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Publisher: Elsevier   (Total: 3184 journals)

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Showing 1 - 200 of 3184 Journals sorted alphabetically
Academic Pediatrics     Hybrid Journal   (Followers: 37, SJR: 1.655, CiteScore: 2)
Academic Radiology     Hybrid Journal   (Followers: 25, SJR: 1.015, CiteScore: 2)
Accident Analysis & Prevention     Partially Free   (Followers: 100, SJR: 1.462, CiteScore: 3)
Accounting Forum     Hybrid Journal   (Followers: 27, SJR: 0.932, CiteScore: 2)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 37, SJR: 1.771, CiteScore: 3)
Achievements in the Life Sciences     Open Access   (Followers: 5)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 7)
Acta Astronautica     Hybrid Journal   (Followers: 430, SJR: 0.758, CiteScore: 2)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 2)
Acta Biomaterialia     Hybrid Journal   (Followers: 28, SJR: 1.967, CiteScore: 7)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription   (Followers: 3)
Acta de Investigación Psicológica     Open Access   (Followers: 3)
Acta Ecologica Sinica     Open Access   (Followers: 10, SJR: 0.18, CiteScore: 1)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.661, CiteScore: 2)
Acta Materialia     Hybrid Journal   (Followers: 293, SJR: 3.263, CiteScore: 6)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 6, SJR: 0.504, CiteScore: 1)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.542, CiteScore: 1)
Acta Oecologica     Hybrid Journal   (Followers: 12, SJR: 0.834, CiteScore: 2)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription  
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 2, SJR: 0.307, CiteScore: 0)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 1, SJR: 1.793, CiteScore: 6)
Acta Poética     Open Access   (Followers: 4, SJR: 0.101, CiteScore: 0)
Acta Psychologica     Hybrid Journal   (Followers: 26, SJR: 1.331, CiteScore: 2)
Acta Sociológica     Open Access   (Followers: 1)
Acta Tropica     Hybrid Journal   (Followers: 6, SJR: 1.052, CiteScore: 2)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 3, SJR: 0.374, CiteScore: 1)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 2)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 3, SJR: 0.344, CiteScore: 1)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 1)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 7, SJR: 0.19, CiteScore: 0)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 3)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 8)
Acute Pain     Full-text available via subscription   (Followers: 15, SJR: 2.671, CiteScore: 5)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.53, CiteScore: 4)
Addictive Behaviors     Hybrid Journal   (Followers: 17, SJR: 1.29, CiteScore: 3)
Addictive Behaviors Reports     Open Access   (Followers: 9, SJR: 0.755, CiteScore: 2)
Additive Manufacturing     Hybrid Journal   (Followers: 11, SJR: 2.611, CiteScore: 8)
Additives for Polymers     Full-text available via subscription   (Followers: 23)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 180, SJR: 4.09, CiteScore: 13)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 12, SJR: 1.167, CiteScore: 4)
Advanced Powder Technology     Hybrid Journal   (Followers: 17, SJR: 0.694, CiteScore: 3)
Advances in Accounting     Hybrid Journal   (Followers: 9, SJR: 0.277, CiteScore: 1)
Advances in Agronomy     Full-text available via subscription   (Followers: 16, SJR: 2.384, CiteScore: 5)
Advances in Anesthesia     Full-text available via subscription   (Followers: 28, SJR: 0.126, CiteScore: 0)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 2)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 11, SJR: 0.992, CiteScore: 1)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 11, SJR: 1.551, CiteScore: 4)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 24, SJR: 2.089, CiteScore: 5)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 15, SJR: 0.572, CiteScore: 2)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.61, CiteScore: 7)
Advances in Botanical Research     Full-text available via subscription   (Followers: 2, SJR: 0.686, CiteScore: 2)
Advances in Cancer Research     Full-text available via subscription   (Followers: 32, SJR: 3.043, CiteScore: 6)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 9, SJR: 1.453, CiteScore: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 5, SJR: 1.992, CiteScore: 5)
Advances in Cell Aging and Gerontology     Full-text available via subscription   (Followers: 5)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 14)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 28, SJR: 0.156, CiteScore: 1)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 10, SJR: 0.713, CiteScore: 1)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 10, SJR: 1.316, CiteScore: 2)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 26, SJR: 1.562, CiteScore: 3)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 20, SJR: 1.977, CiteScore: 8)
Advances in Computers     Full-text available via subscription   (Followers: 14, SJR: 0.205, CiteScore: 1)
Advances in Dermatology     Full-text available via subscription   (Followers: 15)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 13)
Advances in Digestive Medicine     Open Access   (Followers: 11)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 7)
Advances in Drug Research     Full-text available via subscription   (Followers: 26)
Advances in Ecological Research     Full-text available via subscription   (Followers: 43, SJR: 2.524, CiteScore: 4)
Advances in Engineering Software     Hybrid Journal   (Followers: 29, SJR: 1.159, CiteScore: 4)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 8)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 49, SJR: 5.39, CiteScore: 8)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 1)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 9)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 62, SJR: 0.591, CiteScore: 2)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 17)
Advances in Genetics     Full-text available via subscription   (Followers: 20, SJR: 1.354, CiteScore: 4)
Advances in Genome Biology     Full-text available via subscription   (Followers: 10, SJR: 12.74, CiteScore: 13)
Advances in Geophysics     Full-text available via subscription   (Followers: 6, SJR: 1.193, CiteScore: 3)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 24, SJR: 0.368, CiteScore: 1)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 12, SJR: 0.749, CiteScore: 3)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 23)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 3, SJR: 0.193, CiteScore: 0)
Advances in Immunology     Full-text available via subscription   (Followers: 36, SJR: 4.433, CiteScore: 6)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 10, SJR: 1.163, CiteScore: 2)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 2, SJR: 1.938, CiteScore: 3)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 6, SJR: 0.176, CiteScore: 0)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 3)
Advances in Life Course Research     Hybrid Journal   (Followers: 8, SJR: 0.682, CiteScore: 2)
Advances in Lipobiology     Full-text available via subscription   (Followers: 1)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 8)
Advances in Marine Biology     Full-text available via subscription   (Followers: 20, SJR: 0.88, CiteScore: 2)
Advances in Mathematics     Full-text available via subscription   (Followers: 12, SJR: 3.027, CiteScore: 2)
Advances in Medical Sciences     Hybrid Journal   (Followers: 7, SJR: 0.694, CiteScore: 2)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 4, SJR: 1.158, CiteScore: 3)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 23)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 8)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 7, SJR: 0.182, CiteScore: 0)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 4)
Advances in Oncobiology     Full-text available via subscription   (Followers: 2)
Advances in Organ Biology     Full-text available via subscription   (Followers: 2)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 17, SJR: 1.875, CiteScore: 4)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7, SJR: 0.174, CiteScore: 0)
Advances in Parasitology     Full-text available via subscription   (Followers: 5, SJR: 1.579, CiteScore: 4)
Advances in Pediatrics     Full-text available via subscription   (Followers: 25, SJR: 0.461, CiteScore: 1)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 17)
Advances in Pharmacology     Full-text available via subscription   (Followers: 16, SJR: 1.536, CiteScore: 3)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 0.574, CiteScore: 1)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.109, CiteScore: 1)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 10)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 5)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 19)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20, SJR: 0.791, CiteScore: 2)
Advances in Psychology     Full-text available via subscription   (Followers: 65)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6, SJR: 0.371, CiteScore: 1)
Advances in Radiation Oncology     Open Access   (Followers: 1, SJR: 0.263, CiteScore: 1)
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 3, SJR: 0.101, CiteScore: 0)
Advances in Space Biology and Medicine     Full-text available via subscription   (Followers: 6)
Advances in Space Research     Full-text available via subscription   (Followers: 414, SJR: 0.569, CiteScore: 2)
Advances in Structural Biology     Full-text available via subscription   (Followers: 5)
Advances in Surgery     Full-text available via subscription   (Followers: 13, SJR: 0.555, CiteScore: 2)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 36, SJR: 2.208, CiteScore: 4)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 20)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 15)
Advances in Virus Research     Full-text available via subscription   (Followers: 5, SJR: 2.262, CiteScore: 5)
Advances in Water Resources     Hybrid Journal   (Followers: 51, SJR: 1.551, CiteScore: 3)
Aeolian Research     Hybrid Journal   (Followers: 6, SJR: 1.117, CiteScore: 3)
Aerospace Science and Technology     Hybrid Journal   (Followers: 365, SJR: 0.796, CiteScore: 3)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.42, CiteScore: 2)
African J. of Emergency Medicine     Open Access   (Followers: 6, SJR: 0.296, CiteScore: 0)
Ageing Research Reviews     Hybrid Journal   (Followers: 11, SJR: 3.671, CiteScore: 9)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 468, SJR: 1.238, CiteScore: 3)
Agri Gene     Hybrid Journal   (Followers: 1, SJR: 0.13, CiteScore: 0)
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 17, SJR: 1.818, CiteScore: 5)
Agricultural Systems     Hybrid Journal   (Followers: 31, SJR: 1.156, CiteScore: 4)
Agricultural Water Management     Hybrid Journal   (Followers: 44, SJR: 1.272, CiteScore: 3)
Agriculture and Agricultural Science Procedia     Open Access   (Followers: 4)
Agriculture and Natural Resources     Open Access   (Followers: 3)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 58, SJR: 1.747, CiteScore: 4)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.589, CiteScore: 3)
Air Medical J.     Hybrid Journal   (Followers: 6, SJR: 0.26, CiteScore: 0)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.19, CiteScore: 0)
Alcohol     Hybrid Journal   (Followers: 12, SJR: 1.153, CiteScore: 3)
Alcoholism and Drug Addiction     Open Access   (Followers: 11)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 2, SJR: 0.604, CiteScore: 3)
Alexandria J. of Medicine     Open Access   (Followers: 1, SJR: 0.191, CiteScore: 1)
Algal Research     Partially Free   (Followers: 11, SJR: 1.142, CiteScore: 4)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 2)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.504, CiteScore: 1)
Allergology Intl.     Open Access   (Followers: 5, SJR: 1.148, CiteScore: 2)
Alpha Omegan     Full-text available via subscription   (SJR: 3.521, CiteScore: 6)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 10, SJR: 0.201, CiteScore: 1)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 53, SJR: 4.66, CiteScore: 10)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 5, SJR: 1.796, CiteScore: 4)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 5, SJR: 1.108, CiteScore: 3)
Ambulatory Pediatrics     Hybrid Journal   (Followers: 6)
American Heart J.     Hybrid Journal   (Followers: 57, SJR: 3.267, CiteScore: 4)
American J. of Cardiology     Hybrid Journal   (Followers: 62, SJR: 1.93, CiteScore: 3)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 45, SJR: 0.604, CiteScore: 1)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 11)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 13, SJR: 1.524, CiteScore: 3)
American J. of Human Genetics     Hybrid Journal   (Followers: 34, SJR: 7.45, CiteScore: 8)
American J. of Infection Control     Hybrid Journal   (Followers: 29, SJR: 1.062, CiteScore: 2)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 35, SJR: 2.973, CiteScore: 4)
American J. of Medicine     Hybrid Journal   (Followers: 49)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3, SJR: 1.967, CiteScore: 2)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 234, SJR: 2.7, CiteScore: 4)
American J. of Ophthalmology     Hybrid Journal   (Followers: 66, SJR: 3.184, CiteScore: 4)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 5, SJR: 0.265, CiteScore: 0)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.289, CiteScore: 1)
American J. of Otolaryngology     Hybrid Journal   (Followers: 25, SJR: 0.59, CiteScore: 1)
American J. of Pathology     Hybrid Journal   (Followers: 30, SJR: 2.139, CiteScore: 4)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 28, SJR: 2.164, CiteScore: 4)
American J. of Surgery     Hybrid Journal   (Followers: 39, SJR: 1.141, CiteScore: 2)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.767, CiteScore: 1)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 7)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.144, CiteScore: 3)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 63, SJR: 0.138, CiteScore: 0)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 20, SJR: 0.411, CiteScore: 1)
Anales de Cirugia Vascular     Full-text available via subscription   (Followers: 1)
Anales de Pediatría     Full-text available via subscription   (Followers: 3, SJR: 0.277, CiteScore: 0)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription  
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 5, SJR: 4.849, CiteScore: 10)
Analytica Chimica Acta     Hybrid Journal   (Followers: 44, SJR: 1.512, CiteScore: 5)
Analytica Chimica Acta : X     Open Access  
Analytical Biochemistry     Hybrid Journal   (Followers: 202, SJR: 0.633, CiteScore: 2)
Analytical Chemistry Research     Open Access   (Followers: 12, SJR: 0.411, CiteScore: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 14)
Anesthésie & Réanimation     Full-text available via subscription   (Followers: 2)
Anesthesiology Clinics     Full-text available via subscription   (Followers: 24, SJR: 0.683, CiteScore: 2)
Angiología     Full-text available via subscription   (SJR: 0.121, CiteScore: 0)
Angiologia e Cirurgia Vascular     Open Access   (Followers: 1, SJR: 0.111, CiteScore: 0)
Animal Behaviour     Hybrid Journal   (Followers: 208, SJR: 1.58, CiteScore: 3)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 6, SJR: 0.937, CiteScore: 2)
Animal Reproduction Science     Hybrid Journal   (Followers: 7, SJR: 0.704, CiteScore: 2)

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Similar Journals
Journal Cover
Agricultural and Forest Meteorology
Journal Prestige (SJR): 1.818
Citation Impact (citeScore): 5
Number of Followers: 17  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0168-1923
Published by Elsevier Homepage  [3184 journals]
  • Three dimensional mapping of forest canopy equivalent water thickness
           using dual-wavelength terrestrial laser scanning
    • Abstract: Publication date: 15 October 2019Source: Agricultural and Forest Meteorology, Volumes 276–277Author(s): Ahmed Elsherif, Rachel Gaulton, Alexander Shenkin, Yadvinder Malhi, Jon Mills Globally, forests are being subjected to numerous threats, including climate change, wildfires, and insect and disease outbreaks, among others. Satellite optical remote sensing data have been widely utilized in early detection of tree and forest stress by estimating water status metrics such as the leaf Equivalent Water Thickness (EWT). This estimate, however, is affected by soil characteristics and understory vegetation and often ignores the effects of the fine-scale heterogeneity of canopy structure and leaf water content. Such effects can be better understood by studying the EWT distribution in three dimensions. In this study, Terrestrial Laser Scanning (TLS) intensity data from the commercially-available Leica P20 and P40 instruments (808 nm and 1550 nm respectively) were combined in a Normalized Difference Index (NDI). NDI was used to map EWT of 12 trees in three dimensions from floor to canopy in a mixed broadleaf forest plot (Wytham Woods, UK). The average error in EWT estimates across three species was less than 8%. The three dimensional point clouds revealed that, in this snapshot, EWT changes vertically, usually increasing towards canopy top. The proposed method has the potential to provide predawn EWT measurements, is independent of solar illumination, and can lead to a better understanding of the factors affecting satellite estimation of EWT.
  • Estimating canopy gap fraction and diffuse light interception in 3D maize
           canopy using hierarchical hemispheres
    • Abstract: Publication date: 15 October 2019Source: Agricultural and Forest Meteorology, Volumes 276–277Author(s): Weiliang Wen, Xinyu Guo, Baojun Li, Chuanyu Wang, Yongjian Wang, Zetao Yu, Sheng Wu, Jiangchuan Fan, Shenghao Gu, Xianju Lu Studying the detailed organization of plant canopy structure allows a better understanding of functional processes in functional-structural plant models (FSPM). Canopy gap fraction (CGF) is an important indicator describing the canopy structure and affects the way plants capture light to perform photosynthesis, especially the interception of diffuse light. Though efforts have been made to improve the accuracy and efficiency of CGF measurement and estimation, current technologies are usually position limited. Thus, this work developed new virtual methods for computing CGF and diffuse light interception in the 3D space of plant canopies. Five hierarchical hemispheres, containing 15, 40, 360, 1,440, and 5760 triangle patches, respectively, were constructed by applying Sqrt-3 and Butterfly subdivision schemes on an original icosahedron. Compared with traditional hemisphere division strategies using solid angles or crossed arcs of latitude and longitude, the proposed hierarchical hemispheres provide more resolution choices for different accuracy demands. Most of the patches on the hemispheres are regular triangles with similar sizes, which improves the CGF and diffuse light calculation accuracy using the Turtle model. Acceleration mechanism was built when calculating the detection of plant facets in the canopy using the tree relationship between adjacent hemispheres. Two geometric models and six maize canopy geometric models with cultivar and density differences were constructed using measured data to validate the approach. The maximum CGF error was 1.39% for the two geometric models. The average error of the four derived CGFs from hemisphere photographs was 4.23%. The diffuse light distribution correlation coefficients R2 were 0.96, 0.98, and 0.90 for three different canopy densities. Our algorithm provides multi-scale hemisphere choices for CGF and diffuse light interception simulation. The study also paves the way for further investigation into plant canopy structure analysis and simulation of light dynamics in plant canopies.
  • Reconstructing the effects of hurricanes over 155 years on the structure
           and diversity of trees in two tropical montane rainforests in Jamaica
    • Abstract: Publication date: 15 October 2019Source: Agricultural and Forest Meteorology, Volumes 276–277Author(s): Kurt McLaren, Denneko Luke, Edmund Tanner, Peter J. Bellingham, John R. Healey The effects of the spatiotemporal (> 100 years) range of hurricane disturbance intensity on tree diversity and density patterns are largely unknown, because data on past stand or landscape scale hurricane impacts are sometimes unavailable. We therefore reconstructed and mapped topographic exposure (a proxy to disturbance) to twelve category 2–4 hurricanes that affected the rain forests of the Blue Mountains (BM) and the John Crow Mountains (JCM) in Jamaica, over 155 years. Maps of average topographic exposure and the spatial outputs from a pixel-based polynomial regression of the cardinal directions of the tracks of past hurricanes (predictor) and past exposure (response) were then used to represent the aggregate spatiotemporal range of exposure. Next, we used data collected over the period 1974–2009 from 35, 10 x 10 m nested subplots and 1991 to 2004 from 16, 200 m2 circular plots for the BM and 2006–2012 from 45, 25 x 25 m plots for the JCM, and Bayesian spatiotemporal, Integrated Nested Laplace Approximation (INLA) models to determine whether stand-level (≈ 1 km2) tree Shannon diversity and density patterns were primarily influenced by exposure to a single hurricane, the most severe hurricane or to multiple hurricanes and the duration of hurricane effects on Shannon diversity and tree density. In the BM, long-term diversity peaked at locations with intermediate values of average exposure for six hurricanes (five of which made landfall over the period 1903–1988). Short-term diversity peaked at locations that experienced significantly higher exposure situated to the south or north of the hurricane’s track when the tracks were to the north or south of the island, respectively. Short-term density peaked at locations that were always highly exposed. Moreover, the influence of the most severe hurricane on diversity can last up to 101 years and the influence of the most recent hurricane (Gilbert) on diversity became evident after 16–21 years. The JCM were more susceptible to hurricanes and this diminished the influence of past hurricanes. Consequently, density peaked at sites with the highest average exposure to the four most recent hurricanes (1988–2007), only one of which made landfall. If historical hurricane disturbance data are unavailable, reconstructed exposure maps can be used to provide valuable insights into the effects of past hurricanes on stand-level tree diversity and density patterns.
  • Plant water use strategies indicated by isotopic signatures of leaf water:
           Observations in southern and northern China
    • Abstract: Publication date: 15 October 2019Source: Agricultural and Forest Meteorology, Volumes 276–277Author(s): Lucheng Zhan, Jiansheng Chen, Ling Li, Pei Xin Plants act as an important component in the terrestrial hydrosphere. To determine the relationship between vegetation and hydrosphere under different climate conditions of China, large-scale investigations and sampling campaigns were conducted in typical humid lake areas of southern China and in semiarid–arid regions of northern China. Hydrogen and oxygen isotopic signatures were used to reveal the water utilization characteristics of plants in these areas. The results suggest that isotopic signatures of plant leaf water can effectively indicate the water source used by plants. Vegetation in humid lake areas relies mainly on water supplement from surface water, whereas groundwater constitutes the primary water source for plant survival in semiarid–arid areas. The differences in the water utilization strategies of plants suggest considerable differences in the local hydrological processes between southern and northern China. Unlike the humid areas of southern China, the dependence of plants on groundwater in semiarid–arid northern China implies the difficulty for the sparse rainfall to infiltrate and recharge the groundwater system. This study demonstrated that the analysis of plant leaf isotopic signatures could constitute a useful method for further study of the controversial groundwater origin in northern China, which is important for maintaining ecological balance and alleviating the effects of serious water shortages.
  • Soil respiration in a tropical montane grassland ecosystem is largely
           heterotroph-driven and increases under simulated warming
    • Abstract: Publication date: 15 October 2019Source: Agricultural and Forest Meteorology, Volumes 276–277Author(s): Yadugiri V. Tiruvaimozhi, Mahesh Sankaran Soil respiration, a major source of atmospheric carbon (C), can feed into climate warming, which in turn can amplify soil CO2 efflux by affecting respiration by plant roots, arbuscular mycorrhizal fungi (AMF) and other heterotrophic organisms. Although tropical ecosystems contribute>60% of the global soil CO2 efflux, there is currently a dearth of data on tropical soil respiration responses to increasing temperature. Here we report a simulated warming and soil respiration partitioning experiment in tropical montane grasslands in the Western Ghats in southern India. The study aimed to (a) evaluate soil respiration responses to warming, (b) assess the relative contributions of autotrophic and heterotrophic components to soil respiration, and (c) assess the roles of soil temperature and soil moisture in influencing soil respiration in this system. Soil respiration was tightly coupled with instantaneous soil moisture availability in both the warmed and control plots, with CO2 efflux levels peaking during the wet season. Soil warming by ˜1.4 °C nearly doubled soil respiration from 0.62 g CO2 m−2 hr−1 under ambient conditions to 1.16 g CO2  m−2 hr−1 under warmed conditions. Warming effects on soil CO2 efflux were dependent on water availability, with greater relative increases in soil respiration observed under conditions of low (with a minimum of 2.6%), compared to high (with a maximum of 64.3%), soil moisture. Heterotrophs contributed to the majority of soil CO2 efflux, with respiration remaining unchanged when roots and/or AMF hyphae were excluded as the partitioning treatments were statistically indistinguishable. Overall, our results indicate that future warming is likely to substantially increase the largely heterotroph-driven soil C fluxes in this tropical montane grassland ecosystem.
  • Differential responses of soil quality in revegetation types to
           precipitation gradients on the Loess Plateau
    • Abstract: Publication date: 15 October 2019Source: Agricultural and Forest Meteorology, Volumes 276–277Author(s): Shujuan Guo, Yadong Xu, Chao He, Shaojun Wu, Chengjie Ren, Xinhui Han, Yongzhong Feng, Guangxin Ren, Gaihe Yang Vegetation restoration can control soil erosion and improve soil quality; however, these positive effects on soil quality can be challenged with inceasing aridity. It is vital to understand the mechanisms affecting soil quality along aridity gradients and to determine the appropriate revegetation types for soil restoration. In this study, we selected three revegetation types (forest, shrub, and grass) along four precipitation gradients (365, 452, 507, and 600 mm mean annual precipitation [MAP]) to analyze the changes in soil properties from two soil layers (0–10 and 10–20 cm). To quantify the variations in soil quality, a soil quality index (SQI) combining the chemical, physical, and biological properties was developed. The results showed that the SQI was formed based on total nitrogen, clay, urease, and pH. In both soil layers, SQI values increased significantly (P 
  • Nitrogen supply and other controls of carbon uptake of understory
           vegetation in a boreal Picea abies forest
    • Abstract: Publication date: 15 October 2019Source: Agricultural and Forest Meteorology, Volumes 276–277Author(s): Sari Palmroth, Lisbet H. Bach, Marie Lindh, Pasi Kolari, Annika Nordin, Kristin Palmqvist In boreal forests, carbon (C) uptake by understory may be too large to be ignored and too variable in space to be assumed a constant fraction of the ecosystem gross primary production. To improve estimates of understory production in these ecosystems, we need to better account for its main controls. In this study, we estimated C uptake of field-layer vegetation, dominated by Vaccinium myrtillus, V. vitis-idaea, and Deschampsia flexuosa, in a boreal Picea abies stand in northern Sweden. Nitrogen (N) availability in the stand has been manipulated through annual N additions since 1996 at the rates of 0, 12.5, and 50 kg N ha−1 yr−1. To assess the relative importance of N supply, and interannual fluctuations in leaf biomass and weather, in controlling field-layer photosynthetic production, we calculated C uptake over eight growing seasons using a canopy photosynthesis model. Without N additions, tree leaf area index (L) was already high (8.5) and field-layer C uptake was small, 27 g C m−2 (or ∼3% of stand C uptake). An increase in tree L with N additions further reduced light availability for the understory, yet the concurrent increase in the relative abundance of the more physiologically active D. flexuosa sustained the contribution of the field-layer to stand photosynthetic production. Based on a literature survey, in which site quality or stand age generated a wide range in L, understory contribution to ecosystem C uptake increases linearly with the fraction of available light reaching the forest floor across high latitude forests. Understory contributes only ∼5% to ecosystem C uptake where trees intercept ∼80% of incoming light, increasing to 100% after clearcut tree harvest. While the availability of solar energy, both spatially and temporally, is the primary driver of understory production, our analyses suggest that the predicted increases in drought severity and frequency at high latitudes may affect understory communities more than trees. Future empirical and modeling studies should focus on functional and ecological responses to drought of not only trees but also understory species, which contribute to biodiversity and convert their photosynthates to important non-timber products.
  • Spatial complexity and temporal dynamics in viticulture: A review of
           climate-driven scales
    • Abstract: Publication date: 15 October 2019Source: Agricultural and Forest Meteorology, Volumes 276–277Author(s): Etienne Neethling, Gérard Barbeau, Cécile Coulon-Leroy, Hervé Quénol Viticulture is a complex and dynamic system, where climate is a key environmental component of plant suitability and productivity. From field to farm level, climate also plays a prominent role in ongoing practices, shaping winegrowers’ decision making and adaptive management. With a changing climate, the wine sector faces many environmental and socio-economic challenges, to which winegrowers are required to adapt. Given the perennial nature of grape growing, there is a need to develop strategies that deal with both short- and long-term climate changes, while likewise accounting for contextual vulnerability. The content of this article aims to provide an overview of climate-driven scales, outlining the spatial complexity and temporal dynamics in viticulture. In addressing these aspects, this literature review offers a framework of scale and cross-scale interactions for policymakers and stakeholders to use when considering responses to attenuate climate change and to reduce its impacts on grape and wine production. The article concludes by discussing the local and context-dependent nature of viticulture in a changing global climate, by emphasizing that the question of scale is fundamental to assessing expected impacts, understanding uncertainty and framing sustainable policies and responses over space and in time.
  • Exploring interactive effects of climate change and exotic pathogens on
           Quercus suber performance: Damage caused by Phytophthora cinnamomi varies
           across contrasting scenarios of soil moisture
    • Abstract: Publication date: 15 October 2019Source: Agricultural and Forest Meteorology, Volumes 276–277Author(s): Pablo Homet, Mario González, Luis Matías, Oscar Godoy, Ignacio M. Pérez-Ramos, Luis V. García, Lorena Gómez-Aparicio Climate change and exotic pests and pathogens are causing alarming forest declines worldwide. However, we still lack a comprehensive understanding of how damage caused by exotic pests and pathogens might vary under the different scenarios of water availability imposed by a changing climate, particularly in water-limited forests as those that occupy Mediterranean areas. In this paper we aimed to experimentally analyse the interactive effects of the aggressive exotic pathogen Phytophthora cinnamomi and climate change-related reductions in soil moisture on seedling performance of the Mediterranean host Quercus suber. We conducted a full-factorial greenhouse experiment where the physiology and growth of Q. suber seedlings was measured in soils with different combinations of P. cinnamomi inoculum density (0, 30, 60 and 120 colony forming units per gram of dry soil) and soil moisture (15%, 40%, 50% and 100% soil water holding capacity) simulating different invasion and climate change scenarios. We found additive effects of P. cinnamomi and drought on Q. suber performance aboveground, although these effects were not always negative. In fact, seedlings showed a compensatory physiological response to P. cinnamomi infection by increasing their net photosynthetic rates. Our results also supported important interactive effects of pathogens and soil moisture on belowground performance. Thus, the inoculum density in the soil required to cause significant root damage in experimental seedlings decreased as soil moisture increased. From a climate change perspective, these results suggest that an average drier climate might imply sub-optimal conditions for P. cinnamomi infections allowing for a slower advance of the disease in invaded areas. However, this effect will be modulated by the also predicted more frequent extreme climatic events. A higher frequency of extreme rain events that saturate the soil might be particularly beneficial for P. cinnamomi, boosting its soil density beyond any possible response capacity of susceptible hosts.
  • Adjustment of CO2 flux measurements due to the bias in the EC150 infrared
           gas analyzer
    • Abstract: Publication date: 15 October 2019Source: Agricultural and Forest Meteorology, Volumes 276–277Author(s): Eric S. Russell, Victoria Dziekan, Jinshu Chi, Sarah Waldo, Shelley N. Pressley, Patrick O’Keeffe, Brian K. Lamb During the Regional Approaches to Climate Change (REACCH) program, eddy covariance monitoring over agricultural fields were used to estimate annual carbon and water budgets in the inland Pacific Northwest. Here, we assess the effect of a bias in the high-frequency CO2 concentration measurements using the Campbell Scientific EC150 infra-red gas analyzer on the CO2 fluxes and field-scale carbon balances. The bias stems from using a lower frequency temperature measurement to calculate the CO2 density, which misses higher frequency temperature fluctuations. To generate the bias adjustment, data were collected over four similar agricultural sites as part of the Long-Term Agroecosystem Research network for multiple months using the same four instrument sets used in the REACCH project. The difference between the high-frequency and low-frequency CO2 fluxes were regressed against the kinematic heat fluxes to generate a correction equation for each instrument set, which were applied to the historical REACCH data to determine the effect of the bias on the measured and gap-filled flux values. The re-calculated positive biases in the measured fluxes were 40 gC-CO2 m−2 yr-1 to 126 gC-CO2 m−2 yr-1, indicating greater losses to the atmosphere than initially estimated. Once gap-filled, three out of fourteen site-years switched from weak carbon sinks to weak carbon sources. When the carbon exported via harvest was included in the budget calculation the bias correction still impacted the source/sink strength but did not change the sign of the carbon balance. Overall, the total net ecosystem exchange decreased between 300–470 gC-CO2 m-2 per site (29–46%) over the 4 crop-years from the bias adjustment process.
  • Comparison of surface foil materials and dew collectors location in an
           arid area: a one-year field experiment in Kenya
    • Abstract: Publication date: 15 October 2019Source: Agricultural and Forest Meteorology, Volumes 276–277Author(s): J. Tuure, A. Korpela, M. Hautala, M. Hakojärvi, H. Mikkola, M. Räsänen, J. Duplissy, P. Pellikka, T. Petäjä, M. Kulmala, L. Alakukku This study characterized different polyethylene (PE) and polyvinyl chloride (PVC) plastic foil materials effectiveness for dew collection in arid field-conditions in Kenya. Dew yields were collected daily for one year. Ten dew collectors with four different plastic foils were setup in the experimental field. The cumulated dew yields ranged from 18.9 to 25.3 mm. The greatest cumulated dew yields were 25.3 mm (nightly mean 0.096 mm) and 24.3 mm (nightly mean 0.093) measured with PVC and OPUR coated collectors respectively. The lowest cumulated dew yields 18.9 mm (nightly mean 0.075 mm) and 19.1 mm (nightly mean 0.074 mm) were measured with PVC and PE coated collectors respectively. Dew provided a continuous water source during the dry season. The type of the surface material was not found to be a determining factor for the collected dew yield. The location of the collector at the experimental field had impact on the collected dew yields. We also compared harvested dew yields to measured meteorological parameters and calculated dew yields with the use of a diffusion model using the measured surface temperatures and coefficient of mass diffusion to evaluate the dew collecting potential under the prevailing conditions.
  • Mapping daily evapotranspiration over a large irrigation district from
           MODIS data using a novel hybrid dual-source coupling model
    • Abstract: Publication date: 15 October 2019Source: Agricultural and Forest Meteorology, Volumes 276–277Author(s): Bing Yu, Songhao Shang, Wenbin Zhu, Pierre Gentine, Yu Cheng Accurate knowledge of spatially distributed evapotranspiration (ET) is essential for better understanding the availability and utilization of water resources. Over the past several decades, remote sensing (RS) technique has been widely applied to acquire indispensable input data for the estimation of ET at different spatial and temporal scales. Several dual-source ET models that can partition evaporation and transpiration have been developed by utilizing remote sensing data and ancillary meteorological observations. However, due to the significant spatial variability of air temperature over heterogeneous land surface, these models typically cannot be applied in heterogeneous regions with scarce meteorological observations. In the present study, a new model, referred to as the HTEM-ABL model, is developed by coupling the Hybrid dual-source scheme and Trapezoid framework-based ET Model (HTEM) with a simple atmospheric boundary layer (ABL) model for ET estimation without ancillary air temperature observations. This model uses Moderate Resolution Imaging Spectroradiometer (MODIS) data as the main input and is evaluated with field observations over a large irrigation district in North China. Results show that the HTEM-ABL model can be well applied to the study area, and the accuracy of HTEM-ABL model is slightly superior to the original HTEM model. The root mean square errors between the calculated and measured ET are 0.63 mm/day and 29.6 mm/year at the field scale and the regional scale, respectively. Furthermore, the estimated air temperature has been proved to be accurate qualitatively and quantitatively, and provides another aspect to evaluate the HTEM-ABL model. The spatial and temporal distributions of ET produced by the HTEM-ABL model are in good agreement with both the distribution of land use types and the variations of crop growth stages. In addition, the HTEM-ABL model shows less sensitivity to land surface temperature compared with the original HTEM model.
  • Multi-scale temporal variation in methane emission from an alpine peatland
           on the Eastern Qinghai-Tibetan Plateau and associated environmental
    • Abstract: Publication date: 15 October 2019Source: Agricultural and Forest Meteorology, Volumes 276–277Author(s): Haijun Peng, Qian Guo, Hanwei Ding, Bing Hong, Yongxuan Zhu, Yetang Hong, Cheng Cai, Yu Wang, Linggui Yuan Most previous studies on methane (CH4) emissions from peatlands have focused on the boreal, subarctic, and tropical regions. Little is known about CH4 emissions from the alpine peatlands that are widely distributed in the eastern Qinghai-Tibetan Plateau (QTP), which are sensitive to climate change and human disturbance. To assess the magnitudes of daily and seasonal variations in CH4 flux in this area, and to identify the influential environmental factors, an eddy covariance (EC) tower with a LI-7700 open-path CH4 analyzer was established on Hongyuan Peatland. Total annual CH4 emission was 46.8 g CH4 m-2 in 2014, with emissions in the non-growing season accounting for 25% of the annual total. From May to September 2014, diurnal variation in CH4 emissions was observed, with CH4 fluxes varying between 0.15 and 0.25 μmol m-2 s-1. In contrast, during all other periods of 2014, no diurnal variation was observed, and CH4 flux varied below 0.05 μmol m-2 s-1. A clear seasonal pattern in CH4 exchange with small surges in CH4 emission appeared in soil thawing and freezing seasons. Wavelet analysis was applied to the continuous CH4 flux time series to explore temporal variation in ecosystem CH4 exchange during the growing season. On daily timescales, changes in CH4 flux are in phase with changes in air temperature, and influenced by friction velocity and vapor pressure deficit (VPD). On weekly-to-monthly timescales, soil temperature can explain most of the variation in CH4 exchange. Though CH4 fluxes had no apparent correlation with water table level, fluxes were significantly (R2 = 0.86) correlated with soil temperature measured at -25 cm depth, close to the water table level throughout the growing season, suggesting a synergistic effect of water table level and soil temperature on methane emission. This study highlights the need for continuous eddy covariance measurements and time series analysis approaches to adequately describe temporal variability in ecosystem CH4 exchange.
  • Inner log temperatures vary with log direction and forest cover:
           Implications for predicting the phenology of saproxylic insects
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): C.M. Romo, M.K.-F. Bader, S.M. Pawson Ambient temperature is frequently used to model the development of many herbivorous insects. Estimating development rates of cryptic saproxylic species in wood will be biased by the presence of differences between internal log temperatures, where larvae feed, and measured ambient conditions outside of logs. We tested for differences between ambient temperatures at the log surface and internal log temperatures as a function of habitat type (recent clearfell area and pine forest stands), log direction (north- and south-facing), depth (5–20 cm) and season (summer and winter). Internal log temperatures varied from log surface temperatures in all cases and were influenced by depth, depth × habitat, and depth × log direction interactions. A simple constant correction factor could not explain the relationship between log surface and internal log temperatures. Mean internal log temperatures were between 0.88 and 3.68 °C warmer in clearfells compared to forest stands irrespective of log direction or depth. During summer the average daily minimum temperatures were 2.3–4.1 °C warmer in logs compared to the log surface under a conifer canopy and up to 9.8 °C warmer in adjacent recently clearfelled areas. During winter the internal log minimum temperatures were 2.0–2.8 °C warmer under a conifer canopy and 2.6–5.2 °C warmer in recently clearfelled areas compared to log surface temperatures. Differences between log surface and internal minimum temperatures increased consistently with depth into the log. Accurate models that translate observed ambient temperatures to internal log temperatures that are representative of the location of feeding larvae are necessary to model saproxylic insect development at the landscape scale. Results from this study demonstrate that these translation models will have to consider depth, log orientation, and season.
  • Component radiative temperatures over sparsely vegetated surfaces and
           their potential for upscaling land surface temperature
    • Abstract: Publication date: 15 October 2019Source: Agricultural and Forest Meteorology, Volumes 276–277Author(s): Mingsong Li, Ji Zhou, Zhixing Peng, Shaomin Liu, Frank-Michael Göttsche, Xiaodong Zhang, Lisheng Song Ground measured component radiative temperatures are basic inputs for modelling energy and hydrological processes and for simulating land surface temperature (LST) as “viewed” by remote sensors. However, knowledge of factors affecting the component temperatures and about their potential for upscaling LST over sparsely vegetated surfaces with high heterogeneity is still lacking. Here, a MUlti-Scale Observation Experiment on land Surface temperature (MUSOES) was performed under HiWATER over an arid sparsely vegetated surface. Component temperatures were obtained with different instruments on multiple spatial scales; for LST upscaling, a three-dimensional scene model was employed for two forest stations (MFS and PFS) and a two-dimensional model for a shrub station (SUP). Results show that intrinsic characteristics contribute to the temperature variability between different components and even within a single component. Using a thermal infrared (TIR) imager at MFS, average temperature difference of 24.9 K between sunlit bare soil and tree canopy was found; different components exhibit different internal temperature differences at direction-level and pixel-level. Furthermore, illumination conditions, viewing directions, and instrument types significantly affected the measured component temperatures. The measurements of the TIR radiometer and the imager can deviate considerably (e.g. 14.9 K for sunlit bare soil at MFS). When the longwave radiometers were selected as target sensors, the component temperatures measured by the imager exhibit good potential for LST upscaling: the upscaled LST has MBD/RMSD values of 2.0 K/2.3 K at MFS and 2.0 K/2.5 K at PFS. The TIR radiometer’s measurements introduce large uncertainties into LST upscaling at MFS and PFS, but result in good accuracy at SUP, mainly due to its simpler land cover and surface structure. Findings from this study can benefit our understanding of factors affecting observations of component temperatures and the LST upscaling process and are, therefore, relevant for further studying the evaluation of satellite LST products.
  • Improvement of sap flow estimation by including phenological index and
           time-lag effect in back-propagation neural network models
    • Abstract: Publication date: 15 October 2019Source: Agricultural and Forest Meteorology, Volumes 276–277Author(s): Jie Tu, Xiaohua Wei, Bingbing Huang, Houbao Fan, Minfei Jian, Wei Li Sap flow is an important indicator reflecting water transport in a soil-plant-atmosphere continuum system. Therefore, identifying the effects of different factors on sap flow is imperative for understanding its physiological responses to environmental conditions and other associated ecological processes. However, conventional statistical methods have produced unsatisfactory results due to the complex and nonlinear relationship between sap flux density (vs) and its driving factors. This study illustrated the utility of the back-propagation (BP) neural network method for sap flow estimation and compared the performance of BP models with the multiple-linear regression (MLR) technique. Based on the measured sap flow of Pinus massoniana in the field, three-layer BP models trained by the Levenberg-Marquardt algorithm were developed with an architecture of 4-10-1, corresponding to four, ten and one nodes in the input, hidden and output layers, respectively. The BP models were trained and validated in the MATLAB environment with four different combinations of air temperature (Ta), relative humidity (RH), average net radiation (ANR) and the phenological index. High degrees of correlation were observed between the measured and simulated results by BP, and the coefficients of determination (R2) and fitting accuracies (Acc) (greater than 0.9 and 80%, respectively) were higher than the corresponding values from the MLR (0.78 and 69%, respectively). Furthermore, the performance of the BP models could be greatly improved by including the phenological index and a time-lag effect, thereby suggesting that these two factors were crucial variables in modelling vs by BP approaches. The BP models were also tested with cross-validation method and 50% of the collected data that were not used in model development. We conclude that the BP model had a higher degree of accuracy in predicting sap flow due to its superior performance for complicated, nonlinear and uncertain processes, especially with inclusion of the phenological index and time-lag effect.
  • Copula based assessment of meteorological drought characteristics:
           Regional investigation of Iran
    • Abstract: Publication date: 15 October 2019Source: Agricultural and Forest Meteorology, Volumes 276–277Author(s): Sina Nabaei, Ahmad Sharafati, Zaher Mundher Yaseen, Shamsuddin Shahid Arid and semi-arid climate of Iran has made it highly vulnerable to droughts. Comprehensive monitoring of drought characteristics is important for better understanding of drought behaviors for mitigation planning. Spatial analysis of multiple characteristics of meteorological droughts in Iran is conducted in this study using Standardized Precipitation Index (SPI) and Copula functions. Monthly rainfall data of 102 synoptic stations are used to estimate three characteristics of droughts namely Severity (S), Peak (P) and Duration (D). Eight Probability Distribution Functions (PDFs) are used to select the best fit marginal distribution of univariate drought characteristics based on Kolmogorov Smirnov and Chi squared statistics. Archimedean Copulas (Clayton, Frank, and Gumbel) are fitted to the joint S-P, S-D and P-D datasets by Maximum Pseudo Likelihood Estimator (MPLE). The cross-validation Copula Information Criterion (CIC) is used to select the best model according to goodness of fit of the Copulas. The best-fit Copula model is used for the generation of 42 return period maps of different classes of drought characteristics in order to investigate the spatial patterns of joint return period of drought characteristics. Further, the distribution of S, P, and D classes is categorized into different return periods (T) for the generation of maps to facilitate drought management. Results revealed that 1-, 2-, and 3-month mild droughts with slight picks occur mostly in the center of Iran (0 
  • A new spatial modeling and interpolation approach for high-resolution
           temperature maps combining reanalysis data and ground measurements
    • Abstract: Publication date: 15 October 2019Source: Agricultural and Forest Meteorology, Volumes 276–277Author(s): Mariassunta Viggiano, Lorenzo Busetto, Domenico Cimini, Francesco Di Paola, Edoardo Geraldi, Luigi Ranghetti, Elisabetta Ricciardelli, Filomena Romano Despite of their increasing importance as inputs to models for a wide range of scientific fields, high-resolution meteorological variables are not recorded very often on spatially regular grids. This problem is usually overcome by using data from reanalysis models, although they are less accurate. This paper discusses the development of a new spatial downscaling methodology to provide high-resolution maps of daily maximum and minimum air temperature. The application of this approach provides thorough observations in sparsely sampled areas by combining the accuracy of measurements from ground-based stations with the high availability and uniformity of model-based data. The dataset includes more than a decade (2003–2013) of data collected at 113 stations, about 30% of which constituted an independent set for the validation procedure. The efficacy of this approach is evaluated using statistical scores that are regularly employed in model evaluation studies and the improvements over the classical approach are remarkable. The results show that overall the our "hybrid" method provides fair estimates of temperature values. Particularly, MBE is less than 0.29 °C and 0.60 °C for the daily maximum and minimum air temperature respectively; RMSE is less than 1.24 °C for the maximum temperature and 1.86 °C for the minimum temperature, the analysis on MAE assures that there is not contribution of the errors in the spatial variability (MAE ≈ RMSE). The correlation coefficient, close to 1 (ρ ≈ 0.97), indicates a strong positive linear relationship.
  • Surface conductance for evapotranspiration of tropical forests:
           Calculations, variations, and controls
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): Zheng-Hong Tan, Jun-Fu Zhao, Guan-Ze Wang, Meng-Ping Chen, Lian-Yan Yang, Chun-Sheng He, Natalia Restrepo-Coupe, Shu-Shi Peng, Xue-Yan Liu, Humberto R. da Rocha, Yoshiko Kosugi, Takashi Hirano, Scott R. Saleska, Michael L. Goulden, Jiye Zeng, Fang-Jun Ding, Fu Gao, Liang Song Tropical forests are responsible for the evaporation and transpiration of large quantities of water into the atmosphere annually. Surface conductance (gs) is a poorly understood phenomenon that plays a central role in regulating this evapotranspiration. We studied the calculations, variations, and environmental factors controlling gs based on eddy flux measurements from 10 tropical forest sites that covered a wide range of water gradients across continents. We found that boundary layer conductance (gb) is comparable with aerodynamic conductance for momentum (gaM) and thus, it should not be ignored in estimations of total aerodynamic conductance for water vapor (gaV). Based on the findings, we have made some recommendations for gaM estimation both with and without measurements of turbulence. The seasonal variation of gs is low in humid sites but large in sites with a dry season. A value of 24.8 ± 13.8 mm s−1 was suggested for maximum surface conductance (gsmax) for tropical forests. Both water vapor deficit (D) and radiation (Q) play an important role in controlling gs. The model driven by both D and Q could capture the diurnal variations of gs well and could be implemented in large-scale models in future. We believe the findings of this study could contribute substantially to our understanding of tropical forest gs.
  • Assessing consistency of spring phenology of snow-covered forests as
           estimated by vegetation indices, gross primary production, and
           solar-induced chlorophyll fluorescence
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): Qing Chang, Xiangming Xiao, Wenzhe Jiao, Xiaocui Wu, Russell Doughty, Jie Wang, Ling Du, Zhenhua Zou, Yuanwei Qin Accurate phenology characterization is of great importance for measuring ecosystem dynamics, especially for carbon and water exchange between land and the atmosphere. Vegetation indices (VIs), calculated from land surface reflectance, are widely used to estimate phenology from the leaf and canopy structure perspective. Gross Primary Production (GPP) and solar-induced chlorophyll fluorescence (SIF) are used to estimate phenology from the canopy functional (physiological) perspective. To what degree are the spring phenology estimated from these different perspectives consistent with each other' In this study, we evaluated the consistency of the start of the growing season (SOS) in spring for snow-covered evergreen needleleaf forests (ENF) and deciduous broadleaf forests (DBF) using three vegetation indices, in-situ GPP data from the eddy covariance flux towers (GPPEC), GPP data from the Vegetation Photosynthesis Model (GPPVPM), and SIF data from the GOME-2. Results showed that SOSNDVI dates were much earlier than SOS dates from EVI (SOSEVI), land surface water index (LSWI) (SOSLSWI), GPP (SOSGPP; SOSGPP-EC, SOSGPP_VPM) and SIF (SOSSIF) for both snow-covered evergreen needleleaf forest (ENF) and deciduous broadleaf forest (DBF). SOSLSWI dates were more linearly correlated with SOSGPP and SOSSIF than SOS dates from NDVI and EVI. At ENF sites, SOSLSWI dates were 17 (± 27) days later and SOSEVI were 25 (± 34) days later than SOSGPP_EC dates. At DBF sites, SOSLSWI and SOSEVI dates were 1-week (± 13 days) later than SOSGPP_EC dates. In the snow-covered regions at mid- to high-latitude in the Northern Hemisphere, SOSLSWI dates were 2˜3 weeks (± 5 days) later than those of SOSGPP_VPM and SOSSIF for both ENF and DBF. Our results clearly highlight the need for further investigation of NDVI-based SOS dates, which were likely affected by snowmelt in snow-covered forests, and the potential of LSWI for tracking the effects of snow on SOS dates. Estimations of SOS dates in snow-covered forests should consider the effects of both snow cover and temperature on leaf emergence (green-up) and gross primary production.
  • Transpiration dynamics and water sources for selected indigenous trees
           under varying soil water content
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): C.M. Tfwala, L.D. van Rensburg, Z.A. Bello, P.C. Zietsman The major route through which water from the earth’s surface re-enters the hydrologic cycle in forested ecosystems is via tree transpiration (T). It is therefore important to have detailed understanding of the quantity and source of water transpired by different tree species. The aims of this study were to i) assess the trends of T for selected tree species (camel thorn, sweet thorn, shepherd’s tree and buffalo thorn) across a range of soil water content conditions and ii) partition the total T of the selected tree species growing in arid environments dominated by open cast mining activities into soil water and groundwater. Tree T was measured using the compensation heat pulse velocity (CHPV) method, while soil water content was monitored using DFM capacitance probes. The soil water content within the upper 50 cm soil profile ranged from 11 mm during the dry season to 20 mm during the wet season. The deeper soil layer (50–120 cm) was generally wetter compared to the top layer with water content was up to>30 mm during the wet season. The measured tree T ranged from 0.2 mm day−1 on buffalo thorn during the dry season to 1.9 mm day−1 on sheperd’s tree in summer. It was also revealed that T of large (diameter at breast height =46 cm) camel thorn trees is not responsive to seasonal variations of soil water availability and remained constant at approximately 1.2 mm day−1. Diurnal patterns of T did not effect changes on the soil water depletions within the top 120 cm soil profile, which indicated that the trees sourced water beyond this zone. Signs of daytime redistribution were observed within the canopy areas of the investigated trees during very limited soil water conditions of the dry season. It was concluded that the water use of trees is inclined to the seasonal variations, which however is not the case in old trees. Close to 100% of the water transpired by trees in the study area is sourced below 1.2 m (vadose zone and water table). We recommended investigation of daytime redistribution among the indigenous tree species of the study area. We also recommended extension of tree water use studies to other species for comprehensive catchment tree water use calculations to inform water budgets.
  • Crop rotation options for dryland agriculture: An assessment of grain
           yield response in cool-season grain legumes and canola to variation in
           rainfall totals
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): Alireza Houshmandfar, Noboru Ota, Kadambot H.M Siddique, Michael Tausz Crop production in dryland systems is mainly dependent on water availability from rainfall which is highly variable between years and locations. We employed the widely used boundary-line analysis, with an existing industry dataset from across the Australian dryland cropping regions, to investigate the relative sensitivity of grain yield in canola (Brassica napus L.), chickpea (Cicer arietinum L.), faba bean (Vicia faba L.), field pea (Pisum sativum L.), lentil (Lens culinaris L.), and narrow-leafed lupin (Lupinus angustifolius L.) to variation in rainfall totals. Chickpea had the lowest non-productive water use, was more responsive to water supply, and reached its maximum yield at a lower water supply than the other species. In contrast canola had the highest non-productive water use, was less responsive to water supply, and reached its maximum yield at a higher water supply than the other species. These results suggest that chickpea offers the most stable outcome, and canola the greatest variation, in response to the variability in rainfall totals between years and locations.
  • Forest drought-induced diversity of Hyrcanian individual-tree mortality
           affected by meteorological and hydrological droughts by analyzing moderate
           resolution imaging spectroradiometer products and spatial autoregressive
           models over northeast Iran
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): Omid Abdi, Zeinab Shirvani, Manfred F. Buchroithner This study sought to assess the spatial variations of physiological responses of Hyrcanian forests to the hazard intensity of meteorological and hydrological droughts for properly assessing drought-induced tree mortality in northeastern Iran. A variety of time series moderate resolution imaging spectroradiometer (MODIS) products and ground-based measurements were applied to derive the multiple dimensions of droughts and forest stresses. Drought hazard intensity was computed with the combination of the severity, frequency and duration of drought dimensions for each variable. The intensity of tree mortality was calculated by Simpson’s diversity index with surveying 30,000 individuals of commercial species suspected to dieback within 100 intact parcels. Spatial autoregressive models were carried out to determine significant meteorological and hydrological drivers that controlling biological responses of forests to drought events and associations of the diversity of tree mortality with these forest responses. Results showed that the hazard intensity of forest water-content-deficit and greenness loss showed higher relationships with the high land surface temperatures and actual evapotranspiration than the precipitation and surface water deficits, however, they did not show significant relationships with the groundwater deficit. Moreover, diversity of tree mortality was associated with forest water-content-deficit from moderate to death stages and with forest greenness loss in the only very high defoliation stage. The critical values of forest droughts and diversity of mortality were recorded for the climax tree species. Understanding satellite-derived physiological responses of forests to droughts might help to assess the intensity of tree mortality widely to adopt appropriate strategies for mitigating the impacts of droughts on the tree species.
  • An evaluation of the flux-gradient and the eddy covariance method to
           measure CH4, CO2, and H2O fluxes from small ponds
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): Jiayu Zhao, Mi Zhang, Wei Xiao, Wei Wang, Zhen Zhang, Zhou Yu, Qitao Xiao, Zhengda Cao, Jingzheng Xu, Xiufang Zhang, Shoudong Liu, Xuhui Lee Despite their small overall area, small ponds play a large role in the greenhouse gas budgets of inland water bodies. This study aims to evaluate the performance of the flux-gradient (FG) and the eddy covariance (EC) method for measuring the fluxes of CO2, CH4, and H2O at two small fish ponds (fetch < 120 m) in subtropical climate conditions. The EC fluxes were subject to two sources of error: high frequency flux loss and footprint contamination. Of the three gaseous fluxes, the CH4 flux suffered the largest high frequency loss (18%) due to a combination of low EC instrument height and long optical path of the CH4 analyzer. Despite the low measurement height, the EC fluxes were influenced by sources outside the boundary of the target fish ponds, with the footprint contamination most severe on the CO2 flux and least severe on the CH4 flux. With regards to the FG method, one major uncertainty lies in the eddy diffusivity calculation. Of the three eddy diffusivity models evaluated [the aerodynamic (AE) model deploying the full Obukhov stability correction, the modified Bowen-ratio model using H2O as a tracer, and the wind profile model for neutral stability], the AE model yielded the best results for the CO2 and CH4 fluxes. Our results support Horst’s (1999, Boundary-Layer Meteorology 90, 171) theoretical prediction that the footprint of the AE flux based on a two-level concentration profile measurement should be much smaller than that of the gradient flux footprint and the EC flux footprint at the geometric mean of the two heights. We conclude that the most appropriate micrometeorological method for measuring fluxes from small water bodies is a hybrid scheme, whereby an EC system is deployed to measure the eddy diffusivity and a precision gas analyzer is used to obtain the concentration gradient of the target gas.
  • The potential geographical distribution of Haloxylon across Central Asia
           under climate change in the 21st century
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): Jiangyue Li, Hong Chang, Tong Liu, Chi Zhang Members of Haloxylon are unique key species in the deserts of Central Asia (including Soviet Central Asia (SCA) and Xinjiang, China (XJ)). The region is a hotspot of global warming, and the plants’ habitats are threatened by climate change. By using normal-climate data and future climate projections from 17 general circulation models (GCMs), we herein simulate the present and future potential habitats of Haloxylon persicum (H. persicum) and Haloxylon ammodendron (H. ammodendron) in Central Asia using a Maximum Entropy (MaxEnt) model that was developed based on 307 specimen records of Haloxylon vegetation. The MaxEnt model showed high accuracy, with an average training area under the curve (AUC) value of 0.93-0.95. Our analysis indicated that temperature and precipitation play equally important roles in shaping the spatial distribution of these desert shrubs. According to the model estimates, the current (based on 1961–1990 climate normals) potential habitats of H. persicum and H. ammodendron are 1.56 × 106 km2 and 1.53 × 106 km2, respectively, mostly (93.1% and 75%, respectively) distributed in SCA. Model projections based on two future climate scenarios, namely, the Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios (representing stabilized radiative forcing at 4.5 W m−2 and 8.5 W m−2 by the end of the 21st century, respectively), predicted that the potential habitat of H. persicum will increase by 44% (RCP4.5) to 62% (RCP8.5) but that the potential habitat of H. ammodendron will decrease by 22% (RCP4.5) to 34% (RCP8.5) in the late-21st century. The potential habitats of Haloxylon vegetation will gradually be lost in XJ but will expand in southwestern Kazakhstan circa 2041–2060 and 2061-2080. Therefore, it is advisable to protect the habitats of Haloxylon species in XJ (esp. southern XJ), where strong warming in the future might impose severe stress, and establish ecological corridors in central Uzbekistan and southern Kazakhstan to facilitate Haloxylon redistribution, as the geographical centroid of the Haloxylon habitats is shifting northward and westward in Central Asia.
  • Impacts of diffuse radiation fraction on light use efficiency and gross
           primary production of winter wheat in the North China Plain
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): Xiaoya Yang, Jun Li, Qiang Yu, Yuchun Ma, Xiaojuan Tong, Yan Feng, Yingxiang Tong The increase of diffuse radiation fraction (kd) has been reported to significantly impact light use efficiency (LUE) and carbon uptake in terrestrial ecosystems. The impact of kd on LUE should be considered in crop models to accurately evaluate the effect of radiation changes on crop production. However, the magnitude of the kd effect is difficult to quantify because of the complicated interacting relationships among all of the meteorological parameters, as well as the changing effects for various ecosystem types and research sites. Eight site-years of flux data and two years of diffuse radiation data from two field ecosystems in the North China Plain were used to (1) compare the performance of five kd models, (2) explore the impacts of environmental factors on LUE and gross primary production (GPP) of winter wheat (Triticum aestivum L.), and (3) quantify the relationships between kd and both LUE and GPP of winter wheat. Comparison results showed that the kd model developed by Boland et al. performed the best of the five models evaluated. This model was chosen to calculate kd in this research. Path analysis show that kd was the main factor affecting LUE of winter wheat, explaining up to 55% of the variability in LUE. The relationship between kd and LUE was significantly linear (slope of about 0.326 g C mol−1). GPP initially increased and then decreased with increasing kd. A moderate radiation condition (kd = 0.53) was favorable for increasing GPP. The effect of kd on LUE should be added in the LUE module of APSIM-Nwheat to improve simulation accuracy. The results of this study highlight the importance of kd in correctly modeling LUE for winter wheat with a crop model and provide quantitative relationships between these two parameters. These relationships will be helpful in improving crop model simulation accuracy under changed climate conditions.
  • Carbon dioxide fluxes of temperate urban wetlands with different
           restoration history
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): K.V.R. Schäfer, T. Duman, K. Tomasicchio, R. Tripathee, C. Sturtevant Carbon dioxide (CO2) exchange of tidal brackish wetlands and how they may be affected by restoration methods are largely unknown. The New Jersey Meadowlands, a tidal brackish estuary system, have had a long history of pollution, hydrological alterations, multiple restoration and mitigation treatments since the early 1970ies. To understand the effects of restoration, net ecosystem exchange (NEE) was measured with the eddy covariance technique in three urban tidal brackish wetland sites over three years: an organic matter amended restored site, a non-amended restored site and a natural (non-restored) wetland site. Our results showed all three sites to be a CO2 source in the wintertime reverting to a weak sink of CO2 in the summer and annually to be sources of CO2 for some of the sites for some of the time. However, the amended restored wetland was found to have the highest release of CO2. Annual destructive harvest of the major species at these wetlands (Spartina ssp and Phragmites australis) did not show significant differences in the aboveground net primary productivity and leaf area over the course of this study. Overall, aboveground biomass production of the three wetlands sites was within the expected range of tidal brackish marshes, but the sites differed in their NEE, ecosystem respiration, and gross ecosystem production. This investigation suggests that CO2 uptake and potential subsequent carbon sequestration may be strongly affected by the management and restoration history of the wetlands, and in our case these wetlands are often acting as a source of CO2, and not as a sink, as may have been expected.
  • Management and spatial resolution effects on yield and water balance at
           regional scale in crop models
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): Julie Constantin, Helene Raynal, Eric Casellas, Holger Hoffmann, Marco Bindi, Luca Doro, Henrik Eckersten, Thomas Gaiser, Balász Grosz, Edwin Haas, Kurt-Christian Kersebaum, Steffen Klatt, Matthias Kuhnert, Elisabet Lewan, Ganga Ram Maharjan, Marco Moriondo, Claas Nendel, Pier Paolo Roggero, Xenia Specka, Giacomo Trombi Due to the more frequent use of crop models at regional and national scale, the effects of spatial data input resolution have gained increased attention. However, little is known about the influence of variability in crop management on model outputs. A constant and uniform crop management is often considered over the simulated area and period. This study determines the influence of crop management adapted to climatic conditions and input data resolution on regional-scale outputs of crop models. For this purpose, winter wheat and maize were simulated over 30 years with spatially and temporally uniform management or adaptive management for North Rhine-Westphalia (˜34 083 km²), Germany. Adaptive management to local climatic conditions was used for 1) sowing date, 2) N fertilization dates, 3) N amounts, and 4) crop cycle length. Therefore, the models were applied with four different management sets for each crop. Input data for climate, soil and management were selected at five resolutions, from 1 × 1 km to 100 × 100 km grid size. Overall, 11 crop models were used to predict regional mean crop yield, actual evapotranspiration, and drainage. Adaptive management had little effect (
  • Carbon fluxes and stocks in a carbonate-rich chenier plain
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): Weizhi Lu, Chang’an Liu, Yue Zhang, Caifen Yu, Pifu Cong, Junsheng Ma, Jingfeng Xiao Coastal wetlands play an important role in the global carbon cycle because they have high ecosystem productivity and carbon sequestration capability. Previous research focused on the carbon dynamics of organic-rich ecosystems (e.g., salt marshes, mangroves), while little attention has paid to the carbon cycling of carbonate-rich ecosystems such as chenier plains, sandy or shelly beach ridges that are parts of strand plains. Here we examined the carbon stocks and fluxes of the poorly studied chenier plain in the Yellow River Delta, China. The inorganic and organic carbon pools in the top 1 m sediment were 444 ± 92 Mg C ha−1 and 89 ± 7 Mg C ha−1, respectively. The average CO2 net sequestration was −177 ± 51 Mg C ha−1, indicating that the chenier plain had a net CO2 evasion during the entire soil formation process. With plant growth, however, the chenier plain provided a significant carbon sink (395 g C m−2 a−1) on a per-unit area basis. The annual gross ecosystem productivity (GEP) and ecosystem respiration (Re) were 1067 and 672 g C m−2 a−1, respectively. The carbon sink strength of the chenier plain was comparable to that of organic-rich salt marshes on a per-unit area basis. The biomass carbon pool was 5.0 ± 1.4 Mg C ha−1 in the chenier plain. Moreover, the sediment inorganic carbon content in mudflats was significantly lower than that of vegetated habitats. Our results showed that plant grown in a chenier plain could significantly enhance carbon sequestration by increasing organic carbon storage. Inorganic carbon storage should be considered in blue carbon inventories because inorganic carbon dominates the carbon pool and is important in the carbon cycling in a chenier plain. Our findings can help us better understand the carbon cycling of carbonate-rich coastal ecosystems and can inform chenier plain conservation and restoration efforts.
  • An improved surface soil moisture downscaling approach over cloudy areas
           based on geographically weighted regression
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): Peilin Song, Jingfeng Huang, Lamin R. Mansaray This study proposed a methodological framework for downscaling AMSR-2 surface soil moisture (SSM) products over cloudy areas using MODIS LST/NDVI datasets. The experiment was conducted in a relatively large area of 430,000 km2 in the middle and lower reaches of the Yangtze and Huaihe rivers in China, which is characterized by humid climate and frequent cloudy weather conditions. As MODIS LSTs suffer from serious pixel loss due to cloud interference in this area, an effective LST interpolation method was preliminarily applied to achieve daily LST datasets with quasi-full covers. And rather small RMSEs in the range 1.5 K–3.5 K were obtained when the interpolated LST datasets were validated against a reference LST dataset built from observed relationships between LST and ground-based near-surface air temperatures on clear sky days. A regression equation was then established between AMSR-2 SSM and spatially resampled MODIS datasets using “Geographically Weighted Regression (GWR)” to implement the SSM downscaling process. SSM estimates downscaled by the GWR-based method showed a better performance over those downscaled by the traditional “universal triangle feature (UTF)” based method in view of their “non-biased RMSEs (ubRMSEs)”, correlation coefficients, and mean biases with respect to ground-based soil moisture validation data. Comparisons between SSM estimates from MODIS LST inputs and those from interpolated LST inputs were conducted, and they showed that the SSM estimates downscaled by interpolated LST inputs performed only slightly poorer (with an ubRMSE difference no larger than 0.02 cm3/cm3) than those by MODIS data. Time series analysis further showed that the GWR-based downscaled SSM estimates with reconstructed LST data inputs are in phase with the variation in ground-based soil moisture with the exception of areas of extremely high vegetation cover or low temperatures. The framework proposed in this study thus proved feasible for the derivation of reliable downscaled high spatial resolution SSM estimates, an essential application in mitigating pixel loss under cloudy weather conditions.
  • New model for simulating autumn phenology of herbaceous plants in the
           Inner Mongolian Grassland
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): Shilong Ren, Qiming Qin, Huazhong Ren, Juan Sui, Yao Zhang Autumn phenology is important in determining the growing season length and controlling carbon and energy exchanges in terrestrial ecosystems. However, our knowledge on the interaction processes of vegetation autumn phenology and climate changes remains limited, especially for herbaceous plants. In this study, we comprehensively analyzed the responses of autumn phenology of grassland vegetation to climate changes by using ground-observed brown-down date records of 15 grass species and daily temperature, precipitation, and day length data at six stations. Aside from conducting correlation analysis, we also simulated the brown-down date with a newly developed model by incorporating the effect of drought stress (CDDP) into the traditional chilling-degree-days (CDD) model and compared it with the CDD model. Another revised CDD model included the effect of day length (CDDD) and null model (multiyear average, NM). The statistical results showed a predominant significant negative correlation between the brown-down date and previous temperature/day length in 27.3%/40.9% of site species but a predominant significant positive correlation between the brown-down date and previous precipitation in 54.6% of site species. The opposite effects of previous precipitation and previous temperature/day length on the brown-down date were induced by local thermal–moisture conditions. With regard to the modeling results, the CDDP model was selected as the optimal model for 73% of site species with insufficient water supply in preseason, while the CDD model was selected as the optimal model for 18% of site species with a relatively wet but cold preseason. The CDDD model was selected as the optimal model for only two cases. The average estimation error based on the CDDP model (7.4 days) was lower by 2.0/1.5/1.7 days than that based on the CDD/CDDD/NM model. Overall, this study comprehensively demonstrated the important role of water availability in controlling the autumn phenology process of herbaceous plants.
  • Sub-diurnal variability of the carbon dioxide and water vapor
           isotopologues at the field observational scale
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): Jordi Vilà-Guerau de Arellano, Gerbrand Koren, Huug G. Ouwersloot, Ivar van der Velde, Thomas Röckmann, John B. Miller We investigated the sub-diurnal variability of the carbon dioxide and water vapour isotopologues by modelling a representative case measured above the Harvard Forest. To this end, we developed a model that couples the local processes governed by soil and vegetation conditions to non-local atmospheric processes such as entrainment and long-range advection. The model formulation is based on solving the stable isotopologues 12CO2, 13CO2, C18OO, H216O and H218O as conserved variables. It also includes simultaneously solving the meteorological state variables coupled with their respective surface fluxes. Our model results indicate the need for a comprehensive observational data-set to ensure that the essential processes and interactions between the boundary-layer dynamics of a forest and the atmospheric boundary layer are satisfactorily reproduced. We present and discuss the temporal evolution of the budgets of 13CO2 and C18OO, in order to quantify the individual contributions made by soil, plant and entrainment dynamics. All these contributions turn out to be relevant, as they enable us to quantify how the energy, water and carbon fluxes on sub-daily scales are partitioned. Regarding the role played by entrainment, we carried out a set of three systematic experiments in which air, with different CO2 and H2O isotopic compositions originating in the residual layer, mix with the boundary-layer air. Our findings show that both the C18OO and H218O isotopic ratios and their respective isofluxes are influenced by the entrainment event. This result indicates that high frequency and accurate isotopologues surface measurements (seconds or minutes) can be used to quantify how non-local atmospheric processes modify isotopic composition at sub-daily scales.
  • Incorporating machine learning with biophysical model can improve the
           evaluation of climate extremes impacts on wheat yield in south-eastern
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): Puyu Feng, Bin Wang, De Li Liu, Cathy Waters, Qiang Yu Accurately assessing the impacts of extreme climate events (ECEs) on crop yield can help develop effective agronomic practices to deal with climate change impacts. Process-based crop models are useful tools to evaluate climate change impacts on crop productivity but are usually limited in modelling the effects of ECEs due to over-simplification or vague description of certain process and uncertainties in parameterization. In this study, we firstly developed a hybrid model by incorporating the APSIM model outputs and growth stage-specific ECEs indicators (i.e. frost, drought and heat stress) into the Random Forest (RF) model, with the multiple linear regression (MLR) model as a benchmark. The results showed that the APSIM + RF hybrid model could explain 81% of the observed yield variations in the New South Wales wheat belt of south-eastern Australia, which had a 33% improvement in modelling accuracy compared to the APSIM model alone and 19% improvement compared to the APSIM + MLR hybrid model. Drought events during the grain-filling and vegetative stages and heat events immediately prior to anthesis were identified as the three most serious ECEs causing yield losses. We then compared the APSIM + RF hybrid model with the APSIM model to estimate the effects of future climate change on wheat yield. It was interesting to find that future yield projected from single APSIM model might have a 1–10% overestimation compared to the APSIM + RF hybrid model. The APSIM + RF hybrid model indicated that we were underestimating the effects of climate change and future yield might be lower than predicted using single APSIM informed modelling due to lack of adequately accounting for ECEs-induced yield losses. Increasing heat events around anthesis and grain-filling periods were identified to be major factors causing yield losses in the future. Therefore, we conclude that including the effects of ECEs on crop yield is necessary to accurately assess climate change impacts. We expect our proposed hybrid-modelling approach can be applied to other regions and crops and offer new insights of the effects of ECEs on crop yield.
  • Interaction of vegetation, climate and topography on evapotranspiration
           modelling at different time scales within the Budyko framework
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): Tingting Ning, Sha Zhou, Feiyang Chang, Hong Shen, Zhi Li, Wenzhao Liu Vegetation, climate and topography have been empirically formulated into the controlling parameter of the Budyko model (ω) to estimate evapotranspiration (ET). However, these variables, if simultaneously employed, may induce multicollinearity problems because of their potential interactions. Further, these interactions may vary with different time scales and subsequently result in the inaccurate estimation of ω. As such, we investigated the interactions of vegetation, climate and topography and their corresponding effects on ET modelling at different time scales by employing vegetation coverage (M), an improved climate seasonality and asynchrony index (SAI), the fraction of precipitation falling as snow (fs) and relative basin relief (BR/ BR¯), in 30 catchments in China’s Loess Plateau. We found that, on annual scale, M and SAI were significantly related to ω, while being independent from each other; in consequence, both of them should be parameterized into the Budyko model on the annual scale for better ET modelling. However, the links between M and SAI became stronger with increased time scales, the parameterization of ω should thus be reformatted for longer periods. When extended to a 30-year period, ω was closely related to the above variables, but M was highly intercorrelated with SAI and BR/ BR¯, and fs was significantly related to BR/ BR¯. The independent M and fs were finally selected to fit ω, which allowed mean annual ET to be accurately modelled on long-term scale. Identification of the dominant factors applicable at different time scales can simplify the empirical parameterization of the Budyko formula and thereby facilitate more accurate estimation of ET.
  • Transmitted light as a tool to monitor tree leaf phenology and development
           applied to Quercus petraea
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): Thomas Perot, Philippe Balandier, Camille Couteau, Sandrine Perret, Vincent Seigner, Nathalie Korboulewsky Better knowledge and a more complete long-term monitoring of tree species phenology and tree foliage development are crucial to accurately estimating the impact of climate change on forest ecosystems functioning and on forest species distribution. We set up global solar radiation sensors under the forest canopy and continuously recorded solar radiation in order to follow the development of sessile oak (Quercus petraea L.) foliage in pure stands over four consecutive years and for two levels of stand density. At the same time, we made phenological observations to determine bud burst date. One of our goals was to link observed bud burst dates and transmittance measurements. Our results show that solar radiation transmittance during the leaf unfolding period followed a sigmoid-shaped curve; and that it was possible to fit a generalized logistic model to determine a set of parameters characterizing tree foliage and its development during the unfolding period. Among these parameters, we suggest that the date at which solar radiation interception by foliage reaches 50% could be used to monitor the beginning of the growing season over the long term. The relationship between observed bud burst date and the transmittance model parameters was more complex than we expected. We tested several indices to deduce the date of bud burst from transmittance. We showed that when radiation interception due to foliage reached 10%, this indicated the observed bud burst date. Finally, a linear model including parameters from the generalized logistic models of transmittance as predictors explained 57% of the variability in bud burst date. Complementary research combining light measurements and phenological observations over a longer period of time is needed to know whether these relationships could help estimate bud burst date regardless of the year or the stand density.
  • Soil-atmosphere exchange of nitrous oxide in two Tanzanian croplands:
           Effects of nitrogen and stover management
    • Abstract: Publication date: 15 September 2019Source: Agricultural and Forest Meteorology, Volume 275Author(s): Jinsen Zheng, Ying Qu, Method M. Kilasara, William N. Mmari, Shinya Funakawa Cropland intensification is needed to meet the demand for food in sub-Saharan Africa (SSA). This process requires a dramatic increase in resource inputs, including fertilizer-nitrogen (N) and organic residues (e.g., stover), which alter the soil-atmosphere exchange of nitrous oxide (N2O). The dearth of N2O emission data for SSA croplands, however, limits our ability to define regional and global N2O flux and mitigation opportunities. In two soils planted with maize in Tanzania (Iringa, sandy Alfisols; Mbeya, clayey Andisols), we conducted year-round measurements for 2 consecutive years to quantify N2O emissions in response to increasing N rates and in combination with maize stover incorporation. Rainfall and the resulting soil moisture, rather than soil temperature, were important environmental drivers of N2O emissions in these fields. Applied N stimulated N2O fluxes across soil types but with different magnitudes—lower in Iringa because of the dominance of nitrification in N2O production and higher in Mbeya likely from promoted denitrification when the water-filled pore space was>47%. N2O emission increased exponentially or linearly with N rate, depending on the year. The direct N2O emission factors were well below the 1% of the IPCC Tier 1 method, ranging from 0.13% to 0.26% in Iringa and from 0.24% to 0.42% in Mbeya, for a N rate of 50–150 kg N ha−1 during the study. Compared with N application alone, stover plus N did not significantly alter maize yield, but did raise N2O emissions significantly (P ≤ 0.06). Consequently, stover incorporation markedly increased the emission factor (up to 0.46% in Iringa and 1.29% in Mbeya) as well as yield-scaled N2O emissions. Our results suggest that linear and exponential emission responses can occur in SSA croplands and challenge the promotion of combining stover with fertilizer-N as resource input management in this region.
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