近30年东北春玉米发育期对气候变化的响应   总被引：12，自引：4，他引：8       下载免费PDF全文

穆佳  赵俊芳  郭建平 《应用气象学报》2014,25(6):680-689

基于1981—2010年东北地区55个农业气象观测站发育期数据、16个气象站逐日气象资料,采用趋势变率、秩相关分析、主成分分析和结构方程模型等方法,分析了近30年东北春玉米关键发育期的变化特征,探讨了春玉米发育期对不同时间尺度气象因子的响应规律。结果表明:1981—2010年春玉米关键发育期 (播种期、抽雄期、成熟期) 均有延后趋势,大部分地区春玉米生长前期 (播种期—抽雄期) 日数减少,生长后期 (抽雄期—成熟期) 日数增加,全生育期日数增加。在绝大多数年份,春玉米播种期在温度适播期之后,成熟期在初霜日之前。近30年对东北春玉米生育期日数影响最大的气象要素为温度,主成分分析结果显示,年际尺度的升温、温度生长期的延长和作物生长期的高温对生育期日数影响显著;结构方程模型指出,作物生长期的最高温度和最低温度对生育期日数影响有间接效应,主导气象要素能够解释生育期日数变异的44%。全球变暖背景下,东北春玉米发育期变化是作物响应气候变化和农业生产适应气候变化的共同结果。  相似文献   

Situating corporate framings of child labor: Toward grounded geographies of working children in globalized agriculture     

《Geoforum》2015

The expansion of multinational corporations into agricultural production around the world is resulting in new forms of engagement in specific places. In the context of neoliberal restructuring, these engagements are tied to shifting landscapes of societal, governmental and industry-based perceptions on the role of corporations in labor regimes. But how are these engagements developed and how do they connect to the everyday lives of workers? In India, when Monsanto expanded into hybrid cotton seed production in the early 2000s, the corporation came under pressure to address concerns over the widespread employment of children and young workers for seed pollination. In response, the corporation developed an approach to child labor that, I argue, works to reinforce generalized and problematic notions of childhood and work. Corporate engagements in global agriculture need to be situated in time and space, and alongside the experiences of workers. Children experience attempts to shape their patterns of work and mobility as a series of surmountable obstacles, disconnected from the process of deciding whether or not they will engage in this work. Drawing on qualitative fieldwork in Gujarat and Rajasthan, and documentary analysis of public documents, I outline the development of a corporate response to child labor and place it within the context of the rise of corporate social responsibility, global ideas of child labor, and in the specific case of cotton seed production in western India. I demonstrate that contextualized geographies of working children in globalized agriculture reveal the nature of multinational corporations’ engagements in specific places.  相似文献   

基于主成分分析的植被指数与叶面积指数相关性研究   总被引：1，自引：0，他引：1  

翟羽娟  张艳红  刘兆礼  刘宝江 《测绘与空间地理信息》2015,(9):20-23

综合分析了玉米叶面积指数与几种常见光谱植被指数相关性,确定主成分分析方法在反演叶面积指数中的作用。首先,借助MATLAB编程软件,以植被指数与玉米叶面积指数相关性最高为原则,选出遥感影像上各种植被指数,其波段组合为NDVI(752.4/701.5),RVI(752.4/701.5),MSR(752.4/701.5),SAVI(823.7/701.5),MSAVI(823.7/701.5),然后,对这5种植被指数进行主成分分析,建立LAI-VI多元逐步回归模型,并对模型精度进行验证,总体估测精度为96.237%。经实验验证,利用主成分分析方法在反演植被叶面积指数时能够起到较好的效果,具有广泛的应用前景。  相似文献   

石灰土中秸秆还田降解率及其对土壤肥力的影响   总被引：1，自引：0，他引：1  

黄芬  韦红群  曹建华 《资源与生态学报(英文版)》2015,(4)

石灰土具有高的有机碳的积累,但营养成分的供给速率偏低,导致土壤贫瘠。本文通过室内模拟实验,研究相同来源玉米秸秆在岩溶土与非岩溶土中的降解情况,对秸秆降解率、土壤理化性质、土壤肥力等进行动态检测,结果表明：（1）总体上岩溶土秸秆降解速率比非岩溶土快。秸秆降解速度最快主要集中在最初60天,之后呈缓慢上升趋势,到98天基本达到平衡。非岩溶土降解峰值出现时间为第42天,岩溶土为第28天,峰值出现时间前者比后者滞后14天。总降解时间持续160天,岩溶土降解率为77%,非岩溶土为75%。（2）秸秆降解期间,土壤pH值前期有下降的趋势,后期慢慢回升,这与秸秆降解过程中不同时期降解产物变化规律相吻合。秸秆还田可以提高土壤肥力,其中速效氮和速效钾含量增加非常明显。（3）与岩溶土相比,全量检测结果显示各肥力指标在非岩溶土含量低,但升幅百分比高;有效态检测结果显示非岩溶土速效磷和速效钾含量高。说明秸秆还田一些营养元素有效态在非岩溶土中更易于释放,而岩溶土由于其土壤质地的特殊性,许多养分被土壤粘土矿物牢固结合,营养元素供给速率慢,但因此也易于养分全量的累积。  相似文献   

Does smallholder maize intensification reduce deforestation? Evidence from Zambia     

《Global Environmental Change》2020

Increasing food production to meet growing demand while reducing tropical deforestation is a critical sustainability challenge. This is especially true in sub-Saharan Africa, which faces serious food insecurity issues and where smallholder farming is the main driver of forest conversion. Competing theories imply opposite predictions as to whether deforestation increases or decreases with smallholder agricultural intensification, which can improve food security by increasing crop yields per area cultivated. This research provides new empirical evidence on the association between deforestation and smallholders’ use of modern inputs, in particular inorganic fertilizer on maize and improved maize seeds, using Zambia as a case study. We analyze this association nationwide in a spatially disaggregated manner at the lowest administrative level using machine learning-based small area estimation, which makes use of detailed nationally representative surveys on smallholder farm households for 2011 and 2014, and census data to statistically predict modern inputs use country-wide for 2011, when average maize yields were 1.28 tons/ha. Then, we evaluate the association between improved maize seed and fertilizer inputs and subsequent deforestation, while controlling for key geospatial covariates. The results support the land-sparing hypothesis, finding that smallholder farmers’ use of improved maize seed is negatively associated with deforestation on non-acidic (pH ≥ 5.5) soils, an effect that is enhanced by complementary inorganic fertilizer use. Fertilizer use on its own, however, is weakly associated with increased deforestation. Sustainable intensification via use of improved seeds on adequately fertile soils and improving soil health appears compatible with reducing both deforestation and food insecurity.  相似文献   

基于DEM-CFD耦合的气吸式排种器仿真研究     

张凯  洪杨  徐祝欣 《南京气象学院学报》2020,12(6):767-772

为提高大白菜等小粒径精密播种机的机械化水平,设计了一种小粒径气吸式排种器.首先利用JPS-12排种器性能检测试验台对排种器进行测试,得到不同参数组合下的性能指标与最优参数组合.然后使用计算流体力学方法（CFD）,借助FLUENT软件分析了吸种器内部流场的分布,得到了吸种器内部压力分布云图和吸种孔截面云图.最后基于离散元法（DEM）建立大白菜种子颗粒模型,对排种器仿真模型进行简化和网格划分,完成了小粒径气吸式排种器DEM-CFD耦合仿真实验.对比台架与仿真试验结果,得出如下的结论：当排种盘转速为20 r/min,真空度为2.2 kPa时,排种性能最佳.  相似文献   

Evaluation of Agricultural Climatic Resource Utilization During Spring Maize Cultivation in Northeast China Under Climate Change     

GUO Jianping  ZHAO Junfang  YUAN Bin  YE Mingzhu 《Acta Meteorologica Sinica》2013,27(5):758-768

Agricultural climatic resources （such as light,temperature,and water） are environmental factors that affect crop productivity.Predicting the effects of climate change on agricultural climatic resource utilization can provide a theoretical basis for adapting agricultural practices and distributions of agricultural production.This study investigates these effects under the IPCC （Intergovernmental Panel on Climate Change） scenario A1B using daily data from the high-resolution RegCM3 （0.25° ×0.25°） during 1951-2100.Model outputs are adjusted using corrections derived from daily observational data taken at 101 meteorological stations in Northeast China between 1971 and 2000.Agricultural climatic suitability theory is used to assess demand for agricultural climatic resources in Northeast China during the cultivation of spring maize.Three indices,i.e.,an average resource suitability index （Isr）,an average efficacy suitability index （Ise）,and an average resource utilization index （K）,are defined to quantitatively evaluate the effects of climate change on climatic resource utilization between 1951 and 2100.These indices change significantly in both temporal and spatial dimensions in Northeast China under global warming.All three indices are projected to decrease in Liaoning Province from 1951 to 2100,with particularly sharp declines in Isr,Ise,and K after 2030,2021,and 2011,respectively.In Jilin and Heilongjiang provinces,Isr is projected to increase slightly after 2011,while Ise increases slightly and K decreases slightly after 2030.The spatial maxima of all three indices are projected to shift northeastward.Overall,warming of the climate in Northeast China is expected to negatively impact spring maize production,especially in Liaoning Province.Spring maize cultivation will likely need to shift northward and expand eastward to make efficient use of future agricultural climatic resources.  相似文献   

东北地区玉米整地、播种和收获气象适宜度评价模型   总被引：5，自引：0，他引：5  

马树庆  陈剑  韩智平  王琪 《气象》2013,39(6):782-788

天气、土壤条件影响玉米整地、播种和收获作业的质量及作业效率,进而影响到苗情、产量和生产成本,东北地区相关的农业气象要素是土壤湿度、土壤解冻深度、温度、日雨量和风力等.根据气象、土壤条件对玉米整地、播种和收获的影响,用模糊隶属函数建立了这些农事活动气象适宜度评价函数及其农业气象指标,用权重法分别建立了整地、播种和收获综合气象适宜度评价模型.检验结果表明,这些模式和指标符合实际,可以用于相关农事活动的气象适宜度评价业务.在气温和降水等气象要素预报的基础上,该模型还可以用于相关农事气象适宜度和适宜期的预报.  相似文献   

Estimation of groundwater use by crop production simulated by DSSAT‐wheat and DSSAT‐maize models in the piedmont region of the North China Plain     

Yonghui Yang  Masataka Watanabe  Xiying Zhang  Xiaohua Hao  Jiqun Zhang 《水文研究》2006,20(13):2787-2802

Sustainable water use is in serious crisis in the piedmont region of the Taihang Mountains in the North China Plain, owing to rapid groundwater drawdown. Estimating the water requirement for agriculture, the biggest user of groundwater, will be helpful in understanding groundwater decline. Through the use of DSSAT‐3·5 wheat and maize models, we assessed water use in winter wheat and maize, two staple crops in the region, in 1987–2001. Trends between groundwater change and simulated agricultural water use were compared. The results showed that groundwater decline was sensitive to simulated crop water requirement and irrigation requirement. According to regression analysis, 100 mm of water requirement by cultivated land (mainly wheat and maize) resulted in about 0·64 m of groundwater decline. This relationship might be useful in understanding the regional water balance and to help decision‐makers control groundwater decline through controlling crop water use or through long‐distance water transfer. The study demonstrated the usefulness of using the DSSAT model for estimating crop water use and the effectiveness of clarifying the reason for groundwater decline using the simulation results of water use. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Value of Climate Forecasts for Adjusting Farming Strategies in Sub-Saharan Africa     

Abigail?Amissah-ArthurEmail author 《GeoJournal》2005,62(1-2):181-189

Sustaining and increasing crop production and productivity has to be a major policy thrust for developing countries. Using a simulation approach different production strategies were evaluated conditioned on climate information to derive optimal strategies to help farmers reduce risk and increase productivity. By examining the existence of options in this case planting dates the study provides an analyses of the expected value and risks associated with changing decisions based on the availability of climate forecasts. The 15-March planting date produced the highest mean yield for the two cultivars examined although 1-April, 15-April and 1-May plantings had one to zero probability of crop failures compared to 15-March with crop failures in 4 out of 20 years. Results indicate losses of between 25 and 35 kg/day due to delays in planting from 15-March planting to 1-June planting for the 120- and 150-day cultivar. El niño years were associated with positive yield deviations for both cultivars and most planting dates. Farmers are known to make tactical adjustments to their management in light of information perceived relevant to the prospects of forthcoming crop. Although in its present form most current forecast products do not provide information on onset of the rainfall, however the information they do provide could play a crucial role in helping farmers reduce the risks posed by climatic variability.  相似文献