Browsing by Subject "desertification"

Now showing 1 - 6 of 6
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    Erosión y desertificación.-Assessment of the effectiveness of soil and water conservation measures in reducing runoff and soil loss: establishment of a European database
    Maetens, W.; Vanmaercke, M.; Poesen, J.; Universidad de Murcia
    ABSTRACT Soil erosion by water is recognised as a major soil degradation process that requires a global approach. Large regions all over the world are in need of integrated conservation strategies that sustainably prevent and remediate soil erosion. Therefore, quantitative and globally interpretable data are needed in support of models and decision making. The effects of various soil and water conservation techniques (SWCT) on runoff and soil loss in Europe have been extensively studied over the last 60 years. Runoff plots are the most widely used measurement technique to study the effects of SWCT on runoff and soil loss by water erosion. Hence, many data are available. However, the insights gained hereby remain mostly local and often qualitative whereas the full potential of the available data is not exploited yet. This is mainly due to the fragmentation of knowledge and extrapolation difficulties inherently linked with this type of data. This study addresses the issue of the availability of quantitative runoff and soil loss data from plot measurements in Europe and the quantitative assessment of the effectiveness of various SWCT in reducing runoff and soil loss. In the framework of the EU-DESIRE project, a database is currently compiled. The database currently contains 3175 plot-year data on runoff and soil loss measurements from 108 study sites in Europe and the Mediterranean. The SWCT documented herein include crop rotations, conservation tillage, cover cropping, mulching, vegetated buffer strips and terraces. From this dataset, an evaluation can be made of the effectiveness of various SWCT in reducing runoff and soil loss by water for a range of environmental conditions in Europe. A first example, regarding the effectiveness of SWCT in olive orchards, is discussed in this paper.
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    Erosión y desertificación.-Changes in climatic conditions, vegetation cover and erosion during the Holocene in southeast Spain
    Bellin, N.; Vanacker, V.; Universidad de Murcia
    ABSTRACT The present-day landscape in Southeast Spain is the result of a long occupation history. To have a better understanding of the impact of human societies on soil degradation, we analysed the main shifts in vegetation cover, climate and human occupation for the last 12000 years. Our analyses use recently published information from continental and marine pollen series. The data suggest that climatic factors appear to be important driving factors of vegetation degradation induced by an increased aridity that is already recorded at about 5000 years ago.
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    Erosión y desertificación.-Desertification, Ecological and N, P, K, Mg fertilization changes on crop production in Hungary
    László, Márton; Universidad de Murcia
    ABSTRACT Today, all soils and ecosystems in the World and Europe are facing similar threats in particular the impacts of global climate change the effects of land-use changes. So, fragile arid and semi-arid areas are in urgent need to understand of integrated conservation and restoration approaches that can contribute significantly to prevent and reduce the widespread on-going land and biodiversity degradation, desertification processes, such as erosion, flooding, overgrazing, drought, forestfire and salinization. This paper will establish promising integrated climate-soil-fertilization-crop system models taking into account the impact of combined drivers on soil processes, e.g. climate and fertilization changes in land use and management conservation based on a close participation of scientists with stakeholder groups in the degradation and desertification hotspots, that can be transferred across a wide range of temporal and spatial scales. Generally, among natural catastrophes, droughts and floods cause the greatest problems in field crop production. The droughts and the floods that were experienced in Hungary in the early 1980’s have drawn renewed attention to the analyses of these problems. New research on climate change-soilplant systems are focused on yield and yield quality. This paper reports the climate change (rainfall) x soil (acidic sandy brown forest) x mineral N-, P-, K-, Mg fertilisation x plant interactions on rye (Secale cereale L.), on potato (Solanum tuberosum L.) and on winter wheat (Triticum aestivum L.) yields in a long term field experiment set up at Nyírlugos in north-eastern Hungary under temperate climate conditions in 1962. Results are summarised from 1962 to 1990. Main conclusions were as follows: 1. Rye: a., Experimental years were characterised by frequent extremes of precipitation variabilities and changes. b., By an average year, at a satisfactory fertilisation level (N: 90 kg ha-1 and NP, NK, NPK, NPKMg combinations) the maximum yield reached 3.8 t ha-1. But yield was decreased by 17% and by 52% due to drought and excess rainfall respectively. Negative effects (drought, excess rainfall) were diminished by 20-25% with Mg treatments. c., Correlation between rye yields and precipitation during vegetation seasons showed that optimum yield (4.0 t ha-1) will develop in the 430-470 mm range. 2. Potato: a., Trial years were estimated by recurrent extremes of climate. b., In vegetation seasons poor in rainfall yield safety in potato cannot be secured by fertilisation (N, NP, NK, NPK, NPKMg) alone. Under this weather condition yield was decreased by 35%. c., Optimum yields range between 17-21 t ha-1 at 280-350 mm. 3. Winter wheat: a., Climate was manifested mainly by precipitation using average, drought, dry and rainy levels. b., Yields from drought year effects with N, NP and NK combinations were diminished to 48% and with NPK and NPKMg treatments fell to 51%. c., Optimum yields (3.5-4.0 t ha-1) were developed at 450-500 mm. This paper summarises quantified results of rye, potato and winter wheat research with regarding to interaction effects and relationships between climate (rainfall)-mineral nutrition-crop production changes in Hungary during a long term field experiment to agricultural sustainability.
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    Morfología Fluvial.-Olas de calor, sequías intensas y desertificación, durante el verano 1994 en el Sureste español (Murcia)
    Avila, F.; Universidad de Murcia
    ABSTRACT The South-East of Spain, which has semiarid climate, is one of the hottest and driest areas in Europe. This regían is specialized in ·irrigated agricultures and citrus fruits (lemons). The drought can last a long period, sometimes two or three years. The lack of water is becoming the biggest problem, especial\y since the development of irrigated cultures. Drought and heat waves are the major climatic risks and they cause most of the economic losses in agrjcultural activity. 1994 summer was exceptlonal in this region of Spain: heat waves and droughl A majar disaster that revealed a crisis that began many years ago. The need of water is growing while the volume of available water tends to go down. 1-994 surnmer and its disasters (fire, burnt crops by heat) generated social and politk tensions. Desertification is threatening the region. This siluation is not new "the drought" is a normal phenomenon in a semiarid area, but the accurnulalion of drought. aridity and human actions worsening desertification. After 1994, new droughts and heat waves 'increased the lack of water because agriculture needs more and more water. Nonetheless this cultural method is compacting soil by the reduction of organtc matter and by !he heavy falls of rain No solution has been found yet, they have to find new resources of water or change agricultural irrigation methods 1o save water and build up a sustain.able development for this semiarid area.
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    Morfología Fluvial.-Physico-chemical and spectral characteristics of soil crusts in semiarid areas. An ecosystem condition index?
    Chamizo, S.; Miralles, I.; Cantón, Y.; Lazaro, R.; Solé-Benet, A.; Domingo, F.
    ABSTRACT Physical and biological soil crusts occupy a wide extension in arid and semiarid areas all over the world. Numerous authors consider Biological Soil Crusts (BSC) as ecosystem engineers in arid lands because they control resource availability, through the regulation of the water balance, reduction of erosion and enhancement of soil fertility via nitrogen and carbon fixation. Evidences exist of the replacement of some types of BSC by other crust types over time and different types have different effects on resource availability. Therefore, the relative abundance and distribution of the different development stages of BSC can be considered as a soil quality indicator which includes information about the dynamic condition of the ecosystem, as well as its degree of maturity and conservation, as BSC extend slowly. The objective of this work is to verify if the physicochemical characteristics in the crust and the subjacent soil get better as BSC development increases, so the distribution of soil crusts (in different stages of development) in an ecosystem will be largely related to soil physicochemical conditions. Two semiarid areas in the province of Almeria were chosen: El Cautivo (Tabernas) and Amoladeras (Cabo de Gata) and the most representative physical and biological soil crusts were identified at both sites. The stage of development of BSC was considered. For each crust type, physical and chemical characteristics for the crust and the soil underneath were sampled and some spectral features of BSC were measured as an indicator of photosynthetic activity, using a portable spectroradiometer. Amoladeras appeared as an ecosystem with improved physicochemical characteristics in the two sampled fractions in comparison with El Cautivo (a badlands area), except water retention capacity, due to textural differences. Furthermore, the deepness of the absorption peak at 680 nm was higher in the BSC of Amoladeras than of El Cautivo. At both sites, water retention capacity, nitrogen and carbon content were higher in the BSC than in the physical crust both in the crust and the subjacent soil. These parameters, also at both sites, increased along with BSC development both in the crust and the in subjacent soil, except for the soil C and N content in Amoladeras.
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    Ponencias Invitadas.-Desertification: the broader context
    Kirkby, M.J.; Universidad de Murcia
    ABSTRACT After over twenty years of research, there is still not complete consensus on even how to define desertification. This is reflected in the changing emphasis of UNCCD and EU programmes. The focus on physical processes in the 1990s has changed, first to an emphasis on the impacts of desertification and global change, and more recently towards sustainability rather than degradation as the core of most research effort, although much is still concerned with scenarios of possible future change. Different research tools are able to survey different windows on changing degradation status. Remote sensing methods, for example, provide an excellent window on the recent past, but little forecasting potential beyond projecting linear trends. Dynamic models add some understanding of the interaction of different components, and are increasingly engaging with socio-economic as well as strictly bio-physical processes, but are still limited by the intervention of the unexpected – the boom in biofuel demand, the credit crunch etc – that severely limit their forecasting horizons. This survey examines some of the over-arching relationships that must always constrain the relationships between population, food, land, water and energy, constraining the overall sustainability of global systems in a way that can only temporarily be ignored through irreversible mining of resources and exploitation of one region at the expense of another. The land sets constraints on food production that can partially be overcome through technological development, linked as both cause and effect to population growth, and may also be reduced by degradation. Less developed countries generally have a larger proportions of rural population and higher rates of rural-urban migration, but higher overall rates of population increase still lead to increasing rural populations (in contrast to more developed economies with falling rural numbers), adding to pressure on land resources and, almost inevitably, to degradation. This example demonstrates how broader social and economic forces lie at the root of much desertification, so that alleviation measures should not be confined to the directly affected area, but linked to national policies and development.