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1.
Since 1990, Mongolia has experienced a radical change away from centralized livestock production to more traditional rangeland management practices. As the herders now have increased access to the pastures, they need to be able to evaluate the sustainable level of exploitation of the rangeland. This paper demonstrates how pertinent information on the state of the rangeland resources can be made available to herdsmen by using a Geographical Information System (GIS). The focus is on the importance of having a sound data and information framework when assessing rangeland resources. The three main requirements are: first, knowledge of the production system; second, a natural resource inventory; and third, an assessment of the natural resource exploitation. Workshops held in the field brought together herdsmen, administrators, scientists and project personnel to identify and discuss issues of range management. From topographic maps, a digital elevation model was created using GIS, which together with a recent land-cover map elaborated from a SPOT satellite image made it possible to map the important areas suitable for winter grazing. The exact locations of the family winter settlements were recorded and linked to annual livestock statistics using GIS to identify the areas being grazed and to calculate the stocking rates by household. It was shown for the administrative unit of Arbayasgalan that the ratio of stocking rates to carrying capacity exceeded one, which indicates overstocking. However, the uneven distribution of grazing pressure over the study area enabled the proposal of actions to mitigate serious overgrazing. A discussion of range management practices was facilitated by providing the herdsmen with information on the extent and location of the problem. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

2.
Soil degradation in the Mediterranean and other arid and semi-arid regions of the world is caused mainly by cultivation and grazing. A consequence of de-vegetation due to overgrazing has been a decrease in organic matter (litter) input to soil and a decrease of aggregate size and stability making soils more susceptible to erosion and to organic matter losses. This study provided evidence linking the Dissolved Organic Nitrogen (DON) export from river basins to livestock grazing intensity and the resulting decrease in vegetation. Koiliaris River Basin in Crete was selected to study the effects of livestock grazing on water quality because it offers a unique morphologic situation due to its karstic hydrogeology draining the upland grazing areas through karstic springs. Mass balance calculations of N loads indicated that organic N is behaving as a conservative substance. It is postulated that the two potential mechanisms of Mineralization–Immobilization-Turnover and Direct Uptake did not operate in the degraded soils of the karst and arguments are presented justifying the hypothesis. De-vegetated soils of the area had lower C and N content, the same bacterial count, but lower microbial activity, lower fungi counts and species richness and lower mineralizable N compared to naturally vegetated soils. DON was the predominant N species in both extracted soluble N pools. De-vegetated soils had lower decomposition potential compared to vegetated soils. Mineralization and plant uptake appeared to be restricted and leaching of soluble low aromaticity organic matter was favored. A linear relationship between DON export and livestock N load was obtained for five Greek basins suggesting a mechanism that operates on regional scales. The de-vegetation of grazing lands in Koiliaris River highland calcaric leptosols was shown to be a primary factor causing the decline of soil biochemical quality and DON can be used as a reliable indicator for livestock grazing impacts to soil biochemical quality.  相似文献   

3.
Land suitability evaluation is prerequisite for assessing the limitations for sustainable land use planning. We used ten site specific criteria (rainfall, texture, drainage, soil depth, slope, distance to major road, distance to nearest sugar mill, erosion hazard, risk of flooding and pH) and applied weighted multi-criteria evaluation (MCE) technique in a geographic information system (GIS) environment to evaluate land suitability for sugarcane cultivation in Bijnor district, India. The weightage of all the parameters was calculated through fuzzy analytical hierarchy process. Sugarcane suitability map was prepared integrating various parameters through weighted overlay analysis. The map was categorized as highly suitable (S1), moderately suitable (S2), marginally suitable (S3) and unsuitable (N). The analysis revealed that of the total cultivable land of the district, largest area (61%) was highly suitable followed by moderately suitable (24%), marginally suitable (7%) and unsuitable (8%) for sugarcane cultivation. Nagina, Najibabad and Bijnor sub-districts need attention of land managers and policy makers to remove the limitations and increase the suitability of sugarcane in such areas. Only 7% area was unsuitable for sugarcane cultivation. Slope, soil depth and erosion hazard were the major limiting factors making the land unsuitable for sugarcane cultivation. Therefore, these areas should be given priority for land and soil restoration efforts. The study showed effectiveness of integrated GIS and MCE approach for land suitability analysis of sugarcane.  相似文献   

4.
Assessment of soil erosion risk using SWAT model   总被引：3，自引：2，他引：1  
Soil erosion is one of the most serious land degradation problems and the primary environmental issue in Mediterranean regions. Estimation of soil erosion loss in these regions is often difficult due to the complex interplay of many factors such as climate, land uses, topography, and human activities. The purpose of this study is to apply the Soil and Water Assessment Tool (SWAT) model to predict surface runoff generation patterns and soil erosion hazard and to prioritize most degraded sub-catchment in order to adopt the appropriate management intervention. The study area is the Sarrath river catchment (1,491 km2), north of Tunisia. Based on the estimated soil loss rates, the catchment was divided into four priority categories for conservation intervention. Results showed that a larger part of the watershed (90 %) fell under low and moderate soil erosion risk and only 10 % of the watershed was vulnerable to soil erosion with an estimated sediment loss exceeding 10 t?ha?1?year?1. Results indicated that spatial differences in erosion rates within the Sarrath catchment are mainly caused by differences in land cover type and gradient slope. Application of the SWAT model demonstrated that the model provides a useful tool to predict surface runoff and soil erosion hazard and can successfully be used for prioritization of vulnerable areas over semi-arid catchments.  相似文献   

5.
Richard Whitlow 《GeoJournal》1990,20(3):191-202
The conservation status of dambos, a particular type of wetland associated with the headwaters of rivers draining the central plateau area of Zimbabwe, is examined in terms of past and present utilisation and erosion problems. Pre- and post-1950 phases are recognized within both the commercial farming areas and the Communal Lands (or peasant farming areas). The pre-1950 phase on commercial farms was one of exploitation of dambos mainly for winter wheat production, such cultivation contributing towards locally serious erosion. Consequently legislation was passed to restrict disturbance of wetlands, especially for cultivation. The post-1950 phase on commercial farms was one of conservation, with minimal use of dambos for grazing and limited erosion. The pre-1950 phase within the Communal Lands, the former native reserves, was one involving progressive modification of the traditional farming system through, in particular, centralisation. Dambo cultivation, a well-established practice, continued throughout this place, but towards the end of this period there were localised signs of degradation associated, in part, with grazing. The post-1950 phase was one of increased pressure on land with a growing human and livestock population. Thus dambos were required to support more and more cattle throughout the year, whilst efforts to curtail dambo cultivation were not well-recieved by peasant farmers and may have compromised general conservation in the reserves.  相似文献   

6.
内蒙古科尔沁沙地历史上曾是科尔沁大草原,现在是农牧交错区,该区的土地利用关系到生态安全、国家粮食安全和农民生计。该区域“坨甸相间”地貌特点造成不同地形部位土壤含水量存在差异,降水量年际变化大。通过卫星影像数据解译出土地利用/覆被类型图与土壤图进行叠加,获得了显性沙地和隐性沙地数量与分布信息。首先保留耕地以外的其他地类,再利用卫星影像数据反映不同降水年型耕地的归一化植被指数(NDVI),将偏欠水年NDVI低于平均值的耕地退耕还草,消除这些耕地的冬春沙化风险,以进行土地利用布局调整。这种直接利用遥感数据获取土地利用/覆被类型和耕地的NDVI进行土地利用空间布局调整的方法,十分简单实用。本文还根据地貌和沙地降水入渗快的特点,提出了与高标准农田建设模式不同但与区域地理环境相吻合的农田整治模式,即利用自然沙丘作为区域风沙防护工程,土地开发不做大平整,不修建灌溉系统,发展雨养农业。以上根据区域地理环境条件进行土地利用布局和确定农田开发建设模式,可将农业生产与荒漠化防治和谐结合在一起,实现土地可持续利用。  相似文献   

7.
Thomas J. Bassett 《Geoforum》2009,40(5):756-766
Côte d’Ivoire’s adoption of land privatization policies promoted by the World Bank and European Union is producing new land use patterns in the countryside. A centerpiece of these policies is the 1998 Rural Land Law that aims to restructure rural economic life along agrarian capitalist lines. The purported “development” objective of land privatization is to stimulate agricultural productivity based on the assumption that land titling will lead farmers and herders to make greater investments in their production systems. This paper argues that the mobile livestock raising system of immigrant FulBe pastoralists in Côte d’Ivoire is threatened by the new land law. Since mobility is crucial to animal health and fertility rates, I argue that reduced mobility will lead to lower livestock productivity. Although the land law has yet to be implemented, its very existence is leading prospective claimants to test their land rights by planting orchards and lending land to immigrant farmers. The monetization of land lending and grazing rights is increasingly common. Land disputes over who has the power to allocate land are also on the rise. I argue that this heightened interest in “tenure building” is constraining herd mobility, especially for herders with limited resources to negotiate access to rangelands. On the other hand, land privatization is strengthening the hand of local cattle-owning farmers who increasingly practice mobile livestock raising and compete with FulBe herders for grazing lands. Under these new conditions of land access, control, and competition, FulBe herd mobility and productivity are at risk of declining.  相似文献   

8.
Groundwater is a valuable natural resource for drinking, domestic, livestock use, and irrigation, especially in arid and semi-arid regions like the Garmiyan belt in Kurdistan region. The Awaspi watershed is located 50 km east of Kirkuk city, south Kurdistan, Iraq; and covers an area of 2146 km2. The paper presents result of a study aimed at: (1) mapping and preparing thematic layers of factors that control groundwater recharge areas, and (2) determination of sites suitable for groundwater recharge. We used available data such as geological map, groundwater depth map, digital elevation model (DEM), Landsat 8 imagery, and tropical rainfall measuring mission (TRMM) data for this study. These data, supplemented by slope features, lithology, land use land cover, rainfall, groundwater depth, drainage density, landform, lineament density, elevation and topographic position index, were utilized to create thematic maps to identify suitable areas of groundwater recharge, using GIS and remote sensing techniques. Analytic hierarchy process (AHP) was applied to weight, rank, and reclassify these maps in the ArcGIS 10.3 environment, to determine the suitable sites for groundwater recharge within the Awaspi watershed. Fifty-five percent of the total area of the watershed was found to be suitable for groundwater recharge; whereas 45% of the area was determined to have poor suitability for groundwater recharge, but can be used for surface water harvesting.  相似文献   

9.
Scholars attribute the growth and decline of Classic period (AD 200-900) settlements in the semi-arid northern frontier zone of Mesoamerica to rainfall cycles that controlled the extent of arable land. However, there is little empirical evidence to support this claim. We present phytolith, organic carbon, and magnetic susceptibility analyses of a 4000-yr alluvial record of climate and human land use from the Malpaso Valley, the site of one such Classic frontier community. The earliest farming occupation is detected around 500 BC and appears related to a slight increase of aridity, similar to the level of the modern day valley. By AD 500, the valley's Classic period Mesoamerican settlements were founded under these same dry conditions, which continued into the Postclassic period. This indicates that the La Quemada occupation did not develop during a period of increased rainfall, but rather an arid phase. The most dramatic changes detected in the valley resulted from the erosion associated with Spanish Colonial grazing and deforestation that began in the 16th century. The landscape of the modern Malpaso Valley is thus primarily the product of a series of intense and rapid transformations that were concentrated within the last 400 yr.  相似文献   

10.
Livestock grazing is one of the main causes for the change of soil organic carbon (SOC) and total nitrogen (TN) in the arid and semi-arid parts in northern China. This paper examined the SOC, TN, and their components of the local steppe and desert steppe, considering continuous grazing and 4-year livestock exclusion, respectively. In steppe where livestock is excluded, both SOC and TN in the topsoil (0–0.20 m) are found to remain unchanged; however, significant growths are found in microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), particulate organic carbon (POC), and particulate organic nitrogen (PON). On the contrary, both POC and PON progressively decrease at the continuous grazing sites, attributed to the reduction of the mass proportions of soil particulate fraction in the top 0.10 m soil. In the desert steppe where grazing is excluded, the SOC, TN, and their components of the topsoil increase. However, at the continuous grazing sites, POC and PON in the 0.10 m topsoil are reduced, caused by the decrease of C and N content in soil particulate fraction. Besides, microbial quotients were lower in the continuous grazing sites in the two grasslands. It is also found that both MBC and POC are more sensitive to human-induced activities than SOC, and thus could serve as earlier indicators of the soil-fertility variation caused by short-period grazing management.  相似文献   

11.
In the Shixia small watershed,twenty experimental plots and two monitoring channels,the residential area and livestock areas were used to monitor the flow,runoff and erosion,Nitrogen and phosphorous concentrations associated with various land uses were analyzed at the same time.The results are presented as follows:(1)TP ,TN and COD concentrations of runoff samples in the residential area and livestock arease are nearly 10 times those in other land-use areas.High nutrient loads are associated with village land use,which is due to unsuitable livestock rising.These areas should be treated as the critical areas of non-point source pollution.(2)Different land use influences intensity the loss nutrients,especially slope tillings in agricultural land.The amount of nutrient loss from agricultural land per unit is highest,that from forestry is intermediated and that frompastures is lowest,However,in consideration of the variability of land-use areas,agricultural land contributes the greatest to TP and forestry land to TN.(3)The concentrations of TN and TP in sediments from gangues are highest ,those in forestry land are intermediate,and those in agricultural land are lowest.Nutrient loss from hilly areas in much greater than from mountainous areas.  相似文献   

12.
Watershed degradation due to soil erosion and sedimentation is considered to be one of the major environmental problems in Iran. In order to address the critical conditions of watershed degradation in arid and semiarid regions, a study based on the Modified Pacific Southwest Inter-Agency Committee (MPSIAC) model was carried out at Golestan watershed, northeast of Iran. The model information layers comprising nine effective factors in erosion and sedimentation at the watershed site were obtained by digitalization and spatial interpolation of the basic information data in a GIS program. These factors are geology, soil, climate, runoff, topography, land cover, land use, channel, and upland erosion. The source data for the model were obtained from available records on rainfall and river discharge and sediment, topography, land use, geology, and soil maps as well as field surveys and laboratory analysis. The results of the MPSIAC model indicated that 60.75 % (194.4 km2) and 54.97 % (175.9 km2) of the total watershed area were classified in the heavy sedimentation and erosion classes, and the total basin sediment yield and erosion were calculated as 4,171.1 and 17,813.4 m3 km?2 year?1, respectively. In the sensitivity analysis, it was found that the most sensitive parameters of the model in order of importance were topography (slope), land cover and use, runoff, and channel erosion (R 2?=?0.92–0.94), while geology, climate (rainfall), soil, and upland erosion factors were found to have moderate effect to the model output (R 2?=?0.74–0.59).  相似文献   

13.
Soil erosion by water is recognised as a worldwide land degradation issue, particularly in arid and semi-arid regions. The aim of this study is to apply the powerful capabilities of advanced remote sensing and geographic information system techniques to identify the areas at risk to water erosion. This study presents the assessment of water erosion in mountainous areas (eastern Aures, Algeria) based on three main factors: the friability of the bedrock, degree of slope and density of vegetation cover. Alsat1 image was used to produce land use and vegetation (NDVI) maps. Digital elevation model was used in constructing the slope gradient map. The erosion risk map was obtained by the combination of indices assigned to thematic layers following multicriteria decision rules. Water erosion was generally not concerning in the eastern Aures (slight risk = 33 %, moderate risk = 44 % of the area). This simple–qualitative approach gave good results for assessing soil erosion equally to quantitative methods since 89.55 % of field verifications were accurate. The non-alarming state and the low rate of severe and extremely severe risk to erosion are due to (1) the low steep slopes, (2) the good quality of vegetation (forests with thick undergrowth), and which are occurring on (3) resistant materials of the substratum, and (4) the low human pressure. Results of this study, which may be conducted with reasonable costs and accuracy over large areas, are of significant help in prioritising areas in decision making and sustainable planning.  相似文献   

14.
In Algeria, water and soil, vital resources of production, are currently experiencing degradation in terms of quantity and quality. The deficit of rainfall, the frequency and intensity of droughts, and torrential rains exacerbate growing water stress and erosion phenomenon. These conditions involve adaptation strategies and the development of management techniques for the scarcity of excess water. The strategies for the conservation and management of water and soil (WSC) will be one option, among others, to reduce the risks and impacts of climate change. In this sense and to highlight the strategies of WSC, we identified the different techniques of conservation of water and soil; we evaluated their effectiveness and suitability and identified some trends in these techniques. This evaluation has shown the positive role of these techniques in controlling water and conserving natural environments and suitability to the harsh conditions of semi-arid and arid areas.  相似文献   

15.
This paper assesses the contribution of historical and traditional winter grazing to long‐term land degradation in northeast Iceland. To do so, indicators of soil erosion from two contrasting historical winter grazing areas, set in a tephrochronological framework, are compared against their temporal and regional land degradation contexts. The observations made indicate distinctive and different landscape responses to historical winter grazing depending on location. In both study areas, there is an accelerated level of wind and water erosion with settlement at ca. A.D. 874 through to A.D. 1477. One of these areas had a subsequent reduction in erosion rates to considerably below the regional average, possibly as a result of adaptive land management; the second, more inherently sensitive area, is now subarctic desert. These findings confirm early land management practices as a major factor in Icelandic land degradation, they contribute to explanations of early settlement success and failure, and highlight the significance of historical approaches in addressing contemporary issues of land degradation and conservation responses. © 2004 Wiley Periodicals, Inc.  相似文献   

16.
非点源污染模型研究   总被引：5，自引：2，他引：5       下载免费PDF全文
张建云 《水科学进展》2002,13(5):547-551
描述了土壤侵蚀的物理过程,分析了影响土壤侵蚀过程的主要因素,提出包括降雨径流模型、土壤侵蚀模型和畜禽污染模型的非点源污染模拟模型(NPSP),并介绍了该模型在爱尔兰Dodder流域的应用.  相似文献   

17.
青海牧区干旱、 雪灾灾害损失综合评估技术研究   总被引：5，自引：2，他引：3  
颜亮东  李林  刘义花 《冰川冻土》2013,35(3):662-680
利用青海省20个草地生态监测站点2003-2011年监测的牧草、 降水和相应年份的灾害监测调查资料分析表明, 青海高原草地牧草产量与降水相关密切, 8月末牧草产量与5-8月降水量相关系数均达到了0.001的相关性检验, 建立了不同草地类型不同月份牧草产量与降水量的最优模拟方程; 利用降水量距平百分率划分干旱等级, 建立了干旱等级与牧草和牲畜损失的对应关系, 实现了干旱和雪灾对草地、 牲畜直接经济损失的定量评估. 对比分析了干旱和雪灾灾害对畜牧业造成损失比例, 将干旱和雪灾两个不同概念的灾害通过经济损失有机地联系起来, 直观地表明了在不同等级的灾害情况下, 损失造成的大小和比例. 结果表明: 随着灾害等级加重, 雪灾造成的损失比例增大, 在特大灾时, 雪灾造成的损失是旱灾损失的2.5倍.评估模型符合草地牧草生长规律和畜牧业生产特征, 实例评估符合畜牧业实际损失程度. 因此, 能够在降水偏少或偏多时对草地畜牧业评估服务中推广应用.  相似文献   

18.
黄土高原近两千年来土地利用和环境的变迁   总被引：7，自引：0，他引：7  
刘多森 《第四纪研究》2004,24(2):184-190
在220～1368A.D.期间内累计有859年,全部黄土高原在非汉族的管辖之下;而其余289年,该地区的某些部分依然被非汉族所控制。非汉族进入黄土高原以后,土壤侵蚀速度随放牧地的扩张而减小。在隋朝和唐朝期间(581～907A.D.),黄土高原的生态环境较当今温暖湿润,植被更为繁茂,林地约占整个黄土高原面积的25%。在明朝和清朝期间(1368～1911A.D.),黄土高原的大部分森林被破坏,土壤侵蚀速度随自然植被损毁而增大  相似文献   

19.
The semi-arid areas in Northern China are home to a large population and have great ecological vulnerability. Contemporary land use pressures cause these areas to suffer from a severe land use conflict between human activities and environmental conservation. Ignoring the livelihood of humans and the development of semi-arid areas is not possible. However, the rapid increase in human activity recently exposes both the human race and local environment to potential adverse effects. To balance this contradiction, this research puts forth a framework to optimize the land use patterns in these areas in the context of ecological security and land use suitability. Considering the expansion of particular land use forms to meet the land use demand of social development, a revised cellular automata model is employed to shape the path of land expansion. Meanwhile, additional adjustment rules are set to adjust the unreasonable land use units to a suitable form. The city of Ordos is chosen as a case to put this framework into practice, and several landscape pattern indexes are used to evaluate the results. The results reveal that this framework could maintain the environment in a stable state while simultaneously meeting the land use demand of social development.  相似文献   

20.
Some recent land use changes in Albania, such as deforestation, cropland abandonment, and urban sprawl, have caused serious increase of erosion risk. The main objective of this study was to map erosion risk in Korçe region and assess the degree at which every land use is concerned. The G2 erosion model was applied, which can provide erosion maps and statistical figures at month-time intervals using input from free European and global geodatabases. The mapping results in Korçe region were derived at a 30-m cell size, which is an innovation for G2. Autumn-winter months were found to be the most erosive, with average erosion rates reaching the maximum in November and December, i.e. 2.62 and 2.36 t/ha, respectively, while the annual rate was estimated at 10.25 t/ha/yr. Natural grasslands, shurblands, mixed forests, and vineyards showed to exhibit the highest mean erosion rates, while shrublands, broad-leaved forests and natural grasslands were found to be the most extended land covers risky for non-sustainable erosion rates (i.e. >10 t/ha/yr). A detailed examination of the detected hot spots is now necessary by the competent authorities, in order to apply appropriate, site-specific conservation measures. Notably, use of SPOT VGT data did not prevent the maps from having extended gaps due to cloudiness. Sentinel-2 time series, freely available by the European Space Agency (ESA), have the potential to improve spatiotemporal coverage of V-factor, thus further empowering the G2 model, in the near future.  相似文献   

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