Runoff erosion and nutrient depletion in five Mediterranean soils of NE Spain under different land use

We investigated the influence of agricultural management and various plant covers related to the period of abandonment on soil properties, erosion and nutrient depletion in a typical Mediterranean area with sandy loam shallow soils. Cultivated soils (CS) with insufficient management, 5 year abandoned soils covered with meadow (A5), 25 year abandoned soils covered with dense scrubs (A25), 50 year abandoned soils covered with cork trees (A50) and soils in a 50 year pine reforested area (P50) were studied over a period of 6 months (May-October 1999). The soils were classified as Lithic Xerorthents. Both the differences in soil properties and response to rainfall events were mainly attributed to the different vegetation types and stages in land management. Principal components analysis (PCA) was performed on the results, by running the overall data determined after five rainfall events. The factors extracted by PCA of the samples by variables matrix represented the response of the environments to different rainfall intensities as a function of management or natural evolution after abandonment. CS environments showed the highest runoff and sediment yield as well as the highest amount of dissolved organic carbon (DOC) and nitrogen in runoff water. The sequence of abandonment (A5, A25 and A50) showed approximately the same runoff production, whereas eroded sediments (ES) and DOC were inversely correlated. Organic carbon in the ES and DOC in runoff water always increased with the period of abandonment, which accounted for consistent nutrient depletion. Nevertheless, the A50 environment (dominated by Quercus suber) showed the best soil properties, whilst the A25 environment with dense cover of Cistus monspeliensis and Calicotome espinosa seemed to cause a worsening effect on the soil's physical and chemical properties. This is probably because these environments are more severely damaged by wild fire occurrence. In terms of sediment yield, the P50 environment followed CS environment, indicating that reforestation followed by insufficient forest management may negatively affect both soil properties and response to the erosive action of rainfall.     

Soil erosion and sediment yield and their relationships with vegetation cover in upper stream of the Yellow River

Soil erosion is a significant concern when considering regional environmental protection, especially in the Yellow River Basin in China. This study evaluated the temporal-spatial interaction of land cover status with soil erosion characteristics in the Longliu Catchment of China, using the Soil and Water Assessment Tool (SWAT) model. SWAT is a physical hydrological model which uses the RUSLE equation as a sediment algorithm. Considering the spatial and temporal scale of the relationship between soil erosion and sediment yield, simulations were undertaken at monthly and annual temporal scales and basin and sub-basin spatial scales. The corresponding temporal and spatial Normalized Difference Vegetation Index (NDVI) information was summarized from MODIS data, which can integrate regional land cover and climatic features. The SWAT simulation revealed that the annual soil erosion and sediment yield showed similar spatial distribution patterns, but the monthly variation fluctuated significantly. The monthly basin soil erosion varied from almost no erosion load to 3.92 t/ha and the maximum monthly sediment yield was 47,540 tones. The inter-annual simulation focused on the spatial difference and relationship with the corresponding vegetation NDVI value for every sub-basin. It is concluded that, for this continental monsoon climate basin, the higher NDVI vegetation zones prevented sediment transport, but at the same time they also contributed considerable soil erosion. The monthly basin soil erosion and sediment yield both correlated with NDVI, and the determination coefficients of their exponential correlation model were 0.446 and 0.426, respectively. The relationships between soil erosion and sediment yield with vegetation NDVI indicated that the vegetation status has a significant impact on sediment formation and transport. The findings can be used to develop soil erosion conservation programs for the study area.     

Earthworms as colonisers: Primary colonisation of contaminated land, and sediment and soil waste deposits

This paper reviews the role of earthworms in the early colonisation of contaminated soils as well as sediment and waste deposits, which are worm-free because of anthropogenic activities such as open-cast mining, soil sterilisation, consistent pollution or remediation of contaminated soil. Earthworms live in close interaction with their soil environment and are able to change it considerably by their burrowing and litter comminuting behaviour.While earthworms have been studied extensively, several questions still remain unanswered such as:What are the characteristics of successful early colonisers?Do they function well in dispersal, individual establishment or population growth?Do the negative environmental conditions in these kinds of anthropogenic soils hamper colonization or are these colonizers relatively resistant to it?To what extent does colonization change the characteristics of the colonized substrate?In short, do earthworms impact the soil?In this paper, the characteristics that make earthworms successful colonisers are briefly described as well as which species are the most successful and under what circumstances, and what do earthworms contribute to the total process of succession. We propose that it is not so much eco-type or r-K strategy that govern success and succession of earthworm colonisation but rather environmental flexibility not only towards pH, desiccation, and temperature but also towards contaminants such as heavy metals. Moreover, the formation of an organic litter layer, in close connection with re-vegetation of the area, is essential for establishing earthworm populations, which, at first, are mainly superficially and shallow active species. The burrowing and organic matter digesting activity of these earthworms changes the upper soil to a well mixed humus layer suitable for deep burrowing earthworm species.     

Contagion externalities and the conversion of low-intensity land uses on the urban fringe

The last decade has been characterized by a growing concern over the conversion of important farmlands and unique natural environments to developed uses. Preservation of agricultural, recreation, and/or open space uses of land around expanding urban areas faces unique problems. This paper examines the impact of spatial considerations on preservation policy. In particular, the allocative significance of contagion externalities is explored for both short-run and long-run policy formation, and empirical evidence for two U.S. cities is presented. It is concluded that failure to account for the external effects generated from urban development will lead to inefficient preservation strategies based on fiscal incentives and misspecified preservation goals.     

Total sediment transport by the rivers of Abruzzi (Central Italy): prediction with the RAIZAL model

As sediment transport is mainly correlated with accelerated soil erosion, the study attempted to quantify the sediment transport by relying on qualitative classes of soil erosion risk. The classes were obtained by applying a modified RAIZAL model (MICROLEIS software package) to the most representative catchment basins of the Abruzzi area (Central Italy). They are characterized by eight homogeneous lithological groups (terrigenous and carbonatic units). Each lithological group is related to specific types of morphology, soil and land use. The estimates of total sediment transport obtained using the modified RAIZAL Codex were in good agreement with those measured or estimated by other methods, suggesting that the use of this Codex would be a valid alternative. Electronic Publication     

Contamination by chlorinated hydrocarbons (DDT,PCBs) in surface sediment and macrobenthos of the river Adige (Italy)

Surface sediments and macrobenthos communities have been employed as contamination indicators for halogenated hydrocarbons (DDT and PCBs) in the river Adige and its tributaries Fibbio and Alpone in the province of Verona. Two sampling campaigns were carried out, before and after the spring-summer floods, to determine the effects of this event on the contamination of the river. The halocarbons in the sediment were found to be associated with the fine fraction (< 53 μm) and organic carbon. From the relative concentrations of contaminants determined at various sampling stations, some information has been obtained on the sources.     

Impact of different parts of unpaved forest roads on runoff and sediment yield in a Mediterranean area

Surface runoff and sediment production on unpaved forest roads in a humid Mediterranean mountainous area has been studied using a simple portable rainfall simulator at an intensity of 90 mm h^− 1. Thirty six rainfall simulations were carried out on road plots: on the roadbank (12), on the sidecast fill (12), and on the roadbed (12). On the roadbanks, the steady-state runoff coefficient was 85.9% and runoff flow appeared after 63 s on average. On the sidecast fills, the steady-state runoff coefficient was 58.6% and mean time to runoff was 48 s. Finally, on the roadbeds, the steady-state runoff coefficient was 21.5% and mean time to runoff was 41 s. The highest soil loss rate was found on the roadbanks (486.7 g m^− 2), mainly due to low plant cover, soil texture and rock fragments. The total soil erosion on the roadbanks was 3 and 18 times higher than those from the roadbeds and the sidecast fills, respectively. As a consequence, roadbanks can be considered the main source of sediments on the studied sites, but the function of unpaved forest roads as source points for runoff generation is more important.     

The role of geosynthetics in erosion and sediment control: An overview

The use of geosynthetic erosion and sediment materials continues to expand at a rapid pace. From their early beginnings in the late 1950s, geosynthetic materials today are the backbone of the erosion and sediment control industry. Geosynthetic components are an integral part of erosion and sediment materials ranging from temporary products such as hydraulic mulch geofibers, plastic erosion control meshes and nettings, erosion control blankets and silt fences to high performance turf reinforcement mats, geocellular confinement systems, erosion control geotextiles and fabric formed revetments. This paper provides a brief overview of these materials and concepts.     

Relative influence of wildfire on soil properties and erosion processes in different Mediterranean environments in NE Spain

Abandonment of terraced soils and increased brushland cover has increased wildfire occurrence to almost an annual rate in the Cap de Creus Peninsula, NE Pyrenees Range, Province of Girona, Spain. A wildfire occurred in August 2000 and affected an area of 6760 ha of shrubs and cork trees, whereas still cultivated plots were only slightly affected. Five stations of erosion measurements, corresponding to five different environments (from present cultivation to late abandonment) were destroyed by the passage of fire, and were promptly replaced to allow to monitoring post-fire effects on soil erosion. Selected soil properties were determined monthly before the fire and during 6 months after the fire at a monthly rate. Runoff and sediment yield together with dissolved organic carbon (DOC) in runoff water and organic carbon losses in eroded sediments (EOC) were evaluated throughout 2000. The last stage of abandonment, stands of cork trees, had the highest soil stability. Nevertheless, evidence of unfavourable soil conditions was detected at the shrub stage, when Cistus monspeliensis cover was the dominant opportunistic plant. This stage was considered to be a critical threshold leading either to degradation or regeneration processes according to fire frequency. A drastic change in soil properties, erosion and nutrient depletion occurred after the fire in all the environments. Statistics enabled to state that environments differed significantly in main soil properties. By statistically comparing the measured variables between the environments before and after the fire, DOC was found to be the soil parameter showing the highest significance between environments. Absolute values of erosion were low with respect to other Mediterranean environments although the shallow nature of these soils might deserve special attention because of a comparatively higher risk of degradation.     

谈重庆市土地开发整理项目预算定额标准

阐述了重庆市新定额标准出台的必要性,从编制原则、内容组成及调整、主要特点等方面对新定额进行了解析,以提高重庆市土地开发整理项目预算编制的科学性。     

不同土地利用方式对华西雨屏区坡地土壤肥力及土壤酶活性的影响

利用坡面径流场,采用修正后的内梅罗指数法,通过对华西雨屏区坡地不同土地利用方式、不同坡度的自然生草、黑麦草和灌木的土壤肥力及土壤酶活性影响的研究,结果表明:5°坡度,自然生草土壤pH值、有机质和全氮含量小于黑麦草,而土壤全磷、全钾、碱解氮、有效磷和速效钾含量均高于黑麦草.15°坡度,土壤pH值大小顺序为灌木>黑麦草>自然生草;全磷和有效磷含量大小顺序为灌木>自然生草>黑麦草;有机质、全氮、全钾、碱解氮和速效钾含量大小顺序为自然生草>灌木>黑麦草.土壤综合肥力系数大小为5°自然生草>5°黑麦草、15°灌木>15°自然生草>15°黑麦草,且五种土地利用方式的土壤肥力均为一般,说明具有生物多样性的自然生草对华西雨屏区表层土壤的肥力提高效果优于黑麦草,而木本植物对华西雨屏区表层土壤的肥力提高效果最好.     

Changes in arable land use in Siberia in the 20th century and their effect on soil degradation

The paper presents issues related to soil degradation in Siberia caused by wind and water erosion, as the effects of changes in the Siberian agriculture in the 20th century. In order to understand the mechanism of changes in land management and their effects, i.e. the rate of erosion in the previous century, the article presents the development of agriculture from prehistoric times to the end of the 20th century. The paper presents the consequences of soil degradation, i.e. loss of surface layers of soil, humic compounds and biogenic compounds, such as nitrogen, phosphorus and potassium. The range of erosion is also determined. The paper discusses the causes of the 20th century’s soil degradation, mainly by wind and water erosion; the actual range of erosion in agricultural areas; the importance of erosion effects on the environment and the economy of Siberia. There is reference also to conditions in the European continent as such. There is a need for changes that would stop this negative process. The paper notes some positive changes that have occurred in some Siberian regions, which provide a chance to limit or even eliminate the effects of erosive soil degradation.     

The (un)sustainability of the land use practices and agricultural production in EU countries

This paper investigates differences and analogies among European Union (EU) countries concerning the links between agricultural activities and the impact on the environment. It analyses land use practices and agricultural production with two specific sets of indicators provided by the Eurostat database. Factor analysis is used to identify the key aspects of (un)sustainable agriculture and their relative importance. Hierarchical cluster analysis is then applied to classify the 28 EU countries into ‘homogeneous’ groups. The paper concludes that the countries from the centre and the north of the EU have similar agricultural practices and production methods with a high impact on the environment. Mediterranean EU countries and those in the north-west of the EU, instead, use traditional agricultural methods such as meadows and grazing livestock. This study could be useful for policymakers wanting to define tools aimed at guiding producers towards more sustainable production methods.     

Interaction of nitrogen deposition and land use on soil and water quality in Scotland: issues of spatial variability and scale

Over large areas of the Scottish uplands anthropogenic sulfur (S) deposition is declining in response to stringent national and European controls on S emissions. At the same time, however, the relative contribution of nitrogenous (N) compounds to the total anthropogenic deposition loading has increased. To investigate the significance of N deposition on the potential acidification of surface waters, national, regional, and catchment databases were developed to assess the relationships between N deposition, soil C/N ratios, land use and surface water NO3 concentrations. National classification schemes for land use and soils were used as only limited empirical data are available at such large spatial scales. Data were screened to eliminate areas where N inputs are dominated by non-atmospheric sources. From these screened datasets, it was apparent that areas with the highest risk of N leaching were situated predominantly in the upland areas of south-west and west Scotland (areas with low soil C/N ratios). At the regional scale, surface-water NO3 concentration in afforested catchments was negatively correlated with soil C/N ratios below 20. This relationship was not evident in moorland catchments, where NO3 leaching was strongly related to N deposition and the loch/catchment ratio, rather than the soil C/N ratio. Temporal trends of regional water quality highlighted as increasing loch NO3 concentrations between 1988 and 1996-1997, presumably reflecting an increase in N deposition, enhanced leaching losses from the terrestrial component of the catchment, or altered in-lake processes. The hydrochemical records for two catchments in NE Scotland (Lochnagar and Allt a Mharcaidh) highlight the importance of within catchment process in controlling the nitrogen response observed in surface waters. The potential mechanisms through which vegetation and soils may modify incoming deposition are discussed.     

Experimental study of subsurface erosion in granitic under the conditions of different soil column angles and flow discharges

Bulletin of Engineering Geology and the Environment - Soil erosion leads to soil loss and affects the hydraulic and mechanical properties of soils, and as a result, the soil fertility,...     

Use of dendrochronological method in Pinus halepensis to estimate the soil erosion in the South East of Madrid (Spain)

The rate of soil erosion in pine forests (Pinus halepensis) located in the Southeast of Madrid has been estimated using dendrochronological analysis based on the change in ring-growth pattern from concentric to eccentric when the root is exposed. Using 49 roots spread across five inclined areas, it has been found that the length and direction of the hillsides, as well as their vegetation cover affect the rate of erosion, while the slope itself does not. The erosion rates found for the different areas studied vary between 3.5 and 8.8 mm year(-1), that is between 40 and 101 t ha(-1) year(-1) respectively. These values are between 2 and 3 times greater than those predicted by USLE, for which this equation underestimates soil loss for Central Spain's Mediterranean conditions. Nonetheless, both methods (using dendrochronology to determine actual soil loss and theoretical prediction with USLE) are able to establish the same significant differences among the areas studied, allowing for the comparative estimate of the severity of the area's erosion problem.     

Effect of river landscape on the sediment concentrations of antibiotics and corresponding antibiotic resistance genes (ARG)

The purpose of this study was to quantify antibiotic resistance genes (ARG) in the sediments of the mixed-landscape Cache La Poudre River, which has previously been studied and shown to have high concentrations of antibiotics related to urban and agricultural activities. River sediments were sampled during two events (high-flow and low-flow) from five sites with varying urban and agricultural impact levels. Polymerase-chain-reaction (PCR) detection assays were conducted for four sulfonamide resistance gene families, using newly designed primers, and five tetracycline resistance gene families, using previously published primers. Sul(I), sul(II), tet(W), and tet(O) gene families were further quantified by real-time quantitative polymerase chain reaction (Q-PCR). Resistance to four classes of antibiotics (tetracyclines, sulfonamides, ionophores, and macrolides) was also investigated using a culture-based approach. The quantities of resistance genes normalized to the 16S gene copy number were significantly different between the sites, with higher resistance gene concentrations at the impacted sites than at the pristine site. Total resistant CFUs were over an order of magnitude lower at the pristine site, but differences were less apparent when normalized to the total CFUs. Six tetracyclines and six sulfonamides were also quantified in the sediments and were found to be highest at sites impacted by urban and agricultural activity, with no antibiotics detected at the pristine sit. To the knowledge of the authors, this study is the first to demonstrate a relationship between urban and agricultural activity and microbial resistance in river sediments using quantitative molecular tools.     

Soil erosion as a result of the man activity-geological environment relationship an example of quantitative evaluation in the mugello valley (Tuscany,Italy)

The spreading mechanization of the agricultural activities has determined, in the last decades, an enlargement of the fields generally obtained from natural landforms rearrangement without the employment of the necessary support practices. It has brought about a break in the weak equilibrium between the old agricultural practice and the geological environment, increasing on sloping fields morphogenetic processes and especially soil erosion. Therefore the evaluation of soil losses amount assumes a basic role in the agricultural planning. After a synthetic and critical review of the more diffuse methodologies for the evaluation of the erosion risks, a new field rain simulator is briefly described, which rapidly allows to obtain reliable practical answers. The study area was subdivided in homogeneous units for climatic, lithologic, pedologic, morphometric and land use characteristics (land units map). The employed methodology including the use of rain simulator, establishes, for each unit, the analysis of the relation between antropic activities (agricultural practices) and soil erosion, in function of the most important factors acting in the erosive process (rain erosivity, soil erodibility, slope length and gradient, crops and support practices). In this report the results related to the “Mugello Lacustrine Clay” unit are reported; this unit is a part of the sample area under study (Mugello Valley, Tuscany, Italy), and it is representative of a large extension in the ancient interappenninic lacustrine basins.     

The impact of land use regulations on residential land values in the Wa municipality, Ghana

The living standards of the residents of an urban area are influenced, either positively or negatively, by land use regulation via its impact on land values. This paper examines the development control regime in Wa municipality, Ghana, and its implications for residential land values. The dual aim of the study was to find out whether developers are complying with the system of land use regulations in the municipality and also to document the state of enforcement by the planning authority. These aims were achieved through a review of the literature on development controls and by collating empirical data obtained from land developers. It was found that development controls are largely not enforced in Wa municipality. Delays were noted in the land use regulation system and the residents?? image of the system was reported. It was also found that the land use ordinance and the building code are not consistent with the socio-economic state of the municipality??s residents. It is concluded that these conditions have led to haphazard development and have impacted negatively on land values in the municipality. It is suggested that the Wa Municipal Assembly should ensure strict compliance with land use regulations and should also address the regulation-related problems. The paper recommends a revision of the building code and the town and country planning ordinance.