基于Sentinel-2影像和机器学习算法的冬小麦秸秆覆盖度遥感估算

为探究大范围小麦秸秆覆盖度(CRC)估测方法，以冬小麦秸秆为研究对象，基于Sentinel-2遥感卫星影像光谱指数、波段和纹理特征及其不同特征组合，利用灰色关联-随机森林(GRA-RF)敏感特征提取方法，结合高斯过程(GPR)、套索(LASSO)、岭回归(RR)和偏最小二乘(PLSR)等多种机器学习算法，开展小麦CRC估算的最优模型研究。结果表明，基于GRA-RF特征优选后的机器学习模型显著改善了小麦CRC的估算精度，LASSO算法总体对小麦CRC的估测效果最佳，并且针对不同的光谱特征组合表现出差异化的结果。其中，以光谱指数、波段和纹理信息构成的组合特征集构建的CRC遥感估算模型精度最优(r²=0.65,RMSE=9.25%),以波段与纹理两者组合特征估算的CRC精度次之(r²=0.63,RMSE=9.31%),仅利用单一的光谱指数、波段或者纹理特征估算冬小麦CRC的精度均劣于组合特征的结果。这说明应用GRA-RF组合筛选方法能够有效优选秸秆覆盖度的光谱特征；相比于单一特征，光谱指数、波段、纹理信息等构成的组合特征更能有效地监测小麦秸秆覆盖度...     

基于连续投影算法和光谱变换的冬小麦生物量高光谱遥感估算

为探索基于全波段冠层高光谱以及变换光谱的冬小麦地上部生物量的遥感估算方法,以2016、2017年冬小麦田间试验为基础,通过对冠层光谱和地上部生物量的相关性分析,筛选拔节期、抽穗期的冬小麦冠层光谱、一阶导数光谱、对数变换光谱和连续统去除光谱对地上部生物量的敏感波段,并结合偏最小二乘法(PLS)分别建立拔节期和抽穗期基于SPA算法的冬小麦地上部生物量估测模型,再与基于任意两波段组合的最佳归一化光谱指数、比值光谱指数、差值光谱指数和已报道光谱指数的冬小麦地上部生物量估测模型进行比较。结果表明：(1)SPA算法较好地利用了全波段冠层光谱信息,并显著降低了光谱维度,不同变换光谱的地上部生物量敏感波段个数在4~14之间;(2)拔节期和抽穗期冠层光谱与地上部生物量的相关性高于开花期和灌浆期,各生育时期一阶导数光谱与地上部生物量之间的相关性优于连续统去除光谱、对数变换光谱和光谱指数;(3) 利用抽穗期一阶导数光谱敏感波段建立的预测模型和验证模型达到了较高的精度,其预测模型的决定系数和均方根误差分别为0.78和0.87 t·hm^-2,验证模型的决定系数和均方根误差分别为 0.84和0.69 t·hm^-2,预测相对偏差为2.74。这说明,抽穗期是估算地上部生物量的最佳生育时期,且基于冠层一阶导数变换光谱,结合连续投影算法和偏最小二乘回归方法所构建抽穗期地上部生物量估算模型具有最优的精度和预测能力,可用于地上部生物量的定量估算。     

多遥感光谱指标结合进行大田冬小麦叶片叶绿素含量估测研究

为解决大田冬小麦叶片叶绿素含量估测模型精度低、通用性弱的问题,在获取冬小麦拔节期和抽穗期冠层红光波段反射率(BR_red)和近红外波段反射率(BR_nir)的基础上,计算归一化差值植被指数(NDVI)、差值植被指数(DVI)、比值植被指数(RVI)、土壤调节植被指数(SAVI)、改进型比值植被指数(MSR)、重归一化植被指数(RDVI)、II型增强植被指数(EVI2)和非线性植被指数(NLI)等8个植被指数。经统计分析,选择与叶片叶绿素含量(SPAD值)相关性较好的5个遥感光谱指标(NDVI、MSR、NLI、BR_red和RVI)作为输入变量,建立了冬小麦叶片叶绿素含量的BP神经网络估测模型(WWLCC_BP),并对估测模型进行精度验证。结果表明,WWLCC_BP估测模型在拔节期估测的决定系数(r²)为0.84,均方根误差(RMSE)为5.39,平均相对误差(ARE)为9.87%。抽穗期的估测效果与拔节期较为一致。将WWLCC_BP和高分六号影像...     

基于Sentinel-2多光谱数据和机器学习算法的冬小麦LAI遥感估算

为了丰富大田尺度下冬小麦叶面积指数的遥感估算方法并提高估算精度,以关中地区冬小麦为对象,基于Sentinel-2多光谱卫星数据与地面同步观测的冬小麦叶面积指数样点数据,应用偏最小二乘回归(PLSR)、反向传播神经网络(BPNN)和随机森林(RF)法构建冬小麦叶面积指数估算模型,进行区域冬小麦叶面积指数遥感反演。结果表明,Sentinel-2多光谱卫星影像中心842nm近红外B8波段与冬小麦叶面积指数相关性最好,样本总体相关系数为0.778;植被指数中反向差值植被指数(IDVI)与冬小麦叶面积指数相关性最好,样本总体相关系数为0.776。各种估算模型中LAI-RF模型预测效果最佳,r~2为0.72,RMSE为0.53,RE为16.83%。基于LAI-RF估算模型,应用Sentinel-2多光谱卫星数据较好地反演了研究区冬小麦叶面积指数区域分布,其结果总体上与地面真实情况接近,说明以Sentinel-2卫星影像数据建立LAI-RF估算模型,可应用于区域冬小麦LAI反演制图。     

基于主成分分析和随机森林回归的冬小麦冠层叶绿素含量估算

为提高冬小麦冠层光谱对叶绿素含量的估算精度,以陕西省乾县冬小麦为研究对象,利用SVC-1024i光谱仪和SPAD-502型叶绿素仪实测了冬小麦冠层反射率和叶绿素含量,分析了一阶导数光谱、10种特征参数和9种植被指数与叶绿素含量的相关性,并利用主成分分析(PCA)对叶绿素敏感的可见光波段(390～780 nm)一阶导数光谱进行降维,将特征值大于1的主分量结合特征参数和植被指数形成不同的输入变量,用偏最小二乘回归和随机森林回归构建冬小麦冠层叶绿素估算模型,并利用独立样本对模型进行验证。结果表明,小麦冠层叶绿素含量与一阶导数光谱在751 nm处的相关性最高(r=0.71),特征参数中红边蓝边归一化(SDr-SDb)/(SDr+SDb)与叶绿素含量的相关性最高(r=0.66),植被指数(VI)中修正归一化差异指数(mND705)相关性最高(r=0.74)。在输入变量相同的情况下,基于随机森林(RF)回归的预测模型均优于偏最小二乘回归(PLSR)模型,其中PCA-VI-RF模型的各精度指标均达到最优(r²=0.94,RMSE=1.05,RPD=3.70),是冬小麦冠层叶绿素...     

基于新型植被指数的冬小麦覆盖度遥感估算

为提高冬小麦覆盖度估测精度,从增强近红外与红光差别的数学变换原理出发,构建了一种新型植被指数(NDVIn),再基于2013、2014年冬小麦冠层高光谱和模拟的资源三号卫星宽波段多光谱数据,分别构建基于常规植被指数(NDVI)与NDVIn的冬小麦覆盖度估算模型,然后利用留一交叉验证法对模型精度进行评价。结果表明,当n=6时,新生成的植被指数NDVI6对冬小麦农田覆盖度具有最好的估算性能,利用其基于小麦冠层高光谱及卫星多光谱数据建立的冬小麦覆盖度估算模型的决定系数r2分别为0.84、0.85,RMSE分别为0.092、0.091,模型精度均好于常规指数NDVI的估算结果。说明NDVI6用于估测冬小麦覆盖度具有可行性。     

基于机器学习算法的冬小麦不同生育时期生物量高光谱估算

为探索适用于冬小麦不同生育时期的高光谱估算方法,基于4年大田试验,以江苏省主要冬小麦品种为材料,以8种对常用生物量敏感的高光谱指数为基础,分别采用偏最小二乘算法、支持向量回归算法、随机森林算法在冬小麦4个主要生育时期(抽穗期前、抽穗期、开花期和灌浆期)进行了高光谱生物量估算和预测能力比较。结果表明,在冬小麦不同生育时期,高光谱估算生物量精度差异显著;利用随机森林构建的生物量估算模型在4个生育时期均表现出很好的效果,决定系数(r^2)和均方根误差(RMSE)在抽穗期前分别为0.79和44.82 g·m^-2,在抽穗期分别为0.71和62.07 g·m^-2,在开花期分别为0.70和97.63 g·m^-2,在灌浆期分别为0.71和106.98 g·m^-2;随机森林模型在4个生育时期的预测能力都高于或接近于支持向量回归模型,高于偏最小二乘回归模型,r^2和RMSE在抽穗期前分别为0.60和72.54 g·m^-2,在抽穗期分别为0.60和75.07 g·m^-2,在开花期分别为0.68和109.9 g·m^-2,在灌浆期分别为0.61和127.93 g·m^-2。这说明随机森林算法在冬小麦不同生育时期生物量高光谱遥感估算方面具有较高的精度和稳定性。     

基于无人机多时相遥感影像的冬小麦产量估算

为高效准确地预测小麦产量,以浙江省冬小麦为研究对象,利用四旋翼无人机精灵4多光谱相机获取冬小麦5个关键生育时期（拔节期、孕穗期、抽穗期、灌浆期、成熟期）的冠层多光谱数据,选取多光谱相机的五个特征波段计算各生育时期的72个植被指数,分别通过逐步多元线性回归（SMLR）、偏最小二乘回归（PLSR）、BP神经网络（BPNN）、支持向量机（SVM）、随机森林（RF）构建不同生育时期的产量估算模型,最后采用决定系数（R）、均方根误差（RMSE）和相对误差（RE）对估算模型进行评价,筛选出最优估算模型。结果表明,基于随机森林建立的模型估算效果最优,SMLR、PLSR和SVM三种方法建立的模型估算效果接近。利用随机森林算法所建拔节期、孕穗期、抽穗期、灌浆期、成熟期模型的R、RMSE和RE分别为0.92、0.35、11%;0.93、0.33、10%;0.94、0.32、9%;0.92、0.36、9%;0.77、0.67、33%。模型验证时,抽穗期估算效果最好（R、RMSE和RE分别为0.91、0.35和15%）,拔节期、孕穗期、灌浆期估算效果接近且有很好的估算能力,成熟期估算精度最差（R、RMSE和RE分别为0.71、0.47和13%）。由此说明,结合机器学习算法和无人机多光谱提取的植被指数可以提高小麦产量估算效果。     

基于冠层高光谱植被指数的水稻产量预测模型研究

及时、准确、快速的进行粮食产量预测预报对指导农业生产和国家制定粮食政策有重大意义。以不同水稻品种和施氮水平为试验因素，进行两因素裂区设计试验，在水稻拔节期、孕穗期和抽穗期测定其冠层光谱反射率，通过筛选出与产量相关性最高的最佳波段组合，计算最优波段组合组成的12种植被指数，并建立了基于单植被指数和多植被指数组合的水稻产量预测模型。结果表明，孕穗期，在401～723 nm波段范围内水稻冠层原始光谱反射率与产量呈显著负相关关系；各植被指数与产量的相关性达到极显著水平。基于单植被指数构建的水稻产量预测模型，以孕穗期线性模型精度最高(R²=0.436,RMSE=874.57 kg/hm²)，最佳植被指数为重归一化植被指数(RDVI)，模型表达式为y=7.7E+05×RDVI₍(455,456))+1.1E+04；基于逐步回归构建的多植被指数产量预测模型同样以孕穗期表现最佳(R²=0.443,RMSE=861.81 kg/hm²)，最优植被指数为比值植被指数(RVI)、土壤调节型植被指数(...     

冬小麦叶片花青素相对含量高光谱监测

为探究冬小麦叶片花青素含量的高光谱监测方法,以陕西省关中地区冬小麦为研究对象,分析了叶片光谱反射率与花青素含量的相关性,建立以不同波段组合的RSI、DSI和NDSI光谱指数为自变量的一元回归模型以及利用偏最小二乘法构建的多元回归模型,并进行模型精度比较。结果表明,所有模型中,开花期的PLS模型精度最高,预测效果最好(建模r~2=0.872 3,RMSE=0.005 9;检验r~2=0.912 8,RMSE=0.004 8),是预测冬小麦花青素的最优模型;各生育时期中,开花期模型精度较高,表现稳定,是预测冬小麦花青素的最佳生育时期。     

Comparative Assessment of the Efficacy of Various Nitrogen Fertilizers

Summary

The efficiency of N fertilizers is usually poor; often less than 50% of the applied N is taken up by the crop. This review focuses on various N fertilizers with respect to the significance of different N loss pathways, namely (i) ammonia volatilization, (ii) dinitrogen and nitrogen oxide emissions, and (iii) nitrate leaching. Further, the significance of biological N immobilization, ammonium fixation and, finally, the impact of nitrate vs. ammonium uptake on crop yield are also discussed. The reviewed literature shows that N fertilizers may differ markedly in their susceptibility to losses. There is, however, considerable scope to improve N efficiency of each N source by proper N management practices.     

Studies on natural repellents against potato tuber moth (Phthorimaea operculella Zeller) in country stores

Summary The effects of the leaves of five plant species, one from each of the generaAmbrosia, Anemone, Eupatorium, Eucalyptus andLantana, on potato tuber moth were investigated under indigenous storage conditions at the Central Potato Research Station, Shillong (1800 m above sea level). Their action was compared with that of a biological insecticide (spores ofBacillus thuringiensis), a chemical insecticide (carbaryl), and an untreated control. The data collected after six months storage on tuber damage, sprout damage and the rotting indicated that the leaves ofLantana aculeata provided most protection to the tubers, reducing damage from over 70% in the check to below 5%, and sprout damage from over 45% to below 3%. Next best wasEucalyptus globulus followed byB. thuringiensis. They may be used on tubers stored for table use or for seed as they had no adverse effect on germination or on the yield of a subsequent crop.     

Mineral composition of some traditional Mexican teas

Teas of plant origin traditionally consumed by the Mountain Pima of Chihuahua, Mexico, were analyzed for mineral nutritional content. Fe, Cu, Zn, Ca, and Mg composition was determined for native teas made from shoots ofTagetes lucida, T. filifolia, Elytraria imbricata, andHolodiscus dumosus, and from root xylem ofCeanothus depressus andPhaseolus ritensis. Native uses of these teas are also described.     

Novel food and non-food uses for sorghum and millets

Sorghum and millets have considerable potential in foods and beverages. As they are gluten-free they are suitable for coeliacs. Sorghum is also a potentially important source of nutraceuticals such antioxidant phenolics and cholesterol-lowering waxes. Cakes, cookies, pasta, a parboiled rice-like product and snack foods have been successfully produced from sorghum and, in some cases, millets. Wheat-free sorghum or millet bread remains the main challenge. Additives such as native and pre-gelatinised starches, hydrocolloids, fat, egg and rye pentosans improve bread quality. However, specific volumes are lower than those for wheat bread or gluten-free breads based on pure starches, and in many cases, breads tend to stale faster. Lager and stout beers with sorghum are brewed commercially. Sorghum's high-starch gelatinisation temperature and low beta-amylase activity remain problems with regard to complete substitution of barley malt with sorghum malt . The role of the sorghum endosperm matrix protein and cell wall components in limiting extract is a research focus. Brewing with millets is still at an experimental stage. Sorghum could be important for bioethanol and other bio-industrial products. Bioethanol research has focused on improving the economics of the process through cultivar selection, method development for low-quality grain and pre-processing to recover valuable by-products. Potential by-products such as the kafirin prolamin proteins and the pericarp wax have potential as bioplastic films and coatings for foods, primarily due to their hydrophobicity.     

In vitro antimicrobial activity of different accessions ofSolanum commersonii Dun. from Uruguay

Summary The in vitro antimicrobial activity of extracts from accessions ofSolanum commersonii Dun. collected in the south of Uruguay was investigated against five microorganisms including the pathogenRalstonia solanacearum. A total of 30 extracts corresponding to organic and aqueous extracts were studied. Interestingly, most of the positive results for growth inhibition were againstR. solanacearum. The extracts were also analyzed for the presence of glycoalkaloids and lectins. Six of the ten aqueous extracts showed lectin presence and a wide variation in the type and amounts of glycoalkaloids, was found. Results indicate that there is no clear relationship between the antimicrobial activity against the five microorganisms screened and the presence or amounts of lectins and glycoalkaloids, traditionally regarded as possible antimicrobial metabolites in theSolanum genus, which indicates the presence of as yet unidentified antimicrobial compounds.     

Extreme resistance to infection by potato virus X in genotypes of wild tuber-bearingSolanum species

Summary Clones derived from thirty-one different accessions (nineteen of Argentine origin) belonging to eightSolanum species were screened for resistance to infection by potato virus X strain cp (PVX cp) by mechanical inoculation of plantlets that had been micropropagated in vitro. Estimates of PVX multiplication obtained by enzyme linked immunosorbent assay and slot blot nucleic acid hybridization allowed the identification of resistant clones derived from five accessions belonging toS. commersonii S. oplocense, S. sparsipilum andS. tuberosum andigena. Resistant genotypes supported PVX concentrations 5 to 15 times smaller than did the susceptible control cultivar Spunta. Graft inoculation test confirmed the presence of extreme resistance similar to that conferred by the ‘immunity’ gene X¹ (also called RX_act).     

Cyanobacteria Secondary Metabolites as Biotechnological Ingredients in Natural Anti-Aging Cosmetics: Potential to Overcome Hyperpigmentation,Loss of Skin Density and UV Radiation-Deleterious Effects

The loss of density and elasticity, the appearance of wrinkles and hyperpigmentation are among the first noticeable signs of skin aging. Beyond UV radiation and oxidative stress, matrix metalloproteinases (MMPs) assume a preponderant role in the process, since their deregulation results in the degradation of most extracellular matrix components. In this survey, four cyanobacteria strains were explored for their capacity to produce secondary metabolites with biotechnological potential for use in anti-aging formulations. Leptolyngbya boryana LEGE 15486 and Cephalothrix lacustris LEGE 15493 from freshwater ecosystems, and Leptolyngbya cf. ectocarpi LEGE 11479 and Nodosilinea nodulosa LEGE 06104 from marine habitats were sequentially extracted with acetone and water, and extracts were analyzed for their toxicity in cell lines with key roles in the skin context (HaCAT, 3T3L1, and hCMEC). The non-toxic extracts were chemically characterized in terms of proteins, carotenoids, phenols, and chlorophyll a, and their anti-aging potential was explored through their ability to scavenge the physiological free radical superoxide anion radical (O₂^•−), to reduce the activity of the MMPs elastase and hyaluronidase, to inhibit tyrosinase and thus avoid melanin production, and to block UV-B radiation (sun protection factor, SPF). Leptolyngbya species stood out for anti-aging purposes: L. boryana LEGE 15486 presented a remarkable SPF of 19 (at 200 µg/mL), being among the best species regarding O₂^•− scavenging, (IC₅₀ = 99.50 µg/mL) and also being able to inhibit tyrosinase (IC₂₅ = 784 µg/mL), proving to be promising against UV-induced skin-aging; L. ectocarpi LEGE 11479 was more efficient in inhibiting MMPs (hyaluronidase, IC₅₀ = 863 µg/mL; elastase, IC₅₀ = 391 µg/mL), thus being the choice to retard dermal density loss. Principal component analysis (PCA) of the data allowed the grouping of extracts into three groups, according to their chemical composition; the correlation of carotenoids and chlorophyll a with MMPs activity (p < 0.01), O₂^•− scavenging with phenolic compounds (p < 0.01), and phycocyanin and allophycocyanin with SPF, pointing to these compounds in particular as responsible for UV-B blockage. This original survey explores, for the first time, the biotechnological potential of these cyanobacteria strains in the field of skin aging, demonstrating the promising, innovative, and multifactorial nature of these microorganisms.     

Marine Pharmacology in 2009–2011: Marine Compounds with Antibacterial,Antidiabetic, Antifungal,Anti-Inflammatory,Antiprotozoal, Antituberculosis,and Antiviral Activities; Affecting the Immune and Nervous Systems,and other Miscellaneous Mechanisms of Action ?

The peer-reviewed marine pharmacology literature from 2009 to 2011 is presented in this review, following the format used in the 1998–2008 reviews of this series. The pharmacology of structurally-characterized compounds isolated from marine animals, algae, fungi and bacteria is discussed in a comprehensive manner. Antibacterial, antifungal, antiprotozoal, antituberculosis, and antiviral pharmacological activities were reported for 102 marine natural products. Additionally, 60 marine compounds were observed to affect the immune and nervous system as well as possess antidiabetic and anti-inflammatory effects. Finally, 68 marine metabolites were shown to interact with a variety of receptors and molecular targets, and thus will probably contribute to multiple pharmacological classes upon further mechanism of action studies. Marine pharmacology during 2009–2011 remained a global enterprise, with researchers from 35 countries, and the United States, contributing to the preclinical pharmacology of 262 marine compounds which are part of the preclinical pharmaceutical pipeline. Continued pharmacological research with marine natural products will contribute to enhance the marine pharmaceutical clinical pipeline, which in 2013 consisted of 17 marine natural products, analogs or derivatives targeting a limited number of disease categories.