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The effects of four main practices tillage versus no-tillage, and intensive grazing versus extensive grazing, applied in characteristic agricultural and grazing lands of Crete Island were evaluated in situ using nine soil quality indicators. The following nine representative indicators of soil quality were evaluated using the rapid visual assessment methodology adopted at European level in the context of the EU research project iSQAPER: susceptibility to water and wind erosion, surface ponding (under cropping), formation of tillage pan, soil color, soil porosity, soil structure, susceptibility to slaking, infiltration rate, and biodiversity status. These indicators were measured in 48 agricultural field-plots to adequately represent the four above-mentioned practices and the different types of geomorphological patterns existing in the area. Additionally, 38 agricultural fields were sampled in the topsoil to assess cultivation practices (tillage, no-tillage) on soil organic carbon, cation exchange capacity, exchangeable potassium, available phosphorous, and soil aggregate stability. Based on the indicators rating methodology, the appropriate statistical tests were applied and the soils under different managements were characterized in terms of their potential quality and their general agricultural value. The obtained data showed that in agricultural areas, significant differences were detected between tillage and no-tillage management practices for the indicators of soil structure and consistency and infiltration rate. In grazing land, significant differences were found for the soil quality indicators of susceptibility to erosion and infiltration rate for the corresponding practices of intensive and extensive grazing. Organic carbon content, exchangeable potassium content and aggregate stability were greatly affected in tillage versus no-tillage management practices.

A study was carried out to assess if the visual soil assessment method (VSA) would allow recognizing differences between soils receiving organic matter (OM) amendments and similar control soils, by the observation of visual soil quality indicators’ score. 36 practices were identified across 8 pedoclimatic zones. These fields/plots were paired with nearby control fields/plots, without OM amendments, sharing similar farming features. A survey, comprising a VSA of the soil structure status, surface ponding, signs of erosion, earthworm counts and soil stability (slake test), complemented by measurements of soil organic matter (SOM) and permanganate oxidizable organic carbon (LOC) content, soil pH, penetration resistance and texture, on soils of both management system groups (OM addition and Control), was performed in 2016. Correlations of the visual soil quality indicators’ score with SOM, LOC, other soil properties and climate variables and indices were calculated within each group; the correlations between soil properties, and between soil properties (SOM and LOC) and climate variables were also calculated. A statistically significantly higher proportion of soils of the OM group had a good score for “soil structure and consistency” and “soil porosity”. These differences are not directly explained by non-inherent soil properties. No statistically significant Spearman’s correlation coefficients were observed between “soil structure and consistency” and either soil properties or climate variables; concerning “soil porosity”, distinct statistically significant correlations were observed between the two groups with different climate variables and indices. Correlations between the scores of the visual soil quality indicators and climate variables were found to follow the same directions of correlations of LOC content with the same climate variables, although the latter correlations were weak. Mean SOM and LOC content, were slightly higher in the OM group, although differences were not statistically significant. A high linear correlation between LOC (mg/g) and SOM (%) (r = 0.65, n = 26) exists within the Control group, but not within the OM group (r = 0.20 and n = 26). When the relationship of SOM and LOC content with visual soil quality indicators’ score was studied, statistically significant correlations were only observed between SOM and “earthworm count” within the Control group (rs = 0.44), and between LOC and “soil colour” within the OM group (rs=-0.52). Both LOC content and LOC status (ranked as a function of LOC content and soil texture), had only negative statistically significant correlations with visual soil quality indicators’ score, questioning their worth as stand-alone soil quality indicators.

The effect of irrigating with treated municipal wastewater (TMW) and fresh water (FW) on saturated hydraulic conductivity (Ks) was investigated. Ks was determined in undisturbed soil samples, collected from the upper soil layer (0–15 cm) of an illitic clay-loamy soil, after two irrigation periods. Soil samples were analyzed for a number of factors potentially affecting Ks. Analysis of variance for each of these factors was performed between the two treatments in order to detect their differences. Statistically significant differences were found for pH, ECe, SAR, ESP and the concentrations of K+, Na+, Mg2+ which are elements related with TMW and FW quality-characteristics. Correlation between all factors and Ks showed that this was positive for soil ECe, CaCO3 and negative for SAR, ESP, and bulk density. Although the influence of each separate factor was investigated and the differences between the two treatments were verified, their quantitative characteristics could not explain based on existing criteria, (the Ks reduction observed between the TMW-Ks and FW-Ks). The 2:1 type clay minerals which are more susceptible to SAR increase and EC decrease affected Ks values between the two treatments. Our findings are in line with some recently reported results and in this sense, more specific research is needed to clarify all aspects relevant to Ks and the use of TMW for irrigation purposes.

Tertiary reclaimed municipal wastewater was used in order to assess its effectiveness in irrigating olive trees cv Koroneiki against fresh water (FW), for two consecutive cultivating periods. A total of 140 olive trees were used and olive production, oil quality, oil free fatty acid profile and olive nutrition were assessed. The treated municipal wastewater (TMW) used was characterized by relatively low electrical conductivity values, still higher than the FW and higher NH4, Cl, K, Na, Fe, B, Al and Mn concentration than FW. The application of TMW slightly increased fruit production during the year of high tree yield (15.92 kg fruit per tree versus 12.73 kg per tree under FW irrigation) as well as the oil content, during the year of low yield (18.21% versus 16.43% under FW irrigation). It did not have any significant effect on the oil quality characteristics, such as free acidity, K270, K232, peroxide value and Delta K index. The irrigation treatment did not have any significant effect on the free fatty acid profile of the oil. Oleic acid was the dominant free fatty acid in the oil (ranging from 77.7 to 78.6%), followed by palmitic (10.6–11.1%), linoleic (5.5–5.8%) and stearic acid (2.5–2.8%), with their concentration falling within the range of the values for characterizing it as “Extra virgin” olive oil. The levels of K, Ca, Mg, Mn, Fe and Zn in the leaves increased with the application of TMW compared to FW, while the continuous use of TMW for two years led to a significant increase of P, Mg, Fe, Mn and Zn levels. The use of TMW under the experimental conditions described in the present study could be a valuable and profitable alternative to the use of FW in short term, by improving tree nutritional condition and enhancing oil production of superior quality.

The socio-ecological system dominated by pastureland in the Asteroussia Mountains (Crete, Greece) was analyzed over a long time interval (1945–2010) to identify the most relevant system’s characteristics and changes. Vegetation cover and land-uses have been quantified by analyzing aerial photographs exploring the whole study period. Soil characteristics have been assessed by carrying out an extensive field survey for the last reference year (2010) and by estimating the average soil loss for the past period using the PESERA soil erosion model validated by field measurements. Based on environmental, social and economic attributes, three major periods characterizing the socio-ecological system of Asteroussia Mountains have been distinguished. During the first and second period, the land was satisfactorily managed with moderate–low soil erosion rates despite the adverse (prevailing) soil, topographic and climate conditions for vegetation growth. The third time interval featured a rapid growth in the livestock density causing increased soil erosion rates, loss in plant productivity, and a generalized over-exploitation of natural resources. As a consequence, the desertification process has significantly increased in the last period. The analysis of the long-term evolution of socio-ecological system provided evidence to understand the main drivers of land degradation and to recommend mitigation policies specifically addressing Mediterranean pastureland.

iSQAPER project - Interactive Soil Quality Assessment in Europe and China for Agricultural Productivity and Environmental Resilience - aims to develop an app to advise farmers on selecting the best AgricultureManagement Practice (AMPs) to improve soil quality. For this purpose, a soil quality index has to be developed to account for the changes in soil quality as impacted by the implementation of the AMPs. Some promising AMPs have been suggested over the time to prevent soil degradation. These practices have been randomly adopted by farmers but which practices are most used by farmers and where they are mostly adopted remains unclear. This study is part of the iSQAPER project with the specific aims: 1) map the current distribution of previously selected 18 promising AMPs in several pedo-climatic regions and farming systems located in ten and four study site areas (SSA) along Europe and China, respectively; and 2) identify the soil threats occurring in those areas. In each SSA, farmers using promising AMP'swere identified and questionnaires were used to assess farmer's perception on soil threats significance in the area. 138 plots/farms using 18 promising AMPs, were identified in Europe (112) and China (26).Results show that promising AMPs used in Europe are Crop rotation (15%), Manuring & Composting (15%) and Min-till (14%), whereas in China areManuring & Composting (18%), Residuemaintenance (18%) and Integrated pest and disease management (12%). In Europe, soil erosion is the main threat in agricultural Mediterranean areas while soilborne pests and diseases is more frequent in the SSAs from France and The Netherlands. In China, soil erosion, SOM decline, compaction and poor soil structure are among the most significant. This work provides important information for policy makers and the development of strategies to support and promote agricultural management practices with benefits for soil quality. L. Barão and C. Ferreira were supported by the grants SFRH/BPD/115681/2016 and SFRH/BPD/120093/2016, respectively, from the Portuguese Fundação para a Ciência e Tecnologia iSQAPER is funded by the European Union's Horizon 2020 Programme for research & innovation under grant agreement no 635750 the Chinese Ministry of Science and Technology (grant nr:2016YFE011270) the Chinese Academy of Sciences (grant nr:16146KYSB20150001) and the Swiss State Secretariat for Education, Research and Innovation. Contract: 15.0170-1.

Soil degradation and desertification processes in the Mediterranean basin reflect the interplay between environmental and socioeconomic drivers. An approach to evaluate comparatively the multiple relationships between biophysical variables and socioeconomic factors is illustrated in the present study using the data collected from 586 field sites located in five Mediterranean areas (Spain, Greece, Turkey, Tunisia and Morocco). A total of 47 variables were chosen to illustrate land-use, farm characteristics, population pressure, tourism development, rainfall regime, water availability, soil properties and vegetation cover, among others. A data mining approach incorporating non-parametric inference, principal component analysis and hierarchical clustering was developed to identify candidate syndromes of soil degradation and desertification risk. While field sites in the same study area showed a substantial similarity, the multivariate relationship among variables diverged among study areas. Data mining techniques proved to be a practical tool to identify spatial determinants of soil degradation and desertification risk. Our findings identify the contrasting spatial patterns for biophysical and socioeconomic variables, in turn associated with different responses to land degradation.

The need for reliable estimates of soil loss under different land management practices (LMPs) is becoming imperative in the Mediterranean basin to inform decisions on more effective strategies for land management. The effect of LMPs on soil erosion and land degradation has been investigated using experiments from November 2008 to November 2011 in an olive grove in central Crete (Greece). The study area was on sloping land with soils formed on marl deposits which are vulnerable to desertification because of surface runoff and tillage. The experimental design included three treatments with two replicates (3 × 5 m experimental plots) corresponding to the following LMPs: (i) no tillage–no herbicide application, (ii) no tillage–herbicide application and (iii) ploughing to 20 cm perpendicular to the contours. The following variables were monitored: surface water runoff, sediment loss, soil temperature at 10 cm, soil moisture content at depths of 20 and 50 cm, as well as selected climatic variables. The results show that the no tillage–no herbicide management practice gave the lowest sediment loss (1.44–4.78 g/m2/yr), the lowest water runoff (1.8–11.5 mm/yr), the greatest amount of water stored in the soil, the lowest soil temperature and the lowest desertification risk compared with the other treatments. Tillage resulted in the greatest sediment loss (13.6–39.2 g/m2/yr) and surface runoff (16.5–65.0 mm/yr), and an intermediate amount of water stored in the soil. In addition, this treatment led to the loss of soil thickness of 3.7 mm/yr because of ploughing. The results demonstrate the high risk of desertification in the investigated region and the methodology can be used in other Mediterranean areas as an assessment framework for evaluating land degradation and the impact of land management on soil erosion.

Residual soils formed on mountains and hills occupy the 62.6% of the total area of the country. Their classification, morphology, and properties are strongly related to geomorphology, surface geology, and climate as described above.

The dominant soil-forming factors that strongly affect the properties , functions, and productivity of the alluvial soils are the intense stratification of their parent material, its textural configuration and composition, the age of the soils, which is related to the topographic location on the successive terraces and the climate.

The lacustrine mineral and organic soils discussed in this section belong to lands, formed in recent lake beds and river deltas. These landforms frequently coexist with recent alluvial deposits. They belong to the lowest toposequence and youngest chronosequence of allochthonous soils of the country. Geomorphologically, these are parts of recent coastal or inland flood plains, at elevations not exceeding the 20 m from them.

Soil-forming factors affect not only the course of the genesis processes but also the present and future performance of the soil systems. A brief evaluation of these factors and of their influence on the soils of Greece is presented in this section. The properties described below refer to climax undisturbed soil profiles developed under natural vegetation, which has not been disturbed to a degree that would lead to the truncation of the soil profile by erosion. It must be pointed out, however, that these conditions do not prevail in the sloping landscapes of Greece.

Soils on Holocene alluvium are classified as Fluvents (Fluvisols), as it was referred above these soils including the most productive agricultural soils covering about 13% of the total area of Greece.

Yassoglou (1986), reported in the European Communities Berlin Symposium on the Scientific Basis for Soil Protection in the European Community, that soil erosion is the dominant degradation process in southern Europe related to soil productivity deterioration.

This study investigates the relationship between fine resolution, local-scale biophysical and socioeconomic contexts within which land degradation occurs, and the human responses to it. The research draws on experimental data collected under different territorial and socioeconomic conditions at 586 field sites in five Mediterranean countries (Spain, Greece, Turkey, Tunisia and Morocco). We assess the level of desertification risk under various land management practices (terracing, grazing control, prevention of wildland fires, soil erosion control measures, soil water conservation measures, sustainable farming practices, land protection measures and financial subsidies) taken as possible responses to land degradation. A data mining approach, incorporating principal component analysis, non-parametric correlations, multiple regression and canonical analysis, was developed to identify the spatial relationship between land management conditions, the socioeconomic and environmental context (described using 40 biophysical and socioeconomic indicators) and desertification risk. Our analysis identified a number of distinct relationships between the level of desertification experienced and the underlying socioeconomic context, suggesting that the effectiveness of responses to land degradation is strictly dependent on the local biophysical and socioeconomic context. Assessing the latent relationship between land management practices and the biophysical/socioeconomic attributes characterizing areas exposed to different levels of desertification risk proved to be an indirect measure of the effectiveness of field actions contrasting land degradation.

Agricultural soil erosion is thought to perturb the global carbon cycle, but estimates of its effect range from a source of 1 petagram per year –1 to a sink of the same magnitude. By using caesium-137 and carbon inventory measurements from a large-scale survey, we found consistent evidence for an erosion-induced sink of atmospheric carbon equivalent to approximately 26% of the carbon transported by erosion. Based on this relationship, we estimated a global carbon sink of 0.12 (range 0.06 to 0.27) petagrams of carbon per year –1 resulting from erosion in the world's agricultural landscapes. Our analysis directly challenges the view that agricultural erosion represents an important source or sink for atmospheric CO 2 .

Tillage displaces large amounts of soil from upper slopes and deposits soil in lower landscape positions, greatly affecting productivity in these areas. The long-term effect of tillage on soil erosion was studied in four field sites growing mainly rainfed wheat. The soil loss from landscape positions with slopes, ranging from 3 to 28%, was estimated by: (a) comparing data of horizon thickness described at the same position at different times; and (b) using soil movement tracers added to the soil. Existing empirical relationships were used for estimating soil loss by tillage and runoff water, and loss in wheat biomass production. The experimental data showed soil losses of 0.4 to 1.4 cm yr -1 depending on slope gradient, plough depth, and tillage direction. In two of the sites, soil depth has been reduced by 24-30 cm in a period of 63 years. The mean soil displacement of the plough layer (30 cm thick), measured by soil movement tracers, ranged from 31 to 95 cm yr -1 depending mainly on slope gradient, corresponding to a rate of soil loss of 0.3 cm to 1.4 cm yr -1 . Soil eroded from the upper slopes was deposited on the lower slopes increasing soil thickness by 0.4 cm to 1.4 cm yr -1 . The application of empirical relationships, estimating soil loss by tillage and water runoff, showed that soil erosion at the field sites can be mainly attributed to tillage. The loss in wheat biomass production due to erosion was estimated at 26% on upper slopes for a period of 63 years, while a 14.5% increase in wheat production was estimated due to deposition of soil material in the lower landscape.

The Pan-European Soil Erosion Risk Assessment (PESERA) model was evaluated using existing soil erosion data collected under various types of climate, vegetation, landscape and soil conditions. The data used represent a variety of typical Mediterranean land uses such as winter wheat, vines, olives and bare, stony land prevailing in hilly areas. Using this data, the model was calibrated for sediment transport by overland flow and results compared to measured soil erosion values from runoff plots and a watershed on a monthly basis. The performance of the model was assessed statistically, showing that it can be satisfactorily used for predicting soil erosion rates under the conditions included in the study. The overall model estimate including all the available experimental data was 0.69 t ha -1 yr -1 with a maximum error of 1.49 t ha -1 yr -1 . After validation, the model was applied to a small watershed (60 ha) of great ecological importance for the sea turtle Caretta caretta. For this purpose, soil and vegetation maps were compiled from all the necessary data for applying the model. The model was run for three years using daily data from an existing nearby meteorological station. The predicted and measured soil erosion rates for a 7-month period were 0.31 t and 0.18t, respectively. Application of the model to each mapping unit showed the over-riding importance of land use for sediment generation under the given climatic conditions. Bare land, occupying 5.5% of the watershed area, generated up to 69% of the total sediments estimated for the watershed. It is concluded that the PESERA model can be used as a regional diagnostic tool under a range of soil, topographic and climatic conditions for identifying the best land use type and vegetation cover to protect hilly areas from soil erosion. The calculated overall root mean square error for the model is 0.06 t ha -1 yr -1 , compared to a soil erosion rate of 0.04 t ha -1 yr -1 , which can be tolerated for protecting the area for the sea turtle.

Although much research has been carried out on the crop productivity response to soil erosion, little is known about the role of soil erosion as a driver of land-use change. Given, however, the some-times large erosion-induced reductions in crop yields, it appears likely that erosion has a strong impact on land-use. Abandonment of arable land due to declining productivity is a land-use change that may result from soil erosion. To test this hypothesis, the western part of Lesvos, Greece, was chosen as a case study area. Lesvos has experienced accelerated erosion on marginal soils over the last century during which important land-use changes have taken place. Of the 3211 ha that were under cereals in 1886, 53% (1711 ha) was converted to rangeland (only used for extensive grazing) by the mid-20th century. At the same time, however, cereals partly returned to neighbourmg areas that were previously rangeland, implying that certain processes at the local scale resulted in land becoming unsuitable in one place and (relatively) more suitable in other places. In order to identify the relationship between these land-use changes and the occurrence of soil erosion, erosion was modelled backwards for the period 1886-1996 and soil depths reconstructed for the time when the land-use was assumed to have changed (the mid-1950s). A logistic regression was performed with soil depth, erosion and slope as explanatory variables and land-use change as the response variable. Abandonment/real location of cereals was found to be fairly well predicted by slope and soil depth. Path analysis showed erosion to be an important driver for the abandonment and reallocation of cereals, although next to slope and soil depth it has little additional predictive value. Based on the logistic model, it is anticipated that cereal cultivation in western Lesvos will probably be abandoned in the near future. (C) 2004 Elsevier B.V. All rights reserved.

Soil erosion forms a major threat to European soil resources. Although soil is a vital and largely non-renewable resource, it has not been the subject of comprehensive EU action so far. A thematic strategy for soil protection, which recognises soil erosion as one of the major threats, has currently been placed high on Europe’s political Agenda. Assessing and monitoring soil erosion is needed to evaluate the impact of, inter alia, agricultural and land use policies in Europe. The driving force–pressure–state–impact–response (DPSIR) policy framework, applied to soil erosion, is reviewed and suggestions for improvements are proposed. The agri-environmental indicators (AEIs) of soil erosion are discussed in relation to data availability, policy requirements and analytical soundness. We propose a reviewed framework and a set of soil erosion indicators that can be objectively calculated, validated against measurements or observations and evaluated by experts.

Water vapor adsorption by the soil in Mediterranean ecosystems is very important to plant growth. We hypothesized that relative air humidity, soil texture, soil water content, and soil surface conditions affect water vapor adsorption. These factors were studied in four areas in Greece with semi-arid climatic conditions on four soils classified as Xerochrept. The study was conducted on hilly areas with various physiographic and microclimatic conditions greatly affecting daily fluctuations of air humidity. Time domain reflectometers (TDR) continuously monitored soil water content at depths 5, 10 and 25 cm. Rainfall, open pan water evaporation, air temperature, and relative air humidity were measured every 40 s, averaged, and recorded on data loggers every hour. Two weighing lysimeters were used to confirm soil water data measured by TDR-electrodes. The obtained data indicated that night-time water vapor adsorption is very important for areas characterized by high oscillation of air humidity (>25%), favored under certain physiographic and microclimatic conditions. Daily water vapor adsorption by the soil was inversely proportional related to the minimum air humidity, while adsorption increased proportionally as the daily amplitude of humidity increased. Cumulative water vapor adsorption decreased during the dry period as the amount of clay content increased. The depth of penetration of wetness increased as the amplitude of fluctuation in soil water content in the upper 5 cm soil layer increased. The presence of dense perennial shrubs growing in close contact with the soil surface greatly reduced water vapor adsorption by restricting the diurnal fluctuations in air humidity in the soil–atmosphere interface. Rock fragments or plant residues on the soil surface slightly reduced water vapor adsorption but greatly favored soil water conservation. The amount of water vapor adsorbed by the soil may satisfy up to 70% of the loss of water through evaporation during the dry period under semi-arid climatic conditions.

Important land parameters such as soil texture, soil depth, topography, parent material, and climatic conditions were studied in a semi-detailed soil survey conducted in the island of Lesvos, and were related to the vegetation performance and degree of erosion. Rainfall data indicated that . the island could be divided into two major climatic zones: a semi-arid western part and a dry . sub-humid eastern part . A 45% rainfall gradient has been recorded in the above two climatic zones. The great reduction in rainfall combined with the higher evapotranspiraton demands in the semi-arid zone has significantly affected vegetation performance and degree of erosion in the area. Due to the general lack of available water, the semi-arid part of the island is dominated by poor maquis vegetation, while olive trees, oak and pine forests prevail in the dry sub-humid part under similar topographical and geomorphological conditions. Vegetation cover increases with increas- ing rainfall and soil depth. Slope grade has a variable effect on soil erosion in the various climatic zones. Erosion is decreasing with increasing rainfall for the same slope classes. Severely eroded soils prevail in the semi-arid zone with slopes greater than 12%, while slightly to moderately eroded soils are found in the dry sub-humid zone under similar slope classes. The highest rates of land degradation have been measured in areas with soils formed on pyroclastic formations. Areas with soils formed on basic igneous rocks, shale and lava are well vegetated and protected from

The effect of land use change, from arable to abandoned pasture, on soil properties and vegetation establishment was studied in hilly areas of the island of Lesvos. The main purpose of this study was to establish key indicators or land parameters that can be used for defining environmentally sensitive areas to desertification. 106 soil sites were selected in fields cultivated or non-cultivated for 40–45 years and measurements related to protection from land degradation after abandonment, such as fertility status (organic matter content, pH, cation exchange capacity (CEC), exchangeable potassium and sodium), water storage capacity (soil water retention characteristics, soil depth), erosion resistance (soil aggregate stability), and vegetation characteristics (plant species, extent of vegetation cover) were conducted. The selected sites were located on a variety of parent materials such as volcanic lava, pyroclastics, ignimbrite, schist-marble, and shale. The obtained data indicated that soil pH, and CEC were slightly affected after abandonment as compared to the cultivated soils. Levels of exchangeable sodium and potassium were higher in cultivated soils. Organic matter content and soil aggregate stability were greatly enhanced in most of the abandoned soils. Physical characteristics of the parent material greatly influenced the establishment of the natural vegetation. A critical minimum soil depth of 25–30 cm was measured. On more shallow soils, the associated natural perennial vegetation cover was rapidly reduced, under the prevailing climatic conditions of the study area. Reduction of vegetation cover was related to the parent material. Perennial vegetation was not supported at all on soils below a crucial depth, ranging from 4 to 10 cm, depending on the parent material. This study showed that soil depth is the most important parameter which has to be considered in planning land use change from arable to unmanaged pasture under the soil and climatic conditions of the study area.

An analysis has been undertaken of the land-use evolution in the island of Lesvos for the last 5000 years, based on historical and archaeological documents and recent soil and vegetation survey data. A series of maps were compiled using historical documents for the period from 3300 bc to 1886 bc and vegetation field survey data for the period from 1886–1996. A soil survey (scale 1:50 000) was conducted in 1996 in order to relate the land-use changes to the present physical environment. Cultivation of the land started around 3300 bc and intensified during the 18th century bc. During the Roman period forests were already significantly reduced to satisfy the increasing demands for agricultural products, timber and heating. In the Byzantine period (4th–15th century), vineyards and pastures expanded, mainly by clearing the forests. Olive plantations increased during the 13th century, motivated by the allocation of subsidies. During the first centuries of the Ottoman period, there was a further expansion of olive groves and pastures by reducing forests, while vineyards declined. Great changes occurred in the last century in the geographical distribution and the total area occupied by the various types of land use. Olive groves significantly expanded and were redistributed covering more fertile and productive land on hilly areas by clearing mainly pine forests. Oak forests increased on previous pasture areas. Today, pasture is the main type of land use in hilly areas. These previously forested areas have been cleared without any accompanying measures against soil erosion. This highly degraded land with shallow and severely eroded soils is not able to sustain any profitable agricultural use or natural forest. However, areas cultivated with olives remained sustainable for more than seven centuries without being significantly degraded. Copyright © 2000 John Wiley & Sons, Ltd.

In Mediterranean areas the dynamics of gully development act as an important indicator of desertification. However, little is known about the influence of climate and land-use changes, and almost no field data exist to assess the sensitivity of a landscape to gully erosion. Two important components of gully erosion studies are the prediction of where gullies begin and where they end. To address some of these issues, topographical thresholds for gully initiation and sedimentation in six different Mediterranean study areas were established. Field measurements of local soil surface slope (S) and drainage-basin area (A) at the point of initiation of ephemeral gullies in intensively cultivated fields (five datasets) and permanent gullies in rangelands (three datasets) were carried out. A negative power relationship of the form S = aA−b was fitted through all datasets, and defined as the mean topographical threshold for gullying in the respective area. Topographically controlled slopes of sedimentation at the gully bottom were also measured. Compared to theoretical relationships for channel initiation by overland flow, relatively low values for b are obtained, suggesting a dominance of overland flow and an influence of subsurface flow. The influence of landsliding at steeper slopes appeared from the flattening of the overall negative trend in the higher slope range (S > 0·30) of the integrated dataset. Comparing the threshold lines of our datasets to the average trend lines through data found in literature revealed that vegetation type and cover could better explain differences in topographical thresholds level than climatic conditions. In cultivated fields, soil structure and moisture conditions, as determined by the rainfall distribution, are critical factors influencing topographical thresholds rather than daily rainfall amounts of the gully-initiating events. In rangelands, vegetation cover at the time of incision appears to be the most important factor differentiating between topographical thresholds, overruling the effect of average annual rainfall amounts. Soil texture and rock fragment cover contributed little to the explanation of the relative threshold levels. Differences in regression slopes (b) between the S–A relationships found in this study have been attributed to the soil characteristics in the different study areas, determining the relative importance of subsurface flow and Hortonian overland flow. Sedimentation slopes where both ephemeral and permanent gullies end were generally high because of the high rock fragment content of the transported sediment. A positive relationship was found between the rock fragment content at the apex of the sedimentation fan and the slope of the soil surface at this location. Copyright © 2000 John Wiley & Sons, Ltd.

The results of erosion studies carried out at three representative sites in the European Mediterranean basin are discussed. The objectives of the study are to clarify the underlying processes affecting soil erosion and to quantify erosion and runoff in the framework of mitigation of land degradation. The study was carried out at three instrumented field stations using similar layouts and experimental set-ups and harmonized field procedures. Runoff and sediment yield from bounded plots were measured for different types of land use for longer periods. The runoff and sediment values were found to be relatively low, and showed average annual values between 2·0 and 8·9 1 m−2 for runoff, and between 20·2 and 28·1 g m−2 for sediment yield. The results show that the individual plot response on an event basis shows no relationship between runoff and sediment yield for two of the three sites. On an annual average basis a significant relationship is found between the runoff and sediment yield. Significant differences were observed between different types of land use, especially between semi-natural vegetation, burned and abandoned field cover types on the one hand, and agricultural fields on the other hand. The runoff and erosion values were lowest for the semi-natural fields. It was found that in non-cultivated fields the bounded plots might suffer from depletion of available sediment. It can be concluded that erosion figures are very low for the sites studied, and that the maintenance of semi-natural vegetation may help in the prevention of runoff generation and erosion. It can be concluded that the use of bounded plots may not be as ideal as might be expected from its wide application. In some cases open plots, especially under semi-natural land use, may produce much better results, especially when measuring over longer periods. Copyright © 1999 John Wiley & Sons, Ltd.

The effect of land use and precipitation on annual runoff and sediment loss was investigated in eight different sites along the northern Mediterranean region and the Atlantic coastline located in Portugal, Spain, France, Italy and Greece. These sites represent a variety of landscapes and are under a number of land-uses representative of the Mediterranean region, such as agricultural land with rainfed cereals, vines, olives, eucalyptus plantation or natural vegetation (shrubland). It was found that land use can greatly affect runoff and soil erosion. The greatest rates of runoff and sediment loss were measured in hilly areas under vines (average sediment loss 142.8 t km −2 yr −1 ). Areas cultivated with wheat are sensitive to erosion, especially during winter, generating intermediate amounts of runoff and sediment loss (17.6 t km −2 yr −1 ) especially under rainfalls higher than 280 mm per year. Olives grown under semi-natural conditions, as for example with an understory of vegetation of annual plants greatly restrict soil loss to nil values (0.8 t km −2 yr −1 ). Erosion in shrublands increased with decreasing annual rainfall to values in the range 280–300 mm and then it decreased with decreasing rainfall (average sediment loss 6.7 t km −2 yr −1 ).

Red soils in Greece are distributed thoughout the country, but they occur more frequently in the southern provinces and constitute important soil resources supporting several land utilization types. They can be grouped into two categories: the autochthonous and the allochthonous. The former soils are found on hard limestone and on basic igneous rocks in sloping mountainous or hilly landscapes. Moreover, they can be found on mica schists and gneisses in locations adjacent to marble or calcareous mica schists. Allochthonous red soils are wide-spread on late Tertiary and Pleistocene surfaces in the lowlands. Many of these deep deposits have red strata, a few decimeters to several meters thick, or red-colored and fine-textured layers interbedded with light colored deposits of marl, or conglomernates and also with thick strata enriched with calcareous concretions. They are distributed in the thermo- and meso-mediterranean bioclimatic zones. These sites have a common feature, the gently sloping terrain that ensures efficient drainage. There are some differences in chemical and physical properties and in the clay mineralogy of the two groups of Greek red soils. Palygorskite is present in some soils developed on basic rocks: the clay minerals of the allochthonous soils on Pleistocene and late Pliocene seems to be mixed with micas in significant amounts. Soil forming factors required for the formation of red soils are: (a) parent material containing iron-bearing minerals, and rich in bases, (b) slope gradients and/or water permeabilities of the bed-rock securring excessive drainage and (c) vegetation cover that does not produce high amounts of, and deeply distributed organic matter. The allochthonous red soils have likely inherited their color from their parent materials that were transported from the originally formed residual soils on hard limestone. The soils retain the red color in the thermo-mediterranean zone only on sloping terrains. The soils on these landscapes are frequently stratified. The Greek red soils belong to the great groups of: Rhodoxeralfs, Palexeralfs. Xerochrepts, Orthents. Large portions of the allochthnous soils have been desertified or have been severely degraded and their extensive exploitation is not recommended. Soil management practices applied in the allochthnous soils include erosion control, preservation of organic matter, minimum tillage, split application of nitrogen using non-acidifying fertilizers, irrigation, soil water conservation and sheltered agriculture.

The effects of rock fragments on soil temperature, soil moisture conservation, night time water vapour absorption and wheat biomass production were investigated. Under conditions of moderate water stress, water conservation was generally greater in the stony soils. Under conditions of pronounced drought the opposite occurred, with stony soils conserving less water than soils free of stones, though soils with large cobbles on the surface conserved the most water. Stony soils were generally warmer during daytime and cooler at night than soils free of rock fragments. In the warmest month (July) the diurnal amplitude reached 14.3°C in the control soil and 24.1°C in the stony soils. Night time absorption of water vapour in the upper 15-20 cm was less for the stony soil (17.8% cobble cover), than for the stone-free soil. Cobbles on the soil surface increased biomass production by increasing moisture conservation. After removing all the stones from the surface of 16 plots, total dry matter yield of rainfed wheat was on average 20% less than from plots with stones on the surface.

The effects of different sizes, amounts, and positions of rock fragments on soil properties and erosion were studied in experimental plots (10 treatments including bare soils and soils under natural vegetation, with 3 replicates each) installed on a hillslope. Over five events, the largest amounts of runoff were from bare soils containing abundant rock fragments, either partially embedded on the surface or incorporated in the upper part of the soil. Stoneless soils gave smaller amounts, and the smallest runoffs were measured on soils under natural vegetation. Generally, large rock fragments (cobbles) caused greater runoff than smaller fragments (coarse gravel). However, soils with appreciable amounts of coarse gravel on the surface generated considerable runoff under rainfalls of low intensity and long duration, but smaller amounts at greater rainfall intensities. Sediment loss was greater from soils with cobbles than from soils containing coarse gravel ; vegetation greatly decreased sediment loss from both. In a 12-month period, the organic matter content of the soils decreased by 15.5 to 23.0%, decreasing soil aggregate stability. The organic matter content was greater in the collected sediments than in the soil.

An analytical expression describing the moisture retention characteristic was tested using multiple regression on 105 horizons in 34 representative soils from Greece, with textures from loamy sand to heavy clay. All samples were analyzed for particle size distribution, organic carbon content, carbonates content and dry bulk density. It was found that soil moisture retention by the studied soils can satisfactorily be described using a logarithmic model that incorporates simple soil properties such as saturation moisture content, clay and silt contents, and bulk density. The applicability of a simplified model (with saturation moisture content and clay content as the only soil parameters) to small watersheds and considering groups of soil horizons was apparent from the improved coefficients of determination. Homogeneity tests showed, however, that only 2 major groups of soil horizons could be distinguished, namely well-structured horizons and structureless to weakly structured horizons. Incorporating other soil properties in the regression analyses of these soil horizon groups produced only a slightly higher R 2 -value.

Cracking was studied in fifty soils located in two recent alluvial plains and it was related to soil parameters such as clay content, soil moisture content, bulk density and coefficient of linear extensibility (COLE). The total crack area per unit soil surface, the crack width and crack depth were measured by tracing them on transparent sheets. The rate of crack development was also studied in a soil immediately after irrigation. Results showed that crack width increased initially almost linearly with decreasing soil moisture content to a certain level and then increased in a declining rate until a maximum width was attained. Cracks appeared on the soil surface after water was removed from the large soil pores. The total crack area occupied a significant portion of the soil surface reaching a maximum value of 22.7%. Measurements of water flow into the cracks during irrigation were significant and in some soils exceeded the conductivity of the uncracked soil surface. An empirical relation was found, which calculates the total crack area per unit soil surface as a function of clay content, COLE and volumetric moisture content. The average crack width was linearly related to the total crack area measured on the soil surface. Furthermore, the crack depth in the plow layer was logarithmically related to clay content, COLE and moisture content.

Soil boron occurring in various forms was correlated with boron contents in the leaves of olive trees in 51 and in barley leaves in 20 soils. The amounts of boron: in soil solution (CwsB), non specifically adsorbed (NsaB), specifically adsorbed (SaB), occluded in Mn oxides (MnoB), occluded in amorphous Fe-Al oxyhydroxides (FeoB), were correlated with soil properties such as: organic matter content, pH, free aluminum and iron oxyhydroxides (Ald, Fed), amorphous aluminum and iron oxyhydroxides (Alo, Feo). The later correlation studies were conducted on a total number of 153 soil samples inclusive of the soils used for the plant uptake investigations. The results show that the boron contents in the leaves of olive trees were significantly correlated with FeoB, CwsB, SaB and MnoB but with CwsB, NsaB, SaB and FeoB in barley leaves. The respective correlation coefficients suggest that available forms of soil boron vary with plant species. The hot water soluble boron was significantly correlated with all the fractions of boron studied except MnoB, confirming its value as a measure of available soil boron. However, the non significant (a=0.05) correlation with MnoB, which show significant correlation with the contents in the leaves of olive trees and barley, suggest that this procedure does not extract significant amounts of available B held in Mn oxyhydroxides. The highest amount of CwsB originated from the Cws B and to a lesser degree from the SaB and NsaB. The correlation among the boron held in the forms studied and the selected soil properties were either no significant or significant with the highest correlation found between FeoB and pH and Feo.

Bypass flow of water during irrigation by flooding, and associated leaching of nitrates, were investigated in sixty-three, 40 cm high undisturbed cores of nineteen calcareous alluvial Greek soils. Cracks conducting bypass water formed a network of polygons on the soil surface. The sizes of the polygons increased curvilinearly with clay content. Large polygons were associated with deeper cracking of the soil mass than the small polygons did. The size of the polygons decreased with depth in the profile. Upon irrigation cracks developed in dry soil were closed by swelling and by soil material falling from their walls. The closing was either complete or incomplete, the latter leaving a shallow U-shaped trace. Upon drying, cracks reformed along the U-shaped traces. Elsewhere, cracks developed at new places. The volume of bypass water showed a sharp initial decrease with time because of filling of the cracks and swelling, but remained significant even after 2 hours (the usual irrigation time) suggesting that a significant amount of the applied water may move to the subsoil without wetting the surface soil. Bypass flow showed a marked decrease with increasing initial soil moisture. The amounts of nitrate leached by bypass water were rather small, ranging from 0.01 to 1.8% of nitrates present in the soil cores.

Producción Científica, Rainfall is the key factor to understand soil erosion processes, mechanisms, and rates. Most research was conducted to determine rainfall characteristics and their relationship with soil erosion (erosivity) but there is little information about how atmospheric patterns control soil losses, and this is important to enable sustainable environmental planning and risk prevention. We investigated the temporal and spatial variability of the relationships of rainfall, runoff, and sediment yield with atmospheric patterns (weather types, WTs) in the western Mediterranean basin. For this purpose, we analyzed a large database of rainfall events collected between 1985 and 2015 in 46 experimental plots and catchments with the aim to: (i) evaluate seasonal differences in the contribution of rainfall, runoff, and sediment yield produced by the WTs; and (ii) to analyze the seasonal efficiency of the different WTs (relation frequency and magnitude) related to rainfall, runoff, and sediment yield. The results indicate two different temporal patterns: the first weather type exhibits (during the cold period: autumn and winter) westerly flows that produce the highest rainfall, runoff, and sediment yield values throughout the territory; the second weather type exhibits easterly flows that predominate during the warm period (spring and summer) and it is located on the Mediterranean coast of the Iberian Peninsula. However, the cyclonic situations present high frequency throughout the whole year with a large influence extended around the western Mediterranean basin. Contrary, the anticyclonic situations, despite of its high frequency, do not contribute significantly to the total rainfall, runoff, and sediment (showing the lowest efficiency) because of atmospheric stability that currently characterize this atmospheric pattern. Our approach helps to better understand the relationship of WTs on the seasonal and spatial variability of rainfall, runoff and sediment yield with a regional scale based on the large dataset and number of soil erosion experimental stations., Ministerio de Economía y Competitividad - FEDER (CGL2014 52135-C3-3-R; ESP2017-89463-C3-3-R; CGL2014-59946-R; CGL2015-65569-R; CGL2015-64284- C2-2-R; CGL2015-64284-C2-1-R; CGL2016-78075-P; GL2008-02879/BTE; LEDDRA 243857; RECARE-FP7; CGL2017-83866-C3-1-R y PCIN-2017- 061/AEI), Ministerio de Economía y Competitividad (FJCI-2017-33652), Organización para la Cooperación y el Desarrollo Económicos (TAD/CRP JA00088807), Junta de Castilla y León - FEDER (CLU-2018-04)