scholarly journals Variation in Infrared Reflectance of Eucalyptus Radiata Dc.

1971 ◽  
Vol 24 (4) ◽  
pp. 945
Author(s):  
R Story ◽  
GA Yapp
Keyword(s):  
Water Stress ◽  
Infrared Reflectance ◽  
Green Plants ◽  
Colour Image ◽  
Infrared Wavelengths ◽  
Lower Reflectance ◽  
False Colour

Various workers have reported that green plants which are diseased or in need of water have a lower infrared reflectance and consequently a blue image on false colour film. The infrared reflectance of E. radiata leaves rises as they become dry, and produces no blueness of the false colour image. It is suggested that blue images of E. radiata recorded in the field are due to lower reflectance of the infrared wavelengths by flowers. Water stress is not likely to be detected on false colour film until the plants are visibly affected.

Satellite Detection of Water Stress Effects on Terrestrial Latent Heat Flux With MODIS Shortwave Infrared Reflectance Data

2018 ◽  
Vol 123 (20) ◽  
pp. 11,410-11,430 ◽  
Author(s):  
Yunjun Yao ◽  
Shunlin Liang ◽  
Bao Cao ◽  
Shaomin Liu ◽  
Guirui Yu ◽  
...  
Keyword(s):  
Heat Flux ◽  
Water Stress ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Infrared Reflectance ◽  
Stress Effects ◽  
Shortwave Infrared ◽  
Reflectance Data

scholarly journals Fusion of Unmanned Aerial Vehicle Panchromatic and Hyperspectral Images Combining Joint Skewness-Kurtosis Figures and a Non-Subsampled Contourlet Transform

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3467 ◽  
Author(s):  
Jinling Zhao ◽  
Chengquan Zhou ◽  
Linsheng Huang ◽  
Xiaodong Yang ◽  
Bo Xu ◽  
...  
Keyword(s):  
Unmanned Aerial Vehicle ◽  
Contourlet Transform ◽  
Area Index ◽  
Spatial Entropy ◽  
Colour Image ◽  
Central Pixel ◽  
Fused Image ◽  
Aerial Vehicle ◽  
False Colour ◽  
Stage Stage

To obtain fine and potential features, a highly informative fused image created by merging multiple images is usually required. In our study, a novel fusion algorithm called JSKF-NSCT is proposed for fusing panchromatic (PAN) and hyperspectral (HS) images by combining the joint skewness-kurtosis figure (JSKF) and the non-subsampled contourlet transform (NSCT). The JSKF model is used first to derive the three most sensitive bands from the original HS image according to the product of the skewness and the kurtosis coefficients of each band. Afterwards, an intensity-hue-saturation (IHS) transform is used to obtain the luminance component I of the produced false-colour image consisting of the above three bands. Then the NSCT method is used to decompose component I of the false-colour image and the PAN image. The weight-selection rule based on the regional energy is adopted to acquire the low-frequency coefficients and the correlation between the central pixel and its surrounding pixels is used to select the high-frequency coefficients. Finally, the fused image is obtained by applying an IHS inverse transform and an inverse NSCT transform. The unmanned aerial vehicle (UAV) HS and PAN images under low- and high-vegetation coverage of wheat at the flag leaf stage (Stage I) and the grain filling stage (Stage II) are used as the sample data sources. The fusion results are comparatively validated using spatial (entropy, standard deviation, average gradient and mean) and spectral (normalised difference vegetation, NDVI, and leaf area index, LAI) assessments. Additional comparative studies using anomaly detection and pixel clustering also demonstrate that the proposed method outperforms other methods. They show that the algorithm reported herein can better preserve the original spatial and spectral characteristics of the two types of images to be fused and is more stable than IHS, principal components analysis (PCA), non-negative matrix factorization (NMF) and Gram-Schmidt (GS).

Green Plants

2000 ◽  
Author(s):  
Peter R. Bell ◽  
Alan R. Hemsley
Keyword(s):  
Green Plants

Biscogniauxia (Hypoxylon) Canker or Dieback in Trees

EDIS ◽  
2017 ◽  
Vol 2017 (6) ◽  
Author(s):  
Claudia Paez ◽  
Jason A. Smith
Keyword(s):  
Water Stress ◽  
Tree Species ◽  
Soil Compaction ◽  
Urban Areas ◽  
Root Disease ◽  
Poor Health ◽  
Green Spaces ◽  
Opportunistic Pathogens ◽  
Wide Range ◽  
Quercus Spp

Biscogniauxia canker or dieback (formerly called Hypoxylon canker or dieback) is a common contributor to poor health and decay in a wide range of tree species (Balbalian & Henn 2014). This disease is caused by several species of fungi in the genus Biscogniauxia (formerly Hypoxylon). B. atropunctata or B. mediterranea are usually the species found on Quercus spp. and other hosts in Florida, affecting trees growing in many different habitats, such as forests, parks, green spaces and urban areas (McBride & Appel, 2009).  Typically, species of Biscogniauxia are opportunistic pathogens that do not affect healthy and vigorous trees; some species are more virulent than others. However, once they infect trees under stress (water stress, root disease, soil compaction, construction damage etc.) they can quickly colonize the host. Once a tree is infected and fruiting structures of the fungus are evident, the tree is not likely to survive especially if the infection is in the tree's trunk (Anderson et al., 1995).

Citrus Irrigation Management

EDIS ◽  
2017 ◽  
Vol 2017 (5) ◽  
Author(s):  
Davie Mayeso Kadyampakeni ◽  
Kelly T. Morgan ◽  
Mongi Zekri ◽  
Rhuanito Ferrarezi ◽  
Arnold Schumann ◽  
...  
Keyword(s):  
Water Stress ◽  
Physiological Activity ◽  
Irrigation Management ◽  
Fruit Size ◽  
Irrigation Scheduling ◽  
Leaf Expansion ◽  
Tree Canopy ◽  
Limiting Factor ◽  
Irrigation Frequency ◽  
Citrus Production

Water is a limiting factor in Florida citrus production during the majority of the year because of the low water holding capacity of sandy soils resulting from low clay and the non-uniform distribution of the rainfall. In Florida, the major portion of rainfall comes in June through September. However, rainfall is scarce during the dry period from February through May, which coincides with the critical stages of bloom, leaf expansion, fruit set, and fruit enlargement. Irrigation is practiced to provide water when rainfall is not sufficient or timely to meet water needs. Proper irrigation scheduling is the application of water to crops only when needed and only in the amounts needed; that is, determining when to irrigate and how much water to apply. With proper irrigation scheduling, yield will not be limited by water stress. With citrus greening (HLB), irrigation scheduling is becoming more important and critical and growers cannot afford water stress or water excess. Any degree of water stress or imbalance can produce a deleterious change in physiological activity of growth and production of citrus trees.  The number of fruit, fruit size, and tree canopy are reduced and premature fruit drop is increased with water stress.  Extension growth in shoots and roots and leaf expansion are all negatively impacted by water stress. Other benefits of proper irrigation scheduling include reduced loss of nutrients from leaching as a result of excess water applications and reduced pollution of groundwater or surface waters from the leaching of nutrients. Recent studies have shown that for HLB-affected trees, irrigation frequency should increase and irrigation amounts should decrease to minimize water stress from drought stress or water excess, while ensuring optimal water availability in the rootzone at all times.

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