基于叶面积指数反演的区域冬小麦单产遥感估测

利用定量遥感技术反演的叶面积指数（LAI）在中国北方黄淮海地区典型县市进行冬小麦单产预测研究.为提高数据质量和减少估产误差,利用Savitzky-Golay滤波技术降低云对NDVI数据的影响及数据缺失;通过冬小麦实测LAI进行时序内插,模拟得到实测点每日冬小麦LAI,继而获得实测点主要生育时期平均LAI;在此基础上,建立了冬小麦主要生育时期平均LAI与作物单产关系模型,改变目前利用生育时期内某一时间点LAI代替整个生育时期LAI的方法;在模型择优基础上,得到最佳遥感估产关键期--开花期LAI与单产统计模型;最后,利用MODIS-NDVI经验模型反演得到的开花期平均LAI进行2008年冬小麦单产预测.结果表明：与地面实测的冬小麦单产相比,研究区估产平均相对误差为1.21%,RMSE达到257.33 kg·hm^-2,可以满足大范围估产的要求.利用上述方法可以在研究区冬小麦收获前20～30 d进行准确的单产估计.     

NDVI曲线与农作物长势的时序互动规律

利用气象卫星NOAA AVHRR资料,反演出农作物生育期内每日和旬度的NDVI数据,分析了NDVI时间曲线的波动与农作物生长发育阶段及农作物长势的响应规律,并以华北冬小麦为例,探讨了NDVI在冬小麦中生育期的积分值与农作物单产之间的相互关系。结果表明,利用长时间序列的NDVI数据,结合作物的物候历,可以实现作物长势的遥感监测和产量遥感估算。     

基于作物生物量估计的区域冬小麦单产预测

基于2004年中国冬小麦主产区黄淮海平原典型区内石家庄、衡水和邢台3市45个县（市）83个地面典型样区冬小麦地面实测作物单产数据、光合有效辐射、光合有效辐射分量以及相应的气象和土壤湿度数据,建立了简化的冬小麦光能转化有机物效率系数模型,基于冬小麦关键生育期（3—5月）累积作物生物量并采用地面实测的冬小麦收获指数加以校正,建立了作物生物量与作物经济产量间的定量关系,预测了2004年河北和山东平原区235个县（市）的冬小麦单产,并依据国家公布的2004年各县冬小麦统计单产验证了估产的精度.结果表明：该模型预测的2004年研究区冬小麦单产的均方根误差（RMSE）为238.5 kg·hm^-2,平均相对误差为4.28%,达到了大范围估产的精度要求,证明利用以遥感数据估算作物生物量进而预测冬小麦单产的方法是可行的.     

美国玉米和小麦产量动态预测遥感模型

粮食安全问题一直倍受世界各国关注,及时、准确地了解其他国家或地区的粮食生产状况,对于中国粮食贸易和粮食宏观调控,具有十分重要的意义.本文以美国冬小麦和玉米为研究对象,在分析各作物空间分布及生长季节的基础上,利用土地利用数据剔除非耕地信息,使提取的归一化植被指数(NDVI)客观地反映各作物的生长状况.以1998-2007年的SPOT VEGETATION旬最大值合成NDVI资料为数据源,研究了美国玉米和小麦生长季的旬NDVI与产量的关系,确定了不同月份的建模因子,分别建立了美国玉米和冬小麦不同月份的产量动态预报模型.通过对各模型估算产量与实际产量进行比较,各模型预报结果的相对误差大部分在3%以内,精度较高,说明建立的作物产量动态预报模型实用可行,能够投入产量预报业务应用.     

冬小麦单产的光谱数据估测模型研究

 本文在分析冬小麦群体经济产量与叶面积系数关系的基础上,以地面实测冬小麦反射光谱数据为依据,提出了一种新的动态VI-产量模型,即LAD-产量模型。该模型具有冬小麦生育后期(抽穗一灌浆末期)光合面积和光合时间等信息,其冬小麦单位面积产量(简称单产)估测精度为98%。另外,本文根据常用的某一特定生育期VI-产量模型,用冬小麦各生育期的VI值分别估测小麦单产,确定山东省禹城市冬小麦的灌浆中期为最佳估产时间。此时期．小麦单产估测精度为96%。     

华北农业干旱监测与冬小麦估产研究

评估了基于植被光学厚度(VOD)和日光诱导叶绿素荧光(SIF)等植被广义光学特性构建的标准化植被指数(Z_VI)监测农业干旱的适用性;并采用VOD、SIF两种指数和土壤水分等环境变量的不同组合建立冬小麦估产的岭回归模型,以探究其对冬小麦产量的预报能力。结果表明：相较于Z_VOD,旬尺度Z_SIF对华北地区的农业干旱具有更好的监测能力,对重旱的正确检测率达到77%。Z_SIF能够有效反映干旱发生、发展直至减轻的演变过程,其低值区与站点记录的干旱空间分布相吻合。在华北地区南部,生长季C波段和Ku波段的VOD对冬小麦单产的预报能力优于SIF;利用VOD、SIF两种指数和环境变量的全变量模型取得了最好的估产精度,影响冬小麦产量估算精度的关键预测变量为生长高峰期的SIF。研究可为大范围农业干旱监测和粮食安全提供技术支持。     

RS,GPS和GIS集成系统在新疆北部天然草地估产技术中的应用进展

利用１９９１～１９９６年在新疆天山北坡不同草地类型上观测的草地可食产量,环境与遥感资料等,使用ＲＳ技术、ＧＰＳ和ＧＩＳ集成系统进行了多重相关分析和遥感估产技术的深入研究,并在图象处理、信息提取、信息应用和ＲＳ－ＧＰＳ－ＧＩＳ一体化估产方法及遥感知识与草原生态专业知识结合方面获得一定研究进展。研究结果表明,４个草地类型的可食鲜干草产量与两种遥感绿度值间存在着极显著相关性（Ｐ＜０．０１）,ｒ值均在０．６７９以上,且通过Ｆ检查和精度分析。一般在类型Ⅱ、Ⅲ和Ⅳ,是鲜草产量与ＲＶＩ相关性好于ＮＤＶＩ,而在类型Ⅰ则相反。进而从６种数学方程式中选优,建立了地学、光学和非线性遥感估产模型,并在实际估产中加以应用、检验和给出了生态学解释及机理分析,使大面积草地可食牧草遥感估产精度达到７５．８％以上,实现了遥感大面积估产目标和草地生态学意义及ＲＳ－ＧＰＳ－ＧＩＳ与草地专家系统一体化集成的应用。     

江苏省冬小麦湿渍害的风险区划

选取能较好反映冬小麦春季湿渍害特征的3个气象因子:旬降雨量、旬日照时数和旬雨日,计算了江苏省1960—2008期间历年3—5月这3个因子的逐旬统计值,分析了这些因子与冬小麦气候产量的关系,研究结果表明:(1)春季旬降雨量、旬雨日和旬日照时数对江苏省冬小麦气候产量有显著影响;(2)通径分析显示,旬降雨量和旬日照对气候产量有直接影响,而旬雨日对气候产量有间接影响;(3)构建了一个湿渍害判别指数Q用来判别湿渍害发生年份,并结合江苏省各地湿渍害年发生频率和冬小麦气候减产率,建立了冬小麦湿渍害风险指数模型;(4)利用所建风险指数模型对江苏省冬小麦的湿渍害风险进行了区划和评估,并提出了各风险区的防御对策。     

用气象卫星对东亚季风区的生态过渡带的遥感监测研究

用极轨气象卫星的归一化植被指数(NDVI)对中国东亚季风区的生态过渡带(样带)进行遥感监测研究。研究结果表明,在过渡带内的各个生态区的NDVI与东亚季风进退的关系极为密切。在正常季风年NDVI有正常分布;在异常季风年,NDVI呈反常分布;把遥感过渡带内季风气候的变化简化为遥感生态区植被指数的变化。分析了在过渡带内主要生态区,即荒漠草原、干草原、草甸草原、农耕区、森林区ND-VI的变化规律,以及旬NDVI与旬降水量之间的关系。在过渡带内每年NDVI随时间变化的曲线形状可以作为每年季风气候变化特征的量度。     

基于GIS的浙江省水稻遥感估产最佳时相选择

水稻遥感估产最佳时相选择应包括水稻种植面积估算最佳时相和水稻产量预报最佳时相两部分。在水稻遥感估产最佳时相选择中,由于首次引入GIS技术提取水稻可能种植区域,缩小了研究范围,植被种类也较简单一,因此仅用农作物物候历即可确定水稻种植面积估算最佳时相,而不需要考虑所有的植被类型。利用盆栽试验和小区试验研究水稻产量与不同时期的农学参数、农学参数与植被指数及水稻产量与植被指数的关系,结果表明,水稻产量与农业参数、农学参数与光谱变量的关系均以孕穗以抽穗期最好,水稻产量与光谱变量的关系则从分蘖盛期到抽穗期的极显著。因此,以孕穗期到抽穗期作为建立水稻遥感估产模型的最佳时期。再利用1998年各地的水稻发育期观测资料,确定各区水稻产量遥感最佳时相。     

Integrating Remote Sensing and GIS for Prediction of Winter Wheat (Triticum aestivum) Protein Contents in Linfen (Shanxi), China

In this study, relationships between normalized difference vegetation index (NDVI) and plant (winter wheat) nitrogen content (PNC) and between PNC and grain protein content (GPC) were investigated using multi-temporal moderate-resolution imaging spectroradiometer (MODIS) data at the different stages of winter wheat in Linfen (Shanxi, P. R. China). The anticipating model for GPC of winter wheat was also established by the approach of NDVI at the different stages of winter wheat. The results showed that the spectrum models of PNC passed F test. The NDVI_4.14 regression effect of PNC model of irrigated winter wheat was the best, and that in dry land was NDVI_4.30. The PNC of irrigated and dry land winter wheat were significantly (P<0.01) and positively correlated to GPC. Both of protein spectral anticipating model of irrigated and dry land winter wheat passed a significance test (P<0.01). Multiple anticipating models (MAM) were established by NDVI from two periods of irrigated and dry land winter wheat and PNC to link GPC anticipating model. The coefficient of determination R² (R) of MAM was greater than that of the other two single-factor models. The relative root mean square error (R_RMSE) and relative error (RE) of MAM were lower than those of the other two single-factor models. Therefore, test effects of multiple proteins anticipating model were better than those of single-factor models. The application of multiple anticipating models for predication of protein content (PC) of irrigated and dry land winter wheat was more accurate and reliable. The regionalization analysis of GPC was performed using inverse distance weighted function of GIS, which is likely to provide the scientific basis for the reasonable winter wheat planting in Linfen city, China.     

黄土高原冬小麦田光谱特征变化及其与二氧化碳日收支的相关分析

根据光谱辐射仪对黄土高原冬小麦整个生育期光谱反射率的连续观测数据及CO₂通量观测数据,对冬小麦田光谱特征变化及其与CO₂日收支的相关性进行了分析.结果表明：冬小麦田不同波长光谱反射率和归一化植被指数（NDVI）呈现明显的日变化和季节变化.同一天内,反射率随太阳高度角的变化而变化,变化最大的波段（550 nm左右、700～1 050 nm）表现为峰.不同生育期同一时刻,可见光波段（350～670 nm）反射率变化不大,近红外波段（700～1 050 nm）出现较大差异,在出苗期、分蘖期和越冬期后红边位置向长波方向“红移”;越冬期前出现向短波方向“蓝移” 的现象;但成熟期“蓝移”现象不明显,表现为突变;其他生育时期没有观测到波谱位移.NDVI的日变化呈U型,13：00左右最低,16：00后出现较大波动,与抛物线有较好的拟合效果,小麦生长旺盛时期,对其地面遥感观测应选择在NDVI变化不大的13：00左右进行;整个冬小麦生长季11:00反射率及NDVI以播种后第140天为中心对称,NDVI的季节变化表现为M型,可用四次多项式拟合;在整个小麦生育期中NDVI与CO₂的日收支呈极显著负相关,但正午左右的相关性稍差.     

A Study on the Model for Estimation Winter Wheat Yield Using Spectral Data of Wheat Field

A new dynamic vegetation index (VI)-yield model, that is, the leaf area duration (LAD)-yield model was structured for estimating winter wheat yield according to the measured reflection spectral data on the wheat field, and the relationship between wheat yield and LAI. The model had the information on the photosynthetic area and time during the later period of wheat growth, i. e., the period from the heading stage to the end of filling stage. The accuracy of the estimated wheat yield arrived up to 98% .In addition, the winter wheat yield was also estimated by a VI-yield model in a given wheat growing stage, and the VI in several main wheat growing stages were used for this purpose. The results suggested that the best season for estimating wheat yield using the VI-yield model was in the middle of wheat filling stage for the case study in Yucheng, Shandong province. The accuracy of the estimation could arrive at 96%.     

Satellite sun‐induced chlorophyll fluorescence detects early response of winter wheat to heat stress in the Indian Indo‐Gangetic Plains

Extremely high temperatures represent one of the most severe abiotic stresses limiting crop productivity. However, understanding crop responses to heat stress is still limited considering the increases in both the frequency and severity of heat wave events under climate change. This limited understanding is partly due to the lack of studies or tools for the timely and accurate monitoring of crop responses to extreme heat over broad spatial scales. In this work, we use novel spaceborne data of sun‐induced chlorophyll fluorescence (SIF), which is a new proxy for photosynthetic activity, along with traditional vegetation indices (Normalized Difference Vegetation Index NDVI and Enhanced Vegetation Index EVI) to investigate the impacts of heat stress on winter wheat in northwestern India, one of the world's major wheat production areas. In 2010, an abrupt rise in temperature that began in March adversely affected the productivity of wheat and caused yield losses of 6% compared to previous year. The yield predicted by satellite observations of SIF decreased by approximately 13.9%, compared to the 1.2% and 0.4% changes in NDVI and EVI, respectively. During early stage of this heat wave event in early March 2010, the SIF observations showed a significant reduction and earlier response, while NDVI and EVI showed no changes and could not capture the heat stress until late March. The spatial patterns of SIF anomalies closely tracked the temporal evolution of the heat stress over the study area. Furthermore, our results show that SIF can provide large‐scale, physiology‐related wheat stress response as indicated by the larger reduction in fluorescence yield (SIF_yield) than fraction of photosynthetically active radiation during the grain‐filling phase, which may have eventually led to the reduction in wheat yield in 2010. This study implies that satellite observations of SIF have great potential to detect heat stress conditions in wheat in a timely manner and assess their impacts on wheat yields at large scales.     

安徽省冬小麦施肥现状与肥料利用效率

冬小麦是安徽省重要的粮食作物。合理施肥是冬小麦获得高产的重要措施,明确当前安徽省冬小麦施肥现状和存在的问题对于指导冬小麦科学施肥具有重要意义。本研究以安徽省冬小麦为对象,于2018年对全省冬小麦主产区1591户农户进行调查,调查内容包括肥料品种、肥料用量、施肥方式、种植面积和产量水平。根据调查结果统计分析安徽省冬小麦种植过程中的施肥现状及存在问题,并以全省冬小麦平均产量和平均施肥量为基准,采用Cate-Nelson方法(十字交叉法)评估安徽省冬小麦产量与氮、磷和钾肥施用的关系,以探索安徽省冬小麦进一步增产增效的主要施肥途径。结果表明: 安徽省冬小麦平均产量为5185 kg·hm^-2,氮、磷和钾肥平均施用量分别为206、80和78 kg·hm^-2。其中旱茬麦氮、磷和钾肥平均施用水平比稻茬麦分别高14、16和3 kg·hm^-2。总体上,安徽省冬小麦种植中化肥平均用量趋于合理化,但是在施肥方式、养分运筹和肥料品种上还存在不合理现象。Cate-Nelson方法结果表明,全省冬小麦氮、磷、钾肥施用量中,仅有23.8%、21.2%和25.7%低于全省平均水平却获得较高的产量,此时氮、磷、钾肥偏生产力最高;有26.3%、19.3%和22.5%的施用量低于全省平均水平但没有实现高产;有26.2%、29.6%和25.0%的施用量虽然获得了高产,但施用量较高,氮磷钾肥偏生产力较低。这说明安徽省冬小麦增产增效还有很大的空间。全省冬小麦基肥和追肥机械化比例分别为62.7%和10.0%。虽然氮肥普遍实现了分次施用,但氮肥作基肥的比例仍然占到全生育期氮肥总量的69.0%,应适当降低。此外,在肥料品种选择上存在偏施化肥、不重视有机肥等问题。     

Stay-green in spring wheat can be determined by spectral reflectance measurements (normalized difference vegetation index) independently from phenology

The green area displayed by a crop is a good indicator of its photosynthetic capacity, while chlorophyll retention or 'stay-green' is regarded as a key indicator of stress adaptation. Remote-sensing methods were tested to estimate these parameters in diverse wheat genotypes under different growing conditions. Two wheat populations (a diverse set of 294 advanced lines and a recombinant inbred line population of 169 sister lines derived from the cross between Seri and Babax) were grown in Mexico under three environments: drought, heat, and heat combined with drought. In the two populations studied here, a moderate heritable expression of stay-green was found-when the normalized difference vegetation index (NDVI) at physiological maturity was estimated using the regression of NDVI over time from the mid-stages of grain-filling to physiological maturity-and for the rate of senescence during the same period. Under heat and heat combined with drought environments, stay-green calculated as NDVI at physiological maturity and the rate of senescence, showed positive and negative correlations with yield, respectively. Moreover, stay-green calculated as an estimation of NDVI at physiological maturity and the rate of senescence regressed on degree days give an independent measurement of stay-green without the confounding effect of phenology. On average, in both populations under heat and heat combined with drought environments CTgf and stay-green variables accounted for around 30% of yield variability in multiple regression analysis. It is concluded that stay-green traits may provide cumulative effects, together with other traits, to improve adaptation under stress further.     

基于比较优势分析法的冬小麦产量差异

在农户调查基础上,采用比较优势分析法对曲周县2003—2004年度冬小麦产量差异进行分析.调查数据表明,地块间小麦产量差异较大,产量范围为在4.2～7.9 t·hm-²,变异系数为0.14.通过逐步回归建立的由土壤盐碱度、土壤肥力、是否咸水灌溉、品种选择、返青期追施氮肥类型、播种时间、病虫害防治和返青期是否水分胁迫8个因子构成的产量差模型可以解释63%的产量差异.其中土壤盐碱度、土壤肥力和是否咸水灌溉是冬小麦的主要产量限制因子,其引起的产量差为727 kg·hm^-2,占总模拟产量差的52%.小麦品种引起的产量差为202.1 kg·hm^-2,占总模拟产量差的14%.播种时间、返青期追施氮肥类型、病虫害防治和返青期是否水分胁迫4个因子引起的产量差分别占总模拟产量差的7%、14%、10%和3%.因此,除土壤和气候状况外,管理措施也是造成产量差异的重要因素,通过优化管理措施可以大大减小产量差异.     

基于实际蒸散构建的干旱指数在黄淮海地区的适用性

基于NOAH陆面模式模拟的实际蒸散产品,分析了2002—2010年黄淮海地区实际蒸散的时空分布特征.同时,结合MOD17潜在蒸散数据和MOD13 NDVI构建了2002—2010年的农业干旱指数——干旱敏感性指数(DSI),并以2002年1—12月为例,利用帕默尔干旱指数(PDSI)、冬小麦减产率以及实际旱情资料,分析了DSI在该地区干旱监测的适用性.结果表明: 黄淮海地区年均实际蒸散从西北向东南递增,最高值出现在研究区域东南部(800~900 mm),最低值出现在西北部(<300 mm);DSI、PDSI两种干旱指数的年际变化呈正相关(R²=0.61)和变化趋势的一致性,均在2002年达到最低(-0.61和-1.33),2003年最高(0.81和0.92),DSI与冬小麦减产率的相关性(R²=0.43)明显优于PDSI(R²=0.06),且表征干旱的空间分辨率较高,对区域农业干旱程度的判断和旱情的指示比较可靠.