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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Imaging Spectrometry and Fluorometry in Support of Flex: What Can We Learn from Multi-Scale Experiments?
摘要： In advance of the FLEX mission, experimental studies are needed to better understand the factors driving Solar-Induced Fluorescence (SIF) emission from vegetation across different temporal and spatial scales. Here, we present findings from boreal (evergreen and deciduous) forest trees and Midwestern (annual) crops, illustrating effects of seasonal downregulation and drought on the fluorescence signals. Further work is needed to develop defensible, quantitative fluorescence measurements, and to partition the drivers of the fluorescence signals into effects of structure and physiology.
关键词： chlorophyll fluorescence (SIF, Fs),stress,photosynthesis,drought,temperature,chlorophyll/carotenoid pigments
更新于2025-09-23 15:23:52
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[IFIP Advances in Information and Communication Technology] Computer and Computing Technologies in Agriculture XI Volume 546 (11th IFIP WG 5.14 International Conference, CCTA 2017, Jilin, China, August 12-15, 2017, Proceedings, Part II) || Summary of Agricultural Drought Monitoring by Remote Sensing at Home and Abroad
摘要： Drought is one of the major natural disasters which causes very severe impacts on economy and society, remote sensing is the efficient method which can dynamic monitor drought at a great range of scale, the research on agricultural drought monitoring has been an important issue. This paper introduces the principle of agricultural drought monitoring based on remote sensing technology, and reviews the current remote sensing approaches in drought monitoring. Combined with the current research hotspots, this paper offers the further research ideas by discussing the dominances and limitations of these methods.
关键词： Remote sensing,Agricultural drought,Methods,Soil water
更新于2025-09-23 15:22:29
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[Sustainable Development Goals Series] Remote Sensing for Food Security || Application of Vegetation Health Data and Products for Monitoring Food Security
摘要： The year 2018. Almost one-fifth of the twenty-first century has already past and the Earth has still been continuing the previous tendencies for a rapid population growth, declining stock of natural resources, climate warming, land cover changes, increasing natural disasters, etc., which have intensified considerably world’s concerns about the future food supply/demand and global food security (USDA 2017; FAO 2017, 1999; Heibuch 2011). Most of the indicated problems are related to a deterioration of environmental conditions. As has never been before, decision makers of the world, countries, communities, international organizations, and businesses need reliable and timely information to understand, monitor, and predict impacts of weather/climate and environmentally based Earth’s changes on global food security (FS).
关键词： Environmental Monitoring,Food Security,Vegetation Health,Drought Monitoring,Satellite Data
更新于2025-09-23 15:21:01
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Enhancement of Ecological Field Experimental Research by Means of UAV Multispectral Sensing
摘要： Although many climate research experiments are providing valuable data, long-term measurements are not always affordable. In the last decades, several facilities have secured long-term experiments, but few studies have incorporated spatial and scale effects. Most of them have been implemented in experimental agricultural fields but none for ecological studies. Scale effects can be assessed using remote sensing images from space or airborne platforms. Unmanned aerial vehicles (UAVs) are contributing to an increased spatial resolution, as well as becoming the intermediate scale between ground measurements and satellite/airborne image data. In this paper we assess the applicability of UAV-borne multispectral images to provide complementary experimental data collected at point scale (field sampling) in a long-term rain manipulation experiment located at the Kiskun Long-Term Socio-Ecological Research (LTSER) site named ExDRain to assess the effects on grassland vegetation. Two multispectral sensors were compared at different scales, the Parrot Sequoia camera on board a UAV and the portable Cropscan spectroradiometer. The NDVI values were used to assess the effect of plastic roofs and a proportional reduction effect was found for Sequoia-derived NDVI values. Acceptable and significant positive relationships were found between both sensors at different scales, being stronger at Cropscan measurement scale. Differences found at plot scale might be due to heterogeneous responses to treatments. Spatial variability analysis pointed out a more homogeneous response for plots submitted to severe and moderate drought. More investigation is needed to address the possible effect of species abundance on NDVI at plot scale contributing to a more consistent representation of ground measurements. The feasibility of carrying out systematic UAV flights coincident or close to ground campaigns will certainly reveal the consistency of the observed spatial patterns in the long run.
关键词： drought,NDVI,multiscale approach,field experiments,LTSER,Sequoia,unmanned aerial vehicles (UAVs)
更新于2025-09-19 17:15:36
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[IEEE 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Xiamen, China (2019.12.17-2019.12.20)] 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Ultra-wideband Absorber Based on Graphene Metamaterial
摘要： Surface water is a critical resource in semiarid West-African regions that are frequently exposed to droughts. Natural and artificial wetlands are of high importance for different livelihoods, particularly during the dry season, from October/November until May. However, wetlands largely go unmonitored. In this work, remote sensing is used to monitor wetlands in semiarid Burkina Faso over large areal extents along a gradient of different rainfall and land use characteristics. Time series of data from the Moderate Resolution Imaging Spectrometer (MODIS) from 2000 to 2012 is used for near-infrared (NIR)-based water monitoring using a latitudinal threshold gradient approach. The occurrence of 21 new water bodies with a size larger than 0.5 km2 over the 13-year analysis period results from a postclassification change detection. Yearly cumulative spatiotemporal analysis shows lower water extents in the drought seasons of 2000–2001, 2004–2005, and 2011–2012. Multiple wetlands indicate a positive trend toward a larger yearly maximum area, but a negative trend toward shorter flooding duration. Such a negative trend is observed particularly for natural wetlands. The temporal behavior of five selected case studies demonstrates that monthly negative anomalies of water-covered areas coincide with the occurrence of drought seasons. The successful application of remote sensing time series as a tool to monitor wetlands in semiarid regions is presented, and the potential of novel early warning indicators of drought from remote sensing is demonstrated.
关键词： Sahel,Moderate Resolution Imaging Spectrometer (MODIS),monitoring,drought indicators,Burkina Faso,wetlands,time series,surface water
更新于2025-09-19 17:13:59
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Four Dimensional Mapping of Vegetation Moisture Content Using Dual-Wavelength Terrestrial Laser Scanning
摘要： Recently, terrestrial laser scanning (TLS) has shown potential in measuring vegetation biochemical traits in three dimensions (3D) by using reflectance derived from backscattered intensity data. The 3D estimates can provide information about the vertical heterogeneity of canopy biochemical traits which affects canopy reflectance but cannot be measured from spaceborne and airborne optical remote sensing data. Leaf equivalent water thickness (EWT), a metric widely used in vegetation health monitoring, has been successfully linked to the normalized difference index (NDI) of near and shortwave infrared wavelengths at the leaf level. However, only two previous studies have linked EWT to NDI at the canopy level in field campaigns. In this study, an NDI consisting of 808 and 1550 nm wavelengths was used to generate 3D EWT estimates at the canopy level in a broadleaf mixed-species tree plot during and after a heatwave. The relative error in EWT estimates was 6% across four different species. Temporal changes in EWT were measured, and the accuracy varied between trees, a factor of the errors in EWT estimates on both dates. Vertical profiles of EWT were generated for six trees and showed vertical heterogeneity and variation between species. The change in EWT vertical profiles during and after the heatwave differed between trees, demonstrating that trees reacted in different ways to the drought condition.
关键词： drought,leaf water content,vegetation,Lidar,water stress
更新于2025-09-11 14:15:04
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[American Society of Agricultural and Biological Engineers 2017 Spokane, Washington July 16 - July 19, 2017 - ()] 2017 Spokane, Washington July 16 - July 19, 2017 - <i>Phenotyping of Arabidopsis for drought stress response using kinetic chlorophyll fluorescence imaging</i>
摘要： Drought stress is one of the major concerns in global agricultural production. Developing an efficient phenotyping technology can bridge the knowledge gap between the plant phenotype and genotype, which can promote the progress of breeding for drought tolerant accessions and provide economic benefits for the producers and consumers. This research was aimed to investigate the plant phenotyping for drought stress responses of two different genotypes of Arabidopsis using chlorophyll fluorescence imaging. 59 treatment groups (three plants for each group) of each genotype were withholding being watered for 8 days as the drought stress treatment, and the other 59 groups considered as control were regularly watered with 6 ml 1% nutrient solution every day. The kinetic chlorophyll fluorescence images of the drought treatment groups and the control groups were acquired at day 1, 3, 5, 7 and 8 after the drought stress treatment started. The conventional chlorophyll fluorescence parameters and the leaf area index were then extracted from the images. In addition, associated morphological and physiological parameters were also assayed. To construct combinatorial images, the sequential forward selection (SFS) algorithm was used to select the maximum contrast images between two genotypes and the linear discriminant analysis (LDA) was used to build combinatorial images. Finally, combinatorial images were analyzed, indicating combinatorial images are valuable in drought stress studies. Above all, the study showed that AQ and osca1 presented different drought stress responses during the treatment period based on the conventional chlorophyll parameters and combinatorial images.
关键词： drought stress,Arabidopsis,plant phenotyping,combinatorial imaging,Chlorophyll fluorescence imaging
更新于2025-09-10 09:29:36
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[Sustainable Development Goals Series] Remote Sensing for Food Security || Monitoring Drought from Space and Food Security
摘要： Drought is a typical phenomenon of the Earth’s climate. Losses from droughts, especially in agriculture, are staggering. Even in the USA, a country of the most advanced technology, the average annual cost of drought is around $6 billion. However, in extreme drought years such as 1988, costs jumped to $60 billion. During 2001–2017, nearly 20% of global lands were drought-stricken, almost every year and in some years this number jumped up much higher. Developing countries of Africa and Asia have always been the most drought-affected, especially if drought reduced agricultural production and they are facing food security problem. In the twenty-first century, the Horn of Africa experienced several-year droughts, which affected 13 million people in 2011 causing very serious food shortages and hunger. Mongolia’s rangelands suffer from very intensive droughts resulting in a lack of feed for livestock every 2–4 years. Unusual summer dryness affected the main grain-producing countries of the Black and Caspian Seas regions in 2007, 2009, 2010, 2012, and 2013 (AMIS 2017; NOAA 2017; Kogan and Guo 2014; NCDC 2011).
关键词： Climate Change,Remote Sensing,Drought,Food Security,Vegetation Health
更新于2025-09-10 09:29:36
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Drought-induced changes in photosynthetic electron transport in maize probed by prompt fluorescence, delayed fluorescence, P700 and cyclic electron flow signals
摘要： The effect of drought on the prompt chlorophyll a fluorescence (PF) transient (OJIP), delayed chlorophyll a fluorescence (DF), modulated 820-nm reflection (MR), energy conversion efficiencies in photosystems (PS) I and II, and cyclic electron flow (CEF) activity in two maize hybrids with contrasting drought tolerance was investigated. Our aim was to identify the target site of drought stress on the photosynthetic electron transport chain and investigate the relevance of the CEF pathway to the drought tolerance of maize plants. The OJIP analysis showed that drought stress, depending on its duration, decreased FP, increased FJ, and induced a pronounced K-band and a positive L-band. Moreover, OJIP parameters, including PIABS, RC/CSO, TRO/ABS, and ETO/TRO, were significantly reduced. The DF analysis showed that the values of I1 and I2 in the induction curve and L1 and L2 derived from the decay curve decreased progressively with the duration of drought stress. The MR analysis showed that drought stress inactivated both the fast decrease and slow increase phases of the MR transient, resulting in a gradual decrease in both VPSI and VPSII-PSI. The energy conversion analysis showed that drought stress decreased the PSI photochemical quantum yield Y(I) and PSII photochemical quantum yield Y(II). Compared to the tolerant hybrid, the drought-induced changes in the sensitive hybrid were stronger and appeared at an earlier treatment stage. The CEF activity analysis showed that the CEF pathway under drought stress operated for a longer time in the tolerant hybrid than that in the sensitive hybrid. The above results indicate that drought stress damaged the donor and acceptor sides of PSII, the PSII reaction center and the acceptor side of PSI and decreased the efficiency of both PSI and PSII and the capacity of electron transfer. The CEF pathway might play an important role in the tolerance of the maize photosynthetic electron transport chain to drought stress.
关键词： Cyclic electron flow,Delayed fluorescence,Modulated 820 nm reflection,Energy conversion efficiencies in photosystems (PS) I and II,Prompt fluorescence OJIP,Maize,Drought stress
更新于2025-09-10 09:29:36
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[IEEE 2018 37th Chinese Control Conference (CCC) - Wuhan (2018.7.25-2018.7.27)] 2018 37th Chinese Control Conference (CCC) - Wheat Drought Assessment by Remote Sensing Imagery Using Unmanned Aerial Vehicle
摘要： This work aims at evaluating the usability of remote sensing RGB imagery by an Unmanned Aerial Vehicle (UAV) in assessing wheat drought status. A UAV survey is conducted to collect high-resolution RGB imageries by using DJI S1000 for the experimental wheat ?elds of Gucheng town, Heibei Province, China. The soil moisture for different plots of the experimental ?led is kept at an approximately constant level for the whole growing season in a well controlled environment, where ?eld measurements are performed just after the UAV survey to obtain the soil water content for each plot. A machine learning based wheat drought assessment framework is proposed in this work. In the proposed framework, wheat pixels are ?rst segmented from the soil background using the classical normalized excess green index (NExG). Rather than using pixel-wise classi?cation, a pixel square of appropriate dimension is de?ned as the samples, based on which various features are extracted for the wheat pixels including statistical features and spectral index features. Different classi?cation algorithms are experimented to identify a suitable one in terms of classi?cation accuracy and computation time. It is discovered that Support Vector Machine with Gaussian kernel can obtain an accuracy over 90%, which demonstrates the usefulness of RGB imagery in wheat drought assessment.
关键词： UAV imagery,Wheat drought,Remote sensing,Classi?cation
更新于2025-09-09 09:28:46