首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 390 毫秒
1.
The effects of interyear variability of extreme rainfall events on maize yields at locations in Cameroon, in central‐west sub‐Saharan Africa were investigated through a simulation assessment combining a weather generator with a crop growth model. This study analyzes the potential of using dry/wet year predictions to reduce risk in subsistence agricultural production associated with climate variability at the site level. Weather data sets from eight provincial study localities were classified into three precipitation scenarios – dry (lower threshold), normal and wet (upper threshold) years. According to the modelling results, there is a less than 12 per cent variance in mean maize yields across six out of the eight localities when planting occurs in March, May and August. The variance is equivalent to approximately 100–300 kg per ha, which represents a significant amount of food in the household security of the majority impoverished sectors of rural and urban society, and which could greatly impact the socioeconomic activities of the entire populace. The results lead to the conclusion that all extreme dry and wet years are not equal in terms of their regional manifestation. This calls for precise monthly and sub‐seasonal local level forecasts and the effective dissemination of this information to farming communities in Cameroon, thereby facilitating the adaptive management of indigenous cropping practices and reducing their vulnerability to climate related disasters.  相似文献   

2.
  相似文献   

3.
The EPIC (Erosion Productivity Impact Calculator) crop model, developed by scientists of the United States Department of Agriculture (USDA), has been successfully applied to the study of erosion, water pollution, crop growth and production in the US but is yet to be introduced for serious research purposes in other countries or regions. This paper reports on the applicability of the EPIC 8120 crop model for the assessment of the potential impacts of climate variability and climate change on crop productivity in sub‐Saharan West Africa, using Nigeria as the case study. Among the crops whose productivity has been successfully simulated with this model are five of West Africa's staple food crops: maize, millet, sorghum (guinea corn), rice and cassava. Thus, using the model, the sensitivities of maize, sorghum and millet to seasonal rainfall were demonstrated with coefficients of correlation significant at over 98 per cent confidence limits. The validation tests were based on a comparison of the observed and the model‐generated yields of rice and maize. The main problems of validation relate to the multiplicity of crop varieties with contrasting performances under similar field conditions. There are also the difficulties in representing micro‐environments in the model. Thus, some gaps appear between the observed and the simulated yields, arising from data or model deficiencies, or both. Based on the results of the sensitivity and validation tests, the EPIC crop model could be satisfactorily employed in assessing the impacts of and adaptations to climate variability and climate change. Its use for the estimation of production and the assessment of vulnerabilities need to be pursued with further field surveys and field experimentation.  相似文献   

4.
中国粮食生产的综合影响因素分析   总被引：18，自引：1，他引：17  
采用模型模拟的方式, 根据中国社会发展规划, 将未来社会经济发展情景与区域气候模型、水资源模型和作物模型相连接, 综合评估和分析未来中国的粮食生产状况, 以期为宏观决策提供科学参考。结果表明, ①气候变化将影响未来三大作物单产, 如果不考虑 CO2 肥效作用, 未来雨养作物单产将受到更大冲击; 当灌溉条件保障后, 水稻受到冲击更大, 单产降低最多, 尤其是 A2 情景。如果考虑 CO2 肥效作用, 未来玉米平均单产变化不大, 小麦单产明显增加, 尤其是雨养小麦, 水稻单产也有所增加。②未来气候变化、水资源、社会经济发展将影响中国三大作物的需水量和农业供水量, 导致水稻、灌溉玉米和小麦的播种面积下降, 而雨养小麦和玉米的播种面积上升。③未来气候变化、 CO2 肥效、水资源和土地利用变化对粮食生产的影响较为复杂, 依情景和时段的不同而不同。农业可用水资源对粮食总产的影响最不利, 致使三大作物粮食总产量明显降低, 成为未来粮食生产的主要限制因素, 尤其是水稻生产; 土地利用对总产的负面影响最小; 气候变化和 CO2 的相互作用可使总量少许增加。未来各情景下水稻受到冲击最大, 而小麦和玉米则表现为不同程度的增产。  相似文献   

5.
This paper focuses on the large‐scale land use and land cover changes that have taken place in Sarawak state, East Malaysia over the three decades of 1972‐2002. Results are presented from a detailed land use and cover change (LUCC) study in the Niah River catchment using satellite imagery, questionnaire surveys and interviews. Successive waves of land cover changes have taken place. Large forest areas have been logged and gradually replaced by oil palm plantations, which now occupy more than 40 per cent of the total land area in the catchment. Concurrently, small‐scale farming systems have also changed. Formerly dominant Iban shifting cultivation practices are increasingly being replaced by cash crop production on permanent fields and impacted by off‐farm activities involving many ethnic groups. It is argued that land cover changes are continuous and complex processes involving a large number of variables which can be analysed for different time periods at various scales.  相似文献   

6.
作物生产潜力变化具有明显的区域差异性，亟需针对不同地理单元实施有效应对措施和调控策略。选择陕西省三大地理单元（陕北高原、关中盆地和秦巴山区）为研究对象，运用全球生态区模型（GAEZ）分析了陕西省不同地理单元作物生产潜力变化趋势，探讨了不同作物生产潜力变化的区域差异，辨识出影响不同作物生产潜力变化的主要因素，结果显示：（1） 1980—2015年间，陕西省玉米生产潜力总量增加了150.55×104 t，小麦生产潜力总量则下降了402.69×104 t。（2） 关中盆地的玉米和小麦生产潜力皆最大，陕北高原次之，秦巴山区的玉米和小麦生产潜力皆最小；陕北高原和秦巴山区的玉米生产潜力皆表现出先增加后减小再增加的变化趋势，关中盆地的玉米生产潜力则先减小后增加再减小；关中盆地和秦巴山区的小麦生产潜力都呈下降趋势，陕北高原的小麦生产潜力则有所提高。（3） 土地利用变化呈现减产效应，这一效应在关中盆地尤为显著，其次为陕北高原；气候变化导致玉米生产潜力增加，使小麦生产潜力下降；气候变化对不同地理单元的影响也不相同，在陕北高原表现为增产效应，在关中盆地和秦巴山区则为减产效应。（4） 在陕北高原，气候变化的增产效应是玉米和小麦生产潜力提高的主要原因，气候变化对玉米生产潜力的影响大于对小麦的影响，耕地向草地、林地和建设用地的转化是降低作物生产潜力最主要的土地利用变化因素；在关中盆地，作物生产潜力的变化主要是受气候变化的影响，小麦受气候变化的影响较玉米为大，以建设用地占用耕地为特征的土地利用变化对玉米生产潜力的影响大于对小麦的影响；在秦巴山区，土地利用变化是玉米生产潜力变化的主要原因，而小麦生产潜力的变化主要受气候变化影响。  相似文献   

7.
Using data from a survey carried out in six tobacco growing villages across Malawi in 2004–5, this paper summarizes some main differences found in subsistence production and income levels between male‐ and female‐headed households and the disparities among female‐headed households in the light of economic liberalization policies of the past two decades. The disadvantaged position of female‐headed households in terms of land and labour endowment, together with the high cost of inputs since the structural adjustment programmes and removal of subsidies since the 1980s has prevented poorer female‐headed households not only from attaining maize self‐sufficiency, but also from engaging in high‐return agriculture such as tobacco production. Although livelihood diversification is adopted by both male‐ and female‐headed households, many female‐headed households still depend on low‐entry‐barrier activities such as agricultural waged labour and are unable to break out of the poverty cycle. However, female‐headed households are a heterogeneous category and factors such as the availability of nonfarm income opportunities, social networks to access labour and capital, land acquisition through flexible applications of patrilineal inheritance rules, and the existence of formal channels for credit and informal tobacco trading have enabled some to improve agricultural productivity and achieve high incomes.  相似文献   

8.
在农地流转市场日趋完善的背景下,农户间的耕地流转无疑会缓解因部分农户劳动力不足造成的耕地撂荒现象,但仅从农户尺度上分析难以揭示农业劳动力数量与耕地撂荒间的关系。运用重庆市武隆县17 个乡镇40个自然村的308 份农户调查数据,通过二分类Logistic 回归模型、简单相关和偏相关分析,从农户和村庄两个层次上探讨农业劳动力对耕地撂荒的影响程度及农地流转对两者关系的影响。结果显示：① 农户尺度上亩均农业劳动力对耕地是否撂荒的影响不显著,而在村庄尺度上显著。② 亩均务农劳动力与耕地撂荒规模的偏相关回归分析中,控制耕地流转和不控制流转条件下,农户尺度上两者的偏相关系数和简单相关系数分别为-0.138 和-0.027,前者在1%水平上显著,而后者不显著;村庄尺度上,控制流转和不控制流转的相关系数分别为-0.273 和-0.294,均在5%水平上显著。③ 在农地流转市场较为完善的地区,选择在村庄尺度上进行农业劳动力对耕地撂荒影响分析研究是比较合理的。  相似文献   

9.
Successful scaling of agricultural development strategies is fundamental to increased production and yields, yet targeting efforts frequently fail to fully consider the underlying biophysical drivers of agricultural marginality, particularly at fine spatial resolutions. We present a heuristic for intelligent targeting, utilizing remotely sensed information to identify the intersection between marginal conditions for performance of a staple crop and the optimal niche for technologies that improve crop performance. Here, we explore the geographic potential of maize diversification with pigeonpea, a crop with soil productivity enhancing properties. Overall, 79 percent of agricultural land in Malawi exhibits climate conditions optimal for pigeonpea cultivation and, in total, approximately 51 percent of Malawian maize-based farming is expected to receive some benefit from pigeonpea integration, with 9 percent receiving predictable and substantial benefits. These findings illustrate the geographic scaling potential of pigeonpea in Malawi and provide direction for informed pigeonpea deployment and market development across the country.  相似文献   

10.
在理解农户土地利用决策机制的基础上,利用江苏省的铜山县、如东县和常熟市329份农户问卷调查数据,采用Tobit模型以及方差分析方法探讨了影响农户土地用途变更空间决策的影响因素。研究表明:自主经营人数比重越高,农户选择改变用途地块的距离就越远,而打工导致的劳动力转移对于农户土地用途变更空间决策则没有显著影响;农户的存款越多资金越充足,农户改变用途地块的距离可能就越远;相对于铜山县,如东县和常熟市两地农户改变土地用途的地块距离相对较远;变更后地块的用途不同对于改变用途地块的选择也有影响,变更为渔业养殖用地则通常会选择离家较近的地块,而在种植业内改变用途,通常会选择离家较远的地块。  相似文献   

11.
基于生计视角的异质性农户转户退耕决策研究   总被引：1，自引：0，他引：1  
对重庆市贫困与生态脆弱区的云阳县、石柱土家族自治县376 户农户调研基础上, 将农户划为纯农户、农业主导户、非农主导户和弃农农户, 基于生计视角对农户转户退耕决策进行了解释。结果表明:①重庆市农户兼业普遍, 兼业是农户重要的生计策略;从纯农户到弃农农户, 农户生计资产依次递增, 尤其是人力资产、金融资产和社会资产。②随着兼业程度提高, 农户生计策略逐渐多元化。纯农户生计高度依赖土地;农业主导户开始选择非农兼业;非农主导户生计多样化指数最高;弃农农户生计已经转移到非农产业。③生计是影响农户转户退耕决策的关键因素:纯农户生计资产匮乏, 决策受政策导向明显;作为理性经济人, 对土地经济收益的依赖使农业主导户转户退耕意愿不明显, 对政策响应平淡;非农主导户将权衡转户退耕的补偿与损失, 政策响应模糊;弃农农户资产丰富, 对转户退耕决策响应积极。基于户籍制度改革和可持续生计视角, 本文提出了理性政府行为的3 大对策, 即:建立转户退耕的社保及补偿、激励机制;基于农户生计视角, 实施各种工程措施及惠民政策, 促进农户生计策略多元化;针对不同区位的农户实施差别化的政策。  相似文献   

12.
The aim of this study is to evaluate the groundwater quality in shallow aquifers from West Aceh, Sumatra, for irrigation uses. Groundwater samples have been collected from 32 stations for pH, electrical conductivity (EC), sodium adsorption ratio (SAR), total dissolved solids (TDS), sodium percentage (per cent Na) and residual sodium carbonate (RSC) analysis. Evaluation of water quality for irrigation using the United States Salinity Laboratory classifications suggests that the majority of the groundwater samples are good for irrigation. The crop tolerance of irrigation water salinity, as based on EC value, showed that paddy (rice), soybeans and sweet tomatoes are suitable for agricultural cultivation, but that corn and field beans are not suitable. Results indicate that, if used for agricultural irrigation, the groundwater quality ranges from excellent to good, except for a few locations (e.g. Meureubo sub‐district) which indicate signs of deterioration.  相似文献   

13.
东北黑土区是中国重要的粮食生产基地,也是中国气候变化最敏感的地区之一。然而,气候变化背景下东北黑土区气候及物候变化对农业生产力的综合影响并不清晰,未来农业生产风险评估的定量化程度不够,风险等级制定缺乏依据。本文借助遥感产品、气候资料和模拟数据等资料,综合运用多元线性回归、相关分析及干旱危险性指数等方法,探究东北黑土区作物物候动态及其气候响应特征,辨识气候与物候变化对农业生产的复合效应及未来可能风险。结果表明：① 2000—2017年东北黑土区29.76%的区域作物生长季开始期呈显著延后趋势,16.71%的区域作物生长季结束期呈提前态势,生长季开始期受气温的影响范围广,且滞后时间长;生长季结束期与前期气候变化关系更加密切,且带状差异性响应格局尤其明显。② 气候变化和物候期改变对作物生产的解释能力较生长季同期气候变化的解释能力增加了70.23%,解释面积扩大了85.04%。③ RCP8.5情景下东北黑土区粮食总产量呈现上升趋势,粮食生产风险表现出“南增北减”的演变特征,风险区面积不断扩大,全球温升2.0 ℃时,松嫩黑土亚区南部粮食减产量可能达到10%。研究有助于深入认识气候—物候—作物生产的关联机理及未来粮食生产风险,对制定气候变化应对策略,保障国家粮食安全具有重要意义。  相似文献   

14.
In‐field conservation of locally domesticated crop varieties ameliorates agrobiodiversity losses, but the interaction among nationally regulated socioeconomic factors at the local scale tends to discourage this. Analyses of household surveys conducted in Ecuador demonstrate that state and nongovernmental institutions interact to discourage cultivation of locally domesticated varieties of beans (Phaseolus spp.). Land privatization, agricultural extension, and credit programs favor market production of introduced modern bean varieties, and locally domesticated varieties are noted for favorable nutrition, culinary, and agroecological qualities. Resolving disconnections between the market and social values for landrace beans may provide agrobiodiversity conservation opportunities.  相似文献   

15.
This paper provides a detailed analysis of agricultural land use change in Bangladesh over a 59‐year period (1948–2006) and examines how these have impacted crop diversity, productivity, food availability and the environment. The key findings of the analysis are: first, land use intensity has increased significantly over this period, mainly from the widespread adoption of a rice‐based Green Revolution technology package beginning in the early 1960s; second, contrary to expectation, crop diversity too has increased; third, although land productivity has increased significantly, declines in the productivity of fertilizers and pesticides raise doubts over sustaining agricultural growth; fourth, food availability has improved, with a reversal in the dietary energy imbalance in recent years despite a high population growth rate; and finally, the production environment has suffered with widespread soil nutrient depletion experienced in many agroecological regions. The policy implication points towards crop diversification as a desired strategy for agricultural growth to improve resource economy, productivity and efficiency in farming in Bangladesh.  相似文献   

16.
During the past 50 years forests have recolonized extensive areas of Puerto Rico. Between 1950 and 1990 forest cover increased from 9% to 37% of the island's land area. In proportional terms more land has reverted to forest in Puerto Rico than anywhere else on earth during the second half of the twentieth century. This paper explores the geography of this process by matching changes in land cover with the characteristics of the land and communities in Puerto Rico. The reversion of agricultural lands to forest occurred most frequently in humid, upland, coffee‐growing regions characterized by heavy out‐migration and populations of smallholders who earned some of their income from off‐farm sources. These findings suggest that changes in non‐farm labor markets, as well as changes in the political economy of agriculture, have important impacts on the prospects for converting agricultural lands into forests.  相似文献   

17.
Mexico has a heterogeneous climate due to its geographical location. Half of the Mexican territory is dryland, mostly in the centre and north of the country, within which agriculture is the main activity in the primary production sector. At present, climate variability has a strong impact on Mexican agriculture. This study analysed rainfall variability, its impact on the agricultural productivity in terms of harvested quantity and productivity of 1996‐2014, and in parallel, the role that socioeconomic development plays on the well‐being of the population who live in areas with rainfed agriculture and a semi‐dry climate. The data obtained were analysed with the Statistical Analysis System. A positive correlation was found between rainfall and productivity (r = 0.76 for maize; r = 0.711 for beans). Rainfall variations therefore have a great impact on agricultural productivity, on food security and on the economy. Besides production losses, a parallel consequence is marginalization of the population because producers' income is increasingly reduced due to smaller crop volumes.  相似文献   

18.
1IntroductionTheconventionalassessmentSonthepossibleimPactsofclilnateAngehaveahrpothesisofkeepingclimaticvariabilityinaccordtviththatofpresentclimateduetolackofavailableinformationchangesinclimaticvariabiiltyFixedtemperaturechangeandfixedprecipitationadjustingfactorsassumedorderivedffomGCMs'shoulahonareaddedtotheobserveddailytemperatUrormulhpliedwithhiStoricaldailypreeipitahonrespechvelyinthesestUdiest11.Alti1oughthereareanUInerofapparentdeficienciesinGCMs,includinglowertemporalandspatia…  相似文献   

19.
The paper measures the level of crop diversity and identifies factors influencing diversification using a panel data of 17 regions of Bangladesh covering a 19 year period (1990–2008). Results revealed the trends that agricultural areas allocated to high‐yielding variety rice, spices and vegetables has increased, while areas cultivating traditional rice, minor cereals, oilseeds, pulses, jute and sugarcane has declined at variable rates across regions with significant differences. The level of crop diversity is also significantly different across regions and has decreased in 2008 from its 1990 level in most regions except Faridpur, Khulna and Sylhet. Among the determinants, an increase in the relative prices of vegetables and urea fertilizer, extension expenditure, labour stock per farm, average farm size, irrigation and a reduction in livestock per farm significantly increase crop diversity. Price policies to improve vegetable prices and investment in irrigation infrastructure and extension services are suggested to promote crop diversity in Bangladesh.  相似文献   

20.
西藏高原农户的投资行为——以达孜县为例   总被引：7，自引：0，他引：7  
王慎强  刘伟 《山地学报》2001,19(3):243-247
根据农户调查资料和有关的统计数据对西藏达孜县农户的投资行为进行了研究。结果表明：该县农户的投资主要以直接投资为主，间接投资所占的比重较低；在直接投资中，又以家庭经营投资和固定资产投资为主；农户对科技教育、文化娱乐方面的投资较少，而对宗教信仰方面的投资相对较多；其投资资金来源主要是自有资金。其次是银行贷款和其他资金，国家财政拨款所占的比重不大；受投资结构等因素的影响，该县农户的投资效益基本上呈农年降低趋势。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号