不同种植密度烟草叶面积指数的高光谱估测模型

烟草叶面积指数(LAI)是评价其长势和预测产量的重要指标。利用高光谱遥感能够实现LAI的快速无损监测。为建立烟草LAI估算的最佳光谱指数及监测模型,通过设置不同种植密度处理,将田间观测和高光谱遥感技术结合,提取和分析了10个植被指数,并用二次多项式模型、对数模型、逐步回归模型(SMLR)和BP神经网络对烟草LAI进行估算。结果表明,NDVI、RVI、MCARI、GM1、GNDVI2和PSSRb等植被指数同烟草LAI均达到极显著正相关,相关系数均大于0.80。烟草LAI的二次多项式模型、对数模型、逐步回归模型(SMLR)和BP神经网络模型的决定系数R~2分别为0.69、0.57、0.89和0.90。经检验,4个模型的均方根误差RMSE分别为0.69、0.87、0.62和0.44。表明SMLR和BP神经网络LAI都取得了较为理想的结果,其中BP神经网络的精度最高、误差最小,更适合对烟草LAI进行反演。该结果为实现不同种植密度水平下烟草LAI的精确监测提供技术支持和地域参考。     

基于遥感技术的烟草花叶病监测研究

为实现烟草花叶病快速、无损监测。基于染病植株冠层高光谱数据,优选病情指示变量,利用偏最小二乘法建立病害程度估测模型,并进一步将模型应用于资源3号卫星遥感数据,建立烟草花叶病病害等级分布图。结果显示:1)以比值植被指数(RVI),差值植被指数(DVI),再归一化植被指数(RDVI),变换植被指数(TVI),土壤可调植被指数(SAVI)作为烟草花叶病病情的指示因子,能有效估测花叶病的严重程度,决定系数达0.8165。2)在烟草花叶病病害等级分布图上,随机抽取140个样点进行实测,并将实测值与估测值进行线性拟合,拟合优度R2达77.13%。因此该方法能实现对烟草花叶病的大范围实时监测。     

基于合成孔径雷达(SAR)数据的贵州喀斯特山区烟草叶面积指数估算模型

喀斯特山区多云雨天气,地表破碎,耕地分布不集中,农作物套种,导致常规遥感监测手段难以满足烟草实时监测的需要。为实现现代烟草农业实时快速监测,研究选取高分辨率合成孔径雷达(SAR),以贵州清镇流长现代烟草农业基地单元为研究区,在烟叶成熟期,考察不同极化方式(HH、VV以及H/VV)雷达亮度值与烟草叶面积指数(LAI)的相关性,进而构建线性回归模型和二次多项式模型。结果表明:一元线性比值HH/VV模型(Y=0.612X+1.410, R2=0.862)反演精度最高。该模型可用于大面积遥感监测贵州喀斯特山区烟草种植,掌握烟草生长状况。      

MODIS蒸散模型在攀西烟区的适用性验证

准确估算区域生态系统蒸散量（ET）,对研究区域水资源利用时空变化特征、评估气候变化的影响具有重要意义。基于2016年1~10月MODIS遥感数据,利用MODIS蒸散量估算模型,结合气象数据对攀西烟区典型烟田生态系统ET进行模拟,并根据田间通量观测数据对模型模拟结果进行精度检验和参数化调整,以验证和提高MODIS蒸散量模型在攀西烟区的适用性。结果表明:采用默认参数的MODIS蒸散量模型模拟值比实测值偏小12.8%,效率系数为0.767,且在烤烟生育期前期（DOY 105~161）平均相对误差较大。依据田间通量观测数据,对模型中叶片边界层阻抗和叶面积指数（LAI）进行参数化后,ET模拟值与实测值动态曲线非常一致,一元线性回归斜率为0.997,决定系数R2为0.835,效率系数为0.808。经独立性验证,参数校正后的MODIS蒸散量模型在研究区具有较好的适用性,为进一步利用该模型对攀西及西南烟区烟田水热收支平衡研究提供理论依据与数据支持。      

水稻籽粒蛋白质含量的高光谱估测研究

探索不同高光谱模型估测水稻籽粒蛋白质含量的精度,对于快速、无损、准确地监测水稻籽粒品质具有重要意义.在浙江省海宁市晚稻收获期同步采集了水稻籽粒光谱反射率与蛋白质含量数据,并分别对获取的数据进行了单波段相关分析、植被指数回归分析、神经网络模拟.通过分析得出以下结论:(1)水稻籽粒光谱反射率、微分光谱与对应的蛋白质含量密切相关.其中,在蓝光、红光和近红外处光谱反射率与水稻籽粒蛋白质含量的相关系数和确定性系数稳定且较高,而微分光谱与水稻籽粒蛋白质含量之间的相关系数和确定性系数变化较大,在500～750 nm间则相对稳定;(2)5种植被指数和水稻籽粒蛋白质含量均密切相关.线性模型的预测值与实测值之间的相关系数在0.44～0.55之间,均方根差在0.46～0.79之间;(3)神经网络模型可以容纳更多的相关波段参与水稻籽粒蛋白质含量的估算,实测值与预测值的相关系数高于其他模型,而均方根差低于其他模型,可以用于快速无损检测水稻籽粒蛋白质含量.     

南京盐水鸭挥发性风味成分的定量结构-保留相关性

为能得到预测风味化合物保留指数的模型,采用定量结构- 保留相关性(OSRR)方法研究盐水鸭风味化合物的分子结构与其卡瓦茨保留指数(KI)之间的关系,计算得到的拓扑指数(分子形状指数和电性拓扑态指数)与风味化合物的保留指数回归分析,对53 个含氧类化合物、24 个烃类化合物、21 个萜烷及含其他杂原子类化合物建立模型的相关系数分别为0.981、0.992 和0.941,均属于显著性相关,利用前2 个方程计算得到的含氧类化合物、烃类化合物的估算值与实验值基本吻合。对3 个预测模型进行留一法稳定性检验,得到的相关系数检验值基本在控制范围内,总体稳定性良好,表明本法对盐水鸭风味化合物的性质研究较为理想。     

基于多光谱数据的荒漠矿区土壤有机质估算模型

目前运用高光谱数据估算土壤有机质的模型精度已经可以达到精准农业的要求,但其数据的整理和运算过程较为复杂且观测尺度较小。为节省资源,提高效率并为多光谱遥感估算土壤有机质积累经验,该文将Landsat8_OLI多光谱遥感影像各波段的反射率数据与地面土壤有机质SOM(soil organic matter)实测数据相结合,利用SPSS软件及多元线性回归分析方法建立基于反射率R、反射率倒数1/R、反射率倒数对数LN(1/R)、反射率一阶导数FDR(first derivative reflectance)的土壤有机质定量估算模型,精度检验后择取最优模型通过多光谱遥感波段运算的方式推广至整个研究区。结果表明:FDR模型的精度更高,RMSE为0.215,F检验结果为4.072,预测值与实际值之间的决定系数R2为0.963。基于该模型估算研究区空间范围的土壤有机质含量,得出土壤有机质含量在0~5 g/kg之间的面积占总研究区的84.065%,>10 g/kg的面积仅仅为0.001 5%。在4种土地类型中工矿用地SOM平均含量为最高的7.35 g/kg,受开采的煤炭中有机质影响较大。裸地面积2 674.44 km2,占研究区面积的63%,SOM平均含量6.12 g/kg;盐渍地和荒漠林地SOM含量偏低。总之,运用多光谱遥感数据估算干旱区土壤有机质的方法可行,也为遥感估算其他地表参数提供参考。     

基于改进水云模型的土壤水分反演研究

提出了一种基于改进的水云模型的主动微波遥感土壤水分反演方法。首先,分别通过甘肃省张掖市祁连山中段的扁都口研究区的实测数据计算RVI、DVI、NDVI、NDWI、MSAVI等五种植被指数,建立适用于研究区的植被含水量经验方程,然后基于植被含水量经验方程构建水云模型,对总的地表后向散射系数中的植被影响进行改正,结合水云模型和AIEM模型,建立改进的土壤水分反演算法。从五种植被指数中选取与植被含水量相关性最高的三种植被指数,然后利用九组植被指数组合参与土壤水分反演,对比并选择反演结果精度较好的植被指数及其植被含水量经验方程。将文章方法与基于Jackson经验方程建立水云模型的反演算法进行了对比,结果表明,文章提出的改进水云模型的土壤水分反演算法精度较高,体现了该改进算法的优势与潜力。     

HJ-1影像中基于光谱特征的烤烟识别方法

为了监测农作物的种植面积、进而预测其产量,依据HJ-1(环境一号卫星A、B星,简称HJ-1A,1B)遥感资料分析了烤烟及其他地物的光谱反射特性,并分析比较归一化植被指数NDVI、差值植被指数NDVI和比值植被指数RVI对烤烟及其他地物的区分度,确定烤烟遥感信息识别方法。用该方法对广西靖西县烤烟进行种植信息提取,并用野外GPS实地调查采样数据进行精度验证。结果表明,总精度为92.79%,Kappa系数为0.8374。因此,利用遥感技术可快速、准确地获取烤烟种植信息。     

干旱胁迫下旺长期烤烟冠层叶绿素密度的高光谱估测

为精准、实时、无损地估算烤烟冠层叶绿素密度,快速获取烤烟光合性能与营养状况,基于不同程度干旱胁迫处理,采用ASD光谱仪,在综合分析群体原始高光谱反射率、一阶导数光谱反射率及已有光谱指数与冠层叶绿素密度(CCD)关系的基础上,建立烤烟CCD估算模型。结果表明:(1)干旱胁迫后烤烟冠层光谱反射率随叶绿素密度呈现规律性变化。(2)712 nm处的一阶导数与CCD相关性最好(r=0.838)。(3)利用一阶导数光谱建立的反演叶绿素密度的线性模型和BP神经网络模型中,均以BP神经网络模型效果最好,其模型决定系数R~2为0.9686,均方根误差RMSE 0.0778,表明模型的精度和稳定性均较好。研究结果可为实时监测旺长期烤烟群体光合能力及水分胁迫状况提供栽培管理依据。     

Seasonal variability and long term trends of chlorofluorocarbon mixing ratios in the unsaturated zone

To investigate processes that might affect chlorofluorocarbon (CFC) mixing ratios at the water table, a time series was obtained of unsaturated zone soil gas CFCs to depths of ca. 4 m at a site near New York City (NYC). Observed CFC 11, 12, and 113 mixing ratios were lower in winter than expected from either a local, high-resolution time series or remote atmospheric mixing ratios. A diffusion model, which includes seasonal changes in soil temperature, moisture, and CFC solubility, reproduces to first order the observed soil gas mixing ratios for CFC 11 and 12. Underestimation by the model of the seasonal cycle of CFC 11 points to changing levels of sorption to soils due to seasonal changes in temperature as an additional cause of the cycle seen in CFC 11 mixing ratios in soil air. In the case of spring recharge, low CFC mixing ratios in soil air caused by increased solubility may result in low CFC 11 concentrations in groundwater and, when dating groundwater recharged before the 1990s with CFCs, older apparent ages by up to 4 years. Attempts to observe average atmospheric CFC levels from soil gas are also significantly hindered by these seasonal fluctuations. Our results indicate the importance of considering seasonal changes in soil temperature when making precise observations of even very moderately soluble gases in the unsaturated zone and shallow groundwater.     

Relationship between surface and free tropospheric ozone in the Western U.S

Ozone is an important air pollutant that affects lung function. In the U.S., the EPA has reduced the allowable O(3) concentrations several times over the last few decades. This puts greater emphasis on understanding the interannual variability and the contributions to surface O(3) from all sources. We have examined O(3) data from 11 rural CASTNET sites in the western US for the period 1995-2009. The 11 surface sites show a similar seasonal cycle and generally a good correlation in the deseasonalized monthly means, indicating that there are large scale influences on O(3) that operate across the entire western US. These sites also show a good correlation between site elevation and annual mean O(3), indicating a significant contribution from the free troposphere. We examined the number of exceedance days for each site, defined as a day when the Maximum Daily 8-h Average (MDA8) exceeds a threshold value. Over this time period, more than half of these sites exceeded an MDA8 threshold of 70 ppbv at least 4 times per year, and all sites exceeded a threshold value of 65 ppbv at least 4 times per year. The transition to lower threshold values increases substantially the number of exceedance days, especially during spring, reflecting the fact that background O(3) peaks during spring. We next examined the correlation between surface O(3) and free tropospheric O(3) in the same region, as measured by routine balloon launches from Boulder, CO. Using ozone measured by the balloon sensor in the range of 3-6 km above sea level we find statistically significant correlations between surface and free tropospheric O(3) in spring and summer months using both monthly means, daily MDA8 values, and the number of surface exceedance days. We suggest that during spring this correlation reflects variations in the flux of O(3) transport from the free troposphere to the surface. In summer, free tropospheric and surface concentrations of O(3) and the number of exceedance days are all significantly correlated with emissions from biomass burning in the western US. This indicates that wildfires significantly increase the number of exceedance days across the western U.S.     

Environmental effects on cv Cabernet Sauvignon (Vitis vinifera L.) grown in Hawke's Bay, New Zealand.: 2. Development of a site index

Based on observations of Cabernet Sauvignon phenology, cropping and fruit characteristics at six vineyard sites in Hawke's Bay (New Zealand) studied over three seasons, a numerical model is proposed to characterise environmental conditions of a vineyard site. The proposed model is based on air temperature in October and January, seasonal rainfall, rooting depth, gravel percentage and clay-to-silt ratio in topsoil. The 'Site Index' (SI) calculated from these variables was significantly correlated with soil temperature and volumetric soil moisture content, themselves closely linked with clay-to-silt ratio, air temperature and rainfall. Vegetative growth, canopy characteristics, precocity of veraison, total anthocyanins, TSS and malic acid concentration in grapes, as well as wine sensory score, were all significantly correlated with the SI values at six sites and over two seasons. Over the same period, correlation of SI with several viticultural variables was generally stronger than five existing climatic indices for viticulture calculated for these sites. The proposed SI index appears to have potential use for vineyard zoning and site selection and evaluation.     

Diurnal variation of diazinon volatilization: soil moisture effects

Diurnal variations in diazinon volatilization were monitored in three field experiments conducted with differing soil moisture contents. The highest flux rates in all experiments were recorded just after diazinon application, but the magnitudes of those initial rates differed according to the soil moisture content, with wetter soil producing a higher rate: 5.6 × 10(-4) μg cm(-2) min(-1) for initial soil moisture above field capacity, 8.3 × 10(-5) μg cm(-2) min(-1) for initial soil moisture at field capacity, and 2.5 × 10(-5) μg cm(-2) min(-1) for initially very dry soil. Volatilization decreased during the first day in the two experiments with initially wet soils but remained relatively constant in the experiment with initially dry soil. The volatilization rate during the first night for the wettest soil remained about an order-of-magnitude higher than that observed for driest soil. When the surface dried in the experiment conducted at the intermediate water content, the volatilization rate and temporal pattern transitioned and became similar to that observed for the initially dry soil. Around noon of the second day, a daily maximum value was observed in the volatilization rate for wet soil, whereas a minimum value was observed for the dry soil, resulting in an order-of magnitude difference. This study demonstrates the importance of soil moisture on emissions of pesticides to the atmosphere.     

Distribution of atmospheric SF6 near a large urban area as recorded in the vadose zone

Local emissions of SF6 are of interest for studying their impact on the use of SF6 as a groundwater-dating tool near source regions as well as for investigating the spatial distributions of (inert) gaseous compounds spreading from urban or industrial centers. A precondition for the use of SF6 in such studies is the capability to document the temporal and spatial evolution of SF6 in and around source regions with sufficient resolution. Here we present a time series of SF6 measurements in soil air at a site (Sparkill, NY) about 25 km north of New York City carried out between May 2000 and January 2002. The data show that, below about 2 m depth, the vadose zone integrates atmospheric SF6 mixing ratios over time scales greater than 1 month. SF6 mixing ratios in soil air at these depths match averaged high-resolution atmospheric measurements performed at Lamont-Doherty Earth Observatory in Palisades, NY, located about 3 km south of Sparkill. To a first-order approximation, a simple one-dimensional diffusion model reproduces the measured SF6 profiles in the vadose zone, suggesting that the soil indeed acts as a low-pass filter for inert atmospheric gases. These findings indicate that measurements of soil air can be used to determine the spatial pattern of SF6 excess relative to the remote atmosphere for a given region. A transect of soil profiles from Manhattan to the tip of Long Island indicates that emissions from sites close to New York City lead to significant SF6 excesses (ca. 25% or more) above the clean air mixing ratios over distances of the order of 80 km.     

Shoot growth on de-fruited grapevines: a physiological indicator for irrigation scheduling

A simple and inexpensive but biologically meaningful way of gauging grapevine water status that can guide irrigation scheduling is described. The growth rate of shoots on grapevines from which all fruit has been removed (de-fruited shoot growth) is presented as a sensitive indicator of vine and soil water status and we propose a procedure for irrigation scheduling based on monitoring de-fruited shoot growth and soil moisture. These guidelines were derived from corresponding measurements of de-fruited shoot growth and soil moisture potential that were undertaken at frequent intervals (generally 1 to 2 days). De-fruited shoot growth rate between 48 and 71 days after anthesis was linearly correlated with the mean moisture potential of the soil at depths of 60 cm and 90 cm in the centre of the drip-irrigated zone (r = 0.94). De-fruited shoot growth effectively ceased when soil moisture potential at these points had decreased to -70 kPa, although much of the root zone would have been even drier. De-fruited shoot growth thus shows an integrated and dynamic response to vine-available soil water that could aid irrigation scheduling.     

武陵山区旱地烟田土壤水分的时空分布特征

  目的  探讨武陵山区旱地烟田土壤水分的时空分布特征,为烟田抗旱栽培技术研究提供理论支撑。  方法  2018年5—9月,利用等值线图、时间稳定性分析和相关性分析等方法开展研究。  结果  1）垄体表层土壤水分含量较低,等值线破碎化程度较弱;而底层土壤水分含量较高,等值线破碎化程度较强。与垄体土壤相比,垄沟各层土壤均具有较高的水分含量,等值线也都呈破碎化程度较高的斑块状。2）垄体与垄沟土壤均受到伏旱天气的不利影响,导致土壤水分在7月底（伏旱末期）达到最低值。3）基于时间稳定性指数最小值得出的代表性样点,建立了代表性样点土壤含水量与对应土层平均含水量之间的统计回归模型。4）相关性分析显示,垄体土壤与垄沟土壤之间存在明显的水分交换,且交换量随垄沟土壤深度的增加而增大。  结论  起垄和终生覆膜显著改变了武陵山区旱地烟田土壤水分的时空分布特征,并加剧了伏旱天气下烟田土壤水分的亏缺,研究结果可为本区烟田的墒情预测及抗旱栽培技术研究提供理论支撑。      

Evaluation of spatial variability of soil arsenic adjacent to a disused cattle-dip site, using model-based geostatistics

This study investigated the spatial variability of total and phosphate-extractable arsenic (As) concentrations in soil adjacent to a cattle-dip site, employing a linear mixed model-based geostatistical approach. The soil samples in the study area (n = 102 in 8.1 m(2)) were taken at the nodes of a 0.30 × 0.35 m grid. The results showed that total As concentration (0-0.2 m depth) and phosphate-extractable As concentration (at depths of 0-0.2, 0.2-0.4, and 0.4-0.6 m) in soil adjacent to the dip varied greatly. Both total and phosphate-extractable soil As concentrations significantly (p = 0.004-0.048) increased toward the cattle-dip. Using the linear mixed model, we suggest that 5 samples are sufficient to assess a dip site for soil (As) contamination (95% confidence interval of ±475.9 mg kg(-1)), but 15 samples (95% confidence interval of ±212.3 mg kg(-1)) is desirable baseline when the ultimate goal is to evaluate the effects of phytoremediation. Such guidelines on sampling requirements are crucial for the assessment of As contamination levels at other cattle-dip sites, and to determine the effect of phytoremediation on soil As.     

Extraction of Agricultural Phenological Parameters of Sri Lanka Using MODIS,NDVI Time Series Data

Management of crops is an essential part in the food production procedure. Having a thorough knowledge of growth stages of each crop is of paramount importance in this respect. Phenology (transplanting, panicle formation, flowering etc) is the study of cyclic and seasonal natural phenomena that are controlled by environmental and climatic factors. Monitoring the crop condition manually in the field is difficult and time consuming. Therefore recently, several methods have been introduced by using satellite derived vegetation indices. Extraction of phenological parameters is helpful for the purposes like irrigation management, nutrient management, health management, yield prediction and crop type mapping. Easily extracted parameters will be the important data base for agricultural researchers. This research is an attempt to extract paddy phenological parameters of Sri Lanka by using 16 years’ (2000 to 2015) Time series MODIS Normalised Difference Vegetation Index (NDVI), which is highly sensitive for the green vegetation and the data were analysed using SPIRITS and TIMESAT software's. Periodicity converter in SPIRITS and Savitzky Golay filtering in TIMESAT and SPIRITS are helpful in smoothing the time series which are perturbed by noise due to missing values and Clouds. Phenology is considered as a sensitive climate change indicator but, it is very essential to have a comprehensive familiarity about the method of water supply that the study area is irrigated or rain fed so as to eliminate the wrong interpretation. As results, average of long time series of NDVI profile for a few agro ecological zones of Sri Lanka with extracted seven parameters (Start of the season, End of the season, Length of the season, Booting date, Base value, Maximum NDVI during the Season, Amplitude) and generated phenological parameter maps are presented here. The crop phenology is a very important element of agricultural monitoring, to ensure the security of the food crop production.     

Monitoring of landfill leachate dispersion using reflectance spectroscopy and ground-penetrating radar

The utility of ground-penetrating radar and reflectance spectroscopy in the monitoring of landfill sites has been investigated. Strong correlations between red edge inflection position and chlorophyll and heavy metal concentrations have been demonstrated from grassland species affected by leachate contamination of the soil adjacent to the landfill test site. This study demonstrated that reflectance spectroscopy can identify vegetation affected by leachate-contaminated soil at a range of spatial resolutions. To identify the vegetation affected by leachate contamination, the spectroradiometer must have contiguous bands at sufficient spectral resolution over the critical wave range that measures chlorophyll absorption and the red edge (between 650 and 750 nm). The utility of ground-penetrating radar data to identify leachate escaping from breakout points in the contaminant wall has also been demonstrated. An integrated approach using these techniques, combined with field and borehole sampling and contaminant migration modeling, offers a possible cost-effective monitoring approach for landfill sites.