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Showing 1 - 200 of 3120 Journals sorted alphabetically
A Practical Logic of Cognitive Systems     Full-text available via subscription   (Followers: 8)
AASRI Procedia     Open Access   (Followers: 14)
Academic Pediatrics     Hybrid Journal   (Followers: 26, SJR: 1.402, h-index: 51)
Academic Radiology     Hybrid Journal   (Followers: 22, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 90, SJR: 1.109, h-index: 94)
Accounting Forum     Hybrid Journal   (Followers: 25, SJR: 0.612, h-index: 27)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 30, SJR: 2.515, h-index: 90)
Achievements in the Life Sciences     Open Access   (Followers: 4)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 5, SJR: 0.338, h-index: 19)
Acta Astronautica     Hybrid Journal   (Followers: 378, SJR: 0.726, h-index: 43)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 3)
Acta Biomaterialia     Hybrid Journal   (Followers: 26, SJR: 2.02, h-index: 104)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription   (Followers: 1)
Acta de Investigación Psicológica     Open Access   (Followers: 2)
Acta Ecologica Sinica     Open Access   (Followers: 8, SJR: 0.172, h-index: 29)
Acta Haematologica Polonica     Free   (Followers: 1, SJR: 0.123, h-index: 8)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.604, h-index: 38)
Acta Materialia     Hybrid Journal   (Followers: 237, SJR: 3.683, h-index: 202)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.615, h-index: 21)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.442, h-index: 21)
Acta Oecologica     Hybrid Journal   (Followers: 10, SJR: 0.915, h-index: 53)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription   (Followers: 1)
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 3, SJR: 0.311, h-index: 16)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 2)
Acta Poética     Open Access   (Followers: 4)
Acta Psychologica     Hybrid Journal   (Followers: 25, SJR: 1.365, h-index: 73)
Acta Sociológica     Open Access  
Acta Tropica     Hybrid Journal   (Followers: 6, SJR: 1.059, h-index: 77)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 4)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 3)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 4, SJR: 0.383, h-index: 19)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 2)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 5, SJR: 0.141, h-index: 3)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 4, SJR: 0.112, h-index: 2)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 6)
Acute Pain     Full-text available via subscription   (Followers: 13)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.967, h-index: 57)
Addictive Behaviors     Hybrid Journal   (Followers: 15, SJR: 1.514, h-index: 92)
Addictive Behaviors Reports     Open Access   (Followers: 7)
Additive Manufacturing     Hybrid Journal   (Followers: 7, SJR: 1.039, h-index: 5)
Additives for Polymers     Full-text available via subscription   (Followers: 22)
Advanced Cement Based Materials     Full-text available via subscription   (Followers: 3)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 139, SJR: 5.2, h-index: 222)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 11, SJR: 1.265, h-index: 53)
Advanced Powder Technology     Hybrid Journal   (Followers: 17, SJR: 0.739, h-index: 33)
Advances in Accounting     Hybrid Journal   (Followers: 9, SJR: 0.299, h-index: 15)
Advances in Agronomy     Full-text available via subscription   (Followers: 15, SJR: 2.071, h-index: 82)
Advances in Anesthesia     Full-text available via subscription   (Followers: 27, SJR: 0.169, h-index: 4)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 4)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 9, SJR: 1.054, h-index: 35)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 12, SJR: 0.801, h-index: 26)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 23, SJR: 1.286, h-index: 49)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 16, SJR: 3.31, h-index: 42)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.277, h-index: 43)
Advances in Botanical Research     Full-text available via subscription   (Followers: 3, SJR: 0.619, h-index: 48)
Advances in Cancer Research     Full-text available via subscription   (Followers: 26, SJR: 2.215, h-index: 78)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 9, SJR: 0.9, h-index: 30)
Advances in Catalysis     Full-text available via subscription   (Followers: 6, SJR: 2.139, h-index: 42)
Advances in Cell Aging and Gerontology     Full-text available via subscription   (Followers: 4)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 13)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 27, SJR: 0.183, h-index: 23)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 10, SJR: 0.665, h-index: 29)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 9, SJR: 1.268, h-index: 45)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 29, SJR: 0.938, h-index: 33)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18, SJR: 2.314, h-index: 130)
Advances in Computers     Full-text available via subscription   (Followers: 16, SJR: 0.223, h-index: 22)
Advances in Dermatology     Full-text available via subscription   (Followers: 14)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 12)
Advances in Digestive Medicine     Open Access   (Followers: 7)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 6)
Advances in Drug Research     Full-text available via subscription   (Followers: 23)
Advances in Ecological Research     Full-text available via subscription   (Followers: 47, SJR: 3.25, h-index: 43)
Advances in Engineering Software     Hybrid Journal   (Followers: 27, SJR: 0.486, h-index: 10)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 9)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 46, SJR: 5.465, h-index: 64)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 3)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 53, SJR: 0.674, h-index: 38)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 16)
Advances in Genetics     Full-text available via subscription   (Followers: 17, SJR: 2.558, h-index: 54)
Advances in Genome Biology     Full-text available via subscription   (Followers: 11)
Advances in Geophysics     Full-text available via subscription   (Followers: 6, SJR: 2.325, h-index: 20)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 22, SJR: 0.906, h-index: 24)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 0.497, h-index: 31)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 27)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 2, SJR: 0.396, h-index: 27)
Advances in Immunology     Full-text available via subscription   (Followers: 37, SJR: 4.152, h-index: 85)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 1.132, h-index: 42)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 3, SJR: 1.274, h-index: 27)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 6)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 4)
Advances in Life Course Research     Hybrid Journal   (Followers: 8, SJR: 0.764, h-index: 15)
Advances in Lipobiology     Full-text available via subscription   (Followers: 2)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 10)
Advances in Marine Biology     Full-text available via subscription   (Followers: 16, SJR: 1.645, h-index: 45)
Advances in Mathematics     Full-text available via subscription   (Followers: 10, SJR: 3.261, h-index: 65)
Advances in Medical Sciences     Hybrid Journal   (Followers: 6, SJR: 0.489, h-index: 25)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 5, SJR: 1.44, h-index: 51)
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: 10)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 9, SJR: 0.324, h-index: 8)
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: 15, SJR: 2.885, h-index: 45)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7, SJR: 0.148, h-index: 11)
Advances in Parasitology     Full-text available via subscription   (Followers: 7, SJR: 2.37, h-index: 73)
Advances in Pediatrics     Full-text available via subscription   (Followers: 24, SJR: 0.4, h-index: 28)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 13)
Advances in Pharmacology     Full-text available via subscription   (Followers: 16, SJR: 1.718, h-index: 58)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 0.384, h-index: 26)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.248, h-index: 11)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 7)
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: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20, SJR: 1.5, h-index: 62)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6, SJR: 0.478, h-index: 32)
Advances in Radiation Oncology     Open Access  
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 3, SJR: 0.1, h-index: 2)
Advances in Space Biology and Medicine     Full-text available via subscription   (Followers: 5)
Advances in Space Research     Full-text available via subscription   (Followers: 371, SJR: 0.606, h-index: 65)
Advances in Structural Biology     Full-text available via subscription   (Followers: 8)
Advances in Surgery     Full-text available via subscription   (Followers: 9, SJR: 0.823, h-index: 27)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 31, SJR: 1.321, h-index: 56)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 16)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 13)
Advances in Virus Research     Full-text available via subscription   (Followers: 6, SJR: 1.878, h-index: 68)
Advances in Water Resources     Hybrid Journal   (Followers: 45, SJR: 2.408, h-index: 94)
Aeolian Research     Hybrid Journal   (Followers: 5, SJR: 0.973, h-index: 22)
Aerospace Science and Technology     Hybrid Journal   (Followers: 339, SJR: 0.816, h-index: 49)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.318, h-index: 36)
African J. of Emergency Medicine     Open Access   (Followers: 6, SJR: 0.344, h-index: 6)
Ageing Research Reviews     Hybrid Journal   (Followers: 9, SJR: 3.289, h-index: 78)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 434, SJR: 1.385, h-index: 72)
Agri Gene     Hybrid Journal  
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 15, SJR: 2.18, h-index: 116)
Agricultural Systems     Hybrid Journal   (Followers: 31, SJR: 1.275, h-index: 74)
Agricultural Water Management     Hybrid Journal   (Followers: 42, SJR: 1.546, h-index: 79)
Agriculture and Agricultural Science Procedia     Open Access  
Agriculture and Natural Resources     Open Access   (Followers: 3)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 56, SJR: 1.879, h-index: 120)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.434, h-index: 14)
Air Medical J.     Hybrid Journal   (Followers: 5, SJR: 0.234, h-index: 18)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.285, h-index: 3)
Alcohol     Hybrid Journal   (Followers: 11, SJR: 0.922, h-index: 66)
Alcoholism and Drug Addiction     Open Access   (Followers: 8)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 1, SJR: 0.436, h-index: 12)
Alexandria J. of Medicine     Open Access   (Followers: 1)
Algal Research     Partially Free   (Followers: 9, SJR: 2.05, h-index: 20)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.46, h-index: 29)
Allergology Intl.     Open Access   (Followers: 5, SJR: 0.776, h-index: 35)
Alpha Omegan     Full-text available via subscription   (SJR: 0.121, h-index: 9)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 9, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 49, SJR: 4.289, h-index: 64)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 4)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 4)
Ambulatory Pediatrics     Hybrid Journal   (Followers: 5)
American Heart J.     Hybrid Journal   (Followers: 48, SJR: 3.157, h-index: 153)
American J. of Cardiology     Hybrid Journal   (Followers: 48, SJR: 2.063, h-index: 186)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 42, SJR: 0.574, h-index: 65)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 9, SJR: 1.091, h-index: 45)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 14, SJR: 1.653, h-index: 93)
American J. of Human Genetics     Hybrid Journal   (Followers: 32, SJR: 8.769, h-index: 256)
American J. of Infection Control     Hybrid Journal   (Followers: 26, SJR: 1.259, h-index: 81)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 31, SJR: 2.313, h-index: 172)
American J. of Medicine     Hybrid Journal   (Followers: 45, SJR: 2.023, h-index: 189)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 207, SJR: 2.255, h-index: 171)
American J. of Ophthalmology     Hybrid Journal   (Followers: 61, SJR: 2.803, h-index: 148)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 6)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.249, h-index: 88)
American J. of Otolaryngology     Hybrid Journal   (Followers: 24, SJR: 0.59, h-index: 45)
American J. of Pathology     Hybrid Journal   (Followers: 27, SJR: 2.653, h-index: 228)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 26, SJR: 2.764, h-index: 154)
American J. of Surgery     Hybrid Journal   (Followers: 36, SJR: 1.286, h-index: 125)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.653, h-index: 70)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 6)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.066, h-index: 51)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 60, SJR: 0.124, h-index: 9)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 14)
Anales de Cirugia Vascular     Full-text available via subscription  
Anales de Pediatría     Full-text available via subscription   (Followers: 2, SJR: 0.209, h-index: 27)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription   (SJR: 0.104, h-index: 3)
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 4, SJR: 2.577, h-index: 7)
Analytica Chimica Acta     Hybrid Journal   (Followers: 36, SJR: 1.548, h-index: 152)
Analytical Biochemistry     Hybrid Journal   (Followers: 171, SJR: 0.725, h-index: 154)
Analytical Chemistry Research     Open Access   (Followers: 8, SJR: 0.18, h-index: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 12)
Anesthésie & Réanimation     Full-text available via subscription   (Followers: 1)
Anesthesiology Clinics     Full-text available via subscription   (Followers: 22, SJR: 0.421, h-index: 40)
Angiología     Full-text available via subscription   (SJR: 0.124, h-index: 9)
Angiologia e Cirurgia Vascular     Open Access  
Animal Behaviour     Hybrid Journal   (Followers: 177, SJR: 1.907, h-index: 126)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 5, SJR: 1.151, h-index: 83)

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Journal Cover Agricultural and Forest Meteorology
  [SJR: 2.18]   [H-I: 116]   [15 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0168-1923
   Published by Elsevier Homepage  [3120 journals]
  • Adaptation strategies to lessen negative impact of climate change on grain
           maize under hot climatic conditions: A model-based assessment
    • Authors: Sajjad Rahimi-Moghaddam; Jafar Kambouzia; Reza Deihimfard
      Pages: 1 - 14
      Abstract: Publication date: 1 May 2018
      Source:Agricultural and Forest Meteorology, Volumes 253–254
      Author(s): Sajjad Rahimi-Moghaddam, Jafar Kambouzia, Reza Deihimfard
      Rise in temperature, particularly in warmer areas, could have a negative effect on maize productivity. However, careful management practices could reduce the effects of high temperatures by altering the sowing dates and type of cultivar. The current study applied APSIM (The Agricultural Production Systems sIMulator) crop model to investigate the interaction of sowing date and cultivar when dealing with climate change and high temperatures at nine locations in Khuzestan province, in southwestern Iran. Daily climatic data for the baseline period of 1980–2010 was obtained from the Meteorological Organization of Iran. Projections of the future climate of Khuzestan was done in Miroc5 (Model for Interdisciplinary Research on Climate) GCM (Global Climate Model) for 2040–2070 under two RCPs (Representative Concentration Pathways) (RCP4.5 and RCP8.5) using the methodology developed by AgMIP (The Agricultural Model Intercomparison and Improvement Project). The high risk window for extreme temperature was calculated as the number of days having a maximum temperature of over 36 °C (Tmax > 36 °C) during pre-flowering and flowering. Results indicated that for mid-future (2050), the average maize grain yield in almost all study areas except Masjed Soleyman decreased in comparison to baseline at −13.7% and −22.8% for RCP4.5 and RCP8.5, respectively mainly because the length of the high-risk window for extreme temperature had expanded from 18.8 to 26.3 days for RCP4.5 and RCP8.5, respectively, compared to baseline. Most farmers have not realized that they are currently sowing maize during a high-risk window for extreme temperatures (Tmax > 36 °C) in some seasons. If farmers do not apply adaptive options for their regions (most promising sowing date × cultivar), the probability of economical grain yield will be less than 50% for an average economical grain yield of 8.9 t ha−1. The current findings support the hypothesis that climate change by the middle of the 21st century will not be beneficial for maize agroecosystems in hot areas like Khuzestan province unless the best sowing date × cultivar is applied for both winter and summer sowing dates.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2018.01.032
      Issue No: Vol. 253-254 (2018)
  • Assessment of the agro-climatic indices to improve crop yield forecasting
    • Authors: Jordane A. Mathieu; Filipe Aires
      Pages: 15 - 30
      Abstract: Publication date: 1 May 2018
      Source:Agricultural and Forest Meteorology, Volumes 253–254
      Author(s): Jordane A. Mathieu, Filipe Aires
      Weather has a major impact on agriculture. Statistical models have been used to estimate or forecast crop yield from weather information. In this paper, a general statistical framework is developed in order to rank and quantify the information content of weather information. The methodology is tested over the US, for corn yield. The weather sensitivity of different corn production areas is first analyzed. More than fifty agro-climatic indices have been compared. The study shows that variability in yield is more likely to be due to weather variability in medium and low production areas. The two best yield predictors are the temperature and then the Standardized Precipitation–Evapotranspiration Index (SPEI) in July. While corn in the north Eastern regions is not significantly affected by weather variation, on the East coast, the weather-based mixed model is able to explain about 32% (corr = 0.57) of the yield variability, but in some particularly weather-sensitive states, such as Virginia, this number can reach 64% (corr = 0.80). Two applications are tested: yield estimation at the end of the year for monitoring purpose, and seasonal prediction. It is shown that some agro-climatic indices can significantly improve crop yield modeling when compared to simpler direct weather information (average correlation increase of 0.12 at the US scale).

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2018.01.031
      Issue No: Vol. 253-254 (2018)
  • A one-dimensional stochastic model of turbulence within and above plant
    • Authors: Livia S. Freire; Marcelo Chamecki
      Pages: 9 - 23
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Livia S. Freire, Marcelo Chamecki
      The suitability of Kerstein's One-Dimensional Turbulence (ODT) model in the representation of atmospheric boundary layer (ABL) flows within and above plant canopies is investigated. The ODT model was adapted to represent a filtered version of flow and scalar fields, equipped with a Smagorinsky-like sub-grid scale model, a wall model, and a parameterization of the canopy effects on the flow. In the filtered ODT, the entire vertical extension of the ABL is modeled and the “resolved” vertical turbulent transport is represented by stochastic eddies that effectively mix fluid parcels across a path length, representing non-local turbulent fluxes that are a critical feature of the canopy roughness sublayer. Simulations for different canopies and stability conditions are performed and vertical profiles of turbulence and scalar statistics are compared with observational and large-eddy simulation data. This new filtered version of the ODT model yields grid-independent results. Model performance for plant canopies is consistent with previous results from ODT for all cases tested without any case-specific parameter adjustment, generating reasonable agreement in profiles of mean velocity, temperature and water vapor mixing ratio, as well as vertical fluxes of momentum and sensible and latent heat, despite the underestimation of all velocity variances. Non-local transport is intrinsic to the formulation of ODT, which represents a significant advantage compared to other reduced-model approaches employed for canopy flows.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2017.12.211
      Issue No: Vol. 250-251 (2018)
  • In situ measurement of stem water content and diurnal storage of an
           apricot tree with a high frequency inner fringing dielectric sensor
    • Authors: H. Zhou; Y. Sun; G. Shan; D.A. Grantz; Q. Cheng; P. Schulze Lammers; L. Damerow; B. Wen; X. Xue; B. Chen
      Pages: 35 - 46
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): H. Zhou, Y. Sun, G. Shan, D.A. Grantz, Q. Cheng, P. Schulze Lammers, L. Damerow, B. Wen, X. Xue, B. Chen
      Stem water content (StWC) is a key parameter characterizing plant water relations. However, a reliable yet non-invasive method of determining StWC in trees has not been developed. Here we examined an inner fringing frequency domain (FD) sensor in a 12-year old apricot tree. Two strap rings operating at 100 MHz accurately measured StWC in stems 4–12 cm in diameter. Effective sensing depth (ESD) inside the stems, and the allowable maximum stem diameter (AMStD) were systematically evaluated. To determine ESD, a novel experimental method, stepwise stem core removal (SStCR), was developed, and combined with numerical simulation using a High Frequency Structure Simulator (HFSS). The experimental and analytical approaches were in good agreement, demonstrating that the ESD must include substantial sapwood. In apricot, with ring-porous distribution of xylem vessels, performance was excellent up to AMStD ≤ 8 cm following temperature correction. In the current study, we characterize diurnal patterns of water loss and recharge in stems of varying diameter, demonstrate hysteresis in water content between stems of different sizes and heights in the canopy, and evaluate potential interactions with ambient temperature fluctuations. The inner fringing FD sensor can be easily constructed at low cost, suggesting the potential for routine measurement of StWC in diverse woody plants.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2017.12.002
      Issue No: Vol. 250-251 (2018)
  • A novel correction for biases in forest eddy covariance carbon balance
    • Authors: Matthew N. Hayek; Richard Wehr; Marcos Longo; Lucy R. Hutyra; Kenia Wiedemann; J. William Munger; Damien Bonal; Scott R. Saleska; David R. Fitzjarrald; Steven C. Wofsy
      Pages: 90 - 101
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Matthew N. Hayek, Richard Wehr, Marcos Longo, Lucy R. Hutyra, Kenia Wiedemann, J. William Munger, Damien Bonal, Scott R. Saleska, David R. Fitzjarrald, Steven C. Wofsy
      Systematic biases in eddy covariance measurements of net ecosystem-atmosphere carbon dioxide exchange (NEE) are ubiquitous in forests when turbulence is low at night. We propose an alternative to the conventional bias correction, the friction velocity (u* ) filter, by hypothesizing that these biases have two separate, concurrent causes: (1) a subcanopy CO2 storage pool that eludes typical storage measurements, creating a turbulence-dependent bias, and (2) advective divergence loss of CO2, creating a turbulence-independent bias. We correct for (1) using a simple parametric model of missing storage (MS). Prior experiments have inferred (2) directly from atmospheric measurements (DRAINO). For sites at which DRAINO experiments have not been performed or are infeasible, we estimate (2) empirically using a PAR-extrapolated advective respiration loss (PEARL) approach. We compare u* filter estimates of advection and NEE to MS-PEARL estimates at one temperate forest and two tropical forest sites. We find that for tropical forests, u* filters can produce a range of extreme NEE estimates, from long-term forest carbon emission to sequestration, that diverge from independent assessments and are not physically sustainable. Our MS model eliminates the dependence of nighttime NEE on u* , consistent with findings from DRAINO studies that nighttime advective losses of CO2 are often not dependent on the strength of turbulence. Our PEARL estimates of mean advective loss agree with available DRAINO measurements. The MS-PEARL correction to long-term NEE produces better agreement with forest inventories at all three sites. Moreover, the correction retains all nighttime eddy covariance data and is therefore more widely applicable than the u* filter approach, which rejects substantial nighttime data—up to 93% at one of the tropical sites. The full MS-PEARL NEE correction is therefore an equally defensible and more practical alternative to the u* filter, but leads to different conclusions about the resulting carbon balance. Our results therefore highlight the need to investigate which approach’s underlying hypotheses are more physically realistic.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2017.12.186
      Issue No: Vol. 250-251 (2018)
  • A drought indicator reflecting ecosystem responses to water availability:
           The Normalized Ecosystem Drought Index
    • Authors: Kuang-Yu Chang; Liyi Xu; Gregory Starr; Kyaw Tha Paw U
      Pages: 102 - 117
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Kuang-Yu Chang, Liyi Xu, Gregory Starr, Kyaw Tha Paw U
      Drought, one of the most destructive natural disasters is projected by numerous studies to become more severe and widespread under climate change. These water limitations will have profound effects on terrestrial systems across the globe. Yet, most of the existing drought monitoring indices are based on drought stress derived from environmental conditions rather than ecosystem responses. Here, we propose using a new approach, the Normalized Ecosystem Drought Index (NEDI), coupled with modified Variable Interval Time Averaging (VITA) method, to quantify drought severity according to ecosystem transitional patterns with water availability. The method is inspired by Sprengel’s and Liebig’s Law of the Minimum for plant nutrition. Eddy covariance measurements from 60 AmeriFlux sites that cross 8 International Geosphere–Biosphere Programme (IGBP) vegetation types were used to validate the use of NEDI coupled to VITA. The results show that NEDI can reasonably depict both drought stress posed by the environment and drought responses presented by various ecosystems. Water availability becomes a dominant limiting factor for ecosystem evapotranspiration when NEDI falls below zero, and normalized evapotranspiration strength generally decreases with decreasing NEDI under this regime. The widely used self-calibrating Palmer Drought Severity Index (sc-PDSI) and Standardized Precipitation Index (SPI) have difficulty capturing ecosystem responses to water availability, although they can reasonably represent drought conditions detected in the environment. The normalization feature employed in NEDI makes it feasible to compare drought severity over different regions, seasons and vegetation types. The new drought index also provides a valuable tool for irrigation and water distribution management practices which may enhance water conservation efforts as drought conditions become more prevalent.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2017.12.001
      Issue No: Vol. 250-251 (2018)
  • Anthropogenic-management could mitigate declines in growth and survival of
           Qinghai spruce (Picea crassifolia) in the east Qilian Mountains, northeast
           Tibetan Plateau
    • Authors: Bo Wang; Tuo Chen; Guobao Xu; Minghui Wu; Gaosen Zhang; Caijuan Li; Guoju Wu
      Pages: 118 - 126
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Bo Wang, Tuo Chen, Guobao Xu, Minghui Wu, Gaosen Zhang, Caijuan Li, Guoju Wu
      Ongoing climate changes posed significant threats to forest growth, structure and ecological functions. However, in our field survey in the east Qilian Mountains, we found that growth condition of Qinghai spruce under climate changes was better in anthropogenic management forest than disturbance-free stands. Accordingly, we suggested a hypothesis that the environmental change induced suppression in Qinghai spruce growth could be mitigated by anthropogenic management. Such a hypothesis was tested by comparing Qinghai spruce growth and population dynamic patterns between anthropogenic-managed forests and disturbance-free ones. We found that Qinghai spruce radial growth persistently declined since the late 1950s in the disturbance-free forests, while the radial growth of anthropogenic-managed trees almost kept steady-going trends since the 1970s in which anthropogenic-management appeared. Besides, some anomalous growth-declining years occurred in disturbance-free forests did not appear in anthropogenic-managed forests in the same year after anthropogenic-management emerged. Moreover, missing ring and tree mortality took place in disturbance-free stands and became increasingly frequent after the mid-1980s. The frequencies and proportions of missing rings and tree die-off were much lower in anthropogenic-managed forests than disturbance-free ones. Additionally, the occurrence of Qinghai spruce radial growth decline and increased mortality in recent time in our disturbance-free forests could be well explained by global-change-type drought in conjunction with elevated temperature and warming-related pest outbreaks. These results would be of fundamental significance for the further understanding of the changing forests, which could provide new clues for forest management and conservation in the future.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2017.12.249
      Issue No: Vol. 250-251 (2018)
  • Predicting autumn phenology: How deciduous tree species respond to weather
    • Authors: Yingying Xie; Xiaojing Wang; Adam M. Wilson; John A. Silander
      Pages: 127 - 137
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Yingying Xie, Xiaojing Wang, Adam M. Wilson, John A. Silander
      Shifts in the timing of autumnal leaf coloration and leaf drop in temperate forests with climate change can have substantial impacts on community and ecosystem processes (e.g. altered carbon/nitrogen cycling and biotic interactions). However, the environmental control of autumn phenology remains significantly understudied in striking contrast to spring phenology. In this study, we used linear mixed effects model with ground-based phenology observations in northeastern USA and found that both weather stressors (e.g. heat- and drought-stress and heavy rainfall) during the growing season and spring phenology significantly affected inter-annual variation in autumn phenology of twelve dominant deciduous tree species. While warm temperatures and drought lead to later fall phenology for most species, heavy rainfall and heat stress lead to earlier leaf coloration and leaf drop. We also found that the phenological sensitivities to weather stressors are diversely species-specific. Under future climate change projections, we predicted that greater summer heat-stress in the future will cause abbreviated leaf coloration seasons for most species. Our mixed-effects modeling framework suggested that accounting for phenological variations among individual trees, species and sites largely improved model predictions, which should not be overlooked in phenological model development. Our study improves our understanding of how species-specific autumnal phenology responds to weather stresses, and describes a new modeling framework to investigate both inter-annual phenological changes and local variations among trees, species, and sites. Our predictions on autumn phenological shifts will help in assessing the effects of climate change on forest community and ecosystem processes in the future.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2017.12.259
      Issue No: Vol. 250-251 (2018)
  • The transient shift of driving environmental factors of carbon dioxide and
           methane fluxes in Tibetan peatlands before and after hydrological
    • Authors: Junwei Luan; Shirong Liu; Jianghua Wu; Mei Wang; Zhen Yu
      Pages: 138 - 146
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Junwei Luan, Shirong Liu, Jianghua Wu, Mei Wang, Zhen Yu
      Peatlands on the Tibetan Plateau play crucial roles in regional carbon cycling but faced serious degradation in recent decades, and hydrological restoration is being conducted to regain their ecosystem function. However, how restoration affects the environmental controls on carbon processes of these unique ecosystems remains unclear, and the role of vegetation community in regulating carbon processes in response to the restoration is unknown. A long dam was built at the outlet of a large shallow lake on the plateau in order to evaluate the effects of hydrological restoration on the carbon sequestration of the world’s largest alpine peatlands. The carbon dioxide (CO2) and methane (CH4) fluxes from three widely distributed peatland communities, i.e., Kobresia pusilla, Carex enervis, and Carex muliensis commuities, were investigated immediately before and after restoration. The water table rising as a consequence of restoration, at least temporarily, decreased the carbon consumption rate (plant respiration plus soil decomposition) for each unit of carbon fixation by plants, which is community dependent. However, a positive relationship between temperature sensitivity of ecosystem respiration (Reco ) and optimal water table for respiration implies a positive feedback between water table rising and warming on Reco . Meanwhile, the dominant factor explaining the variance of Reco shifted from soil temperature (explained 56%) to water table (explained 68%) after restoration. Water table rising enhanced the CH4 emissions by 3–12 times, with significantly different changes in CH4 flux over a standard variation in water table level among the communities. Temperature was excluded while only water table and vegetation type were included in the model to predict CH4 fluxes after restoration in contrast to before. We argue that the shift of driving environmental factors and the role of vegetation community are essential in evaluating the effects of hydrological restoration on carbon cycling of Plateau peatlands, particularly during the transitional period.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2017.12.248
      Issue No: Vol. 250-251 (2018)
  • Monthly microclimate models in a managed boreal forest landscape
    • Authors: Caroline Greiser; Eric Meineri; Miska Luoto; Johan Ehrlén; Kristoffer Hylander
      Pages: 147 - 158
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Caroline Greiser, Eric Meineri, Miska Luoto, Johan Ehrlén, Kristoffer Hylander
      The majority of microclimate studies have been done in topographically complex landscapes to quantify and predict how near-ground temperatures vary as a function of terrain properties. However, in forests understory temperatures can be strongly influenced also by vegetation. We quantified the relative influence of vegetation features and physiography (topography and moisture-related variables) on understory temperatures in managed boreal forests in central Sweden. We used a multivariate regression approach to relate near-ground temperature of 203 loggers over the snow-free seasons in an area of ∼16,000 km2 to remotely sensed and on-site measured variables of forest structure and physiography. We produced climate grids of monthly minimum and maximum temperatures at 25 m resolution by using only remotely sensed and mapped predictors. The quality and predictions of the models containing only remotely sensed predictors (MAP models) were compared with the models containing also on-site measured predictors (OS models). Our data suggest that during the warm season, where landscape microclimate variability is largest, canopy cover and basal area were the most important microclimatic drivers for both minimum and maximum temperatures, while physiographic drivers (mainly elevation) dominated maximum temperatures during autumn and early winter. The MAP models were able to reproduce findings from the OS models but tended to underestimate high and overestimate low temperatures. Including important microclimatic drivers, particularly soil moisture, that are yet lacking in a mapped form should improve the microclimate maps. Because of the dynamic nature of managed forests, continuous updates of mapped forest structure parameters are needed to accurately predict temperatures. Our results suggest that forest management (e.g. stand size, structure and composition) and conservation may play a key role in amplifying or impeding the effects of climate-forcing factors on near-ground temperature and may locally modify the impact of global warming.
      Graphical abstract image

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2017.12.252
      Issue No: Vol. 250-251 (2018)
  • Improving crop yield estimation by assimilating LAI and inputting
           satellite-based surface incoming solar radiation into SWAP model
    • Authors: Ali Mokhtari; Hamideh Noory; Majid Vazifedoust
      Pages: 159 - 170
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Ali Mokhtari, Hamideh Noory, Majid Vazifedoust
      Precise crop yield forecast at regional scales would increase global food security, especially in strategic crops such as wheat and barley. Soil Water Atmosphere Plant (SWAP) is an agro-hydrological model based on a crop growth detailed module that could properly estimate crop yield using satellite observations as input data. In this study, in order to reduce crop yield estimation errors in wheat and barley, MODIS-based leaf area index (LAI) was assimilated using a sequential update algorithm into SWAP, and GLDAS/Noah-derived surface incoming solar radiation (SISR) was used as an alternative to measured SISR. The assimilation of remotely sensed LAI and using SISR as input was examined in nine different cases. Results showed that soil adjusted vegetation index (SAVI) was the best VI for LAI estimation with coefficient of determination (R2) of 0.72 and root mean square error (RMSE) of 0.87 m2 m−2. Also noise equivalent variations indicated an appropriate sensitivity of SAVI along the entire range of LAI variability. GLDAS/Noah-derived SISR showed good agreement with measured SISR; therefore LAI and SISR were jointly used in the model. Simulation results showed that the lowest percent absolute error (PAE) for aboveground dry biomass and grain yield was obtained in case 7 (the assimilation of the peak LAI in addition to ten days after and before the peak LAI is reached) with 1.59% and case 5 (the daily assimilation of LAI until twenty days after the peak LAI is reached) with 6.06%, respectively. Crop yield estimates were improved by 26.25 and 14.4% compared with no LAI assimilation case. Overall, LAI assimilation into SWAP associated with the most efficient cases in this study would result in an accurate crop yield forecast in wheat and barley.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2017.12.250
      Issue No: Vol. 250-251 (2018)
  • Water availability controls Pinus pinaster xylem growth and density: A
           multi-proxy approach along its environmental range
    • Authors: Alberto Arzac; Vicente Rozas; Philippe Rozenberg; José M. Olano
      Pages: 171 - 180
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Alberto Arzac, Vicente Rozas, Philippe Rozenberg, José M. Olano
      Deciphering climatic factors limiting cambial activity is critical to forecast the potential of trees to respond to ongoing climatic change. We explored multiple xylem traits, including tree-ring width, inter-annual microdensity variation and intra-annual density fluctuations (IADF), to unveil the climatic factors constraining cambial activity of a Mediterranean conifer (Pinus pinaster) along a continental-aridity gradient. Secondary growth responded mainly to water availability, explaining as much as 64.7% of earlywood growth variance for earlywood growth. The continuous and non-overlapping timing of the climatic signals of earlywood and latewood growth reflected a continuous water limitation of secondary growth along the growing season. Drought also had an extraordinary impact on minimum (Dmin) and maximum (Dmax) density, with maximal explained variances reaching 47.4% and 39.1%, respectively. Dmin was negatively associated to water availability during the initiation of earlywood formation, whereas Dmax responded positively to water availability during two distinct periods: previous winter and the initiation of latewood formation. IADFs in the latewood were quite common along the gradient, occurred in 21–51% of the rings, and responded to episodes of high rainfall and elevated temperature at different phases of latewood formation. Xylem traits identity outperformed site as a driver of climatic signal, revealing the potential of a multi-proxy approach to unveil multiple facets of the xylogenetic cycle. Cambial plasticity, i.e. the ability to adjust the xylogenesis rate and to arrest and resume cambial activity to exploit favorable climatic windows, was critical for Pinus pinaster to thrive within wide climatic envelopes. Nevertheless, the pervasive effect of water availability on all analyzed traits indicates that forthcoming reduced precipitation and increased evapotranspiration, as predicted by climate change models, will negatively impact P. pinaster secondary growth along its whole environmental range.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2017.12.257
      Issue No: Vol. 250-251 (2018)
  • Forest structure in space and time: Biotic and abiotic determinants of
           canopy complexity and their effects on net primary productivity
    • Authors: Alex T. Fotis; Timothy H. Morin; Robert T. Fahey; Brady S. Hardiman; Gil Bohrer; Peter S. Curtis
      Pages: 181 - 191
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Alex T. Fotis, Timothy H. Morin, Robert T. Fahey, Brady S. Hardiman, Gil Bohrer, Peter S. Curtis
      The structural dynamics of forest canopies involve complex interactions among the abiotic environment, stand structure, species composition and disturbance regimes. How the re-arrangement of tree canopies in space and time affects forest aboveground net primary productivity (ANPP) remains poorly understood, however. In this study, we analyzed a long-term dataset from a temperate deciduous forest in Northern Michigan, USA, to investigate two primary objectives: 1) what abiotic and biotic factors influence canopy complexity and its inter-annual variability, and 2) the direct and indirect effects that abiotic, biotic and canopy complexity variables have on ANPP. We hypothesized that inter-annual variability in canopy complexity would be lower in high complexity canopies and that temporal variability in complexity metrics would be inversely related to ANPP. We found that canopy complexity was highest in more taxonomically diverse stands with high variability in tree diameters and in stands dominated by Populus tremuloides and Populus grandidentata. Canopy complexity was lowest in stands dominated by Quercus rubra and Pinus strobus, which also had lower ANPP. Stands with a high stem density had lower inter-annual variation in canopy complexity, exhibited more height growth and an increase in canopy open space, which in turn enhanced ANPP. Our results provide novel empirical evidence linking temporal stability in canopy complexity to ANPP, and suggest that variability in canopy complexity over time, in addition to the overall mean canopy complexity, may be important when considering drivers of forest carbon uptake.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2017.12.251
      Issue No: Vol. 250-251 (2018)
  • Canopy transpiration of Pinus sylvestris var. mongolica in a sparse wood
           grassland in the semiarid sandy region of Northeast China
    • Authors: Lining Song; Jiaojun Zhu; Mingcai Li; Jinxin Zhang; Xiao Zheng; Kai Wang
      Pages: 192 - 201
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Lining Song, Jiaojun Zhu, Mingcai Li, Jinxin Zhang, Xiao Zheng, Kai Wang
      In a semiarid sandy ecosystem, water is the most important factor in determining survival and growth of Mongolian pine (Pinus sylvestris var. mongolica) in a sparse wood grassland. However, little is known about canopy transpiration of the Mongolian pine in the sparse wood grassland and its influence on the ecosystem water cycling. In this study, we quantified canopy transpiration of Mongolian pine in a sparse wood grassland by using sap flow techniques in combination with observations of climatic factors and soil moisture during two consecutive growing seasons in 2011 and 2012. Results showed that daily canopy transpiration ranged from 0.02 to 0.27 mm day−1 and 0.01 to 0.29 mm day−1, with mean values of 0.14 and 0.15 mm day−1 in 2011 and 2012, respectively. Daily canopy transpiration increased significantly with solar radiation and vapor pressure deficit, and tended to level off at vapor pressure deficit ≥1.5 kPa in both observation years. Although precipitation and soil moisture in August and September were lower in 2011 than in 2012, monthly canopy transpiration in these two months of 2011 were no less than that in 2012, suggesting that trees were able to tap groundwater in August and September of 2011. Throughout the growing seasons, the accumulated canopy transpiration was 20.9 and 22.9 mm in 2011 and 2012, respectively, occupying 6.6 and 4.5% of precipitation (316.7 and 510.3 mm) and 8.0 and 6.1% of evapotranspiration (260.5 and 372.7 mm), indicating that canopy transpiration accounted for a small proportion of the ecosystem water budget. Thus, water budget was balanced in both years. These findings suggest that Mongolian pine in a sparse wood grassland could use groundwater to maintain the canopy transpiration, and the water supply could satisfy the transpiration requirements for growth, therefore, Mongolian pine in a sparse wood grassland could maintain stable under current water conditions.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2017.12.260
      Issue No: Vol. 250-251 (2018)
  • Non-oscillatory response to wind loading dominates movement of Scots pine
    • Authors: Dirk Schindler; Manuel Mohr
      Pages: 209 - 216
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Dirk Schindler, Manuel Mohr
      The response of four trees in a Scots pine (Pinus sylvestris L.) plantation to wind loading was studied using time series decomposition methods. For this purpose, wind speed and stem displacement time series recorded on a windy day were divided into intervals adjusted according to stem displacement. The real wind load acting on the sample trees during the intervals was estimated by the momentum flux at canopy top. To identify components in wind-induced stem displacement that are correlated with the wind, wavelet coherence was calculated. Results from these calculations indicate that the trees mainly responded to wind components with periods longer than their damped fundamental sway periods. Therefore, stem displacement data were decomposed into non-oscillatory and oscillatory components as well as noise using singular spectrum analysis. Results from singular spectrum analysis demonstrate that with increasing momentum flux, the importance of oscillatory components in the stem displacement time series decreases whereas the importance of non-oscillatory displacement components increases. The decreasing importance of the oscillatory components suggests that wind loading in the range of the damped fundamental sway period of the trees is inefficient and insignificant for total tree movement under non-destructive wind conditions. Consequently, there was no evidence of the occurrence of resonance effects between wind and tree response.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2017.12.258
      Issue No: Vol. 250-251 (2018)
  • Spatial variation in springtime temperature index values during ENSO and
           IOD events shows non-equivalent phase response for viticultural regions in
    • Authors: C. Jarvis; R. Darbyshire; I. Goodwin; E. Barlow; R. Eckard
      Pages: 217 - 225
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): C. Jarvis, R. Darbyshire, I. Goodwin, E. Barlow, R. Eckard
      Seasonal variations in winegrape production are intimately connected with growing season weather, with unusually hot or cold temperatures impacting grape and subsequent wine composition. El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) phases impact weather across Australia, particularly at the start of the Southern Hemisphere winegrape growing season; however, impacts are spatially and temporally variable. Temperature-based viticultural climatic indices (e.g. daily maximum springtime temperature) summarise growing season conditions, which allows for inter-annual and inter-regional comparison of conditions and can be used to assess changes to temperature that occur during ENSO and IOD events. This analysis investigated variations in values of a viticultural index, summed daily maximum springtime temperature (SONmax), relative to ENSO-only, IOD-only and ENSO and IOD combined events (ENSOIOD), with the objective of determining whether or not SONmax values changed during the winegrape growing season. Representative sites in 18 viticultural regions in Australia that included a range of climates were selected for analysis. Regional SONmax response to ENSO, IOD, and ENSOIOD event phases was variable. Opposing phases of an event (e.g. IOD positive and IOD negative phases) differed in spatial impact and strength of impact, with some regions responding disproportionately to opposing phases. SONmax values recorded during ENSOIOD event phases showed the most deviation from the mean, suggesting combined ENSOIOD events caused greater SONmax anomalies than either an ENSO or IOD event alone; however, the magnitude of the anomalies differed between regions and varied by phase. Cluster analysis by event phase showed that while some regions consistently had a similar variance of SONmax values relative to other regions, different regions were inconsistent in response. Regional correlation strength and direction (positive or negative) was also related to event and phase, with response to warm and cool phases being non-equivalent. This highlights that impacts of opposing phases are not equal-but-opposite in strength and also vary regionally. Improving regional understanding of impact and prediction for ENSO, IOD, and particularly ENSOIOD would therefore be useful for seasonal planning of viticultural management, as these events can often be predicted before the start of the winegrape growing season in Australia.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2017.12.261
      Issue No: Vol. 250-251 (2018)
  • Probabilistic maize yield prediction over East Africa using dynamic
           ensemble seasonal climate forecasts
    • Authors: Geoffrey E.O. Ogutu; Wietse H.P. Franssen; Iwan Supit; P. Omondi; Ronald W.A. Hutjes
      Pages: 243 - 261
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Geoffrey E.O. Ogutu, Wietse H.P. Franssen, Iwan Supit, P. Omondi, Ronald W.A. Hutjes
      We tested the usefulness of seasonal climate predictions for impacts prediction in eastern Africa. In regions where these seasonal predictions showed skill we tested if the skill also translated into maize yield forecasting skills. Using European Centre for Medium-Range Weather Forecasts (ECMWF) system-4 ensemble seasonal climate hindcasts for the period 1981–2010 at different initialization dates before sowing, we generated a 15-member ensemble of yield predictions using the World Food Studies (WOFOST) crop model implemented for water-limited maize production and single season simulation. Maize yield predictions are validated against reference yield simulations using the WATCH Forcing Data ERA-Interim (WFDEI), focussing on the dominant sowing dates in the northern region (July), equatorial region (March-April) and in the southern region (December). These reference yields show good anomaly correlations compared to the official FAO and national reported statistics, but the average reference yield values are lower than those reported in Kenya and Ethiopia, but slightly higher in Tanzania. We use the ensemble mean, interannual variability, mean errors, Ranked Probability Skill Score (RPSS) and Relative Operating Curve skill Score (ROCSS) to assess regions of useful probabilistic prediction. Annual yield anomalies are predictable 2-months before sowing in most of the regions. Difference in interannual variability between the reference and predicted yields range from ±40%, but higher interannual variability in predicted yield dominates. Anomaly correlations between the reference and predicted yields are largely positive and range from +0.3 to +0.6. The ROCSS illustrate good pre-season probabilistic prediction of above-normal and below-normal yields with at least 2-months lead time. From the sample sowing dates considered, we concluded that, there is potential to use dynamical seasonal climate forecasts with a process based crop simulation model WOFOST to predict anomalous water-limited maize yields.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2017.12.256
      Issue No: Vol. 250-251 (2018)
  • Biological factors dominate the interannual variability of
           evapotranspiration in an irrigated cropland in the North China Plain
    • Authors: Huimin Lei; Tingting Gong; Yuchui Zhang; Dawen Yang
      Pages: 262 - 276
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Huimin Lei, Tingting Gong, Yuchui Zhang, Dawen Yang
      Understanding the interannual variability (IAV) and investigating the physical and biological controls on the IAV of evapotranspiration (ET) is fundamental for better simulating the hydrological processes in cropland where ET is the dominant component of water cycle. However, this topic has not been fully studied, although the number of long-term field observations is growing. By using a combination of long-term field observations (10 years) and agro-hydrological modelling, this study attempted to examine the IAV of ET and the physical and biological controls on the IAV of ET in an irrigated cropland in the North China Plain. This study reveals that the IAV of ET was only 7% in the selected dry subhumid area, which was much smaller than that of water supply (i.e., the sum of precipitation and irrigation). Moreover, the water supply was not the primary controlling factor that influenced the IAV of annual ET. Biological factors, including the leaf area index and bulk stomatal conductance, were found to be the dominant contributors to the IAV of annual ET. Irrigation was an essential water source for crop growth, particularly for winter wheat growth, whereas its contribution to the IAV of ET was smaller than that of precipitation because of the sufficient amount of irrigation. This study demonstrates that the variability of biological factors should be adequately represented in eco-hydrological models to accurately simulate the IAV of annual ET.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2018.01.007
      Issue No: Vol. 250-251 (2018)
  • Soil autotrophic and heterotrophic respiration respond differently to
           land-use change and variations in environmental factors
    • Authors: Shuaidong Hu; Yongfu Li; Scott X. Chang; Yongchun Li; Wenjia Yang; Weijun Fu; Juan Liu; Peikun Jiang; Ziwen Lin
      Pages: 290 - 298
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Shuaidong Hu, Yongfu Li, Scott X. Chang, Yongchun Li, Wenjia Yang, Weijun Fu, Juan Liu, Peikun Jiang, Ziwen Lin
      Converting natural forests to intensively managed plantations markedly alters soil carbon (C) dynamics. However, the impact of such land-use change on soil respiration (RS) components remains unclear. The objective of this study was to examine the effect on RS, autotrophic respiration (RA) and heterotrophic respiration (RH) of converting a natural evergreen broadleaf forest to an intensively managed Moso bamboo (Phyllostachys edulis) plantation. A two-year field study was carried out to assess the seasonal dynamics of RS, RA and RH in three broadleaf forest-bamboo plantation pairs, using a portable soil CO2 flux measurement system. Results showed that converting the evergreen broadleaf forest to the bamboo plantation increased the annual cumulative RS and RH by 18.8% and 20.9%, respectively, but did not change the annual cumulative RA. Soil temperature alone explained 48% and 79% of seasonal variations in RA and RH, respectively, in the evergreen broadleaf forest, and 68% and 79%, respectively, in the bamboo plantation. The land-use change increased the apparent temperature sensitivity (Q 10) of RA, but did not affect that of RH. Regardless of the land-use type, both RA and RH were positively correlated with soil water soluble organic C, but not with soil moisture content. The RH was positively correlated to soil microbial biomass C (MBC) in the evergreen broadleaf forest, but not in the bamboo plantation. The RA was not correlated with soil MBC, regardless of the land-use type. Therefore, soil RA and RH responded differently to land-use change and variations in environmental factors, suggesting that partitioning of RS to different components is essential to elucidate mechanisms associated with changes in RS induced by land-use change and to predict RS under different climate change scenarios.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2018.01.003
      Issue No: Vol. 250-251 (2018)
  • A three-year experiment of annual methane and nitrous oxide emissions from
           the subtropical permanently flooded rice paddy fields of China: Emission
           factor, temperature sensitivity and fertilizer nitrogen effect
    • Authors: Minghua Zhou; Xiaoguo Wang; Yanqiang Wang; Bo Zhu
      Pages: 299 - 307
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Minghua Zhou, Xiaoguo Wang, Yanqiang Wang, Bo Zhu
      Annual CH4 and N2O emissions from these rice production systems that accounts for over 10% of national rice cultivation of China are rarely reported. To improve understanding of greenhouse gas emissions from croplands in China, we measured methane (CH4) and nitrous oxide (N2O) emissions from the subtropical permanently flooded rice paddy fields through a 3-year field experiment that utilized three nitrogen fertilizer application rates (0 [N0], 150 [N150] and 250 [N250] kg N ha−1) in southwestern China. Results showed that seasonal patterns of CH4 and N2O emissions were consistent with temporal weather patterns. The average annual cumulative CH4 fluxes were in the range of 794 to 883 kg CH4-C ha−1 yr−1 and N2O fluxes ranged from 1.61 to 3.10 kg N2O-N ha−1 yr−1 across the experimental treatments. The Q10 values (soil temperature sensitivity coefficient) of CH4 and N2O emissions were 2.72–3.67 and 3.32–6.05, respectively, for the three treatments. Inconsistent with our hypothesis, the nitrogen fertilizer application did not increase seasonal and annual N2O emissions over three years, compared to the control. Thus, the annual direct N2O emission factors (EFd) averaged 0.07%, which was substantially lower than the IPCC default value of 0.30% for rice paddy fields. Nitrogen fertilizer application significantly decreased the mean seasonal global warming potential (GWP) and yield-scaled GWP for the rice season, whereas this was not true on an annual basis if fallow season was also considered. Since CH4 emission was the major contributor to total GWP, it is necessary to propose mitigation options, which could include draining the floodwater layer and introducing upland crops during the fallow season. However, it will be challenging to reduce N2O emissions and retain soil organic carbon if the floodwater layer is drained and upland crops are introduced during the fallow season.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2017.12.265
      Issue No: Vol. 250-251 (2018)
  • Intensity and temporality of airborne Quercus pollen in the southwest
           Mediterranean area: Correlation with meteorological and phenoclimatic
           variables, trends and possible adaptation to climate change
    • Authors: M. Recio; A. Picornell; M.M. Trigo; D. Gharbi; J. García-Sánchez; B. Cabezudo
      Pages: 308 - 318
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): M. Recio, A. Picornell, M.M. Trigo, D. Gharbi, J. García-Sánchez, B. Cabezudo
      This paper deals with aerobiological analyses realised during last 25 years in the atmosphere of Malaga, a coastal city located in the southwest of the Mediterranean Basin. Air sampling was performed by means of 7-day recording volumetric pollen and spore traps, and pollen grains were counted with the aid of a light microscope, according to the methodology proposed by the Spanish Aerobiology Network. Pollen data were expressed as number of pollen grains per cubic metre of air. A peak in Quercus pollen production approximately every four years was detected, coinciding with drought periods. Although the natural vegetation of the studied area has been altered by urban growth and reforestation with pines, it is still represented by a disperse natural population of cork oak, holm oak and kermes oak (predominantly located to the northwest and northeast of the city). In this period the seasonal behaviour of anemophilous pollination of Quercus was studied, along with the relation between its intensity (pollen production) or temporality (phenophase of flowering) and meteorological or climatic variables. Also a study of trends in production and phenology of flowering was carried out. The annual intensity of anemophilous pollination of Quercus was significantly associated with the meteorological conditions of each spring, with the same parameters involved and in the same way as were seen on the daily and weekly scale (positive correlation with temperature and insolation, and negative with precipitation and relative humidity). The tendency for temperature and atmospheric aridity to increase is probably the cause of the trend observed in the spring Quercus pollen production to increase in the western Mediterranean. The temporality of Quercus anemophilous pollination (start date, peak date, end date and duration) changes each year and is positively associated with accumulated temperature and sun hours from 1st January until the dates in question. An accumulation of approximately 796 °C above the 9 °C threshold temperature from 1st January is necessary to trigger the start of the flowering period. We conclude that the effect of climatic change is mainly reflected in the pollination intensity of woody anemophilous species, which, in turn, have adapted their flowering time (phenology) to climate change. It is important to remember that climate change is leading to more arid conditions and that Mediterranean plants are adapted to this macrobioclimate (Mediterranean), which is characterized by a long dry period and high temperatures.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2017.11.028
      Issue No: Vol. 250-251 (2018)
  • Modelling maize phenology, biomass growth and yield under contrasting
           temperature conditions
    • Authors: Na Wang; Enli Wang; Jing Wang; Jianping Zhang; Bangyou Zheng; Yi Huang; Meixiu Tan
      Pages: 319 - 329
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Na Wang, Enli Wang, Jing Wang, Jianping Zhang, Bangyou Zheng, Yi Huang, Meixiu Tan
      Crop modelling has become an effective means to assess climate change impact on crop yield and to assist in development of adaptation strategies. Previous studies found large uncertainty in simulated crop yields, especially beyond optimal temperature range. In this paper, we combined the data reported in literature and our controlled-temperature experiment to derive the temperature response functions of phenological development and biomass growth of maize crop based on the Wang-Engel function (Agricultural systems, 58(1): 1–24), and compared them with those adopted in two mostly used maize growth models APSIM-Maize and CERES-Maize. Our results support the previous findings that leaf elongation, leaf appearance and the rate of development towards flowering have the same temperature response. Our results indicate that a curvilinear response with cardinal temperatures of 5 °C (base), 30 °C (optimum), and 41 °C (maximum) best describes the maize developmental response to temperature. For radiation use efficiency (RUE-biomass growth per unit intercepted radiation) of maize, the corresponding cardinal temperatures are likely to be 2 °C, 24 °C, and 38 °C respectively. All the cardinal temperatures are lower than what are used in current APSIM model. Replacing the default temperature responses with the newly derived ones led to contrasting differences in simulated flowering and maturity time across China’s Maize Belt, while the differences in simulated maize yield were relatively smaller. This implies the importance to use the correct temperature response in maize growth modelling so that the genotype by environment interactions in response to rising temperature can be correctly captured.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2018.01.005
      Issue No: Vol. 250-251 (2018)
  • Do windbreaks reduce the water consumption of a crop field'
    • Authors: Michiaki Sugita
      Pages: 330 - 342
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Michiaki Sugita
      Two ratios, A c = [ ( q * c − q a ) u = α u 0 ( q * c − q a ) u = u 0 ] / [ ( r c + r a v c ) u = α u 0 ( r c + r a v c ) u = u 0 ]   for the canopy layer and equivalent ratio Ag for the soil layer, were proposed for use to assess if soil evaporation (Eg ) and canopy transpiration (Ec ) decrease when wind speeds are reduced by windbreaks by a fraction of α, with qa being the specific humidity of the air, q* c the saturated specific humidity of the canopy layer, rc the canopy resistance, and ravc the aerodynamic resistance for moisture transfer. These ratios can be organized to form criteria, ΔEc  <  0 (Ac  <  1) and ΔEg  <  0 (Ag  < 1). Thus ΔE < 0 if Ac < 1 and Ag  <  1. If only one of the ratios is smaller than unity, the sign of ΔE depends on that of ΔEg  + ΔEc . The criteria were examined by a dual-source crop community model to simulate energy and water balances of a crop field with data obtained in the Nile Delta. It was found that both ΔE ≥ 0 and ΔE < 0 were possible and ΔE was mainly determined by ΔEg during the fallow and early stages of the cropping seasons and by ΔEc in the late cropping period. Overall, the scale of the roughness elements hc and soil moisture θ were found to be the major factors to determine ΔEc , ΔEg , and ΔE. A larger hc tends to produce ΔE ≥ 0; and ΔEc and ΔEg decrease as θ increases.

      PubDate: 2018-02-05T12:24:30Z
      DOI: 10.1016/j.agrformet.2017.11.033
      Issue No: Vol. 250-251 (2018)
  • Earlier leaf-flushing suppressed ecosystem productivity by draining soil
           water in the Mongolian Plateau
    • Authors: Zhen Yu; Chaoqun Lu; Peiyu Cao; Hanqin Tian; Amy Hessl; Neil Pederson
      Pages: 1 - 8
      Abstract: Publication date: 15 March 2018
      Source:Agricultural and Forest Meteorology, Volumes 250–251
      Author(s): Zhen Yu, Chaoqun Lu, Peiyu Cao, Hanqin Tian, Amy Hessl, Neil Pederson
      Recent earlier greening trends are believed to enhance terrestrial ecosystem productivity. However, advanced onset of growing season may also deplete soil water in early spring, leading to summer water stress for plant growth. In this study, we linked soil moisture with start of growing season (SGS, represented by day of year) to examine the responses of ecosystem productivity to water stress during 1982–2011 on the Mongolian Plateau. Results showed that, though not significant, earlier SGS has tendency to enhance spring productivity at north part of the study area. Nonetheless, we observed that suppressed summer photosynthesis due to phenology-induced water stress dramatically reduced annual carbon assimilation. Thus, phenology-associated changes in soil moisture have profound potential in regulating seasonal and annual productivity in arid and semi-arid ecosystems. The relationship between SGS and GPP was not observed in more mesic forest ecosystems (R2 =0.04, p> 0.10) nor in the agricultural area (R2 =0.03, p> 0.10) where practices like irrigation aim to alleviate summer water stress. Therefore, at the scale of the entire study area, earlier growing season did not translate to higher productivity (R2 =0.006). On the contrary, advanced SGS aggravated growing-season water stress, which in turn, supressed annual carbon assimilation in water limited area. This mechanism implies the advanced greening trends may not necessarily lead to more carbon uptake in terrestrial ecosystems but rather a carbon loss, especially in the arid and semi-arid regions.
      Graphical abstract image

      PubDate: 2017-12-13T01:06:03Z
      DOI: 10.1016/j.agrformet.2017.11.035
      Issue No: Vol. 250-251 (2017)
  • Simple models to predict grassland ecosystem C exchange and actual
           evapotranspiration using NDVI and environmental variables
    • Authors: Stephen J. Del Grosso; W.J. Parton; Justin D. Derner; Maosi Chen; Compton J. Tucker
      Pages: 1 - 10
      Abstract: Publication date: 15 February 2018
      Source:Agricultural and Forest Meteorology, Volume 249
      Author(s): Stephen J. Del Grosso, W.J. Parton, Justin D. Derner, Maosi Chen, Compton J. Tucker
      Semiarid grasslands contribute significantly to net terrestrial carbon flux as plant productivity and heterotrophic respiration in these moisture-limited systems are correlated with metrics related to water availability (e.g., precipitation, Actual EvapoTranspiration or AET). These variables are also correlated with remotely sensed metrics such as the Normalized Difference Vegetation Index (NDVI). We used measurements of growing season net ecosystem exchange of carbon (NEE), NDVI from eMODIS and AVHRR, precipitation, and volumetric soil water content (VSWC) from grazed pastures in the semiarid, shortgrass steppe to quantify the correlation of NEE with these driving variables. eMODIS NDVI explained 60 and 40% of the variability in daytime and nighttime NEE, respectively, on non-rain days; these correlations were reduced to 41 and 15%, respectively, on rain days. Daytime NEE was almost always negative (sink) on non-rain days but positive on most rain days. In contrast, nighttime NEE was always positive (source), across rain and non-rain days. A model based on eMODIS NDVI, VSWC, daytime vs. nighttime, and rain vs. non-rain days explained 48% of observed variability in NEE at a daily scale; this increased to 62% and 77%, respectively, at the weekly and monthly scales. eMODIS NDVI explained 50–52% of the variability in AET regardless of rain or non-rain days. A model based on eMODIS NDVI, VSWC, Potential EvapoTranspiration (or PET), and rain vs. non-rain days explained 70% of the observed variability in AET at a daily scale; this increased to 90 and 96%, respectively, at weekly and monthly scales. Models based on AVHRR NDVI showed similar patterns as those using eMODIS, but correlations with observations were lower. We conclude that remotely-sensed NDVI is a robust tool, when combined with VSWC and knowledge of rain events, for predicting NEE and AET across multiple temporal scales (day to season) in semiarid grasslands.

      PubDate: 2017-11-24T07:10:28Z
      DOI: 10.1016/j.agrformet.2017.11.007
      Issue No: Vol. 249 (2017)
  • A steady-state approximation approach to simulate seasonal leaf dynamics
           of deciduous broadleaf forests via climate variables
    • Authors: Qinchuan Xin; Yongjiu Dai; Xia Li; Xiaoping Liu; Peng Gong; Andrew D. Richardson
      Pages: 44 - 56
      Abstract: Publication date: 15 February 2018
      Source:Agricultural and Forest Meteorology, Volume 249
      Author(s): Qinchuan Xin, Yongjiu Dai, Xia Li, Xiaoping Liu, Peng Gong, Andrew D. Richardson
      As leaves are the basic elements of plants that conduct photosynthesis and transpiration, vegetation leaf dynamics controls canopy physical and biogeochemical processes and hence largely influences the interactive exchanges of energy and materials between the land surface and the atmosphere. Given that the processes of plant leaf allocation is highly sensitive to climatological and environmental conditions, developing robust models that simulate leaf dynamics via climate variables contributes a key component to land surface models and coupled land-atmosphere models. Here we propose a new method to simulate seasonal leaf dynamics based on the idea of applying vegetation productivity as a synthesized metric to track and assess the climate suitability to plant growth over time. The method first solves two closed simultaneous equations of leaf phenology and canopy photosynthesis as modeled using the Growing Production-Day model iteratively for deriving the time series of steady-state leaf area index (LAI), and then applies the method of simple moving average to account for the time lagging of leaf allocation behind steady-state LAI. The seasonal LAI simulated using the developed method agree with field measurements from a selection of AmeriFlux sites as indicated by high coefficient of determination (R2 =0.801) and low root mean square error (RMSE=0.924m2/m2) and with satellite-derived data (R2 =0.929 and RMSE=0.650m2/m2) for the studied flux tower sites. Moreover, the proposed method is able to simulate seasonal LAI of deciduous broadleaf forests that match with satellite-derived LAI time series across the entire eastern United States. Comparative modeling studies suggest that the proposed method produces more accurate results than the method based on Growing Season Index in terms of correlation coefficients and error metrics. The developed method provides a complete solution to modeling seasonal leaf dynamics as well as canopy productivity solely using climate variables.

      PubDate: 2017-11-24T07:10:28Z
      DOI: 10.1016/j.agrformet.2017.11.025
      Issue No: Vol. 249 (2017)
  • Stronger ecosystem carbon sequestration potential of mangrove wetlands
           with respect to terrestrial forests in subtropical China
    • Authors: Xiaowei Cui; Jie Liang; Weizhi Lu; Hui Chen; Fang Liu; Guangxuan Lin; Fanghong Xu; Yiqi Luo; Guanghui Lin
      Pages: 71 - 80
      Abstract: Publication date: 15 February 2018
      Source:Agricultural and Forest Meteorology, Volume 249
      Author(s): Xiaowei Cui, Jie Liang, Weizhi Lu, Hui Chen, Fang Liu, Guangxuan Lin, Fanghong Xu, Yiqi Luo, Guanghui Lin
      Mangrove wetlands and terrestrial forests are considered as important carbon sinks for alleviating climate changes, but the sequestration processes and regulations of climate factors on controlling the variability of carbon fluxes of these ecosystems may differ. In order to compare the different mechanisms of carbon sequestration in mangrove and terrestrial forest ecosystems, we analyzed ecosystem CO2 flux data measured by eddy covariance (EC) technique from four forests ecosystems in subtropical China: two mangrove wetlands and two terrestrial forests. Our results showed that the mangrove wetlands could sequester much more carbon than the nearby terrestrial forests because of significantly higher gross ecosystem production (GEP) and lower ecosystem respiration (Re) values. Moreover, our analysis of the responses of net ecosystem exchange (NEE) to photosynthetically active radiation showed that the mangrove wetlands had lower light compensation point but higher maximum photosynthesis rates than the terrestrial forests. Furthermore, the relationships between Re and air temperature (T air ) showed the ecosystem respiration rate (Re ref ) at 20°C values were lower but that the temperature sensitivity (Q10) values were higher in the mangrove wetlands than in the terrestrial forests, which might be caused by tides in the mangrove ecosystems. In addition, the relationships between the logarithmic values of soil organic carbon ln(SOC) and δ13C indicated that SOC decomposition rates were lower in mangrove forests than in terrestrial forests, which thus led to lower Re values compared to terrestrial forests. Our results imply that mangrove forests can sequester more CO2 from the atmosphere than nearby terrestrial forests due to relatively higher GEP and lower Re values. Moreover, the regulation of ecosystem carbon exchange by tides in mangrove wetlands should be investigated in more detail in future studies.

      PubDate: 2017-12-13T01:06:03Z
      DOI: 10.1016/j.agrformet.2017.11.019
      Issue No: Vol. 249 (2017)
  • Surface energy exchanges over contrasting vegetation types on a
           sub-tropical sand island
    • Authors: Michael A. Gray; Hamish A. McGowan; Andrew L. Lowry; Adrien Guyot
      Pages: 81 - 99
      Abstract: Publication date: 15 February 2018
      Source:Agricultural and Forest Meteorology, Volume 249
      Author(s): Michael A. Gray, Hamish A. McGowan, Andrew L. Lowry, Adrien Guyot
      The surface energy balance of sub-tropical coastal vegetation has received little attention. Here we present a multi-year observational data set using the eddy covariance method to quantify, for the first time, the surface energy balance over three contrasting representative vegetation types on a sub-tropical sand island in eastern Australia: a periodically inundated sedge swamp, an exotic pine plantation and a palustrine wetland. On seasonal time scales, the palustrine wetland exhibited a Bowen ratio (β)≈1, the pine plantation β>1, and the swamp β varied from β≤1 during wet seasons and inundation to β>1 during dry seasons. The partitioning of energy is similar to a variety of Australian ecosystems and coastal vegetation types in other latitudes. Energy fluxes responded to seasonal changes in background meteorology with the most important influences being net radiation and the surface layer temperature gradient, with the soil temperature-ambient temperature gradient, ground temperature, and vapour pressure deficit also important. Sites differed according to soil water content, with the remnant palustrine wetland and swamp having ready access to water but the exotic pine plantation having much drier soils. We conclude that should the current balance between vegetation types change, there would be a corresponding shift in the overall surface energy balance of the island, affecting its micrometeorology, and water table depth.

      PubDate: 2017-12-13T01:06:03Z
      DOI: 10.1016/j.agrformet.2017.11.018
      Issue No: Vol. 249 (2017)
  • Microclimate differences above ground-layer vegetation in lichen-dominated
           pine forests of north-central British Columbia
    • Authors: Sean R. Haughian; Philip J. Burton
      Pages: 100 - 106
      Abstract: Publication date: 15 February 2018
      Source:Agricultural and Forest Meteorology, Volume 249
      Author(s): Sean R. Haughian, Philip J. Burton
      Lodgepole pine forests of north-central British Columbia have patchy ground-layer vegetation, typically dominated by either fruticose lichens, feathermosses, or ericaceous vascular plants; this patchy structure has been shown to correspond with environmental variables that likely moderate the ground-layer microclimate. To investigate the potential role of microclimate on patterns of dominance of ground-layer functional groups, we recorded temperature and relative humidity above the ground-layer vegetation during 25 summer days over patches dominated by mat-forming lichens, feathermosses, or vascular plants. Data were summarized for raw microclimate attributes and daily water potential of the air, and in terms of modelled equilibrium water content of moss or lichen thalli. Analysis of variance revealed significant differences in the water potential of air above the three patch types under sunny conditions, but not under overcast conditions. Differences in vegetation cover were only associated with differences in atmospheric moisture when using data from sunny periods during the daytime. These data confirm that lichens occupy microclimatic niches that are distinctly drier than those of feathermosses or vascular plants, and corroborate the suggested mechanism by which canopy or soil properties influence these types of ground-layer vegetation.

      PubDate: 2017-12-13T01:06:03Z
      DOI: 10.1016/j.agrformet.2017.11.029
      Issue No: Vol. 249 (2017)
  • Evaluation of six indices for monitoring agricultural drought in the
           south-central United States
    • Authors: Liyan Tian; Shanshui Yuan; Steven M. Quiring
      Pages: 107 - 119
      Abstract: Publication date: 15 February 2018
      Source:Agricultural and Forest Meteorology, Volume 249
      Author(s): Liyan Tian, Shanshui Yuan, Steven M. Quiring
      Drought indices are widely used for drought monitoring. This study evaluates the performance of six indices (Palmer’s Drought Severity Index (PDSI), Palmer’s Z-index, precipitation percent normal, precipitation percentiles, Standardized Precipitation Index (SPI), and the Standardized Precipitation Evapotranspiration Index (SPEI)) to determine which are most appropriate for monitoring agricultural drought in the south-central United States. Soil moisture and crop yield data for winter wheat, corn and cotton are used to assess the performance of drought indices. The results indicate that SPEI is the most representative of soil moisture conditions. The best drought index for crop yield varies depending on crop type and growth stage. Z-index and SPEI have relatively higher correlations with all the crop yields. However, when only considering years with weather and yield conditions that are substantially above or below normal, all of the drought indices are highly correlated with crop yield. Our results demonstrate that no single drought index can capture all aspects of agricultural drought in the south-central United States. Therefore, it is important to quantitatively evaluate multiple drought indices to determine which is most appropriate for the location and crop of interest.

      PubDate: 2017-12-13T01:06:03Z
      DOI: 10.1016/j.agrformet.2017.11.024
      Issue No: Vol. 249 (2017)
  • Different genotypes of Dalbergia sissoo trees modified microclimate
           dynamics differently on understory crop cowpea (Vigna unguiculata) as
           assessed through ecophysiological and spectral traits in agroforestry
    • Authors: Badre Alam; Rashmi Singh; A.R. Uthappa; Mayank Chaturvedi; Anil Kumar Singh; Ram Newaj; A.K. Handa; O.P. Chaturvedi
      Pages: 138 - 148
      Abstract: Publication date: 15 February 2018
      Source:Agricultural and Forest Meteorology, Volume 249
      Author(s): Badre Alam, Rashmi Singh, A.R. Uthappa, Mayank Chaturvedi, Anil Kumar Singh, Ram Newaj, A.K. Handa, O.P. Chaturvedi
      Microclimate being a crucial and challenging issue for the growth, survivability and ecological relevance of understory crops in agroforestry system, major aim of the present study was to determine that how the micro-environment was modulated by the canopies of different genotypes of a same tree species. Field experiments were conducted at Central Agroforestry Research Institute, Jhansi, during kharif (rainy) season located in a semi-arid region of Central India. Cowpea [Vigna unguiculata (L.) Walp. variety Gomti] was grown under three genotypes namely Bundel-2 (PT-2), Bundel-6 (PT-6) and one local of Dalbergia sissoo Roxb. tree. Cowpea was also grown in adjacent open field (treeless area) for comparison. Microclimate variables as incident photosynthetic photon flux density (PPFD), air temperature, leaf temperature, canopy temperature depression and soil surface temperature were monitored for understanding microclimate dynamics with reference to the understory crop. Several ecophysiological and leaf spectral traits were also evaluated for assessing the efficiency of the understory crop keeping relevance with microclimate modulation and their use as determinants. Light interception was remarkably different under the canopies of three different genotypes of D. sissoo trees. Intercepted PPFD (iPPFD) was higher by PT-2 and PT-6 than the local. Higher iPPFD was related to the higher leaf area index (LAI) of the corresponding tree genotypes indicating the larger canopy of the improved genotypes captured more light than the local one and thus a strong linear correlation was obtained between iPPFD and LAI. Microclimate variables such as air temperature, canopy temperature, canopy temperature depression, soil surface temperature and relative humidity (RH) were conspicuously different in the areas under the different tree genotypes in the field. There was clear vertical gradient of temperature at the top, middle and bottom layer of the tree canopies. Similarly, RH of the spaces in between the tree-rows showed a vertical gradient. Vertical profile of temperature was different depending on the tree genotypes and RH was much higher inside canopy than in the open field. Intensity of shade varied depending upon the tree genotypes and it was strongly associated with the LAI and iPPFD. Deep shade (50–60%) was observed under the PT-2 and PT-6, whereas moderate shade (up to 30%) was observed under the local genotype. Grain yield of cowpea was relatively less under the PT-2 and PT-6.Thus yield was found associated with the iPPFD by the respective tree canopies and the modulation of the microclimate dynamics. Various ecophysiological traits namely CO2 assimilation, electron transport rate across PS-II (ETR), transpiration, stomatal conductance, reflectance based leaf spectral traits like CCI, NDVI and PRI were also observed to be associated with differential responses of the understory crop. Our results highlighted about the relevance and significance of the ecophysiological and spectral traits evaluated as indicators towards better understanding of the microclimate modulation by the tree canopies of different genotypes and efficiency of the understory crop in agroforestry. Overall, these results demonstrated that the tree canopies of a same species played critical role not only in controlling the efficiency of understory crop, but also in modulating the microclimate which has significance for various ecosystem services perspectives.

      PubDate: 2017-12-13T01:06:03Z
      DOI: 10.1016/j.agrformet.2017.11.031
      Issue No: Vol. 249 (2017)
  • Contrasting responses of grassland water and carbon exchanges to climate
           change between Tibetan Plateau and Inner Mongolia
    • Authors: Dan Liu; Yue Li; Tao Wang; Philippe Peylin; Natasha MacBean; Philippe Ciais; Gensuo Jia; Mingguo Ma; Yaoming Ma; Miaogen Shen; Xianzhou Zhang; Shilong Piao
      Pages: 163 - 175
      Abstract: Publication date: 15 February 2018
      Source:Agricultural and Forest Meteorology, Volume 249
      Author(s): Dan Liu, Yue Li, Tao Wang, Philippe Peylin, Natasha MacBean, Philippe Ciais, Gensuo Jia, Mingguo Ma, Yaoming Ma, Miaogen Shen, Xianzhou Zhang, Shilong Piao
      The grassland ecosystems in Tibetan Plateau (TP) and Inner Mongolia (IM) of China play important roles in climate change mitigation and food and livestock production. These two regions have increasingly experienced higher temperatures and changing precipitation regimes over the past three decades. However, it remains uncertain to what extent rising temperature and varying precipitation regulate the water and carbon fluxes across alpine (TP) and temperate (IM) grasslands. Here, we first optimize a process-based model of carbon and water fluxes using eddy-covariance data (three sites in TP and six sites in IM), and analyze the simulated carbon and water fluxes based upon the optimized model exposed to a range of annual temperature and precipitation anomalies. We found that the changes in net ecosystem-atmosphere carbon exchange (NEE) of TP grassland are relatively small because the ecosystem respiration (Re) and the gross primary productivity (GPP) increase at comparable rate with warming across multiple sites (Re: 22.1±21.4gCm−2 year−1 °C−1, GPP: 22.43±36.41gCm−2 year−1 °C−1), which is due to the possibility that grasslands cannot respire more than the available supply of photosynthesis. The NEE of IM grassland increases (more carbon loss from ecosystem) with warming, which is mainly because GPP decreases faster than Re under warm-induced reduction in moisture availability, and the sensitivity of Re to warming (1.17±3.56gCm−2 year−1 °C−1) is much smaller than that of GPP (15.53±15.91gCm−2 year−1 °C−1). These results indicate that water is the major limiting factor in IM grasslands, but not in TP grasslands. In contrast to warming, we found an asymmetric response of water and carbon fluxes to drying and wetting in TP grasslands (i.e. a large decrease under the drying condition and a small increase under the wetting condition) but almost a linear response in IM grasslands. We therefore highlight that the underlying processes regulating the responses of water and carbon cycles to warming are fundamentally different between TP and IM grasslands, with the moisture being the major limiting factor in IM while grasslands in TP are much more limited by thermal conditions. Our results also imply that warming would significantly stimulate the net ecosystem carbon loss to atmosphere but not significantly enhance ET in IM grasslands, which may provide a positive feedback to accelerate climate change. Inversely, warming could not significantly affect the ecosystem carbon exchange but significantly enhance ET in TP grasslands, which may provide a negative feedback to mitigate climate change in alpine grasslands.

      PubDate: 2017-12-13T01:06:03Z
      DOI: 10.1016/j.agrformet.2017.11.034
      Issue No: Vol. 249 (2017)
  • Modeling vegetation green-up dates across the Tibetan Plateau by including
           both seasonal and daily temperature and precipitation
    • Authors: Ruyin Cao; Miaogen Shen; Ji Zhou; Jin Chen
      Pages: 176 - 186
      Abstract: Publication date: 15 February 2018
      Source:Agricultural and Forest Meteorology, Volume 249
      Author(s): Ruyin Cao, Miaogen Shen, Ji Zhou, Jin Chen
      Shifts in vegetation phenology induced by climate change are substantially modifying various ecosystem processes, and those changes can in turn affect weather and climate systems. Realistic modeling of spring vegetation green-up is critical to improving process-based ecosystem models of the Tibetan Plateau (TP) and for better understanding of the coupling between TP terrestrial biophysical processes and the Asian monsoon system. However, no model is available for simulating the vegetation green-up date (VGD) across the entire TP. In this study, we first assessed the ability of several existing state-of-the-art phenological models to estimate VGD across the TP. We then modified the existing models by adding environmental constraints identified by partial least-squares analyses. The modified models simulated VGDs with lower estimation errors than other models (Mean absolute error: 8.2days vs. 8.7–12.9days; P<0.01, t-test). Moreover, although our model captured the inter-annual variations in VGD better than any previous model, the correlation coefficient between predicted and remotely sensed VGDs was still low, especially in the western TP. This study revealed the necessity of considering multiple factors in VGD models and highlighted the challenge of developing models that will better represent phenology in future ecosystem models.

      PubDate: 2017-12-13T01:06:03Z
      DOI: 10.1016/j.agrformet.2017.11.032
      Issue No: Vol. 249 (2017)
  • Measured and modelled wind variation over irregularly undulating terrain
    • Authors: John D. Wilson
      Pages: 187 - 197
      Abstract: Publication date: 15 February 2018
      Source:Agricultural and Forest Meteorology, Volume 249
      Author(s): John D. Wilson
      The steady-state, Reynolds-averaged momentum equations, with a simple eddy viscosity closure, are solved numerically to compute the spatial variation in surface-layer mean windspeed over irregular, gently rolling terrain. Simulations, with both this non-linear model “ASL3D” and (for comparison) with the pre-existing linear “Mixed Spectral Finite-Difference” or MSFD model, are compared with observed winds from anemometers aligned on a 140m transect in a rolling field near Lacombe, Alberta. Recorded wind speeds, normalized and aggregated by wind direction sector, characterize local wind variation over terrain whose elevation varied by roughly ±10m over a radius of about half a kilometer from the instrumented transect. For northeast and southwest winds particularly, both models agree well with the observations. In southeast winds, observed spatial variation of the wind was weak, except that an anemometer close to fences and gates recorded distinctly lower speeds: provided those obstructions are represented by adding a localized sink in the momentum equations, the ASL3D model transect is (again) in quite good agreement with the observations. For northwest winds, however, agreement of modelled and measured transects is poor, presumably because a steep, wooded slope lay upwind from the anemometer array. Overall the linear correlation coefficient between modelled and observed fractional deviations of wind speed from the reference value is 0.72. Other than as regards the flexibility to represent such complications as fences, plant canopies (etc.), computed wind fields over for the present terrain do not suggest any compelling advantage of the more laborious non-linear model (ASL3D) over the semi-analytical MSFD treatment. It is concluded that, when applied over gentle terrain, the skill intrinsic to even such a simple paradigm as ASL3D (and MSFD) represents a meaningful and potentially useful alternative to the neglect of lateral inhomogeneity.

      PubDate: 2017-12-13T01:06:03Z
      DOI: 10.1016/j.agrformet.2017.11.026
      Issue No: Vol. 249 (2017)
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
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