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1.
ABSTRACTSustainable intensification of existing cropland is one of the most viable options for meeting the escalating food demands of the ever-increasing population in the world. Accurate geospatial data about the potential single-crop (rice-fallows) areas is vital for policymakers to target the agro-technologies for enhancing crop productivity and intensification. Therefore, the study aimed to evaluate and understand the dynamics of rice-fallows in the Odisha state of India, using SAR (Sentinel-1) and Optical (Landsat OLI) datasets. This study utilized a decision-tree approach and Principal component analysis (PCA) for the segmentation and separation of different vegetation classes. The estimated overall accuracy of extracted rice-fallow maps was in the range of 84 to 85 percent. The study identified about 2.2, 2.0 and 2.1mha of Rice-Fallows in the years 2015–16, 2016–17, and 2017–18, respectively. The combined analysis (all three years) of rice-fallow maps identified about 1.34mha of permanent rice-fallows, whereas the remaining 0.6–0.8mha area was under the current-fallow category. About 50% of the total permanent rice-fallows were detected in the rainfed areas of Mayurbhanj, Bhadrak, Bolangir, Sundargarh, Keonjhar, Baleswar, Nawarangpur and Bargarh districts. The study also illustrated the time-series profiles of SMAP (soil moisture) datasets for the ten agroclimatic zones of the Odisha, which can be utilized (along with rice-fallow maps) for the selection of crop and cultivars (e.g. short or medium duration pulses or oilseeds) to target the rice fallows. The approach utilized in the current study can be scaled up in similar areas of South and South-east Asia and Africa to identify single-crop areas for targeting improved technologies for enhanced crop productivity and intensification. 相似文献
2.
On-going tenure changes in the cotton zone in southern Mali are discussed. Land tenure in the area is changing and adapting to the rapid agricultural development taking place. This adaptation supports the main tenets of Property Rights Theory (PRT). The driving forces behind enclosure of land rights as described by PRT, such as population pressure and increased market access, are acknowledged. Enclosure takes two forms in the study area. First, some customary authorities in villages where population pressure is relatively high attempt to restrict access to pastures and woods on village land to create exclusive village commons. Second, holdings are being subdivided and farmers are increasingly confining their fields through tree planting. Except around the towns, where semi-formal land sales are becoming increasingly frequent, this individualisation does not imply exclusive and absolute private property to land. Bundles of overlapping rights still exist where various individuals or groups control access to different resources on the same piece of land. 相似文献
3.
利用"淮河流域东北部一次异常特大暴雨的数值模拟研究Ⅰ"的数值模拟结果,分析了几种不稳定对流涡度矢量(CVV)与中尺度深湿对流系统之间的关系,并分析了不稳定条件的增强和维持机制,结果表明:(1)中低层对流不稳定是深湿对流系统发生的先决条件,由于低层存在辐合,使得周围湿空气向暴雨区集中,对流单体在暴雨区汇聚,且发生合并增强,台风左前方向暴雨区输送对流不稳定能量等,是使得暴雨区对流不稳定重新建立和加强的重要机制.(2)深湿对流系统的中低层不仅有对流不稳定,而且还有斜压不稳定、条件对称不稳定,而中高层必须有湿斜压不稳定和条件对称不稳定.深湿对流系统中高层西(北)侧为负MPV2柱,东(南)侧为正MPV2柱;(3)深湿对流系统中惯性不稳定柱与惯性稳定柱相间分布,西(南)侧为负CVV柱,东(北)侧为正CVV柱,负CVV柱对深湿对流起激发作用;(4)惯性不稳定、湿倾斜不稳定和条件不稳定产生强的倾斜式对流,而强的倾斜式上升运动加强了深对流系统北侧高层的南风分量,因深对流系统南侧低层出现补偿性下沉气流,因而低层南风加强,高低空急流中心的加强会进一步加强对流的发展,使得惯性不稳定、湿倾斜不稳定及条件不稳定增强和维持,这是一个正反馈过程.(5)在暴雨中心以东维持一顺切变环流,同时暴雨中心的浅对流单体吸收来自南方的水汽和不稳定能量,中尺度辐合线与β中尺度涡旋对对流单体起组织和增强作用,对流系统中辐合、辐散柱相间分布,强散度柱与强涡柱互伴互耦,都有利于形成中尺度深湿对流系统,使不稳定向纵深方向发展,从而使得不稳定得到增强和维持. 相似文献
4.
强台风"云娜"登陆过程的研究——基于AREM模式的数值分析 总被引：3，自引：0，他引：3
使用新改进的双重嵌套AREM数值预报模式,并与高时空分辨率的探测资料相结合,针对台风“云娜”登陆加强的特点进行数值模拟分析,结果表明该模式对“云娜”台风环流特征、强度变化趋势和台风降雨等都有较强的预报能力。在此基础上,定量研究其登陆加强过程中三维大气中尺度场动、热力特征及演变过程,并探讨了其登陆加强的机理。由此得出了与“云娜”登陆加强相关的重要影响因子:(1)副热带高压西南侧的偏东引导气流加强是“云娜”登陆前移速加快、强度增强的有利环境场条件。(2)“云娜”近海移速加快时有较强的东密西疏的不对称流场结构,特别是其垂直速度场以及强对流发展的水平分布的强不对称特征与该气旋登陆加强同时发生,也可能与台风强度维持和加强存在一定的相关。(3)在“云娜”中心西南侧的强凝结潜热释放过程,有可能助其在登陆时加强。此外,在“云娜”发展加强阶段,低层暖湿、中层干冷的位势不稳定层结,有利于对流的强盛发展。(4)“云娜”登陆前后有强低空急流与之联结,并有垂直对流运动发展,由此可获得不断增强的潜热能量是其登陆加强的另一个重要机制。 相似文献
5.
《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(1):21-31
In this study some light is shed on farmers' changing land-use and management practices in two mountain watersheds located in the Western Hills of Nepal. The study is based on a survey of 300 households, group discussion, interviews of key informants, and field observation in project and non-project watersheds conducted from April to September 1999. Confronted with shrinking landholding size, owing to a steadily growing population and scarcity of non-farming employment opportunities, farmers in both watersheds have gradually intensified land use and cultivated new crops to increase farm production and income. They are shifting from cereal crops to livestock husbandry, particularly along the road in the project watershed, and to vegetables and other cash crops in the accessible foothills of the non-project watershed. They have also adopted various structural and biological measures to control soil erosion, landslides, gully expansion and soil nutrient loss in order to maintain or enhance land productivity. The degree of adoption of the structural and biological measures is higher in the project watershed than in the non-project watershed. Contrary to the traditionally held belief of some researchers, population pressure on a finite land resource has brought about positive changes in land-use and management practices. Farmers have innovated and adopted different land management technologies to increase farm production as they are exposed to the risk of food insecurity because of shrinking landholding size and land degradation. 相似文献
6.
Globalized supply chains: Emergent telecouplings in Mexico’s beef economy and environmental leakages
This article analyzes how trade liberalization in Mexico, particularly following the North American Free Trade Agreement (NAFTA), has transformed that nation’s cattle economy into a feedlot system manifesting multiple telecouplings and based on the transnational provision of inputs. A conceptual model is presented that suggests how environmental effects involving land use and GHG emissions emerge from changes in the beef supply chain. The article then presents an empirical analysis establishing that the production of corn and beef has intensified in the wake of NAFTA, and that deforestation rates have declined over the same period. Evidence is also presented showing that this has not precipitated a land sparing effect, given the leakage of deforestation into Central America, which supplies Mexican feedlots with 36 % of their source materials. The article calculates associated GHG emissions and establishes that enteric fermentation dominates deforestation as a source, and that ∼14% of GHGs produced by the post-NAFTA Mexican supply chain are emitted in Central America. This raises accounting questions for signatories to the Paris Climate Treaty, given commitments are nation-based. 相似文献
7.
农地利用变化假说与相关的环境效应命题 总被引：15，自引：0，他引：15
将用途转移和集约度升降这两种类型的土地利用变化整合在一个过程中,解释变化机制的理论,有古典经济学的地租理论,还有若干理论性假说。这些假说又常常与一些土地利用的环境效应命题联系在一起,扩充为解释人地关系的假说。综述了解释农地利用变化的四大假说（包括基于马尔萨斯人口论的土地面积持续扩张假说、博斯鲁普的需求诱发型集约化假说、吉尔茨的集约度弹性假说、土地利用粗放化假说）和农地利用环境效应的三大命题（包括农地面积扩张造成土地退化、优质土地的集约化间接促使生态脆弱地区环境改善、农地利用粗放化和弃耕促使环境和生态恢复）,以及围绕这些假说和命题的争论和实证研究,旨在为土地利用变化的情景构建、模型模拟及愿景设计提供学术依据。 相似文献
8.
《Geoforum》2014
The System of Rice Intensification (SRI) and rice genetic improvement are proposed as two approaches to improving and increasing rice production. In recent exchanges, they have been represented by their respective supporters as starkly contrasting, almost mutually incompatible alternatives. However, advocates on both sides of this argument have tended to stress the genetic and physiological characteristics of rice plants and place less emphasis on the spatially and temporally situated knowledge and management skills of farmers, which are the means by which any agricultural technology is locally adapted and integrated into livelihood strategies, and technological potential is translated into real outcomes in specific settings. Taking this proposition seriously would entail a substantial reorganisation of agricultural research and extension, bridging the historical divide between these two wings of professional agronomy. It would require agronomists of both types to work more collaboratively with farmers. It would also require scientists to produce new kinds of outputs, such as analytical frameworks, heuristics and decision-making tools to help farmers apply scientific insights to their own constrained circumstances. This argument is made with reference to the cases of SRI (a cultivation system that is said to boost farm yields without the need for genetically improved germplasm) and C4 rice (a crop-improvement project intending to ‘supercharge’ rice photosynthesis to increase rice yields). The paper uses the agronomic concepts of the ‘yield gap’ and the ‘yield ceiling’ to offer a perspective on strategic questions about the goals and organisation of agricultural research and extension. 相似文献
9.
利用具有完备物理过程的中尺度模式MM5对发生于南海的0214号热带气旋(TC)“黄蜂”进行高分辨率的数值模拟,以此来研究热带气旋在近海发展为强热带风暴过程中结构变化对强度的作用,并对近海加强的内部动力机理做一些探讨。模拟结果发现在加强阶段,气旋环流中存在类似于涡旋Rossby波性质的波动在西北侧对流激发下绕中心逆时针传播,波动与眼墙区对流带相耦合,使得眼区趋于闭合;中尺度涡旋系统的轴对称化过程,通过与对称环流系统非线性相互作用,向气旋环流提供能量,其自身也得到维持与发展。这些结构的变化对TC近海加强和登陆后迅速减弱都产生了重要的影响。 相似文献
10.
文中探讨了中尺度地形背风驻波及对天气系统发生发展的影响问题,通过建立一个含类似大别山地形作用的简化数学模型并进行了数值计算,结果表明,当过山气流u取１０１ｍ／ｓ量级,层结参数Ｎ取１０(－３)ｓ(－１)量级,其比值Ｕ／Ｎ约为３×１０３～４×１０３时可出现一种相当正压的地形背风波,其波长近于Ｕ／ｆ～１０２ｋｍ（ｆ为柯氏参数）。结合上述理论结果和实际暴雨个例,分析指出在江淮梅雨期间,当有移动性的暴雨区移至大别山定常背风波的适当位置时,暴雨会得到增幅。 相似文献