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1.
In order to investigate changes caused in clay mineralogy and potassium (K) status by different land-use types, 42 soils samples (0–30 cm) were monitored and analyzed. Soil samples belonging to Reference Soil Groups of Cambisols and Vertisols were collected from three neighboring land uses involving cropland (under long-term continuous cultivation), grassland, and forestland. The soils reflected an alkaline and calcareous aspect as were characterized by high pH (mean of 7.1 to 7.5) and calcium carbonate equivalent (mean of 35 to 97 g?kg?1) in the three land-use types. X-ray diffraction patterns of the clay fraction showed that the soils were mainly composed of illite, smectite, chlorite, and kaolinite. Chlorite and kaolinite remained unweathered irrespective of land use and soil types, soil processes, and physicochemical attributes assessed. Some changes in the XRD diffractograms of illite and smectite (the intensity or the position of peaks) were observed in the cultivated soils compared to those of the adjoining grassland that may explain the dynamics of the K trapped in illite interlayer sites. Potassium issues reflected a heterogeneous response to changes in land-use types. In light of this, a pronounced variation in soluble K (4–22 mg?kg?1), exchangeable K (140–558 mg?kg?1), and non-exchangeable K (135–742 mg?kg?1) appeared among the land-use types for both Cambisols and Vertisols, corresponding to variability in clay content, nature and type of clay mineral (mainly illite and smectite), cation exchange capacity (CEC), and soil organic carbon (SOC). In general, the largest amounts of soluble K and exchangeable K were recorded in the forestland, whereas the highest contents of non-exchangeable K were found in the grassland for both Cambisols and Vertisols. Exchangeable K, available K, CEC, and clay contents in the soils with higher smectite values (25–50 %) were significantly different (P?≤?0.05) compared to those of the lower smectite values (10–25 %). This suggests that smectite is a major source for surface sorption of K in the studied soils.  相似文献   

2.
Monitoring general variability of soil attributes is a fundamental requirement from the point of view of understanding and predicting how ecosystems yield. In order to monitor impact of different land use types on the combination of morphological, clay mineralogical and physicochemical characterizes, 42 soil samples (0–30 cm) were described and analyzed. Soil samples belonging to Cambisols and Vertisols reference soil groups collected from three neighboring land use types included cropland (under long-term continuous cultivation), grassland, and forestland. The soils were characterized by high pH (mean of 7.1–7.5) and calcium carbonate equivalent (CCE) (mean of 35–97 g kg?1) in the three land use types. The weakening in soil structure, hardening of consistency, and lighting of soil color occurred for the cropland under comparable condition with grassland and forest. Changes in land use types produced a remarkable change in the XRD patterns of clay minerals containing illite and smectite due the dynamic and removal of potassium. Continuous cultivation resulted in an increase in sand content up to 35 % while silt and clay content decreased up to 22 and 18 %, respectively, as compared to the adjoining grassland and forest mainly as a result of the difference of dynamic alterational and erosional process in the different land use. Long-term cultivation caused a negative and degradative aspects on soil heath as is manifested by the increasing in soil pH (a rise of 0.3–0.46 unit), electrical conductivity (EC) (a rise of 1.78–5.5 times), sodium absorption ration (SAR) (a rise of 10–51 %), exchangeable sodium percentage (ESP) (a rise of 3–46 %), and the decrease in soil organic C (a drop of 12–41 %), along with soil fertility attributes. Overall, the general distribution of soil organic C, total N, available P and K, cation exchange capacity (CEC), and exchangeable cations (Ca, Mg, and K) followed the order: forestland > grassland > cropland. The general distribution of EC, SAR, ESP, and exchangeable Na, however, followed the order: cropland > grassland > forestland. Soil quality index (SQI), calculated based on some physicochemical properties, specified that cultivation led to a negative effect in SQI for both Cambisols (a drop of 10–17 %) and Vertisols (a drop of 17 %) as compared to those of under grassland and forestland.  相似文献   

3.
With few available soil organic carbon (SOC) profiles and the heterogeneity of those that do exist, the estimation of SOC pools in karst areas is highly uncertain. Based on the spatial heterogeneity of SOC content of 23,536 samples in a karst watershed, a modified estimation method was determined for SOC storage that exclusively applies to karst areas. The method is a “soil-type method” based on revised calculation indexes for SOC storage. In the present study, the organic carbon contents of different soil types varied greatly, but generally decreased with increasing soil depth. The organic carbon content decreased nearly linearly to a depth of 0–50 cm and then varied at depths of 50–100 cm. Because of the large spatial variability in the karst area, we were able to determine that influences of the different indexes on the estimation of SOC storage decreased as follows: soil thickness > boulder content > rock fragment content > SOC content > bulk density. Using the modified formula, the SOC content in the Houzhai watershed in Puding was estimated to range from 3.53 to 5.44 kg m?2, with an average value of 1.24 kg m?2 to a depth of 20 cm, and from 4.44 to 14.50 kg m?2, with an average value of 12.12 kg m?2 to a depth of 100 cm. The total SOC content was estimated at 5.39 × 105 t.  相似文献   

4.
This study examined topographic influence on spatial and temporal variability in the normalized difference vegetation index (NDVI) derived from the Satellite Pour l’Observation de la Terre-Vegetation at the regional and landscape scales in the Jiaodong Peninsula. The generalized additive models were used to quantify the spatial variation of NDVI attributable to local terrain and topographically related variables including altitude, exposure to incoming solar radiation, topographic wetness index, distance to the nearest stream and distance from the coast. NDVI distribution shows significant dependence on topography. The variables explained 38.3 % of variance in NDVI at the peninsula, and 30–45.3 % of variance in NDVI at the woodland, cropland, and grassland landscapes. At the Jiaodong Peninsula scale, NDVI is influenced primarily by distance from the coast. However, topographic wetness index has the most explanatory power for NDVI at the woodland, cropland, and grassland landscapes. Through a statistical nonparametric correlation analysis (Spearman’s r), the study indicates that spatial distribution of NDVI changes during the period 1998–2009 and future change trend of persistence determined by Hurst exponent is closely associated with topography and topography-based attribution. These results highlight the importance of topographic changes at landscape and regional scales as an important control factor on NDVI patterns.  相似文献   

5.
Ecological restorations over time may have profound effects on ecological and socio-economic systems. However, land-use changes and landscape functions that accompany ecological restorations can have spatial differentiations due to varied biophysical and socio-economic contexts. Therefore, these spatial differentiations caused by ecological restoration must be understood for better planning and management of restoration activities. The Baota District, with 576 villages in the center of the Chinese Loess Plateau, was selected as the study area because of its dramatic transition from cropland to grassland and shrubland from 1990 to 2010. Using the ArcGIS software and a k-means clustering analysis, an approach to identify types of land-use change patterns (TLCPs) at the village level was developed, and four TLCPs were delineated. The analysis indicated a general pattern of cropland decline by 21.6 %, but revealed significant spatial variations between villages in different TLCPs. Vegetation cover and soil retention, which are key proxies for landscape functions, increased by 22.70 and 108 %, respectively, from 2000 to 2010 with significant spatial heterogeneity. The Universal Soil Loss Equation was employed for the assessment of soil retention. The analysis of landscape metrics revealed a major trend of fragmentation and regularity on the county and village scale; however, spatial variations remained. Physical attributes were used to characterize different TLCPs, and notable differences were found. The spatial heterogeneous change in land use and landscape functions on the village scale may be useful for land use and ecological restoration management policy makers.  相似文献   

6.
Estimation of soil erosion using RUSLE in Caijiamiao watershed,China   总被引：4，自引：1，他引：3  
Jinghu Pan  Yan Wen 《Natural Hazards》2014,71(3):2187-2205
Soil erosion is a serious environmental and production problem in China. In particular, natural conditions and human impact have made the Chinese Loess Plateau particularly prone to intense soil erosion area. To decrease the risk on environmental impacts, there is an increasing demand for sound, and readily applicable techniques for soil conservation planning in this area. This work aims at the assessment of soil erosion and its spatial distribution in hilly Loess Plateau watershed (northwestern China) with a surface area of approximately 416.31 km2. This study was conducted at the Caijiamiao watershed to determine the erosion hazard in the area and target locations for appropriate initiation of conservation measures using the revised universal soil loss equation (RUSLE). The erosion factors of RUSLE were collected and processed through a geographic information system (GIS)-based approach. The soil erosion parameters were evaluated in different ways: The R-factor map was developed from the rainfall data, the K-factor map was obtained from the soil map, the C-factor map was generated based on Landsat-5 Thematic Mapper image and spectral mixture analysis, and a digital elevation model with a spatial resolution of 25 m was derived from topographic map at the scale of 1:50,000 to develop the LS-factor map. Support practice P factor was from terraces that exist on slopes where crops are grown. By integrating the six-factor maps in GIS through pixel-based computing, the spatial distribution of soil loss in the study area was obtained by the RUSLE model. The results showed that spatial average soil erosion at the watershed was 78.78 ton ha?1 year?1 in 2002 and 70.58 ton ha?1 year?1 in 2010, while the estimated sediment yield was found to be 327.96 × 104 and 293.85 × 104 ton, respectively. Soil erosion is serious, respectively, from 15 to 35 of slope degree, elevation area from 1,126 to 1,395 m, in the particular area of soil and water loss prevention. As far as land use is concerned, soil losses are highest in barren land and those in waste grassland areas are second. The results of the study provide useful information for decision maker and planners to take appropriate land management measures in the area. It thus indicates the RUSLE–GIS model is a useful tool for evaluating and mapping soil erosion quantitatively and spatially at a river watershed scale on a cell basis in Chinese Loess Plateau and for planning of conservation practices.  相似文献   

7.
This study was carried out to determine the effects of different land-use types on the properties of an Alfisol on the Jos Plateau, Nigeria. Areas being used for nature conservation (forest), grazing and maize cultivation were chosen, and the three are contiguous within a nearly level, moderately well-drained site. Within each of the three land-use areas, a plot of 30 x 20 m was chosen. Each plot was divided into 6 grids of 100 m2 size. Within each of these grids, four sampling sites were chosen by throwing up a coin four times. The four surface soil (0–5 cm depth) samples taken at the points where the coin landed, were mixed to form the composite sample, out of which sizeable portion was taken. This means that six soil samples were taken for each land use area (forest, grass, and cultivated). Same procedure was repeated for each of the following soil depths 5–15, 15–30 and 30–50 cm. Laboratory soil analyses were carried out while analysis of variance was used to test the significance of mean difference. The results show that forest clearing for grazing and maize cultivation has lead to significant decreases in most soil fertility variables. Organic matter levels of the grassland and cultivated soils are just about 28% and 13%, respectively, of that of the forest soil in the 0–5 cm depth, while they are 36% and 19%, respectively, in the 5–15 cm depth. Exchangeable cations and effective cation exchange capacity are also significantly higher in the forest soils. The effects are attributable to soil organic matter decomposition and nutrient removal resulting from forest clearance, maize cultivation and grazing. Hence, for sustained agricultural productivity, the soils require adequate inorganic and organic fertilizer additions together with appropriate cultural practices such as agroforestry, crop rotation and mixed cropping involving legumes.  相似文献   

8.
The universal soil loss equation (USLE) is an erosion model to estimate average soil loss that would generally result from splash, sheet, and rill erosion from agricultural plots. Recently, use of USLE has been extended as a useful tool predicting soil losses and planning control practices by the effective integration of the GIS-based procedures to estimate the factor values on a grid cell basis. This study was performed for five different lands uses of Indağı Mountain Pass, Cankırı to predict the soil erosion risk by the USLE/GIS methodology for planning conservation measures in the site. Of the USLE factors, rainfall-runoff erosivity factor (USLE-R) and topographic factor (USLE-LS) were greatly involved in GIS. These were surfaced by correcting USLE-R site-specifically using DEM and climatic data and by evaluating USLE-LS by the flow accumulation tool using DEM and watershed delineation tool to consider the topographical and hydrological effects on the soil loss. The study assessed the soil erodibility factor (USLE-K) by randomly sampled field properties by geostatistical analysis. Crop management factor for different land-use/land cover type and land use (USLE-C) was assigned to the numerical values from crop and flora type, canopy and density of five different land uses, which are plantation, recreational land, cropland, forest and grassland, by means of reclassifying digital land use map available for the site. Support practice factor (USLE-P) was taken as a unit assuming no erosion control practices. USLE/GIS technology together with the geostatistics combined these major erosion factors to predict average soil loss per unit area per unit time. Resulting soil loss map revealed that spatial average soil loss in terms of the land uses were 1.99, 1.29, 1.21, 1.20, 0.89 t ha−1 year−1 for the cropland, grassland, recreation, plantation and forest, respectively. Since the rate of soil formation was expected to be so slow in Central Anatolia of Turkey and any soil loss of more than 1 ton ha−1 year−1 over 50–100 years was considered as irreversible for this region, soil erosion in the Indağı Mountain Pass, to the great extent, attained the irreversible state, and these findings should be very useful to take mitigation measures in the site.  相似文献   

9.
Soil degradation resulted from unreasonable land use and erosion has been a serious problem in the black soil region of northeastern China. This paper seeks to understand the relationships between topsoil properties and topography and land use for land management targeting at improving soil quality in this region. A total of 292 soil samples and 81 volumetric rings were taken from a typical small watershed of the region in June 2005 for examining total carbon (TC), total nitrogen (TN), soil texture (classified into gravel, sand, silt, and clay), and bulk density (ρ b), respectively. Spatial variability of these soil properties was evaluated with classical statistics and geostatistics methods. The results of classical statistics indicated that TC, TN, sand, silt, clay content, and ρ b were moderate variables while gravel had great variability. Soil properties were mainly correlated to slope position, elevation and land types. Geostatistical analyses showed that the spatial autocorrelation for TC, TN, and silt was weak, strong for clay and moderate for and ρ b sand, respectively. The spatial variations of soil properties are affected comprehensively by topographic factors, land use, erosion, and erosion control in this watershed. Past erosion, however, is the most important component to induce change of soil properties. In this small watershed, current soil and water conservation measures play an important role in controlling soil loss. But the restoration of soil properties was unsatisfactory. Comparing with untilled soil of this region, TC, TN, silt content are excessively low; whereas ρ b, sand and clay content are excessively high; gravel appears at most sampling locations. It is necessary for improving soil properties to protect forest and grassland and change cultivation system of farmlands.  相似文献   

10.
Information on soil water storage (SWS) within soil profiles is essential in order to characterize hydrological and biological processes. One of the challenges is to develop low cost and efficient sampling strategies for area estimation of profile SWS. To test the existence of certain sample locations which consistently represent mean behavior irrespective of soil profile wetness, temporal stability of SWS in ten soil layers from 0 to 400 cm was analyzed in two land uses (grassland and shrub land), on the Chinese Loess Plateau. Temporal stability analyses were conducted using two methods viz. Spearman rank correlation coefficient (r s) and mean relative differences. The results showed that both spatial variability and time stability of SWS increased with increasing soil depth, and this trend was mainly observed at above 200 cm depth. High r s (p?<?0.01) indicated a strong temporal stability of spatial patterns for all soil layers. Temporal stability increased with increasing soil depth, based on either r s or standard deviation of relative difference index. The boundary between the temporal unstable and stable layer of SWS for shrub land and grassland uses was 280 and 160 cm depth, respectively. No single location could represent the mean SWS for all ten soil layers. For temporal stable layers, however, some sampling locations could represent the mean SWS at different layers. With increasing soil depth, more locations were able to estimate the mean SWS of the area, and the accuracy of prediction for the representative locations also increased.  相似文献   

11.
Drought is a great concern in agricultural yield. Super-absorbent polymers (SAPs) can assist in easing water shortage. Therefore, it is significantly important to study the water absorbing and desorbing capacity of SAPs when applied into soil as well as their effective time. The aim of this study was to investigate the effect of different SAP types under the same moisture condition and the effect of the same SAP type under different moisture conditions on saturated soil water content, saturated soil hydraulic conductivity and soil water diffusivity. With SAP application, saturated soil water volumetric content increased significantly, up to 0.186 cm3 cm?3, while saturated hydraulic conductivity and diffusivity significantly decreased because the soil pores were blocked by SAP’s swelling volume during the repeated wetting and drying cycles. After SAPs were mixed in the soil, their capacity of absorbing and desorbing water showed a downward trend with time and outside water condition. Under a relatively stable water condition, such capacity reduced more slowly. As for the soil with SAP application, successful simulation for diffusivity D(θ, T) was also applicable to other parameters of the equation of water movement, which made it possible to study the water movement under the same condition.  相似文献   

12.
In recent times, soil erosion interlocked with land use and land cover (LULC) changes has become one of the most important environmental issues in developing countries. Evaluation of this complex interaction between LULC change and soil erosion is indispensable in land use planning and conservation works. This paper analysed the impact of LULC change on soil erosion in the north-western highland Ethiopia over the period 1986–2016. Rib watershed, the area with dynamic LULC change and severe soil erosion problem, was selected as a case study site. Integrated approach that combined geospatial technologies with revised universal soil loss equation model was utilized to evaluate the spatio-temporal dynamics of soil loss over the study period. Pixel-based overlay of soil erosion intensity maps with LULC maps was carried out to understand the change in soil loss due to LULC change. Results showed that the annual soil loss in the study area varied from 0 to 236.5 t ha?1 year?1 (tons per hectare per year) in 1986 and 0–807 t ha?1 year?1 in 2016. The average annual soil loss for the entire watershed was estimated about 40 t ha?1 year?1 in 1986 comparing with 68 t ha?1 year?1 in 2016, a formidable increase. Soil erosion potential that was estimated to exceed the average soil loss tolerance level increased from 34.5% in 1986 to 66.8% in 2016. Expansion of agricultural land at the expense of grassland and shrubland was the most detrimental factor for severe soil erosion in the watershed. The most noticeable change in soil erosion intensity was observed from cropland with mean annual soil loss amount increased to 41.38 t ha?1 year?1 in 2016 from 26.60 in 1986. Moreover, the most successive erosion problems were detected in eastern, south-eastern and northern parts of the watershed. Therefore, the results of this study can help identify the soil erosion hot spots and conservation priority areas at local and regional levels.  相似文献   

13.
Soil organic carbon (SOC) is one of the key components for assessing soil quality. Meanwhile, the changes in the stocks SOC may have large potential impact on global climate. It is increasingly important to estimate the SOC stock precisely and to investigate its variability. In this study, Yangjuangou watershed was selected to investigate the SOC distribution under different land uses. We found that SOC concentration decreased with increasing soil depth under all land uses and was significantly different across the vertical soil profile (P < 0.01). However, considering effect of land use on SOC, it is only significant (P < 0.01) in the topsoil (0-5 cm) layer. This indicated that land use has a large effect on the stocks of SOC in the surface soil. The stratification ratio of SOC > 1.2 may mean that soil quality is improving. The order of the SOC density (0-30 cm) under different land uses is forestland > orchard land > grassland > immature forestland > terraced cropland. The SOC stock is found to be as large as 2.67 × 103 t (0-30 cm) in this watershed. Considering time effect of restoration, the slope cropland just abandoned is more efficient for SOC accumulation than trees planted in the semi-arid hilly loess area.  相似文献   

14.
The effects of urban stormwater on the soil of an infiltration/ holding basin were studied within the framework of research carried out by OTHU (Urban Hydrology Field Observatory of Lyon, France). The biophysicochemical impacts of stormwater from an industrial watershed on the local soil (to a depth of 4 m in the unsaturated zone) were measured. Several types of measurement (pH, organic matter, particle size, heavy metals content, and heterotrophic viable bacterial counts) for three vertical soil profiles were carried out. High concentrations of heavy metals and significant variations in pH and silt to a depth of 1.5 m were observed. The concentrations decreased as a function of distance from the stormwater discharge pipe. Changes in the bacterial population were also observed, varying in accordance with the depth and location of the profile.
Resumen Se estudiaron los efectos de tormentas en zonas urbanas sobre el suelo de una cuenca retenedora/de infiltración dentro del marco de investigación llevado a cabo por OTHU (Laboratorio de Observación de Campo de Hidrología Urbana, Lyon, Francia). Se midieron los impactos biofisicoquímicos de la tormenta en una cuenca industrial sobre el suelo local (a una profundidad de 4m en la zona no saturada). Se llevaron a cabo varios tipos de mediciones (pH, materia org′nica, tama?o de partículas, contenido de metales pesados, y conteo de bacterias viables heterotróficas) en tres perfiles ed′ficos. Se observaron altas concentraciones de metales pesados y variaciones significativas en pH y limo a una profundidad de 1.5m. Las concentraciones disminuyeron en función de la distancia del tubo de descarga de las aguas de la tormenta. También se observaron cambios en las poblaciones de bacterias los cuales variaban en función de la profundidad y localización del perfil.
Résumé Dans le cadre de la fédération de recherche OTHU (Observatoire de Terrain en Hydrologie Urbaine de Lyon) une étude sur l’impact des eaux pluviales sur le sol d’un bassin d’infiltration / rétention est présentée. Il s’agit d’évaluer l’impact biophysicochimique des eaux pluviales issues d’un bassin versant industriel sur une profondeur d’environ 4 m de zone non saturée. Pour cela plusieurs types de mesures ont été effectuées (pH, perte au feu, teneur en Cu, Pb, Cd, dénombrement bactérien) suivant trois profils verticaux. Les résultats montrent des concentrations importantes de métaux et des variations de pH jusqu’à 1.5 m de profondeur. De plus, les résultats montrent une variation suivant la position des points de prélèvements. Des modifications de la population bactérienne sont également observées suivant la profondeur et l’emplacement des profils.
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15.
Land use patterns are changing and the environment has become more vulnerable in an agro-pastoral ecotone in Inner Mongolia. Modeling studies can be done through studying the relationships between the soil organic carbon density (SOCD) and the influencing factors in differing land uses such as cropland, forest and grassland. Such studies can provide the basis for predicting soil organic carbon (SOC) stocks and using land resources efficiently. Therefore, the relationships between the SOCD of surface soils and the influencing factors, such as soil type, slope and elevation, were selected for a study in differing land uses of Duolun County, Inner Mongolia. The results showed that: (1) The variation in SOCD among the soil types followed the same order in the three land uses: chernozems > meadow soils > bog soils > castanozems > gray-cinnamon soils > eolian soils. The sensitivity of SOCD to land use change was different for the six soil types. Both the degradation of grassland and the application of the government policy of returning forest from cropland induced the greatest variation in SOCD. (2) SOCD correlated significantly with soil type and elevation in each land use. There was a significant correlation between SOCD and slope in the forest. (3) Statistical models showing SOCD and the influencing factors were developed and provided the basis for predicting SOC stocks in Duolun County, Inner Mongolia.  相似文献   

16.
The spatial heterogeneity of soil nutrients influences crop yield and the environment. Previous research has focused mainly on the surface layer, with little research being carried out on the deep soil layers, where high root density is highly related to crop growth. In the study, 610 soil samples were collected from 122 soil profiles (0–60 cm) in a random-sample method. Both geostatistics and traditional statistics were used to describe the spatial variability of soil organic matter (SOM) and total nitrogen (TN) deeper in the soil profile (0–60 cm) with high root density from a typical Mollisol watershed of Northeast China. Also, the SOM and TN in farmland and forest (field returned to forest over 10 years) areas was compared. The spatial autocorrelations of SOM at 0–50 cm depth and TN at 30–60 cm depth were strong, and were mainly influenced by structural factors. Compared to farmland, SOM and TN were typically lower in the 0–30 cm depth of the forest areas, while they were higher in the 30–60 cm depth. As well, both SOM and TN decreased from the 0–20 cm layer to the 30–40 cm layer, and then discontinues, while they continuously decreased with increasing soil depth in the farmland. SOM and TN were typically higher at the gently sloped summit of the watershed and part of the bottom of the slope than at mid-slope positions at the 0–30 cm depth. SOM and TN were lower on the back slope at the 30–60 cm depth, but were higher at the bottom of the slope. Also, the spatial distribution of the carbon storage and nitrogen storage were all highest at the bottom of the slope and part of the summit, while they were lowest in most of back slope in depth of 0–60 cm, and mainly caused by soil loss and deposition. SOM at 0–60 cm and TN at 0–40 cm greater than the sufficiency level for crop growth (3.7–79.2 and 0.09–3.09 g kg?1, respectively) covered 99 % of the total area, yet for TN, over 35 % of the total area was less than the insufficiency level at the 40–60 cm depth. Generally, accurately predicting SOM and TN is nearly impossible when based only on soil loss by water, although the fact that variability is influenced by elevation, soil loss, deposition and steepness, was shown in this research. Nitrogen fertilizer and manure application were needed, especially in conjunction with conservation tillage in special conditions and specific areas such as the back slope, where soil loss was severe and the deep soil that lacked TN was exposed at the surface.  相似文献   

17.
Soil particle-size distribution (PSD) is an important index for soil classification because it has large influences on soil hydrological characteristics, salinity, fertility, erodibility, nutrient content, swelling/shrinking, and degradation. We present a case study of the fractal characteristics of soil PSD and its relationship with soil properties of gravel-mulched fields in an arid area of northwestern China using single-fractal calculation. Particle size was unimodally distributed within the narrow range of 20–100 μm, with silt as the most common component. Horizontally, silt content was the highest, followed by sand and clay contents. Vertically, clay content increased with depth, while there were no obvious change rules for both silt and sand contents. The volume fractal dimension (D) of PSD ranged from 2.4307 to 2.5260, increased with the content of fine particles but decreased with the content of coarse particles. D was correlated positively with soil-water content and salt content and negatively with bulk density. The saturated soil-water content was strongly correlated negatively with silt content (p < 0.01) and positively with sand content (p < 0.01). The results indicate that D can be a potential indicator of the physical and chemical properties of soil and can also provide a theoretical basis and technical guidance for the effective use and management of the region.  相似文献   

18.
Soil samples from 0 to 100 cm depth were collected in four sampling sites (Sites A, B, C and D) along a 250-m length of sampling zone from the Yellow River channel to a tidal creek in a seasonal flooding wetland of the Yellow River Delta of China in fall of 2007 and spring of 2008 to investigate spatial and seasonal distribution patterns of total phosphorous (TP) and available phosphorus (AP) and their influencing factors. Our results showed that TP contents in spring and AP contents in both seasons in surface soils increased with increasing distances away from the Yellow River channel. TP contents in surface soils (0–10 cm) followed the order Site A (698.6 mg/kg) > Site B (688.0 mg/kg) > Site C (638.8 mg/kg) > Site D (599.2 mg/kg) in fall, while Site C (699.6 mg/kg) > Site D (651.7 mg/kg) > Site B (593.6 mg/kg) > Site A (577.5 mg/kg) in spring. Generally, lower TP content (630.6 mg/kg) and higher AP level (6.2 mg/kg) in surface soils were observed in spring compared to fall (656.2 mg/kg for TP and 5.2 mg/kg for AP). Both TP and AP exhibited similar profile distribution patterns and decreased with depth along soil profiles with one or two accumulation peaks at the depth of 40–80 cm. Although the mean TP content in soil profiles was slightly higher in spring (635.7 mg/kg) than that in fall (628.0 mg/kg), the mean TP stock was obviously lower in spring (959.9 g/m2) with an obvious accumulation at the 60–80 cm soil depth compared to fall (1124.6 g/m2). Topsoil concentration factors also indicated that TP and AP had shallower distribution in soil profiles. Correlation analysis showed that AP had significant and positive correlation with these soil properties such as soil organic matter, salinity, total nitrogen and Al (p < 0.01), but TP was just significantly correlated with TN and Al (p < 0.05).  相似文献   

19.
A study was conducted to estimate the runoff in urbanized zone using Soil Conservation Services Curve Number (SCS-CN) method through remote sensing and GIS techniques. In this study, the region was identified as Cochin Corporation (Kerala State, India) with an aerial extent of 96.44 km2. The spatial and non-spatial data were collected from different sources, and the thematic layers of soil hydrologic group and land-use maps were prepared and overlaid with one other. The overlaid output results were assigned by curve numbers with respect to soil and land-use categories, and the CN map was prepared with the help of Visual Basic (VB) language in ArcGIS platform. Through supervised classifications, 13 different land-use classes were identified from Quickbird data for the year of 2005 and 2010. The most prominent land-use classes were water bodies, residential, mixed crops, commercial and industrial, and 3 types of soil hydrologic groups were identified namely A, B, and C categories. The B group is most prominent occupying 60 km2 of the study area. The CN map shows the ranges that 92–100 is the major CN area with high runoff potential zone of the study region. At the final stage, the runoff was estimated by the maximum successive rainfall received in this study area in two different years—2005 and 2010 along with their land-use pattern. The runoff model is applied for temporal variation in land-use change, and impact of runoff was studied. The study area showed significant changes in land-use pattern between 2005 and 2010 particularly in the land-use change from agricultural into industrial, commercial, and residential (high density). The area covered by the highest runoff depth with the range of 92–100 CN values increased from 43.87 to 45.32 km2 from 2005 to 2010. The volume of runoff was increased from 135.56 to 141.49 Mm3 from 2005 to 2010 due to the land-use change pattern.  相似文献   

20.
Rapid land use change has taken place in many arid and semi-arid regions of China including the Loess Plateau. In this study, changes in land use and landscape fragmentation in the small Shanghuang watershed on the Loess Plateau were investigated by the combined use of remote sensing, GIS and landscape metrics. Land use classes were mapped and analyzed from a time series of maps and remotely sensed images that were ground truthed in 2008. Analyses of the data showed that land use had undergone substantial changes in this small watershed from 1982 to 2008, and these changes could be divided into three phases according to the change in the landscape matrix whereby the dominant land use was grassland (1982–1990), cropland (1990–2002) and forestland (2002–2008). During each phase, conversions between different land use types took place frequently, especially among cropland, orchards, grassland and forestland. Landscape fragmentation increased from 1982 to 1990 and then decreased from 1990 to 2008 as indicated by four landscape metrics. These changes in land use and landscape fragmentation in this small watershed were mainly controlled by human factors (land management, construction, population pressure, and government policy) rather than natural factors.  相似文献   

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