Influence of leaf water potential on diurnal changes in CO2 and water vapour fluxes

Mass and energy fluxes between the atmosphere and vegetation are driven by meteorological variables, and controlled by plant water status, which may change more markedly diurnally than soil water. We tested the hypothesis that integration of dynamic changes in leaf water potential may improve the simulation of CO₂ and water fluxes over a wheat canopy. Simulation of leaf water potential was integrated into a comprehensive model (the ChinaAgrosys) of heat, water and CO₂ fluxes and crop growth. Photosynthesis from individual leaves was integrated to the canopy by taking into consideration the attenuation of radiation when penetrating the canopy. Transpiration was calculated with the Shuttleworth-Wallace model in which canopy resistance was taken as a link between energy balance and physiological regulation. A revised version of the Ball-Woodrow-Berry stomatal model was applied to produce a new canopy resistance model, which was validated against measured CO₂ and water vapour fluxes over winter wheat fields in Yucheng (36°57′ N, 116°36′ E, 28 m above sea level) in the North China Plain during 1997, 2001 and 2004. Leaf water potential played an important role in causing stomatal conductance to fall at midday, which caused diurnal changes in photosynthesis and transpiration. Changes in soil water potential were less important. Inclusion of the dynamics of leaf water potential can improve the precision of the simulation of CO₂ and water vapour fluxes, especially in the afternoon under water stress conditions.     

小麦出苗至抽穗期土壤湿度预报及喷灌量计算

以黑龙江省８５０农场的资料进行分析,５至６月份小麦出苗、拔节至抽穗阶段,经常出现干旱,是需水关键期,对产量影响极大。所以利用麦田土壤湿度资料,建立经验公式,对土壤墒情进行预测预报,从而获得最佳喷灌时间及喷灌量,为节约用水、计划用水提供了可靠依据。     

广武新灌区春小麦土壤水分变化规律研究

通过对广武新灌区春小麦土壤水分的垂直变化、季节变化和时空变化的研究,将广武新灌区０～１００ｃｍ土层划分为活跃层、贮水层、阻隔层和无效水分层,为寻找新灌区节水途径奠定了基础。     

基于高分六号WFV数据的冬小麦种植面积提取

冬小麦是我国重要的粮食作物之一,准确获取冬小麦种植面积具有重要的现实意义。为探究高分六号卫星影像进行冬小麦遥感监测的可行性和精确性,本文选取甘肃省崆峒区为研究区,运用红边波段+监督分类中的支持向量机法,提取了2019年崆峒区冬小麦种植面积,并利用混淆矩阵对分类结果进行精度验证。结果表明:提取崆峒区冬小麦种植面积为15045 hm 2,与实际种植面积相比,误差率为1.02%;该模型能有效地提取崆峒区冬小麦,总体精度为98.88%,Kappa系数为0.97;红边波段能有效地提取干扰地物,提取精度比直接使用监督分类高7.88个百分点;GF6影像在提取冬小麦种植面积上具有明显优势。     

利用不同方法反演冬小麦叶面积指数研究

基于高光谱数据的叶面积指数监测是快速获取冬小麦叶面积指数的重要方法。为了探究回归方法和高光谱数据变换对冬小麦叶面积指数反演精度的影响,采用逐步回归和偏最小二乘回归方法,分别建立基于冬小麦拔节期冠层高光谱数据、一阶导数光谱数据、二阶导数光谱数据和对数光谱数据的叶面积指数多元线性回归模型。结果显示,导数和对数变换能够提高冬小麦LAI反演精度,以蓝紫光、绿光、红光和近红外波段建立的一阶导数光谱数据逐步回归模型最优,建立回归模型的决定系数R2为0.974,交叉验证的RMSE为0.131,可为冬小麦LAI估算的方法选择和数据处理提供依据和参考。     

安徽省冬小麦水分盈亏特征及其对产量的影响

利用安徽省1971—2010年的气象资料和冬小麦产量资料,采用水分盈亏指数分析了安徽省冬小麦全生育期和关键期（孕穗至乳熟期）水分盈亏的时空变化特征,以及旱涝对产量的影响。结果表明：冬小麦全生育期和关键期水分盈亏指数基本呈纬向分布,合肥以北水分亏缺明显,江淮南部及其以南地区水分供应基本充足,越往南水分盈余程度越大,总体来看缺水程度关键期大于全生育期;近40年冬小麦水分盈亏指数的时间变化趋势不明显,但年际波动大,旱涝灾害风险增加。干旱主要发生在沿淮淮北地区,涝渍在江淮及其以南地区发生频率较高,典型旱涝年平均减产率分别为4.2%和12.4%;造成冬小麦减产10%的中度旱灾风险北部大于南部,中度涝灾风险南部大于北部。南部涝渍风险和造成的产量损失明显大于北部的干旱,水分偏多的南部地区要尽量减少冬小麦的种植。     

微塑料添加对小麦苗期生长及干物质分配的影响

土壤环境中微塑料污染已成为全球关注的环境问题。关于微塑料对于植物生长的直接影响和由于土壤理化性状改变的间接影响研究已逐步开展,但针对小麦的研究鲜见报道。试验选择两个旱地小麦品种(甘春27和禾尚头)作为研究对象,选取高密度聚乙烯作为微塑料添加,设置3种质量浓度(0、1、4 g·kg^-1)开展盆栽试验,对不同微塑料组合处理下小麦的出苗率、株高、全株生物量和地上/地下干物质分配进行了分析。结果表明：(1)微塑料添加对两个品种出苗率没有影响。(2)禾尚头在添加1 g·kg^-1微塑料时比添加0、4 g·kg^-1时全株生物量分别高46.7%、8.5%,甘春27在添加1 g·kg^-1微塑料时比添加0、4 g·kg^-1时全株生物量分别高28.7%、17.2%;甘春27整体比禾尚头在3种浓度处理下全株生物量分别高24.9%、9.6%、1.5%。(3)不同试验处理条件下,甘春27将更多的干物质分配在地上植株的构建,其在地下(根系)和地上(茎叶)部分的分配比例整体小于禾尚头。整体上,适度微塑料添加可...     

基于面向对象的山东省冬小麦种植面积监测

利用遥感技术,使用eCognition软件的面向对象分类技术,对RAPIDEYE卫星影像进行分类识别,从而快速、准确的监测小麦种植面积,为冬小麦财政补贴提供数据和技术支持。以兖州市为例,行政区面积6.501 9万hm2,小麦监测面积3.1715万hm2,小麦面积监测精度达到了90.5%。     

1990年以来中国小麦农业气象灾害时空变化特征(英文)

Agro-meteorological disasters(AMD) have become more frequent with climate warming. In this study, the temporal and spatial changes in the occurrence frequency of major meteorological disasters on wheat production were firstly explored by analyzing the observed records at national agro-meteorological stations(AMS) of China from 1991 to 2009. Furthermore, impact of climate change on AMD was discussed by comparing the warmer decade(2000–2009) with another decade(1991–2000). It was found that drought was the most frequent disaster during the last two decades, with a highest proportion of 79%. And the frequency of AMD increased significantly with climate change. Specifically, the main disasters occurred more frequently in the reproductive period than in the vegetative period. Besides, the spatial changes in the AMD frequency were characterized by region-specific. For example, the wheat cultivation areas located on the Loess Plateau and the middle-lower reaches of the Yellow River suffered mainly from drought. All these results were strongly linked to climate change in China. Therefore, sound adaptation options should be taken based on the latest changes of AMD under global warming to reduce agricultural damages.     

Impact of the shrinking winter wheat sown area on agricultural water consumption in the Hebei Plain简

This study firstly analyzed the shrinkage of winter wheat and the changes of crop- ping systems in the Hebei Plain from 1998 to 2010 based on the agricultural statistic data of 11 cities and meteorological data, including daily temperature, precipitation, water vapor, wind speed and minimum relative humidity data from 22 meteorological stations, and then calcu- lated the water deficit and irrigation water resources required by different cropping systems, as well as the irrigation water resources conserved as a result of cropping system changes, using crop coefficient method and every ten-day effective precipitation estimation method. The results are as follows. 1） The sown areas of winter wheat in the 11 cities in the Hebei Plain all shrunk during the study period. The shrinkage rate was 16.07% and the total shrinkage area amounted to 49.62×10^4 ha. The shrinkage was most serious in the Bei- jing-Tianjin-Tangshan metropolitan agglomerate, with a shrinkage rate of 47.23%. 2） The precipitation fill rate of winter wheat was only 20%-30%, while those of spring maize and summer maize both exceeded 50%. The irrigation water resources demanded by the winter wheat-summer maize double cropping system ranged from 400 mm to 530 mm, while those demanded by the spring maize single cropping system ranged only from 160 mm to 210 ram. 3） The water resources conserved as a result of the winter wheat sown area shrinkage during the study period were about 15.96×10^8 m^3/a, accounting for 27.85% of those provided for Beijing, Tianjin and Hebei by the first phase of the Mid-Route of the South-to-North Water Diversion Project.