气候变暖有益于中国的社会和谐

中国传统农业的产量受气候控制,气候表现为冷暖和干湿交替的循环,因此农业产量也出现循环演变的规律,在冷期中生活资源的短缺所造成的生存压力,加剧了矛盾,促进了战争。而气候变暖可以缓解这些矛盾,因此,气候变暖有益于中国的社会和谐。     

Eddy covariance‐based evapotranspiration for a subtropical wetland

The eddy covariance (EC) method was used in a 30‐month study to quantify evapotranspiration (ET) and vegetation coefficient (K_CW) for a wetland on a ranch in subtropical south Florida. To evaluate the errors in ET estimates, the EC‐based ET (ET_C‐EC) and the Food and Agricultural Organization (FAO) Penman–Monteith (PM) based ET (ET_C‐PM) estimates (with literature crop coefficient, K_C) were compared with each other. The ET_C‐EC and FAO‐PM reference ET were used to develop K_CW. Regression models were developed to estimate K_CW using climatic and hydrologic variables. Annual and daily ET_C‐EC values were 1152 and 3.27 mm, respectively. The FAO‐PM model underestimated ET by 25% with ET_C‐EC being statistically higher than ET_C‐PM. The K_CW varied from 0.79 (December) to 1.06 (November). The mean K_CW for the dry (November–April) season (0.95) was much higher than values reported for wetlands in literature; whereas for the wet (May–October) season, K_CW (0.97) was closer to literature values. Higher than expected K_CW values during the dry season were due to higher temperature, lower humidity and perennial wetland vegetation. Regression analyses showed that factors affecting the K_CW were different during the dry (soil moisture, temperature and relative humidity) and wet (net radiation, inundation and wind speed) seasons. Separate regression models for the dry and wet seasons were developed. Evapotranspiration and K_CW from this study, one of the first for the agricultural wetlands in subtropical environment, will help improve the ET estimates for similar wetlands. Copyright © 2013 John Wiley & Sons, Ltd.     

REGIONALIZATION FOR LARGE AREA CROP ESTIMATES BY REMOTE SENSING——A Case Study of Chinese Wheat

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黑龙江省粮食产量结构与影响产量的气象因子分析

通过黑龙江省1949～2006年粮食产量结构分析及近30年的粮食单产与5～9月气象要素相关分析,得出黑龙江省粮食总产的波动主要取决于粮食作物平均单产波动及作物种植结构的调整.1949年以来,在粮食作物中,玉米和大豆所占比例变化不大,水稻呈逐年增加的趋势,春小麦在20世纪90年代以前呈逐步增加的趋势,而90年代以后则急速下降;水稻的单产最高,其次是玉米,再次是春小麦,大豆单产最低;从单产的增减趋势来看,各种粮食作物单产基本呈逐步增长的趋势.影响黑龙江省粮食产量丰歉的主要气象因子为6月平均温度、9月降水量、5月和6月日照时数.     

垄行结构玉米冠层方向亮温模型研究

基于热红外成像仪获取的玉米冠层图像，对垄行结构玉米的方向亮温（DBT）进行模型化描述并开展了初步验证工作。模型中假设某一方向上的冠层DBT是组分亮温及各组分在视场中所占面积权重的函数，它们在视场中的比例依赖太阳与传感器的几何位置关系，以及在作物行内，作物行与行之间孔隙的分布。对于玉米冠层的几何特征，简化为横截面是矩形的、其中有空隙透光的一组无限长的平行立方体；立方体内双向孔隙率的方向变化由Kuusk函数来描述。模型模拟表明，玉米亮温组分在视场中的权重具有垄行特性。中午前后，通过对中等密度的冠层DBT模拟，在DBT极坐标图形上发现了一个明显位于垄行方向的热条带的出现，热点出现在太阳位置的周围。最后，利用实地观测的结果与模型模拟结果作对比，对该模型的不足和以后的改进作了初步分析。     

An evaluation of the universal soil loss equation and field techniques for assessing soil erosion on a tropical alfisol in western Nigeria

Four techniques for soil erosion assessment were compared over two consecutive seasons for bare-fallow plots and a maize-cowpea sequence in 1985 at IITA, Ibadan, Nigeria. The techniques used were: tracer (aluminium paint), nails (16 and 25), the rill method, and the Universal Soil Loss Equation (USLE). Soil loss estimated by these techniques was compared with that determined using the runoff plot technique. There was significantly more soil loss (P < 0·01) in bare-fallow than in plots under maize (Zea mays) or cowpea (Vigna unguiculata). In the first season, soil loss from plots sown to maize was 40·2 Mg ha^?1 compared with 153·3 Mg ha^?1 from bare-fallow plots. In the second season, bare-fallow plots lost 87·5 Mg ha^?1 against 39·4 Mg ha^?1 lost from plots growing cowpea. The techniques used for assessing erosion had no influence on the magnitude of soil erosion and did not interfere with the processes of erosion. There was no significant difference (P < 0·05) between soil erosion determined by the nails and the runoff plot technique. Soil loss determined on six plots (three under maize, three bare-fallow) by the rill technique, at the end of the season, was significantly lower (P < 0·05) than that determined by the runoff plot technique. The soil loss estimated by the rill method was 143·2, 108·8 and 121·9 Mg ha^?1 for 11, 11, and 8 per cent slopes respectively, in comparison with 201·5, 162·0, and 166·4 Mg ha^?1 measured by the runoff plot method. Soil loss measured on three bare-fallow plots on 10 different dates by the rill technique was also significantly lower (P < 0·01) than that measured by the runoff plot. In the first season the USLE significantly underestimated soil loss. On 11, 11, and 8 per cent slopes, respectively, soil loss determined by the USLE was 77, 92, and 63 per cent of that measured by the runoff plot. However, in the second season there was no significant difference between soil loss determined by the USLE and that determined by the conventional runoff plot technique.     

2002年江苏主要农业气象灾害及其影响

2002年江苏省日照略少，降水量分布不均，淮河以南地区多持续阴雨，对夏熟作物危害重；淮北北部地区夏秋连旱使稻麦种植面积减少；全省台风、暴雨少。夏熟作物生长不断遭遇气象灾害，属减产气候年景。水稻全生育期间气象条件利大于弊，获得丰收。棉花生育期气象条件有利有弊，属于一般气候年型。     

利用无人机遥感监测农作物种植面积

南方平原耕地具有地块破碎、农作物种植品种多且空间分布混杂程度高等特点,运用传统的遥感技术方法精确监测农作物面积较为困难。无人机航拍具有拍摄时间灵活、空间分辨率高、成本低等优势,为解决这一难题提供了有利途径。本文通过地面样地调查,获取杭州市余杭区瓶窑镇农作物样地的位置及种植品种数据,利用面向对象的多尺度分割方法与随机森林的分类方法对无人机航拍数据进行分割、分类,深入挖掘高分辨率遥感数据信息,用于提取农作物种植品种及其空间分布信息,实现高精度的农作物种植面积遥感监测,推进无人机遥感在农业中的深入应用,提高农业遥感应用效益。     

A simple assessment approach for winter wheat loss risk impacted by water stress

In this study, an empirical assessment approach for the risk of crop loss due to water stress was developed and used to evaluate the risk of winter wheat loss in China, the United States, Germany, France and the United Kingdom. We combined statistical and remote sensing data on crop yields with climate data and cropland distribution to model the effect of water stress from 1982 to 2011. The average value of winter wheat loss due to water stress for the three European countries was about ?931 kg/ha, which was higher than that in China (?570 kg/ha) and the United States (?367 kg/ha). Our study has important implications for the operational assessment of crop loss risk at a country or regional scale. Future studies should focus on using higher spatial resolution remote sensing data, combining actual evapotranspiration to estimate water stress, improving the method for downscaling of statistical crop yield data and establishing more sophisticated zoning methods.     

灌溉区与雨养区作物长势差异比较分析——以美国内布拉斯加为例

以美国内布拉斯加为例,按照耕地灌溉比例0%—30%,30%—60%,60%—100%将农业区分为雨养农业区、混合农业区与灌溉农业区,同时筛选丰水年(2008年)、平水年(2005年)、枯水年(2012年),比较相同年份雨养农业区、混合农业区与灌溉农业区的作物长势的峰值特征差异,以及相同农业区在丰水年、平水年、枯水年的长势过程线的相似性,并定量分析作物长势随灌溉百分比的变化规律与趋势。研究表明:(1)相同年份,灌溉农业区作物长势好于混合农业区,混合农业区的作物长势好于雨养农业区,耕地灌溉比例越高,作物长势越好;(2)不同年份的灌溉农业区作物长势差异最小,混合农业区次之,雨养农业区长势差异最大,即耕地灌溉比例越高,作物长势越稳定;(3)枯水年雨养农业区的作物长势过程线与降水过程线同增同减,受灌溉与降水的双重影响,灌溉农业区的作物长势过程线的峰值滞后于降水峰值;丰水年,作物水分胁迫减弱,灌溉农业区、混合农业区与雨养农业区作物长势过程线与降水过程线变化趋势基本一致;(4)作物长势增幅与灌溉百分比之间呈现显著的分段二次函数变化关系,当灌溉百分比增幅小于60%时,作物长势增长幅度逐步加快,当灌溉百分比大于60%时,作物长势增速逐步放缓,在枯水年时,长势随灌溉百分比增加而增长的幅度高于丰水年与枯水年。鉴于不同农业区作物长势差异,作物长势的定量监测需要进一步区分灌溉与雨养农业。