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1.
This study was conducted to quantify agricultural land degradation in the Ruba Gered watershed, Ethiopia. The watershed was divided into 12 land mapping units (LMU) after superimposing maps of soil, slope, land use/cover, and elevation. Subsequently, cultivated land was delineated to assess degradation types and severity based on standard approaches. Sheet erosion was estimated using the revised universal soil loss equation. Composite soil samples were collected from each LMU to quantify key soil nutrients (OM, total nitrogen, available phosphorus, and available potassium) lost by sheet erosion. The annual average soil loss due to sheet erosion was estimated to be 17.4 t ha?1 yr?1, with average annual nutrient losses estimated as 246.5 kg ha?1 organic matter, 12.4 kg ha?1 total nitrogen, 0.1 kg ha?1 available phosphorus, and 1.6 kg ha?1 available potassium. The study revealed that substantial quantities of soil and nutrients are lost every year in the study area due to severe sheet erosion. This amount of nutrient loss severely degrades soil and reduces soil fertility. 相似文献
2.
Land degradation resulting from land-use changes and soil erosion has been a serious environmental problem in Ethiopia. This study addressed the effects of land use and slope position on soil physical and chemical properties in the Gelana sub-watershed, Northern highlands of Ethiopia. A total of 63 soil samples were collected and analyzed using a two-way ANOVA. Results showed that clay, soil pH, soil organic matter, total nitrogen, cation exchange capacity, and exchangeable base contents of the cultivated land were significantly (p < 0.001) lower than those of the forest land, while soil bulk density, available phosphorous, and percentage base saturation were higher for cultivated land than forest land. In general, soil fertility declines as land use changes from forest to grazing and cultivated lands. Sand, clay, bulk density, soil pH, organic matter, total nitrogen, carbon:nitrogen ratio, available phosphorous, cation exchange capacity, exchangeable cations, and percentage base saturation showed significant variation due to slope position differences. Therefore, the study reinforces the need for integrated watershed management for sustainable agricultural production in the study area. 相似文献
3.
中国土壤有效含水量分布 总被引：7，自引：0，他引：7
1IntroductionAvailable soil water capacity (ASWC) is the volume of soil water that should be available to plants. It is commonly estimated as the amount of water held between field capacity (FC) and permanent wilting point (PWP) with corrections for salin… 相似文献
4.
Soil degradation is perceived as a major threat in the Mediterranean region due to changes in land-use and possible future climate change. Soil aggregation parameters are used here to demonstrate their potential as a key-indicator for land degradation studies. The monitoring of these indicators offers a means of establishing the vulnerability and resilience of geo-ecosystems. Soil aggregation stability and distribution were studied on soils with an open shrubby vegetation cover, from several places in southeastern Spain and southern France, by applying drop tests and determining aggregate size distributions. Aspect and vegetation cover were incorporated in the soil sampling. Several indices were derived from these analyses to indicate the degree of soil aggregation. This was done by referencing to a base level of aggregation (bare soil aggregation). It was found that soil aggregates were more stable and were often coarser under vegetation, when compared to their immediate surrounding bare areas. A similar, slightly less clear effect was noted on N-facing exposed slopes when compared to S-facing exposed slopes. Long-term changes were found by studying cultivated land, abandoned fields and land covered by semi-natural vegetation, on comparable substrate and comparable land units. It is clear that soil aggregation and aggregate stability increases with time (years). It is argued that soil aggregation indices can be used as a key-indicator for degradation processes at a fine scale with implications for runoff and sediment generating processes at the hillslope scale. 相似文献
5.
三峡库区重庆段水土流失的时空格局特征 总被引：2，自引：0，他引：2
Soil and water loss has been the most serious eco-environmental problem in the Three Gorges Reservoir Area of Chongqing. In
this paper the authors studied the spatiotemporal features of soil and water loss from 1999 to 2004 based on RS and GIS techniques.
The results showed that: (1) The soil and water loss area decreased from 1999 to 2004. (2) Soil and water loss mainly exists
in purple soil, yellow soil, limestone soil, paddy soil and yellow brown soil distributed areas. (3) The dry slope land and
sparse woodland that are intensively influenced by human activities experienced most serious soil and water loss. (4) Soil
and water loss in the study area indicated an obvious vertical differentiation characteristic. (5) There is a significant
correlation between soil and water loss and slope. (6) There is no obvious correlation between soil and water loss and aspect.
(7) Soil and water loss mainly exists in the values of R between 300 and 340 distribution area. The very-high soil and water
loss has obvious correlation with R.
Foundation: National Natural Science Foundation of China, No.40801077; Science & Technology Research Project Supported by Chongqing Municipal
Education Commission, No.KJ070811; Doctoral Fund of Chongqing Normal University, No.06XLB004; Project by Chongqing Water Conservancy
Bureau
Author: Li Yuechen (1974–), Ph.D and Associate Professor, specialized in the study of remote sensing application and land use/land
cover change. 相似文献
6.
贵州猫跳河流域土地利用变化和土壤侵蚀(英文) 总被引：4，自引：2，他引：2
Due to the extremely poor soil cover, a low soil-forming rate, and inappropriate intensive land use, soil erosion is a serious problem in Guizhou Province, which is located in the centre of the karst areas of Southwest China. In order to bring soil erosion under control and restore environment, the Chinese Government has initiated a serious of ecological rehabilitation projects such as the Grain-for-Green Programme and Natural Forest Protection Program and brought about tremendous influences on land-use change and soil erosion in Guizhou Province. This paper explored the relationship between land use and soil erosion in the Maotiao River watershed, a typical agricultural area with severe soil erosion in central Guizhou Province. In this study, we analyzed the spatio-temporal dynamic change of land-use type in Maotiao River watershed from 1973 to 2007 using Landsat MSS image in 1973, Landsat TM data in 1990 and 2007. Soil erosion change characteristics from 1973 to 2007, and soil loss among different land-use types were examined by integrating the Revised Universal Soil Loss Equation (RUSLE) with a GIS environment. The results indicate that changes in land use within the watershed have significantly affected soil erosion. From 1973 to 1990, dry farmland and rocky desertified land significantly increased. In contrast, shrubby land, other forestland and grassland significantly decreased, which caused accelerated soil erosion in the study area. This trend was reversed from 1990 to 2007 with an increased area of land-use types for ecological use owing to the implementation of environmental protection programs. Soil erosion also significantly varied among land-use types. Erosion was most serious in dry farmland and the lightest in paddy field. Dry farmland with a gradient of 6°-25° was the major contributor to soil erosion, and conservation practices should be taken in these areas. The results of this study provide useful information for decision makers and planners to take sustainable land use management and soil conservation measures in the area. 相似文献
7.
Valdemir Antoneli Edivaldo Lopes Thomaz Joo Ansio Bednarz 《Singapore journal of tropical geography》2019,40(1):34-49
The Brazilian faxinal is a traditional agrosilvopastoral system, which combines extensive grazing, subsistence cropping and low impact forest extraction, managed within a communal property system. Today it is at serious risk of disappearing due to increasing grazing pressure and logging activities that are leading to environmental problems such as forest fragmentation and soil degradation. The objectives of the study were to: a) evaluate soil physical degradation levels in different grazing areas within the faxinal system; and b) correlate soil degradation, fodder quantity and livestock dynamics in different pasture areas according to the household's location. Landscape mapping, vegetation surveys, and livestock grazing dynamics were assessed. In addition, soil physical parameters were evaluated for each land use (e.g., resistance, bulk density, porosity, moisture, and water infiltration rates). Results showed that livestock grazing and household locations are the main driving forces that lead to forest fragmentation. The household location creates three interrelated gradients in the communal grazing land: 1) soil physical degradation decreases from the pasture areas to araucaria forests; 2) fodder quantity decreases from pastures to araucaria forests; and 3) the livestock grazing intensity decreases from pastures to araucaria forests. In addition, some management practices to mitigate land degradation, including improvement of pastures, installation of removable troughs for drinking water in the upland areas and restriction of livestock from the riparian zone, have been proposed. 相似文献
8.
Soil and water loss has been the most serious eco-environmental problem in the Three Gorges Reservoir Area of Chongqing. In this paper the authors studied the spatiotemporal features of soil and water loss from 1999 to 2004 based on RS and GIS techniques. The results showed that: (1) The soil and water loss area decreased from 1999 to 2004. (2) Soil and water loss mainly exists in purple soil, yellow soil, limestone soil, paddy soil and yellow brown soil distributed areas. (3) The dry slope land and sparse woodland that are intensively influenced by human activities experienced most serious soil and water loss. (4) Soil and water loss in the study area indicated an obvious vertical differentiation characteristic. (5) There is a significant correlation between soil and water loss and slope. (6) There is no obvious correlation between soil and water loss and aspect. (7) Soil and water loss mainly exists in the values of R between 300 and 340 distribution area. The very-high soil and water loss has obvious correlation with R. 相似文献
9.
Regional soil erosion risk mapping in Lebanon 总被引：10，自引：0，他引：10
Soil erosion by water is one of the major causes of land degradation in Lebanon. The problem has not yet been treated in detail although it affects vast areas. This study elaborates a model for mapping soil erosion risk in a representative area of Lebanon at a scale of 1:100,000 using a spatial database and GIS. First, three basic maps were derived: (1) runoff potential obtained from mean annual precipitation, soil-water retention capacity and soil/rock infiltration capacity; (2) landscape sensitivity based on vegetal cover, drainage density and slope; and (3) erodibility of rock and soil. Then two thematic maps were derived: potential sensitivity to erosion obtained from the runoff potential and landscape sensitivity maps, and erosion risk based on the potential erosion and erodibility maps. The risk map corresponds well to field observations on the occurrence of rills and gullies. The model used seems to be applicable to other areas of Lebanon, constituting a tool for soil conservation planning and sustainable management. 相似文献
10.
卧龙自然保护区土地利用变化对土壤性质的影响 总被引：24，自引：2，他引：24
森林景观受干扰后的次生演替、人工林种植与农业耕作等在许多方面影响着土壤性质的变化。研究选取了四川卧龙自然保护区作为研究地点 ,阐述湿润高山区的土地利用方式与土壤性质之间的关系。选择了六种典型的土地利用方式加以比较 ,方差分析结果表明 ,不同土地利用之间土壤容重、全氮、有机碳、速效磷、速效钾的含量差异显著。相比之下 ,农田土壤养分含量偏低 ,而灌丛有着较高的有机碳、总氮与有效氮含量。 0～ 4 0cm土壤碳的储量变化幅度不大。综合土壤退化指数表明 ,坡耕地 ,撂荒地与人工林有土壤退化的趋势 ,而灌丛与次生林对土壤的性质有着改善的作用。人工林年龄与土壤有机碳、有机氮的含量正相关。 相似文献
11.
土地利用变化会改变土壤质地与结构,影响土壤水力性质,进而改变土壤水分有效性,影响植物生长。由于区域气候的干湿交替与水资源利用效率的提高,干旱区绿洲耕地普遍存在着撂荒-复耕现象。为了明确干旱区耕地撂荒与复耕对土壤水力性质的影响,以民勤绿洲北部边缘的耕地、撂荒地与撂荒复耕地为研究对象,测定0—40 cm深度土壤理化性质,分析不同土地利用下土壤水力性质差异及其影响因素。结果表明：耕地撂荒导致0—40 cm深度黏粒与粉粒比重增加,有机质含量降低,容重降低（P<0.05）,土壤孔隙度显著增加（P<0.05）,犁底层消失;在高水势阶段,土壤持水与导水能力增强,在土壤有效含水量对应的水势阶段,土壤持水与导水能力变差,有效含水量显著降低（P<0.05）。撂荒地复耕后,0—40 cm深度黏粒与粉粒含量继续增加,有机质含量转而增加,容重增加（P<0.05）,土壤孔隙度降低（P<0.05）,犁底层重新出现,土壤持水与导水能力又逐渐趋向于耕地水平。撂荒对干旱区绿洲土壤肥力与蓄水能力的提升不显著,而留茬免耕、深耕灭茬还田等保护性耕作措施能有效提高持水能力。利用研究区易测的土壤黏粒、砂粒含量与土壤容重,采用多元线性回归方法,可以准确、快捷预测土壤水分常数,这将有利于研究区农田灌溉制度的准确制定与优化,以及耕地利用变化对土壤水力性质影响的快速评估。 相似文献
12.
Impact of land cover changes and topography on soil quality in the Kasso catchment,Bale Mountains of southeastern Ethiopia 
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下载免费PDF全文 Hussein Haycho Warra Mohammed Assen Ahmed Melanie D. Nicolau 《Singapore journal of tropical geography》2015,36(3):357-375
This study assessed land cover change and topographic elevation on selected soil quality parameters in the Kasso catchment, southeastern Ethiopia. Twenty‐seven soil samples collected from 0–30cm depth under four land cover types across three elevation gradients were analysed for selected soil quality parameters. Results indicated that soil particle size distribution is different (p<0.001) in the catchment because of the effect of land cover change and elevation. Most cultivated lands occupy lower elevations where clay accumulates as a result of its movement from higher to lower elevations. Ploughing accentuates weathering, making cultivated lands richer in finer materials. Cation exchange capacity and exchangeable magnesium and potassium negatively correlated with elevation, total nitrogen and available phosphorous. Conversion of natural vegetation to cropland contributed to changes in pH (p<0.05), exchangeable calcium (p<0.01), potassium (p<0.001), available phosphorous (p<0.01) and nitrogen (p<0.01) contents. Parameter soil degradation index results showed that soil organic carbon, nitrogen, available phosphorous and exchangeable potassium contents declined and bulk density increased because of the land cover change. This negative effect on agricultural development and environmental health of the catchment makes an integrated land resource management approach indispensable for sustaining agricultural productivity and the environmental health of the Kasso catchment. 相似文献
13.
Wouter Lannoeye Cornelis Stal Etefa Guyassa Amanuel Zenebe Jan Nyssen Amaury Frankl 《自然地理学》2016,37(6):430-451
AbstractWith the recent technological advances offered by SfM-photogrammetry, we now have the possibility to study gully erosion at very high spatial and temporal scales from multi-temporal DEMs, and thus to enhance our understanding of both gully erosion processes and controls. Here, we examine gully degradation and aggradation at a gully headcut and at four re-incisions along a gully reach in Northern Ethiopia. Environmental controls recorded are topography rainfall, runoff, land use and cover, land management, and soil characteristics. The overall vulnerability of the catchment to erosion is low as calculated from the RUSLE (average 11.83 t ha?1 y?1). This reflects the successful land management of the past years. The runoff coefficient was on average 7.3% (maximum 18.2%). Runoff events caused most geomorphic change in the gully, but slumping of the gully bank also occurred on dry days. Most geomorphic change was caused by one major rainfall event of 54.8 mm d?1, and smaller runoff events caused both degradation and aggradation, often asynchronous between studied sites. Although most research focuses on gully heads alone, re-incisions at lower locations can still cause important gully degradation, which ultimately will reach the gully head and cause instability. 相似文献
14.
利用安徽省第二次土壤普查资料和2010-2011年土壤调查数据,运用GIS技术,研究1980-2010年安徽省表层（0~20 cm）和1 m土体中土壤有机碳（SOC）密度和储量的时空变化,并探讨土地利用变化对SOC储量变化的影响。研究表明：① 1980-2010年安徽省表层和1 m土体中SOC密度平均减少0.37 kg/m2和1.63 kg/m2,但耕地的SOC密度增加。② 1980-2010年,全省SOC密度空间变化呈现北增南减的趋势,且增加幅度由北向南依次减小。表层和1 m土体的SOC密度增加的面积为56.97%和58.21%。③ 1980-2010年,全省表层SOC储量减少34.23×109 kg,1 m土体中SOC储量减少197.26×109 kg。淮北平原、江淮丘陵岗地和沿江平原的SOC储量增加,皖西大别山区和皖南丘陵山区减少。④ 非耕地转换为耕地,比保持用地类型不变或变为其他非耕地类型,SOC密度和储量减少较慢。耕地类型内部转换（水田和旱地间转换）比保持类型不变的SOC密度和储量增加较多。研究成果为区域土壤固碳潜力、土壤肥力变化等研究提供科学依据。 相似文献
15.
以典型荒漠区原生盐碱荒地及开垦农田为研究对象,通过对比研究,以阐明原生盐碱荒地开垦后不同管理措施下土壤可溶盐总量的变化规律,开垦后土壤剖面中可溶盐总量的垂直分布和季节变化规律。结果表明：开垦显著降低了0～50 cm土壤的可溶性盐含量,开垦达100 a以上老耕地的可溶性盐含量（2.31 g/kg）仅为原生盐碱荒地（26.62 g/kg）的11%;长期的耕作改变了土壤可溶性盐分在土层中的分布,原生荒漠土壤盐分具有鲜明的表聚特征,0～30 cm土层的盐分含量占整个土壤剖面的79%,开垦50 a后,土壤中的盐分分布趋于均匀,各离子浓度的垂直分布不再明显;开垦使土壤中的盐分离子组成也发生了变化,Cl-、K+、Na+离子浓度降低,而SO42-、Mg2+、Ca2+离子浓度增加,耕作层土壤由SO4-2-Cl-1盐土转变为Cl-1-SO4-2盐土;盐碱荒地土壤可溶盐浓度伴随着降水变化具有显著的季节变化特征,而季节对开垦耕地没有显著影响。总体而言,盐碱荒地经过多年开垦利用后,土壤可溶性盐分和pH值均显著降低。 相似文献
16.
红壤退化中的土壤质量评价指标及评价方法 总被引：97，自引：4，他引：93
土壤质量评价与监测是评价土壤退化的重要工作,也是重新设计持续性的土壤管理系统的基础。目前缺乏统一的评价指标以及将各项土壤性质与土壤管理措施结合起来的评价方法。本文首先提出了选择红壤质量评价指标的原则,并从化学、物理学和生物学三个方面初步探讨了评价红壤质量动态变化可资采用的指标体系,综述了国内在南方丘陵区红壤质量演化的研究中应用的指标;最后从土地评价方法中选择了可用于红壤质量评价的方法,并简要综述了国际上最新的土壤质量评价方法。 相似文献
17.
This paper reports soil losses from 15 erosion plots in the Middle Hills, Nepal, for the 1992 and 1993 monsoon and pre-monsoon seasons. In total, 912 rainfall events were monitored. Land cover varied from grassland and relatively undisturbed mixed broadleaf forest, to degraded Sal forest and bare ground. Soil losses ranged from less than 0.1 t ha-1 yr-1 for grassland and undisturbed forest plots, to 3–10 t ha-1 yr-1 for Sal forest in various states of degradation, and over 15 t ha-1 yr-1 for the bare sites. These results are broadly consistent with those reported in other parts of the Himalayan Middle Hills. Soil loss values could be explained by variations in runoff amounts and rainfall intensity, as well as by the nature of the land cover. Ground and low shrub cover was more important than canopy cover in protecting the forest soils. Human activity has unquestionably led to accelerated rates of soil loss but the degree of acceleration depends on the nature of the human activity and especially the care with which the land is managed. [Key words: soil loss, land use, Nepal, land degradation.] 相似文献
18.
Characterizing spatial and temporal variability of soil salinity is tremendously important for a variety of agronomic and environmental concerns in arid irrigation areas. This paper reviews the characteristics and spatial and temporal variations of soil salinization in the Ili River Irrigation Area by applying a geostatistical approach. Results showed that:(1) the soil salinity varied widely, with maximum value of 28.10 g/kg and minimum value of 0.10 g/kg, and was distributed mainly at the surface soil layer. Anions were mainly SO_4~(2-) and Cl~-, while cations were mainly Na~+ and Ca~(2+);(2) the abundance of salinity of the root zone soil layer for different land use types was in the following order: grassland cropland forestland. The abundance of salinity of root zone soil layers for different periods was in the following order: March June September;(3) the spherical model was the most suitable variogram model to describe the salinity of the 0–3 cm and 3–20 cm soil layers in March and June, and the 3–20 cm soil layer in September, while the exponential model was the most suitable variogram model to describe the salinity of the 0–3 cm soil layer in September. Relatively strong spatial and temporal structure existed for soil salinity due to lower nugget effects; and(4) the maps of kriged soil salinity showed that higher soil salinity was distributed in the central parts of the study area and lower soil salinity was distributed in the marginal parts. Soil salinity tended to increase from the marginal parts to the central parts across the study area. Applying the kriging method is very helpful in detecting the problematic areas and is a good tool for soil resources management. Managing efforts on the appropriate use of soil and water resources in such areas is very important for sustainable agriculture, and more attention should be paid to these areas to prevent future problems. 相似文献
19.
土壤盐分的动态分析与监测,是实现盐渍化土地科学管理与利用的必要前提。运用GIS技术,结合地统计学方法,分析了渭干河绿洲土壤盐渍化的分布格局,探讨了不同土地利用类型下土壤盐分的变化规律。结果表明：土壤盐分离子含量随土层深度增加而减少,CO2-3和HCO3-变化不明显,整个剖面表现为：Na++K+>Ca2+>Mg2+,SO2-4>Cl->HCO3->CO2-3,具有中-强变异性,除了HCO3-、CO2-3和Ca2+外,其他盐分离子变异系数随深度增加而减小。不同土地利用类型的土壤含盐量具有显著差异垂向分布,耕地、荒地和草地、林地分别呈现为平均型、表聚型和底聚型盐分剖面,且各类型表层土壤（0～40 cm）含盐量依次为荒地（38.42 g·kg-1）>草地（16.30 g·kg-1） > 耕地（5.37 g·kg-1） > 林地（4.62 g·kg-1）。渭干河绿洲土壤属于重盐土类型,自然因素（蒸降比和地下水波动等）是土壤盐渍化的形成条件,而人为干扰（土地利用方式、灌排、施肥等）则促进了土壤盐渍化的发展。 相似文献
20.
东北黑土区容许土壤流失量研究(英文) 总被引：1，自引：0，他引：1
Soil loss tolerance(T) is the maximum rate of annual soil erosion that is tolerated and still allows a high level of crop productivity to be sustained economically and indefinitely.In the black soil region of Northeast China,an empirically determined,default T value of 200(t/km2?a) is used for designing land restoration strategies for different types of soils.The ob-jective of this study was to provide a methodology to calculate a quantitative T for different black soil species.A field investigation was conducted to determine the typical soil profiles of 21 black soil species in the study area and a quantitative methodology based on a modified soil productivity index model was established to calculate the T values.These values,which varied from 68 t/km2?a to 358 t/km2?a,yielded an average T value of 141 t/km2?a for the 21 soil species.This is 29.5% lower than the current national standard T value.Two significant factors that influenced the T value were soil thickness and vulnerability to erosion.An ac-ceptable reduction rate of soil productivity over a planned time period of 1% is recommended as necessary for maintaining long-term sustainable soil productivity.Compared with the cur-rently used of regional unified standard T value,the proposed method,which determines T using specific soil profile indices,has more practical implications for effective,sustainable management of soil and water conservation. 相似文献