Showing papers in "Catena in 2016"

Application of GIS-based data driven random forest and maximum entropy models for groundwater potential mapping: A case study at Mehran Region, Iran

Abstract: Groundwater is considered as the most important natural resources in arid and semi-arid regions. In this study, the application of random forest (RF) and maximum entropy (ME) models for groundwater potential mapping is investigated at Mehran Region, Iran. Although the RF and ME models have been applied widely to environmental and ecological modeling, their applicability to other kinds of predictive modeling such as groundwater potential mapping has not yet been investigated. About 163 groundwater data with high potential yield values of ≥ 11 m 3 /h were obtained from Iranian Department of Water Resources Management (IDWRM). Further, these selected wells were randomly divided into a dataset 70% (114 wells) for training and the remaining 30% (49 wells) was applied for validation purposes. In total, ten groundwater conditioning factors that affect the storage of groundwater occurrences (e.g. altitude, slope percent, slope aspect, plan curvature, drainage density, distance from rivers, topographic wetness index (TWI), landuse, lithology, and soil texture) were used as input to the models. Subsequently, the RF and ME models were applied to generate the groundwater potential maps (GPMs). Moreover, a sensitivity analysis was used to identify the impact of variable uncertainties on the produced GPMs. Finally, the results of the GPMs were quantitatively validated using observed groundwater dataset and the receiver operating characteristic (ROC) method. Area under ROC curve (AUC) was used to compare the performance of RF with ME. The uncertainty on the preparation of conditioning factors was taken in account to enhance the model. The validation results showed that the AUC for success rate of RF and ME models was 86.5 and 91%, respectively. In contrast, the AUC for prediction rate of RF and ME methods was obtained 83.1 and 87.7%, respectively. Therefore, RF and ME were found to be effective models for groundwater potential mapping.

Comparison of a logistic regression and Naïve Bayes classifier in landslide susceptibility assessments: The influence of models complexity and training dataset size

Abstract: The main objective of the present study was to compare the performance of a classifier that implements the Logistic Regression and a classifier that employs a Naive Bayes algorithm in landslide susceptibility assessments. The study provides an evaluation concerning the influence of model's complexity and the size of the training data, while it identifies the most accurate and reliable classifier. The comparison of the two classifiers was based on the assessment of a database containing 116 sites located at the mountains of Epirus, Greece, where serious landslides events have been encountered. The sites are classified into two categories, non-landslide and landslide areas. The identification of those areas was established by analysing airborne imagery, extensive field investigation and the examination of previous research studies. The geo-environmental conditions in those locations where analyzed in regard with their susceptibility to slide. In particular, seven variables where analyzed: engineering geological units, slope angle, slope aspect, mean annual rainfall, distance from river network, distance from tectonic features and distance from road network. Multicollinearity analysis and feature selection was implemented in order to estimate the conditional independence among the variables and to rank the variables according to their significance in estimating landslide susceptibility. By the above processes the construction of nine different datasets was accomplished. Further partition allowed creating subsets of training and validating data from the original 116 sites. Each dataset was characterized by the number of the variables used and the size of the training datasets. The comparison and validation of the outcomes of each model was achieved using statistical evaluation measures, the receiving operating characteristic and the area under the success and predictive rate curves. The results indicated that model's complexity and the size of the training dataset influence the accuracy and the predictive power of the models concerning landslide susceptibility. In particular, the most accurate model with high predictive power was the eighth model (five variables and 92 training data), with the Naive Bayes classifier having a slightly higher overall performance and accuracy than the Logistic Regression classifier, 87.50% and 82.61% on the validation datasets, respectively. The highest area under the curve was achieved by the Naive Bayes classifier for both the training and validating datasets (0.875 and 0.806 respectively) while the Logistic Regression classifier achieved a lower AUC values for the training and validating datasets (0.844 and 0.711, respectively). When limited data are available it seems that more accurate and reliable results could be obtained by generative classifiers, like Naive Bayes classifiers. Overall, landslide susceptibility assessments could serve as a useful tool for the local and national authorities, in order to evaluate strategies to prevent and mitigate the adverse impacts of landslide events.

Soil water erosion on Mediterranean vineyards: A review

Abstract: Soil water erosion on cultivated lands represents a severe threat to soil resources in the world, and especially in Mediterranean areas, due to their topographic, edaphic and climatic conditions. Among the cultivated lands, vineyards deserve a particular attention because, aside representing one of the most important crops in terms of income and employment, they also have proven to be the form of agricultural use that causes one of the highest soil losses. Although the topic of soil water erosion on vineyards has been studied, it still raises uncertainties, due to the high variability of procedures for data acquisition, which consists into different scales of analysis and measurement methods. There is still a great gap in knowledge about the effect of triggering factors on soil water erosion and, so far, an effort to quantify this effect on the Mediterranean viticulture has not been made yet. Therefore, this paper review aims to (i) develop a documented database on splash, sheet and rill erosion rates in Mediterranean vineyards, (ii) identify and, if possible, quantify the effect of triggering factors such as topography, soil properties, rainfall characteristics and soil conservation techniques on soil water erosion, and (iii) provide suggestions for a more sustainable viticulture. Although the large variability of data, some general trends between erosion rates and triggering factors could be found, as long as data were categorized according to the same measurement method. However, no general rule upon which to consider one triggering factor always predominant over the others came out. This paper review supports the importance of monitoring soil water erosion by field measurements to better understand the relationship between the factors. However, protocols should be established for standardizing the procedure of collecting data and reporting results to enable data comparison among different study areas.

Effects of precipitation and restoration vegetation on soil erosion in a semi-arid environment in the Loess Plateau, China

Abstract: Soil erosion is a critical environmental problem of the Loess Plateau, China As an important project for soil and water conservation in the semi-arid environment, the Grain-for-Green extensively transformed a wide range of farmland into vegetated land after the 1980s Yet, the effects of vegetation restoration on soil erosion reduction are not well understood In this study, we monitored runoff and sediment yield at sites restored with six typical restoration vegetation types including shrubs (Armeniaca sibirica, Spiraea pubescens and Artemisia coparia), grasses (Andropogon), and shrub–grass-compounds (Andropogon and A coparia) in the Loess Plateau We employed structural equation modelling (SEM) to systematically analyze the relative effects of precipitation and vegetation on soil erosion The results showed that the runoff and sediment yield at the grasslands were significantly higher than other cover types The shrub cover had the strongest soil conservation capacity of all restoration vegetation SEM results showed varying impacts of precipitation (ie, total amount and erosive rainfall intensity) on runoff and soil erosion under different vegetation types owing to differences in canopy structure and surface litter layer Our study quantitatively revealed the interactive effects of precipitation and vegetation on runoff and sediment, which may be beneficial to conserving available water and soil resources in the semi-arid environment

Physically based soil erosion and sediment yield models revisited

Abstract: A plenty of models exist for study of the soil erosion and sediment yield processes. However, these models vary significantly in terms of their capability and complexity, input requirements, representation of processes, spatial and temporal scale accountability, practical applicability, and types of output they provide. The present study reviews 50 physically based soil erosion and sediment yield models with respect to these factors including shortcomings and strengths. The literature generally suggests the use of models like SWAT, WEPP, AGNPS, ANSWERS and SHETRAN for soil erosion and sediment studies. Most of the developed soil erosion and sediment yield models are capable of simulating soil detachment and sediment delivery processes at hillslope scale; a limited development was found in the field of reservoir siltation and channel erosion processes. The study proposes a guideline for selection of an appropriate model to the reader for a given application or case study. The future research suggested to improve the simulation and prediction capability of physically based soil erosion and sediment yield models, and should focus on incorporation of improved global web based weather database, inclusion of sediment associated water quality and gully erosion simulation module, and improvement in reservoir siltation and channel erosion simulation processes.

Impacts of land use–land cover change and urbanization on flooding: A case study of Oshiwara River Basin in Mumbai, India

Abstract: In the present study, the impact of land use–land cover (LULC) change and urbanization on floods are investigated for an expanding urban catchment of the Oshiwara River in Mumbai, India. For the study area, the land use change was estimated between 1966, 2001 and 2009 by using the topographic map and satellite images. The analysis of LULC change revealed that the change between 1966 and 2001 was slower than that between 2001 and 2009. The LULC analysis revealed a 74.84% increase in the built up area with a 42.8% decrease in open spaces between the years 1966 and 2009, with substantial increase in urbanization. The impact of LULC on flood hydrograph for different return periods was ascertained by using the HEC-GeoHMS and HEC-HMS models. In the past 43 years, the increase in peak runoff and runoff volume is marginally varied by 3.0% and 4.45% for the 100-year return period and 10.4% and 12.2% for the 2-year return period respectively, although the built-up area increased by 74.84%. The flood inundation area is increased by 5.61% for the 100-year return period and 6.04% for the 10-year return period between the same time period. The results showed that lower return periods led to a maximum change in peak discharge/volume of runoff compared to higher return periods for change in land use conditions. Further, a flood hazard analysis has been carried out and it showed that the area in highly hazardous zone is increased by 64.29% as compared to less hazardous zone where it is decreased by 32.14%. Overall, the total flood hazard area is increased by 22.27%. The developed flood plain and flood hazard maps can be used by the local Municipal body to prepare flood mitigation and early evacuation management plans during floods and as a criteria for insurance of any property by insurance organizations.

Effects of climate, land cover and topography on soil erosion risk in a semiarid basin of the Andes

Abstract: Understanding soil erosion processes in the Ecuadorian Andes with a tropical wet-dry climate and a variable topography, is fundamental for research on agriculture sustainable, environmental management, as well as for a stable water supply for the local populations. This work proposes method to estimate soil erosion risk in the semiarid Catamayo basin with limited data. The results show that the rainfall distribution and the erosivity along with the rugged topography, followed by the land cover (C-factor), are the most important factors to estimate soil erosion risk. The soil erodibility is the most important factor in the dry season for agricultural areas and where the ground cover is sparse. Soil erosion risk is higher in the centre and southwest than in the northeast of Catamayo basin. In protected areas with evergreen vegetation, the soil erosion risk is very low, even with steep slopes and high annual rainfall amounts. The methodology developed allows understanding of the soil erosion processes and the factors that lead to the spatio-temporal variability of soil erosion risk, and as a consequence improves the potential to achieve sustainability of this ecosystem through proposed conservation measures.

Spatial prediction of soil surface texture in a semiarid region using random forest and multiple linear regressions

Abstract: Soil texture is an essential and extremely variable physical property that strongly influences many other soil properties that are highly relevant for agricultural production, e.g., fertility and water retention capacity. In plain areas, terrain properties derived from a digital elevation model are not effective for digital soil mapping, and the variation in the properties of such areas remains a challenge. In this regard, remote sensing can facilitate the mapping of soil properties. The purpose of this study was to evaluate the efficiency of using of data obtained from the Thematic Mapper (TM) sensor of Landsat 5 for digital soil mapping in a semi-arid region, based on multiple linear regression (MLR) and a random forest model (RFM). To this end, 399 samples of the soil surface layer (0–20 cm) were used to predict the sand, silt and clay contents, using the bands 1, 2, 3, 4, 5 and 7, the Normalized Difference Vegetation Index (NDVI), the grain size index (GSI), and the relationships between bands 3 and 2, bands 3 and 7, and bands 5 and 7 (clay index) of the Landsat 5 TM sensor as covariates. Among these covariates, only band 1 (b1), the relationship between bands 5 and 7 (b5/b7) for sand, silt and clay, and band 4 (b4) for silt were not significantly correlated according to Pearson's correlation analysis. The validation of the models showed that the properties were best estimated using the RFM, which explained 63% and 56% of the spatial variability of sand and clay, respectively, whereas the MLR explained 30% of the spatial variation of silt. An analysis of the relevance of the variables predicted by the RFM showed that the covariates b3/b7, b5, NDVI and b2 explained most of the variability of the considered properties. The RFM proved to be more advantageous than the MLR with respect to insensitivity to overfitting and the presence of noise in the data. In addition, the RFM produced more realistic distribution maps of the soil properties than did the MLR, taking into account that the estimated values of the soil attributes were in the same range as the calibration data, while the MLR model estimates were out of the range of the calibration data.

Spatial distribution, contamination and ecological risk assessment of heavy metals in surface sediments of Erhai Lake, a large eutrophic plateau lake in southwest China

Abstract: The concentrations of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) and major metals (Al, Fe and Ti) in 42 surface sediment (0–2 cm) samples from Erhai Lake, a large eutrophic plateau lake in southwest China, were analyzed. The heavy metal contamination was studied by comparing the multivariate statistical analysis and enrichment factor (EF) results, and the potential eco-risks were comparatively discussed by combining the sediment quality guidelines (SQGs), potential ecological risk index (Er and RI) and EF indices. The heavy metal concentrations displayed obvious spatial diversity in the surface sediments due to human contamination and variations in sediment texture, such as grain size and organic matter content. Principal component analysis (PCA) indicates that Cr, Cu and Ni were mainly lithogenic in origin and that the As, Cd, Hg, Pb and Zn levels were influenced by anthropogenic contamination. The EFs show that Cu, in addition to As, Cd, Hg, Pb and Zn, was also influenced by anthropogenic contamination. The contamination levels of the metals were zero to minor for Cu, Pb and Zn and moderate to significant for As, Cd and Hg on a whole lake basis. The different origins assigned to Cu by the PCA and EF results suggest that the PCA is less effective at differentiating pollutants when the pollution level is low. Anthropogenic As in the surface sediments was derived primarily from agricultural sources, and the other anthropogenic metals were mainly from atmospheric deposition and secondarily from industrial discharges. The mean concentrations of As and Cd are above the threshold effect concentrations (TECs) of the SQGs, suggesting adverse effects of the metals are likely to occur, which is in agreement with the Er assessment. The mean concentration of Hg is lower than the TEC; however, it may also pose adverse effects to the organisms because of its high contamination level (mean EF = 6.7) and toxicity, which is supported by the Er value. The RI values (average 431) indicate that the heavy metals may pose very high eco-risks, with higher contributions from As, Cd and Hg. Generally, As, Cd and Hg are suggested to be the most concerning metals with respect to environmental monitoring and management in Erhai Lake due to their high contamination levels and potential eco-risks.

Assessment of soil erosion change and its relationships with land use/cover change in China from the end of the 1980s to 2010

Abstract: An empirical approach was employed to monitor changes in soil erosion status in China, incorporating landform, slope, vegetation coverage, land use/cover, and expert interpretation of remote sensing images. We built up a National Soil Erosion Database of China (NSED-C) at 1:100,000 scale that contains Chinese soil erosion data for five periods (the end of the 1980s, 1995, 2000, 2005, and 2010), and established the soil erosion situation for China in 2010 and changes in erosion since the end of the 1980s. The results show that water erosion is the most widely distributed erosion type, affecting 56% of the land area of China, followed by wind erosion and freeze–thaw erosion. But the most serious erosion type is wind erosion. Most of the change in soil erosion was concentrated within regions of northern China that have fragile ecosystems, such as the Loess Plateau, Mu Us Sandy Land, Hunshandake Sandy Land, Horqin Sandy Land, Xianghai Wetland and the Tarim River basin. Hilly regions in southern China were also widely affected by differing soil erosion changes. Impacted by some environmental protection measures and economic activities such as reclaim in northern and western China, Grain for Green Project, and planting of fast-growing woods on hills in southern China, two different trends of soil erosion change are identified during the monitoring period: soil erosion in China was getting worse before 2000 after which it has subsequently improved. Nevertheless, a series of environmental protection measures implemented after 2000 did not recover the previous negative impact before, so that the overall soil erosion situation in China in 2010 is worse than at the end of the 1980s.

Spatial variability of soil organic matter using remote sensing data

Abstract: Estimation of soil organic matter (SOM) at unsampled locations is crucial in agronomical and environmental studies. In this study, the ability of geostatistical methods such as ordinary kriging (OK), simple kriging (SK) and cokriging (CK) and hybrid geostatistical methods such as regression-simple kriging (RSK)/-ordinary kriging (ROK) and artificial neural network-simple kriging (ANNSK)/-ordinary kriging (ANNOK) was evaluated to predict SOM content. To this end, a set of 100 soil samples were collected from 0 to 15 cm depth of agricultural soils in Selin plain, northwest of Iran. The organic carbon was measured using Walkley–Black method. An auxiliary variable was provided by remote sensing data (Landsat 7 ETM +). Three performance criteria including mean error (ME), root mean square error (RMSE) and coefficient of determination (R 2 ) were used to evaluate the performance of the derived models. The results showed that the ANN model that used principal components (PCs) as input variables, performed better than the multiple linear regression (MLR) model. The hybrid geostatistical methods, which include ANNOK, ANNSK, ROK and RSK provided more reliable predictions than the geostatistical methods, which include SK, OK and CK. In general, the best prediction method for the estimation of SOM spatial distribution was the ANNOK model, which had the smallest RMSE (0.271%) and the highest R 2 (0.633). It was concluded that information from Landsat ETM + imagery is potential auxiliary variables for improving spatial prediction, monitoring SOM and development of high quality SOM maps, which is the primary step in site-specific soil management.

Quantitative assessment of the relative roles of climate change and human activities in desertification processes on the Qinghai-Tibet Plateau based on net primary productivity

Abstract: Accurately identifying the contributions of climate change and human activities to desertification will support effective strategies for combating desertification. In this study, we employed the changes in net primary productivity (NPP) in areas of aeolian desertification on the Qinghai-Tibet Plateau from 2000 to 2014 to determine the dynamics of desertification. Changes in the potential NPP (PNPP) and the difference between PNPP and actual NPP (ANPP) revealed the relative contributions of climate change and human activities to desertification. We found overall mitigation of desertification during the study period. However, desertification varied both spatially and temporally. Areas with mitigation accounted for 80.1% of the total desertified land; other areas experienced exacerbation. In 67.3% of the area of mitigation, the improvement was attributed to climate change, and especially to increased precipitation. Climate change also accounted for the exacerbation of desertification in 38.0% of the total area in which desertification worsened, largely due to reduced precipitation. Therefore, climate change was the dominant factor for mitigation of desertification, and human activities were the dominant factor for exacerbation of desertification. The dominant factors for mitigation and exacerbation varied spatially. In the central and northeastern Qinghai-Tibet Plateau, climate change was the primary factor for mitigation of desertification and human activities dominated the exacerbation of desertification. In the southern and western Qinghai-Tibet Plateau, the reverse was the case. The ecological protection projects that have been implemented since 2000 in most of the Qinghai-Tibet Plateau have not yet become a dominant factor in controlling desertification processes.

Utilizing portable X-ray fluorescence spectrometry for in-field investigation of pedogenesis

Abstract: In recent years portable X-ray fluorescence (pXRF) spectrometers have been recognised as an in-field tool for soil analyses as they offer rapid, real-time, simultaneous multi-element analysis of soil samples with no or minimal sample preparation. Portable XRF has been used quite extensively to estimate the degree of soil contamination with heavy metals and to measure the concentration of elements in soils that are important for the soil's fertility, but more recently it has also been used to calibrate for a range of soil chemical and physical properties to perform digital soil morphometrics. However, this still relatively new technology also offers an opportunity for soil scientists to investigate processes of pedogenesis in the field, which in turn will complement the in-field descriptions of soils profoundly. Here, we employed a handheld pXRF spectrometer to investigate the pedogenesis pathways and likely parent materials of three different soil types, utilizing elemental concentration data and geochemical indices. Our study site, a property called ‘Nowley’, is situated on the Liverpool Plains in the Spring Ridge district on the North West Slopes of New South Wales, Australia, in one of the most versatile dryland cropping regions of the continent. The variation in soil types and parent materials across the property offers an unique opportunity to study the impact of parent materials and topography on soil formation. A total of three soil pits were excavated to a depth of 1.0 m to expose the lower B horizons. Soil pit faces were then scanned at 0.1 m depth increments starting from the top of the soil profile to the lowest B horizon exposed. Our results show that elemental data acquired in field condition, which are affected by sample heterogeneities and soil moisture content, are comparable to elemental data acquired in air-dried, ground condition, as geochemical index values show similar trends down the soil profile. We found that the use of pXRF is a very effective in-field tool to assess pedogenic pathways and parent material origin, because of the instant computation of weathering indices and elemental ratios. We conclude that pXRF can be applied successfully and readily to study the soil's weathering history and identify processes of soil formation in the field.

Soil erosion resistance of “Grain for Green” vegetation types under extreme rainfall conditions on the Loess Plateau, China

Abstract: Objectives Soil erosion, which is pronounced on the Loess Plateau of China, is generally caused by heavy rain or thunderstorms. To control soil and water losses and improve the eco-environmental condition of the Loess Plateau, the Chinese Central Government issued the “Grain for Green (GFG)” policy in 1999 to restore vegetation on previously farmed steep lands. This study will explore the value of the “GFG” policy by examining the response of three different “GFG” vegetation types (grassland, woodland and orchard) in controlling erosion from an extreme rainfall event in the Northern Shaanxi Province on the Loess Plateau of China. Methods The vegetation types, coverage, biological soil crust (BSC) coverage, plant species diversity, slope gradient, gully erosion of different “GFG” vegetation types under extreme rainstorm conditions (called “727” rainstorm) were assessed using field surveys. Results It was found that the grassland and woodland are more effective at reducing gully erosion than orchards, and compared with the sloping farmland, the conversion of sloping farmland to grassland or woodland can reduce gully erosion by more than 90%, whereas conversion of sloping farmland to orchards actually increases gully erosion by more than 60%. Furthermore, having a high surface vegetation cover and well-developed BSC were the most important factors in reducing soil erosion. Conclusions The “GFG” measures are beneficial in reducing soil erosion on the Loess Plateau, and rehabilitation efforts should focus on grassland and/or woodlands rather than attempting to achieve dual goals with economic gain (i.e., from orchard crops), as it appears that orchards are not conducive for controlling soil erosion.

Mapping and evaluating land suitability using a GIS-based model

Abstract: Wheat is considered the most important crop in Egypt; however, not all of the land in Egypt is equally suitable for growing wheat. The main objective of this study was to develop a spatial model for land suitability assessment for wheat crop integrated with geographic information system (GIS) techniques. Organic matter, N, P, K, Zn, drainage, texture, depth, topography, surface stoniness, hard pan, hydraulic conductivity, water holding capacity, salinity, ESP, CaCO3 and pH were recognized as factors affecting land suitability for wheat crop in the study area. Three thematic indicators were used in assessing land suitability, soil fertility, chemical and physical properties quality indices. The results of the proposed model were compared with the Square root and Storie methods. The results from the proposed model showed that most of the units fall within the highly suitable class and the moderately suitable class which together represent 71.44% of the total area. About 29% of the study area was marginally suitable and unsuitable for wheat crop and those areas correspond to the adverse physical and chemical properties of the soil. The comparison of the results of the three approaches used showed that the present model has a high level of agreement with the Square root method, whereas all land units have the same classes of suitability with the exception of one unit. The present model allows obtaining results that seems to be corresponded with the current conditions in the area.

Spatial variability in soil organic carbon and its influencing factors in a hilly watershed of the Loess Plateau, China

Abstract: In the last 30 years, a number of large-scale multi-ecological projects have been implemented on the Chinese Loess Plateau, where there has been a significant trend toward ecological restoration, which will certainly affect the spatial distribution of soil cabon sequestration. We investigated 180 topsoil sites (to 20 cm depth) to enhance the understanding of the spatial patterns of soil organic carbon (SOC) and its dominant influencing factors in the Luoyugou watershed (72 km2), which is a typical watershed in the gully-hill area of the Loess Plateau, China. The results indicate that the SOC in the Luoyugou watershed follows a distinct spatial pattern, whereby the SOC increases as altitude increases. The SOC of the mountain ridge area (high elevation area) is measurably higher than that of the sides of the valley. Four spatially interpolated methods (IDW, Ordinary Kriging, land use types and multiple linear regression) were used to express the SOC spatial patterns, but all of them have low estimate accuracy because the SOC in the hilly loess area is highly heterogeneous given the complex topography and land use/cover. The estimate accuracy should improve with the Normalized Difference Vegetation Index (NDVI), given auxiliary information. SOC in the Luoyugou watershed is influenced by altitude, land use, and NDVI. Altitude has a significant relationship with SOC in the Luoyugou watershed. Annual precipitation significantly increases with increased altitude, and land use/vegetation cover changes between terraced cropland, orchard to grassland, and woodland. The SOC of Luoyugou has no significantly correlated relationship to topographic indices (slope, upslope area, and TWI), which have been profoundly disturbed by human activity, particularly by the conversion from sloped land to terraced cropland. The study results show that afforestation can significantly increase SOC. The SOC in immature forests (10 years old) is 17.91% higher than that in terraced cropland, but 32.25% lower than that in 30-year-old forests. The SOC concentration of 30-year-old forest is significant higher than that in other land cover. On a 10-year time scale, orchard is not a good ecological restoration type for increasing SOC; the contribution to enhancing SOC is not obvious and even shows a weak decreasing trend. In general, the SOC sink role of the Loess Plateau is being enhanced by ecological restoration.

Spatio-temporal analysis of rainfall erosivity and erosivity density in Greece

Abstract: Rainfall erosivity considers the effects of rainfall amount and intensity on soil detachment. Rainfall erosivity is most commonly expressed as the R-factor in the Universal Soil Loss Equation (USLE) and its revised version, RUSLE. Several studies focus on spatial analysis of rainfall erosivity ignoring the intra-annual variability of this factor. This study assesses rainfall erosivity in Greece on a monthly basis in the form of the RUSLE R-factor, based on a 30-min data from 80 precipitation stations covering an average period of almost 30 years. The spatial interpolation was done through a Generalised Additive Model (GAM). The observed intra-annual variability of rainfall erosivity proved to be high. The warm season is 3 times less erosive than the cold one. November, December and October are the most erosive months contrary to July, August and May which are the least erosive. The proportion between rainfall erosivity and precipitation, expressed as erosivity density, varies throughout the year. Erosivity density is low in the first 5 months (January–May) and is relatively high in the remaining 7 months (June–December) of the year. The R-factor maps reveal also a high spatial variability with elevated values in the western Greece and Peloponnesus and very low values in Western Macedonia, Thessaly, Attica and Cyclades. The East–West gradient of rainfall erosivity differs per month with a smoother distribution in summer and a more pronounced gradient during the winter months. The aggregated data for the 12 months result in an average R-factor of 807 MJ mm ha− 1 h− 1 year− 1 with a range from 84 to 2825 MJ mm ha− 1 h− 1 year− 1. The combination of monthly R-factor maps with vegetation coverage and tillage maps contributes to better monitor soil erosion risk at national level and monthly basis.

Assessment of soil properties of different land uses generated due to surface coal mining activities in tropical Sal (Shorea robusta) forest, India

Abstract: Large scale surface coal mining activities resulted disturbance of the local ecosystem by creating different land uses that alter soil properties and hydrological balance of the mining area and surrounding environment. The present study aims to evaluate the changes in soil properties in mining affected lands (mine face topsoil, wasteland and agriculture land) and reclaimed mine soil (RMS), and to quantify the changes of the selected soil properties with respect to reference Sal forest ( Shorea robusta Gaertn. F.). Changes in soil properties were analyzed on a profile basis (0–20, 20–40 and 40–60 cm). The study indicates that soil pH, electrical conductivity, and bulk density were increased significantly, while a decrease in nutrient content (N, P, and K) was observed in the mining affected lands. The infiltration rate in RMS was found ten times lower than the Sal forest. In comparison to Sal forest, the cumulative infiltration rate declines 85%, 80% and 75%, in RMS, topsoil and agriculture soil, respectively. The overall findings of this study indicated that conversion of Sal forest into other land uses due to mining significantly reduced the nutrient contents and soil quality of the area. Reclamation of the mine degraded land in short duration does not restore the overall properties of the soils, particularly the infiltration rate, which has long term impacts on the surrounding ecosystem.

Effect of biochar amendment on morphology, productivity and water relations of sunflower plants under non-irrigation conditions

Abstract: Three biochars (B1: pine wood, B2: paper-sludge, B3: sewage-sludge) produced under controlled pyrolysis conditions and one produced in kilns (B4: grapevine wood) were used as organic ameliorants in a Calcic Cambisol, which represents a typical agricultural soil of the Mediterranean region. This field study was performed with plants of sunflower (Helianthus annuus L.) at the experimental station “La Hampa”, located in the Guadalquivir river valley (SW Spain). The soil was amended with doses equivalent to 1.5 and 15 t ha− 1 of the four biochars in two independent plantations. In addition, un-amended plots were prepared in both experiments for comparison purposes. The major goal of this study was the assessment of the effect of biochar amendment on the physiology and development of sunflower plants at field conditions. During most of the growing period plants of un-amended and amended plots showed no stress symptoms either by their appearance or by stress-sensitive biochemical parameters such as the stability of the photosystem II (QY). Biochar addition had no effect on seed germination. Addition of 1.5 t ha− 1 biochar did not significantly change the pH of the soil, its electrical conductivity (EC) or its water holding capacity (WHC). Concomitantly the plant development and plant biomass production remained unaltered. Amendments with 15 t ha− 1 slightly increased the WHC of the soil but showed no lasting impact on the soil pH. It stimulated plant growth and led to a greater leaf area, larger plant stems and wider inflorescences of the sunflower plants than those cultivated on the un-amended soil. At the end of the experiment, biochar amendment of soil caused no significant increase of the total biomass production excepting B4, the biochar with the lowest capacity of water retention, which exhibited the highest vegetative growth and seed production. The lack of rain during the last weeks caused a water shortage in the culture that produced greater QY loss in non-amended plants. Interestingly, better growth of amended plants during the drought period correlated with higher reduction of stomatal conductance, indicating that the greater water use efficiency is at the origin of the better crop performance of biochar-amended plants. This finding points to the agronomic relevance of biochar amendment of Mediterranean rain fed crops.

Impacts of land use change and climate variability on green and blue water resources in the Weihe River Basin of northwest China

Abstract: Background Land use change and climate variability influence water resources availability and separation of these influences are important for water resources management. Methods SWAT model and the Mann–Kendall method were used in this study which investigated the spatiotemporal variations of blue and green water resources under different land use change, agricultural irrigation expansion and climate variability scenarios during the 1980s–2000s for the Weihe River Basin. Results Farmland area decreased by 1.4% and woodland, grassland, and construction land area increased by 0.6%, 0.2%, and 0.6%, respectively. The combined impact of land use change, agricultural irrigation expansion and climate variation decreased the blue water flow, green water flow, and green water storage by 21.62 mm year− 1, 35.01 mm year− 1 and 28.07 mm year− 1, respectively. Climate variability decreased the blue/green water flow and green water storage, land use change decreased the blue water and green water flow while it increased the green water storage, irrigation expansion decreased the blue water flow while it increased the green water flow/storage. The spatial distribution showed an uneven change in the Weihe River Basin. Together, we suggested that the variability of water resources availability in the Weihe River Basin was mainly attributed to climate variability, while land use change plays a key role in the sub-basins which experienced dramatic changes in land use.

882 lakes of the Cordillera Blanca: An inventory, classification, evolution and assessment of susceptibility to outburst floods

Abstract: Filiacion institucional de autor: Alejo Cochachin Rapre /Autoridad Nacional del Agua - Unidad de Glaciologia y Recursos Hidricos (ANA-UGRH), Huaraz, Peru

The impact of manure, straw and biochar amendments on aggregation and erosion in a hillslope Ultisol

Abstract: Soil erosion is a serious problem in subtropical China where hillslope red soils (Ultisols in US soil taxonomy) are intensively cultivated. Manure and amendments have been reported to improve crop growth and soil structural stability in long-term experiments so the objective of this study was to determine the effect of different organic amendments on soil aggregate stability, agronomic performance, runoff, and erosion. Four treatments consisted of inorganic NPK fertilizer (NPK), NPK fertilizer plus rice straw mulch (NPK + Str), NPK fertilizer plus rice straw-derived biochar (NPK + BC), and NPK fertilizer plus swine manure (NPK + OM) located on land with a 9–14% slope planted with peanut (Arachis hypogaea L.). During the peanut season, soil erosion ranged from around 2600 ton km− 2 with just inorganic NPK fertilizer down to 627 ton km− 2 with fertilizer plus swine manure, while addition of swine manure also increased the above-ground biomass and SOC (P 0.05) except the SOC, because biochar was susceptible to erosion (2115 ton km− 2). The least erosion was observed in the straw mulch treatment (225 ton km− 2), while it improved the above-ground biomass (P < 0.05) but not the C stock. The results indicated that the application of organic manure was a more appropriate practice for hillslope Ultisols management than using biochar.

Phytostabilization of As, Sb and Pb by two willow species (S. viminalis and S. purpurea) on former mine technosols

Abstract: It is becoming increasingly popular to use phytoremediation methods for the reclamation of mine sites containing metal(loid)s. This study aims to assess the phytostabilization ability of two willow species (Salix viminalis and Salix purpurea) on technosols from a former gold mining site presenting polymetallic contamination (As, Sb and Pb). Different reconstituted soils using a mixture of the litter and the technosol collected on this previously mined site and a non-contaminated control garden soil were investigated in a 2 laboratory mesocosm. The physico-chemical soil parameters and the total metal(loid)s content in pore water were determined. After 45 days of growth, roots, leaves and stems from the two willow species were harvested. The biomass, metal(loid) concentrations and the mineral mass were determined for the different plant organs. Both Salix species were able to develop root systems on the different reconstituted soils and a variable aboveground biomass according to the soil composition. As, Sb and Pb accumulated mainly in the Salix rhizosphere. S. purpurea was more efficient in accumulating As in the plant's upper parts than S. viminalis. S. viminalis showed an ability to transfer Pb and Sb to its shoots whereas S. purpurea did not translocate these elements.

Effect of different vegetation cover on the vertical distribution of soil organic and inorganic carbon in the Zhifanggou Watershed on the loess plateau

Abstract: Understanding the carbon cycle of the terrestrial ecosystem and estimating the potential of carbon sequestration in soils requires adequate information on the relationship between soil organic carbon (SOC) and inorganic carbon (SIC). The vertical distribution and transformation of SOC and SIC under different types of vegetation and slope aspects in the Zhifanggou Watershed on the Loess Plateau were investigated. The distribution of SOC with soil depth in the 0–200 cm soil can be described by the exponential model. The theoretical initial accumulation of organic carbon at the litter/soil contact increased with the decrease in the C/N ratio of the litter from the vegetation and followed the order shrub > forest > grass. Compared to the shady slope, the low theoretical initial accumulation of organic carbon at the litter/soil contact resulted from the relatively small quantity of SOC formation by the decomposition of litter on the sunny slope. The variation tendency of SIC in the 0–50 cm is opposite to that of SOC. The transfer of the soil carbonate slowed down with the decrease in the soil water content (SWC), which was reflected by the significant negative correlation between SIC content and SWC (r = − 0.400, p

Rock fragments and soil hydrological processes: Significance and progress

Abstract: In this review, we explore the significance of rock fragments in studies of soil hydrological processes, because according to research, the effects of rock fragments on soil hydrological processes are inconsistent (positive/negative). Rock fragments play a critical role in the biosphere as the primary filter for water and solutions containing contaminants and heavy metals. Rock fragments have a complex influence on soil hydrological processes (e.g. soil erosion, runoff generation, water infiltration, solute transport and water flow) and are highly relevant in a typical system in the soil–plant–atmosphere continuum. Cracks related to rock fragments provide preferential flow paths through which pollutants are transported into groundwater. In this paper, the published literature is reviewed concentrating on rock fragments and their effects on soil hydrological processes. Systematic studies and examples illustrate the effects of rock fragments architecture (i.e. coverage, content, size, position, spatial heterogeneity, morphology, weathering and topography) on soil hydrological processes. Methods and models applied to evaluate the effects of rock fragments on soil hydrological processes are examined in detail. We conclude that the relationship between rock fragments and soil hydrological processes is complicated and requires more international research efforts. This review concludes with a discussion of perspectives on areas of research that can improve understanding of the effects of rock fragments on soil hydrological processes, with insights and suggestions also being provided regarding potential research trends, requirements and solutions.

Patterns and environmental controls of soil organic carbon and total nitrogen in alpine ecosystems of northwestern China

Abstract: Soil carbon (C) and nitrogen (N) in alpine ecosystems are of special interest because of high concentration and potential feedbacks to climate changes. Alpine ecosystems of the Qilian Mountains in the northern margin of the Tibetan Plateau are characterized by complex topography, suggesting large variability in the spatial distribution of soil C and N. However, the patterns and environmental controls on C and N storage are not well understood. This study was conducted to determine the soil organic carbon (SOC) and total nitrogen (TN) stocks under different vegetation types and environmental conditions in a typical catchment in the Qilian Mountains, and explore their environmental control factors. The results showed that SOC and TN stocks varied significantly with vegetation type, ranging from 9.50 to 31.09 and 1.07 to 3.14 kg m − 2 , respectively, at 0–50 cm soil depth. SOC storage in grasslands on sunny slopes and in Picea crassifolia forest together accounted for about 80% of the total SOC storage in the catchment due to the extensive distribution area of these vegetation types. SOC stocks in grasslands on sunny slopes and in P . crassifolia forest were generally higher than their counterparts in other regions. SOC stocks on shady slopes were mainly regulated by elevation-induced differences in temperature and precipitation, with temperature being the most important factor influencing the distribution of SOC. For the whole catchment, the distribution of SOC stocks was significantly affected by topographic aspect and elevation; aspect and elevation together explained 97.5% of the overall variation in SOC stocks at a soil depth of 0–50 cm, and aspect alone explained 68.2% of the overall variation. These results confirmed that topography was the most significant factor controlling the distribution patterns of SOC in alpine ecosystems.

High variability of soil erosion and hydrological processes in Mediterranean hillslope vineyards (Montes de Málaga, Spain)

Abstract: Conventional Mediterranean vineyards from the Montes de Malaga (Axarquia region, Spain) are characterized by high average temperatures, extreme rainfall events during autumn and winter, elevated stoniness and steep slopes (20–50°). Traditionally, several problems of high soil loss, rill and ephemeral gully generation, and elevated runoff are observed by farmers, which are increasing land degradation processes and a decrease of the productivity. According to this, the main aims of this paper were: i) to quantify the initial soil loss, surface flow and infiltration processes; ii) to characterize and describe the hydrological and geomorphological dynamics; iii) to detect the key factors, which control the soil erosion processes. For this purpose, a combined methodology was applied, using soil analysis, a small portable rainfall simulator and a Guelph permeameter on one experimental plot cultivated with vineyards with steep slopes. Results showed a high variability of soil erosion and permeability processes. Soil analysis showed an elevated concentration of silt particles and stoniness, with higher contents of sand particles between 0 and 5 cm, and clays from 5 cm. With a Guelph permeameter, high average of permeability and saturated hydraulic conductivity with elevated standard deviation were observed. Furthermore, an increase of these parameters from the upper to the foot slope was registered. By using rainfall simulations, on the upper and the foot slope positions the highest runoff coefficient and soil loss were registered. The most elevated peak of sediment concentration was obtained on the middle slope. In general, high infiltration coefficients between 66.5 and 100% were observed. In conclusion it was observed that the activation of the soil erosion processes was due to the distribution of the surface soil components (high roughness, several cracks and high stoniness and silt content), the steep slopes and the impact of the soil traditional tillage practices. These Mediterranean hillslope vineyards registered a mixed Hortonian-Hewlettian model, which combines surface and sub-surface flow conditioned by the micro-topographical changes and its saturation degree.

Influence of HCl pretreatment and organo-mineral complexes on laser diffraction measurement of loess–paleosol-sequences

Abstract: The influence of different sample pretreatment methods on grain size distributions in particle size analysis has been subject to controversial discussions. Standard sample preparation typically comprises the disaggregation of aggregated and agglomerated particles into single primary particles, i.e., the organic binding material is oxidized by hydrogen peroxide (H2O2) and the contained carbonates are dissolved by hydrochloric acid (HCl). The aim of this study is to evaluate the effects of HCl treatment on grain size analyses of Late Pleistocene and Holocene loess–paleosol-sequences investigated by a Beckman Coulter LS 13320 laser particle analyzer. For this purpose, samples from two different sections with different weathering degrees and sedimentary genesis were measured: (1) the Suohuoduo section on the northeastern fringe of the Tibetan Plateau (China) containing loess and paleosols, and (2) a vibracore from Dusseldorf-Grafenberg (Germany) containing calcareous loess and intercalated interglacial, interstadial and periglacial soils and soil sediments. All samples were pretreated with hydrogen peroxide and sodium pyrophosphate. Subsequently, the samples were prepared with and without the addition of HCl. There is no significant association of the HCl-induced grain size modifications after the HCl treatment with the calcium carbonate content. Conversely, a distinct dependence of the modification of grain size distributions on the content of organic matter, the weathering degree of the sediment, and the presence of stable aggregates as well as organo-mineral complexes was observed. Consequently, pretreating post-depositionally modified aeolian sediments with HCl may result in misleading grain size distributions and should be avoided in standard analyses of loess–paleosol-sequences. However, the HCl-induced modification of grain size distributions provides an indication of the existence of stable aggregates or organo-mineral complexes.

Integration of the Statistical Index Method and the Analytic Hierarchy Process technique for the assessment of landslide susceptibility in Huizhou, China

Abstract: A landslide susceptibility assessment was accomplished in Huizhou, Guangdong province, by adopting the Statistical Index Method and the Analytic Hierarchy Process. Eight landslide causing factors were considered including elevation, slope, aspect, lithology, land cover, distance to a fault, distance to a road, distance to a river and precipitation. The Statistical Index Method was used to determine the weighted value (Si) for classes of every landslide causing factor, the Analytic Hierarchy Process was utilized to determine the weighted value (Wi) for every factor, and the summation of the product of Si by Wi represent the Landslide Susceptibility Index (LSI) value for every pixels. Based on the derived LSI, the study area was grouped into five susceptibility classes in the study area. The densities of landslide for five susceptibility classes from very high to very low show a linear increasing trend implying there is a satisfactory agreement between the susceptibility map and the actual landslide data. The ROC curves for training and prediction datasets suggest that the model could have a reasonably good predictive capability. The landslide susceptibility map derived in this study shows the settlement and sparse forest area with lithology of unit II (red layered moderate soft mixture of clastic rocks), unit III (layered moderate hard to hard mixture of clastic rocks) and unit V (massive moderate hard to hard mixture) at the elevation of 0–200 m are the most susceptible to slope failure. The result could be very useful in identification of the most problematic areas, which is very critical for investigating landslide hazard and risk management and community & regional planning.

Nitrogen and phosphorus losses by runoff erosion: Field data monitored under natural rainfall in Three Gorges Reservoir Area, China

Abstract: Nitrogen (N) and phosphorous (P) from agricultural non-point source (ANPS) pollution are the great threats to the regional water quality in the Three Gorges Reservoir Area (TGRA) of China. To explore the pollution of N and P loss from the sloping land in TGRA agricultural areas, field-scale plot experiment under natural rainfall was conducted from May 1 to October 31 in 2012. We monitored and analyzed rainfall, runoff volume, sediment yield, and nutrient concentration under different conditions (3 soil types, 3 surface slopes, and 5 cropping systems) in 30 experimental plots of 20 m2 during the rainy season. The results indicated that average loss ratio of N was 1.90%, while that of P was 1.54%. N and P loss ratios from surface runoff in 15° plots of sloping farmland were the highest. Purple soil (PS) was the most severe soil and nutrient loss. Within all the 5 cropping systems, the loss ratios of N and P from intercropping of citrus and grass (C-G) were the lowest. The practice of C-G, which was the most beneficial cropping system, should be further encouraged especially in TGRA to cope with the serious issues of N and P losses. These findings provide useful and valuable information for decision makers and planners to take sustainable measures for the control of ANPS pollution in TGRA, and are beneficial for the agro-ecological environment management of the local agricultural watersheds.