrix potential from 800 g kg^–1 to 200 g kg^–1 in humid zones, from 350 to less than 100 g kg^–1 in drier areas. They showed also a decrease in the macrostructure and the development of a highly water repellent microstructure. All these important transformations favour the development of aeolian erosion in dry areas, runoff on bare surfaces, and gully erosion on slopes. The role of the páramo in water-regulation of this ecosystem seems to have been adversely affected for the future.     

Evaluation of the land reclamation project at the As Pontes Mine (NW Spain) in relation to the suitability of the soil for plant growth

The reclamation and monitoring methodologies implemented at the mining waste dump at the As Pontes Lignite Mine in Galicia (NW Spain) are briefly described. In addition the factors affecting achievement of reclamation objectives and an evaluation of the factors limiting plant growth on the constructed soils are outlined. The most serious limitations were found in the oldest mine soils constructed from sulphide-bearing spoils; high acidity, toxicity, nutrient deficiency, seasonal waterlogging due to their impermeability, and compaction. The youngest soils were constructed using sulphide-free spoils as topsoil substitutes and had fewer limitations for plant development. The results show that proper handling of spoils, and paying special attention to selective placement of sulphide bearing materials, are the most important factors in providing a suitable medium for plant growth. © 1998 John Wiley & Sons, Ltd.     

Ecology of soil springtails (Collembola, Insecta) from pine woods and Rhododendron shrublands in the Central and Eastern Pyrenees (North Spain)

The collembological composition of samples from the Central and Western Pyrenees (Northern Spain) was studied. Soils from two biotopes (pine forest and Rhododendron shrub) were studied in Nuria and Vallibierna, using different diversity indices and multivariate analyses. Ten species were found that were endemic to the Iberian Peninsula. Three of these are exclusive to the Pyrenees: Ceratophysella elegans, Hypogastrura dasiensis and Protachorutes pyrenaeus. The greatest diversity was observed in the soils of Rhododendron, above all at Nuria. Collembola were most poorly represented in the pine forest of Vallibierna, where the endemic Hypogastrura meridionalis was the dominant species. Multivariate analyses indicated that the latter species characterizes this pine forest and separates it from all other biotopes studied. The evenness (E) was most pronounced in Nuria, where Folsomia manolachei was the characteristic species.     

Landscape,Soil, and Plant Analysis of Japanese Stiltgrass (Microstegium vimineum) Invasion in the Piedmont Region,SC

Japanese stiltgrass (Microstegium vimineum), an exotic invasive plant, is native to Southeast Asia. This study was conducted to determine the chemical composition of Japanese stiltgrass as well as soil and landscape characteristics that correlate with invasion of Japanese stiltgrass around Lake Issaqueena in the upper Piedmont of South Carolina. Geographic Information Systems (GISs) and Light Detection and Ranging (LiDAR) were used to determine the spatial pattern of invasion with respect to the aspect, slope, canopy cover, soils, and distance to roads and trails. Japanese stiltgrass was distributed on both sides of Lake Issaqueena in Pacolet and Madison soil map units (Fine, kaolinitic, thermic Typic Kanhapludults) on the average slopes of 21%, but it was particularly common on the eastern shore of the lake in low-lying wet and shaded areas (mean canopy cover 51%). In addition, invasion by Japanese stiltgrass was correlated with the proximity to roads and trails. Plant tissue analysis revealed many differences in the distribution of macronutrients, macrominerals, and micronutrients in the leaves, stems, and roots of Japanese stiltgrass, although those differences were not always statistically significant. Concentrations of nitrogen (N), phosphorus (P), and calcium (Ca) were the highest in leaves while zinc (Zn) concentrations were the highest in stems and concentrations of magnesium (Mg), copper (Cu), manganese (Mn), iron (Fe), and sodium (Na) tended to be higher in roots. Carbon (C), sulfur (S), and potassium (K) concentrations were generally higher in above-ground tissues versus roots. Soil chemical analysis revealed no statistical differences between control and invaded plots. Our findings suggest that watershed areas surrounding lakes may be particularly susceptible to the invasion of Japanese stiltgrass due to their microclimates, low-lying wet pathways for seed distribution and recreational uses.