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Publisher: Elsevier   (Total: 3031 journals)

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Showing 1 - 200 of 3031 Journals sorted alphabetically
AASRI Procedia     Open Access   (Followers: 15)
Academic Pediatrics     Hybrid Journal   (Followers: 20, SJR: 1.402, h-index: 51)
Academic Radiology     Hybrid Journal   (Followers: 16, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 79, SJR: 1.109, h-index: 94)
Accounting Forum     Hybrid Journal   (Followers: 22, SJR: 0.612, h-index: 27)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 27, 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: 302, SJR: 0.726, h-index: 43)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 3)
Acta Biomaterialia     Hybrid Journal   (Followers: 25, SJR: 2.02, h-index: 104)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription  
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   (SJR: 0.123, h-index: 8)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.604, h-index: 38)
Acta Materialia     Hybrid Journal   (Followers: 195, 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: 9, 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: 21, SJR: 1.365, h-index: 73)
Acta Sociológica     Open Access  
Acta Tropica     Hybrid Journal   (Followers: 5, 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: 3, 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: 4)
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: 5)
Additive Manufacturing     Hybrid Journal   (Followers: 7, SJR: 1.039, h-index: 5)
Additives for Polymers     Full-text available via subscription   (Followers: 20)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 119, 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: 16, SJR: 0.739, h-index: 33)
Advances in Accounting     Hybrid Journal   (Followers: 8, 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: 24, SJR: 0.169, h-index: 4)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 3)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 6, SJR: 1.054, h-index: 35)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 10, SJR: 0.801, h-index: 26)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 21, 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: 5, SJR: 2.139, h-index: 42)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 12)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 24, 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: 8, SJR: 1.268, h-index: 45)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 28, 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 Developmental Biology     Full-text available via subscription   (Followers: 11)
Advances in Digestive Medicine     Open Access   (Followers: 4)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 5)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Ecological Research     Full-text available via subscription   (Followers: 39, SJR: 3.25, h-index: 43)
Advances in Engineering Software     Hybrid Journal   (Followers: 25, SJR: 0.486, h-index: 10)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 7)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 38, SJR: 5.465, h-index: 64)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 3)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 41, SJR: 0.674, h-index: 38)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 14)
Advances in Genetics     Full-text available via subscription   (Followers: 15, 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: 18, SJR: 0.906, h-index: 24)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 0.497, h-index: 31)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 22)
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: 33, 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: 4)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 4)
Advances in Life Course Research     Hybrid Journal   (Followers: 7, SJR: 0.764, h-index: 15)
Advances in Lipobiology     Full-text available via subscription   (Followers: 1)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 8)
Advances in Marine Biology     Full-text available via subscription   (Followers: 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: 5, SJR: 0.489, h-index: 25)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 4, SJR: 1.44, h-index: 51)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 21)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 10)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 6, SJR: 0.324, h-index: 8)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 3)
Advances in Oncobiology     Full-text available via subscription   (Followers: 3)
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: 20, SJR: 0.4, h-index: 28)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 14)
Advances in Pharmacology     Full-text available via subscription   (Followers: 13, SJR: 1.718, h-index: 58)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 7, 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: 8)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 5)
Advances in Porous Media     Full-text available via subscription   (Followers: 4)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 17, SJR: 1.5, h-index: 62)
Advances in Psychology     Full-text available via subscription   (Followers: 56)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5, SJR: 0.478, h-index: 32)
Advances in Radiation Oncology     Open Access  
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 1, SJR: 0.1, h-index: 2)
Advances in Space Research     Full-text available via subscription   (Followers: 332, SJR: 0.606, h-index: 65)
Advances in Structural Biology     Full-text available via subscription   (Followers: 7)
Advances in Surgery     Full-text available via subscription   (Followers: 6, SJR: 0.823, h-index: 27)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 28, SJR: 1.321, h-index: 56)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 14)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 12)
Advances in Virus Research     Full-text available via subscription   (Followers: 5, SJR: 1.878, h-index: 68)
Advances in Water Resources     Hybrid Journal   (Followers: 42, 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: 303, 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: 4, SJR: 0.344, h-index: 6)
Ageing Research Reviews     Hybrid Journal   (Followers: 7, SJR: 3.289, h-index: 78)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 389, 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: 29, SJR: 1.275, h-index: 74)
Agricultural Water Management     Hybrid Journal   (Followers: 36, SJR: 1.546, h-index: 79)
Agriculture and Agricultural Science Procedia     Open Access  
Agriculture and Natural Resources     Open Access   (Followers: 1)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 48, 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: 3, 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: 9, SJR: 0.922, h-index: 66)
Alcoholism and Drug Addiction     Open Access   (Followers: 5)
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  
Algal Research     Partially Free   (Followers: 7, 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)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 6, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 45, SJR: 4.289, h-index: 64)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 5)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 3)
American Heart J.     Hybrid Journal   (Followers: 45, SJR: 3.157, h-index: 153)
American J. of Cardiology     Hybrid Journal   (Followers: 47, SJR: 2.063, h-index: 186)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 34, SJR: 0.574, h-index: 65)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 6, 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: 25, 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: 48, 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: 173, SJR: 2.255, h-index: 171)
American J. of Ophthalmology     Hybrid Journal   (Followers: 51, SJR: 2.803, h-index: 148)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 2)
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: 22, SJR: 0.59, h-index: 45)
American J. of Pathology     Hybrid Journal   (Followers: 23, SJR: 2.653, h-index: 228)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 21, SJR: 2.764, h-index: 154)
American J. of Surgery     Hybrid Journal   (Followers: 32, SJR: 1.286, h-index: 125)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 13, SJR: 0.653, h-index: 70)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 5)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.066, h-index: 51)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 52, SJR: 0.124, h-index: 9)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 3)
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: 2, SJR: 2.577, h-index: 7)
Analytica Chimica Acta     Hybrid Journal   (Followers: 38, SJR: 1.548, h-index: 152)
Analytical Biochemistry     Hybrid Journal   (Followers: 152, SJR: 0.725, h-index: 154)
Analytical Chemistry Research     Open Access   (Followers: 7, SJR: 0.18, h-index: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 10)
Anesthésie & Réanimation     Full-text available via subscription  
Anesthesiology Clinics     Full-text available via subscription   (Followers: 21, 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: 141, SJR: 1.907, h-index: 126)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 5, SJR: 1.151, h-index: 83)
Animal Reproduction Science     Hybrid Journal   (Followers: 5, SJR: 0.711, h-index: 78)
Annales d'Endocrinologie     Full-text available via subscription   (SJR: 0.394, h-index: 30)
Annales d'Urologie     Full-text available via subscription  
Annales de Cardiologie et d'Angéiologie     Full-text available via subscription   (SJR: 0.177, h-index: 13)
Annales de Chirurgie de la Main et du Membre Supérieur     Full-text available via subscription  
Annales de Chirurgie Plastique Esthétique     Full-text available via subscription   (Followers: 2, SJR: 0.354, h-index: 22)
Annales de Chirurgie Vasculaire     Full-text available via subscription   (Followers: 1)

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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  [3031 journals]
  • Aboveground net primary productivity and carbon balance remain stable
           under extreme precipitation events in a semiarid steppe ecosystem
    • Authors: Y.B. Hao; C.T. Zhou; W.J. Liu; L.F. Li; X.M. Kang; L.L. Jiang; X.Y. Cui; Y.F. Wang; X.Q. Zhou; C.Y. Xu
      Pages: 1 - 9
      Abstract: Publication date: 15 June 2017
      Source:Agricultural and Forest Meteorology, Volumes 240–241
      Author(s): Y.B. Hao, C.T. Zhou, W.J. Liu, L.F. Li, X.M. Kang, L.L. Jiang, X.Y. Cui, Y.F. Wang, X.Q. Zhou, C.Y. Xu
      Global climate change is projected to increase both the intensity and frequency of extreme precipitation events (EPEs), which are considered to have stronger impacts on ecosystem functions than gradual changes in mean precipitation conditions. In this study, a consecutive 20-day extreme precipitation event (282mm) was applied during the mid- and late-growing season periods in a semiarid steppe for three years to investigate the effects of extreme large precipitation events on aboveground net primary productivity (ANPP) and ecosystem carbon dioxide (CO2) fluxes, including net ecosystem carbon absorption (NEE), gross primary productivity (GPP) and ecosystem respiration (Re). Although soil moisture was significantly increased by extreme precipitation, and even exceeded field capacity during the treatment periods, ANPP remained stable across all the treatments. There was also little change in mean growing season ecosystem CO2 fluxes under the two precipitation treatments, despite GPP rates decreased by 34.4 and 26.3%, and NEE rates were suppressed by 77 and 68% during the mid- and late-season treatment periods, respectively. The stable CO2 fluxes could be attributed to the recovery of GPP and NEE in 7 and 12 days after the end of EPEs. Our study demonstrated that both ANPP and CO2 fluxes in this semiarid steppe were very stable in the face of extreme large precipitation events, regardless of the timing of events occur. Nevertheless, future, long-term studies need to investigate the potential tipping points or thresholds for ecosystem function shifts, as an increasing occurrence of EPEs has been forecasted in future climate change scenarios.

      PubDate: 2017-04-05T10:50:37Z
      DOI: 10.1016/j.agrformet.2017.03.006
      Issue No: Vol. 240-241 (2017)
       
  • Canopy hydrometeorological dynamics across a chronosequence of a globally
           invasive species, Ailanthus altissima (Mill., tree of heaven)
    • Authors: Seyed Mohammad Moein Sadeghi; John Toland Van Stan; Thomas Grant Pypker; Jan Friesen
      Pages: 10 - 17
      Abstract: Publication date: 15 June 2017
      Source:Agricultural and Forest Meteorology, Volumes 240–241
      Author(s): Seyed Mohammad Moein Sadeghi, John Toland Van Stan, Thomas Grant Pypker, Jan Friesen
      Many mechanisms aid invasive plants’ competitive interactions. Yet, the extent to which invasive plants alter canopy hydrometeorological mechanisms determining the quantity and distribution of rainwater resources to soils have never been assessed. We examine these mechanisms for a global invader, Ailanthus altissima, across an invasion chronosequence (stands aged 20, 30, 40 years) for 99 storms, each with ∼200 net rainfall observations. With age woody area index, ratio of wet canopy evaporation and rainfall rates, and stem drainage coefficient increased; while leaf area index, canopy water storage, and gap fraction declined. This corresponded to increased stemflow and decreased throughfall across annual, seasonal, and interstorm scales. Promotion of stemflow may be advantageous to the invasive species as it increases water supply to roots and may help distribute allelopathic chemicals through the soil. Further research is needed on relationships between canopy hydrometeorological changes during invasion and redistribution of water to soils.

      PubDate: 2017-04-05T10:50:37Z
      DOI: 10.1016/j.agrformet.2017.03.017
      Issue No: Vol. 240-241 (2017)
       
  • Characteristics of lightnings igniting forest fires in Austria
    • Authors: Mortimer M. Müller; Harald Vacik
      Pages: 26 - 34
      Abstract: Publication date: 15 June 2017
      Source:Agricultural and Forest Meteorology, Volumes 240–241
      Author(s): Mortimer M. Müller, Harald Vacik
      Besides anthropogenic causes, lightning is the major reason for forest fire ignition worldwide. Information on lightning characteristics and impact points is missing or controversial, due to the difficulty of lightning stroke localization and the relation to single forest fire events. Austria as an Alpine country experiences a high number of thunderstorms and lightnings, which ignite more than one third of forest fires from June to August. With data from the “Austrian Lightning Detection and Information System” (ALDIS) it was possible to link single lightnings and their characteristics to the location and attributes of individual forest fires. Three subsets with lightning data were compiled and analyzed regarding their strength (kA), polarity (positive or negative) and multiplicity (number of re-strokes). Additional data on the time of ignition, burned area, sea level, exposition and burned vegetation were investigated. Two fire weather sub-indices (FFMC − Fine Fuel Moisture Code and BUI − Build Up Index) of the Canadian FWI (Fire Weather Index) were calculated for the location of the impact point of each lightning and over a period of twenty days, including the day of ignition. Positive lightnings were significantly more likely to induce a fire. Both the FFMC and BUI showed a significant mean decrease after the day of ignition. Precipitation was significant lower at those impact points where forest fires were ignited. Burned area was larger when lightnings ignited during day hours. Most lightning fires occurred at higher altitudes with southerly or western exposition, mainly in stands of Norway spruce (Picea abies L.). Pine species were four times more often affected than the natural tree species distribution would assume. The study results contribute to the international discussion on lightning fires and will help to provide recommendations for further modelling studies on the forecast of lightning caused forest fires.

      PubDate: 2017-04-12T13:25:08Z
      DOI: 10.1016/j.agrformet.2017.03.020
      Issue No: Vol. 240-241 (2017)
       
  • Linking crop yield anomalies to large-scale atmospheric circulation in
           Europe
    • Authors: Andrej Ceglar; Marco Turco; Andrea Toreti; Francisco J. Doblas-Reyes
      Pages: 35 - 45
      Abstract: Publication date: 15 June 2017
      Source:Agricultural and Forest Meteorology, Volumes 240–241
      Author(s): Andrej Ceglar, Marco Turco, Andrea Toreti, Francisco J. Doblas-Reyes
      Understanding the effects of climate variability and extremes on crop growth and development represents a necessary step to assess the resilience of agricultural systems to changing climate conditions. This study investigates the links between the large-scale atmospheric circulation and crop yields in Europe, providing the basis to develop seasonal crop yield forecasting and thus enabling a more effective and dynamic adaptation to climate variability and change. Four dominant modes of large-scale atmospheric variability have been used: North Atlantic Oscillation, Eastern Atlantic, Scandinavian and Eastern Atlantic-Western Russia patterns. Large-scale atmospheric circulation explains on average 43% of inter-annual winter wheat yield variability, ranging between 20% and 70% across countries. As for grain maize, the average explained variability is 38%, ranging between 20% and 58%. Spatially, the skill of the developed statistical models strongly depends on the large-scale atmospheric variability impact on weather at the regional level, especially during the most sensitive growth stages of flowering and grain filling. Our results also suggest that preceding atmospheric conditions might provide an important source of predictability especially for maize yields in south-eastern Europe. Since the seasonal predictability of large-scale atmospheric patterns is generally higher than the one of surface weather variables (e.g. precipitation) in Europe, seasonal crop yield prediction could benefit from the integration of derived statistical models exploiting the dynamical seasonal forecast of large-scale atmospheric circulation.
      Graphical abstract image Highlights

      PubDate: 2017-04-12T13:25:08Z
      DOI: 10.1016/j.agrformet.2017.03.019
      Issue No: Vol. 240-241 (2017)
       
  • Environmental and physiological controls on sap flow in a subhumid
           mountainous catchment in North China
    • Authors: Qiang Tie; Hongchang Hu; Fuqiang Tian; Huade Guan; Henry Lin
      Pages: 46 - 57
      Abstract: Publication date: 15 June 2017
      Source:Agricultural and Forest Meteorology, Volumes 240–241
      Author(s): Qiang Tie, Hongchang Hu, Fuqiang Tian, Huade Guan, Henry Lin
      To accurately quantify tree transpiration and determine related hydrologic and physiological processes, it is important to have reliable information on environmental and physiological controls on sap flow. The objective of this study is to explore the environmental and physiological controls on sap flow in a headwater catchment in the subhumid mountainous region of North China, which has pronounced environmental specificities in hydro-climatic conditions, bedrock properties, and edaphic features. Sap flow in Aspen (Populus davidiana) (one of the dominant tree species in the region) and relevant environmental and physiological factors were measured from 2013 to 2014. The results indicate the following: (1) The dominant controlling factor of sap flow switched from a meteorological to a physiological factor when leaf area index (LAI) dropped to a low value (approximately <1m2 m−2) around early October; (2) LAI exhibited a threshold control on possible maximum sap flow with a LAI threshold value of 3.5m2 m−2, while environmental factors led to fluctuations in sap flow within the upper bound that was determined by the physiological factor LAI; (3) Photosynthetically active radiation (PAR) was the key environmental factor controlling sap flow as a whole, while at the monthly timescale the controls of environmental factors on sap flow had significant seasonal variability; (4) The diurnal relationships between sap flow and environmental factors revealed evident hysteresis loops, which were markedly influenced by the radiation factor. With the combination of the environmental factor PAR and the physiological factor LAI, an empirical regression equation (SFD =0.7059PAR * LAI +4.5068, R2 =0.8862, n=207) was established for sap flow estimation in the study area. These results shed light on the hydrologic and physiological processes involved in tree transpiration, and contribute to the refinement of tree transpiration models in regions under similar environmental conditions.

      PubDate: 2017-04-12T13:25:08Z
      DOI: 10.1016/j.agrformet.2017.03.018
      Issue No: Vol. 240-241 (2017)
       
  • Assessing the environmental controls on Scots pine transpiration and the
           implications for water partitioning in a boreal headwater catchment
    • Authors: Hailong Wang; Doerthe Tetzlaff; Jonathan J. Dick; Chris Soulsby
      Pages: 58 - 66
      Abstract: Publication date: 15 June 2017
      Source:Agricultural and Forest Meteorology, Volumes 240–241
      Author(s): Hailong Wang, Doerthe Tetzlaff, Jonathan J. Dick, Chris Soulsby
      Climate change projections indicate reduced summer precipitation and increased air temperature for the northern high latitudes. These climate changes are likely to alter forest water budgets of which plant transpiration (T) forms a significant component. Plant transpiration is regulated by stomata behavior of particular species, which is constrained by ambient air and soil conditions. Here, we measured sap flow in a Scots pine (Pinus Sylvestris) plantation in a low energy Scottish headwater catchment during the main summer growth period. Effects of rainfall on forest transpiration, as well as the response of T to four environmental variables were investigated at a daily scale. In this boreal environment, transpiration was mainly restricted by radiation and vapor pressure deficit. Air temperature was the least important controlling factor. Soil water became an important factor when rainfall was limited. Frequent but small rain events dictated that precipitation met short-term transpiration demand most of the time. The trees needed supplementary water from antecedent soil water stores when weekly rainfall was below ∼8mm, but such periods were rare. Water exchange mainly occurred in the canopy or upper 10cm of the soil, with 47% of rainfall transpired, 45% intercepted and <8% evaporated from the soil surface. Understanding interactions between forests and their hydroclimate, as well as the role of forests in water partitioning is crucial to assist a sustainable land and water management in a changing climate. Whilst such studies are common in semi-arid regions, they are limited in boreal zones, therefore, our findings are a valuable contribution to understanding plant-water relations in a changing environment.

      PubDate: 2017-04-12T13:25:08Z
      DOI: 10.1016/j.agrformet.2017.04.002
      Issue No: Vol. 240-241 (2017)
       
  • A global evaluation of apple flowering phenology models for climate
           adaptation
    • Authors: Rebecca Darbyshire; Isabelle Farrera; Johann Martinez-Lüscher; Gabriel Berenhauser Leite; Vincent Mathieu; Adnane El Yaacoubi; Jean-Michel Legave
      Pages: 67 - 77
      Abstract: Publication date: 15 June 2017
      Source:Agricultural and Forest Meteorology, Volumes 240–241
      Author(s): Rebecca Darbyshire, Isabelle Farrera, Johann Martinez-Lüscher, Gabriel Berenhauser Leite, Vincent Mathieu, Adnane El Yaacoubi, Jean-Michel Legave
      This study presents the first evaluation of apple flowering phenology models using data from 14 sites across the globe. The dataset includes large variability in growing climates, a prerequisite to investigate phenology models for use in climate change applications. Two flowering stages, early and full, were investigated allowing for unique model evaluation based on both statistical performance and biological assumptions. Two overarching phenology models (Sequential and Chill Overlap) and two sub-models of chill (Dynamic and Triangular) and heat (GDH and Sigmoidal) were tested. Flowering times from the different sites illustrated the differing effects of contrasting winter and spring temperatures. Sites with similar springtime temperatures, but different winter temperatures, had different flowering patterns (warmer winter sites flowered later). Across all analyses, results from the Chill Overlap model were better than those from the Sequential model. Of the Chill Overlap models, those fitted with the Triangular or Dynamic chill model and the GDH heat sub-model performed well statistically and met the assumptions of the model across both flowering stages. The mild sites in the analysis were least well represented, regardless of model selection. This global evaluation demonstrated that flowering modelling in temperate fruit trees would progress through appropriate choices of overarching model, sub-models and parameters.

      PubDate: 2017-04-12T13:25:08Z
      DOI: 10.1016/j.agrformet.2017.03.021
      Issue No: Vol. 240-241 (2017)
       
  • Wheat yield benefited from increases in minimum temperature in the
           Huang-Huai-Hai Plain of China in the past three decades
    • Authors: Fulu Tao; Dengpan Xiao; Shuai Zhang; Zhao Zhang; Reimund P. Rötter
      Pages: 1 - 14
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Fulu Tao, Dengpan Xiao, Shuai Zhang, Zhao Zhang, Reimund P. Rötter
      Our understanding of climate impacts and adaptations on crop growth and productivity can be accelerated by analyzing historical data over the past few decades. We used crop trial and climate data from 1981 to 2009 at 34 national agro-meteorological stations in the Huang-Huai-Hai Plain (HHHP) of China to investigate the impacts of climate factors during different growth stages on the growth and yields of winter wheat, accounting for the adaptations such as shifts in sowing dates, cultivars, and agronomic management. Maximum (T max) and minimum temperature (T min) during the growth period of winter wheat increased significantly, by 0.4 and 0.6°C/decade, respectively, from 1981 to 2009, while solar radiation decreased significantly by 0.2MJ/m2/day and precipitation did not change significantly. The trends in climate shifted wheat phenology significantly at 21 stations and affected wheat yields significantly at five stations. The impacts of T max and T min differed in different growth stages of winter wheat. Across the stations, during 1981–2009, wheat yields increased on average by 14.5% with increasing trends in T min over the whole growth period, which reduced frost damage, however, decreased by 3.0% with the decreasing trends in solar radiation. Trends in T max and precipitation had comparatively smaller impacts on wheat yields. From 1981 to 2009, climate trends were associated with a≤30% (or ≤1.0% per year) wheat yield increase at 23 stations in eastern and southern parts of HHHP; however with a≤30% (or ≤1.0% per year) reduction at 11 other stations, mainly in western part of HHHP. We also found that wheat reproductive growth duration increased due to shifts in cultivars and flowering date, and the duration was significantly and positively correlated with wheat yield. This study highlights the different impacts of T max and T min in different growth stages of winter wheat, as well as the importance of management (e.g. shift of sowing date) and cultivars shift in adapting to climate change in the major wheat production region.

      PubDate: 2017-03-09T21:25:05Z
      DOI: 10.1016/j.agrformet.2017.02.033
      Issue No: Vol. 239 (2017)
       
  • Validation and in situ application of a modified thermal dissipation probe
           for evaluating standing water use of a clumped bamboo: Bambusa chungii
    • Authors: Zhenzhen Zhang; Juan Zhou; Ping Zhao; Xiuhua Zhao; Liwei Zhu; Lei Ouyang; Guangyan Ni
      Pages: 15 - 23
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Zhenzhen Zhang, Juan Zhou, Ping Zhao, Xiuhua Zhao, Liwei Zhu, Lei Ouyang, Guangyan Ni
      To assess the water use of a clumped bamboo species, Bambusa chungii, we modified original 20mm long thermal dissipation probes (TDPs) by shortening each prototypical probe to 5mm in length. Before applying the modified TDPs in the field, we calibrated the measured sap flow (J S) against gravimetric measurements (J g) with a cut experiment with B. chungii culm and corrected J S derived transpiration with actual water loss from a pot experiment under outdoor conditions. The validated TDP underestimated J S by 27.5% compared with the actual water loss from the pot. The optimal sample sizes of J S and culm area (A C) were evaluated to be 17 and 8 with random sampling, respectively. Meanwhile, the former was shown to be a lower value based on the stratified method (n =15), mirroring the age effect on the J S variances. As a result, the annual stand transpiration for three clumps during the field experiment (January 2014–December 2014) was 397.0mm with an error of 7.77% (considering the individual variance of J S and A C) when all of the sample culms (n =45) were pooled together. This transpiration value was lower than that of a native broadleaf species Schima superba stand (461mm) and higher than a widely planted Eucalyptus urophylla stand (327.4mm) that grew nearby when the same microclimatic conditions were assumed. However, the unlimited transpiration with increased VPD indicated the potentially increased pressure on the regional water balance.

      PubDate: 2017-03-09T21:25:05Z
      DOI: 10.1016/j.agrformet.2017.02.023
      Issue No: Vol. 239 (2017)
       
  • Temporal changes in the climate sensitivity of Norway spruce and European
           beech along an elevation gradient in Central Europe
    • Authors: Tomáš Kolář; Petr Čermák; Miroslav Trnka; Tomáš Žid; Michal Rybníček
      Pages: 24 - 33
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Tomáš Kolář, Petr Čermák, Miroslav Trnka, Tomáš Žid, Michal Rybníček
      Norway spruce has experienced unprecedented forest declines in recent decades, leading to extensive salvage logging. Currently, because of the conversion of conifer forests into more natural mixed forests in Central Europe, spruce has begun to be replaced, mainly by European beech. The frequently discussed changing climate has a crucial effect on the vitality of both species. To improve our understanding of spruce and beech responses to climate change, including more frequent temperature and drought extremes, we investigated the impact of temporal climate variability on the growth of these species along an elevation gradient. In total, 79 spruce and 90 beech trees were used to build species-specific tree-ring width chronologies representing the altitudinal range in which both species grow (450, 650, 800, and 950m asl) under the conditions of the Czech Republic. The climate–growth relationship indicates strong dependence of spruce and beech tree-ring growth on spring temperature (Mar–May) at all sites and summer (Jun–Aug) water availability at lower altitudes. Significant temporal shifts in the climate–growth relationships of both species indicate an increasing negative effect of summer temperature and positive effect of water availability in summer. The increasing drought and temperature sensitivity of both species suggest a significant impact of the predicted climate change on such forest ecosystems. Discussion emphasizes the current importance of adaptive forest management strategies.
      Graphical abstract image

      PubDate: 2017-03-09T21:25:05Z
      DOI: 10.1016/j.agrformet.2017.02.028
      Issue No: Vol. 239 (2017)
       
  • Chilling and heat requirements for local and foreign almond (Prunus dulcis
           Mill.) cultivars in a warm Mediterranean location based on 30 years of
           phenology records
    • Authors: Haïfa Benmoussa; Mohamed Ghrab; Mehdi Ben Mimoun; Eike Luedeling
      Pages: 34 - 46
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Haïfa Benmoussa, Mohamed Ghrab, Mehdi Ben Mimoun, Eike Luedeling
      Most temperate fruit and nut trees require fulfillment of chilling and heat requirements during their dormant phase in order to flower regularly and produce economically satisfying yields. Recent and expected temperature increases are cause for concern for many orchard managers, especially in warm growing regions, because they may compromise the trees’ ability to fulfill their climatic needs. To explore temperature responses across different cultivars, we applied Partial Least Squares (PLS) regression to correlate bloom dates of 12 local and 25 foreign almond (Prunus dulcis Mill.) cultivars in Sfax, Tunisia with daily chill and heat accumulation based on more than 30 years of phenology records from 1981 to 2014 and long-term daily minimum and maximum temperatures between 1973 and 2016. We used three chilling models (the Chilling Hours, Utah and Dynamic Models) and one forcing model (Growing Degree Hours; GDH) to quantify climatic needs. Chilling and forcing phases derived from the PLS outputs appeared discontinuous for all almond cultivars and were shorter for the local almond cultivars than for the foreign cultivars. The Dynamic Model provided the most precise estimates of chilling requirements but still appeared to have some shortcomings. According to the Chilling Hours Model, chilling needs were very low, but still higher than for the Utah Model, where the negative chill contributions by high temperatures implied negative chilling requirements. The Chilling Hours and Utah Models therefore do not seem suitable for the climate of the Sfax region. For local almond cultivars, chilling requirements were estimated at between 3.4 and 15.5 Chill Portions (CP) and heat needs between 3962 and 8873 GDH. For foreign cultivars, chilling requirements varied from 6.7 to 22.6 CP and heat needs from 2894 to 10,504 GDH. High temperatures during the chilling phase showed a significant bloom-delaying effect on most of the local and the foreign almond cultivars.

      PubDate: 2017-03-09T21:25:05Z
      DOI: 10.1016/j.agrformet.2017.02.030
      Issue No: Vol. 239 (2017)
       
  • A revised hydrological model for the Central Amazon: The importance of
           emergent canopy trees in the forest water budget
    • Authors: Norbert Kunert; Luiza Maria T. Aparecido; Stefan Wolff; Niro Higuchi; Joaquim dos Santos; Alessandro Carioca de Araujo; Susan Trumbore
      Pages: 47 - 57
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Norbert Kunert, Luiza Maria T. Aparecido, Stefan Wolff, Niro Higuchi, Joaquim dos Santos, Alessandro Carioca de Araujo, Susan Trumbore
      The Amazon forest is integral to the global climate system in part because of the high rate of rainfall recycling through tree transpiration and biodiversity (size and species composition). However, the partitioning of precipitation into evaporation, transpiration and runoff, has been quantified at only a few sites. At our study site in the central Amazon, annual rainfall in 2013 was 2302mm and latent heat flux measurements made using eddy covariance revealed that 1360mm (59%) was returned to the atmosphere through evaporation and transpiration. Runoff accounted for 41% of the net ecosystem water loss. Combining annual xylem sap flux estimates with total stand sap wood area, we estimated annual stand transpiration rate to be 851mm (36% of annual rainfall). Emergent canopy trees (diameter >30cm; average height of 28m) were responsible for the majority (71%) of the transpired water flux, recycling potentially 26% of the rainfall back to the atmosphere. By difference, we estimate that 510mm of intercepted rainwater (22% of rainfall) was evaporated directly back to atmosphere from the canopy. Highest stand transpiration rates occurred during the dryer months due to both increased water vapor pressure deficit and the onset of new leaf flush. This study provides further evidence for convergent water use characteristics of tropical trees and highlights the importance of large trees in tropical moist forests. Large trees have been demonstrated to be vulnerable to drought-related mortality, and thus potentially will make up a critical component of the response of tropical forests to climate change.

      PubDate: 2017-03-17T09:04:59Z
      DOI: 10.1016/j.agrformet.2017.03.002
      Issue No: Vol. 239 (2017)
       
  • Physical controls on frost events in the central Andes of Peru using in
           situ observations and energy flux models
    • Authors: Miguel Saavedra; Ken Takahashi
      Pages: 58 - 70
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Miguel Saavedra, Ken Takahashi
      Radiative frosts are a major hazard to agriculture in the tropical Andes of Peru, but there are very few studies of their physical controls. In this study we focus on identifying and approximately estimating the effect that physical variables have on both the downward surface longwave flux (LW↓) and the minimum temperature (T min ). Through a combination of case studies and statistical analysis of in situ data in the IGP Huancayo Observatory, we found that low cloud cover (CC), surface specific humidity (q), and soil moisture are key factors controlling the day-to-day variability of T min , which is more pronounced in the dry/cool season. We found that all frost days had q <7g/kg in the dry season and q <5g/kg in the wet season, although it should be emphasized that q covaries with CC and soil moisture. We successfully validated a numerical soil heat diffusion model with data from a field campaign in July 2010 and we used it, together with a radiative transfer model, to estimate the sensitivities of T min and LW↓ to atmospheric and soil variables. With these results we estimated the partial contributions of these variables to the overall day-to-day variability in T min and LW↓. We found that low cloud cover is the dominant factor, although specific humidity has a comparable role in the wet season. Lack of information on the cloud liquid water path is an important source of uncertainty. Enhanced soil moisture has a strong mitigating effect on frosts, although strong variability of soil moisture in the wet season could contribute substantially to the development of frosts.

      PubDate: 2017-03-17T09:04:59Z
      DOI: 10.1016/j.agrformet.2017.02.019
      Issue No: Vol. 239 (2017)
       
  • Controls of water and energy fluxes in oil palm plantations: Environmental
           variables and oil palm age
    • Authors: Ana Meijide; Alexander Röll; Yuanchao Fan; Mathias Herbst; Furong Niu; Frank Tiedemann; Tania June; Abdul Rauf; Dirk Hölscher; Alexander Knohl
      Pages: 71 - 85
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Ana Meijide, Alexander Röll, Yuanchao Fan, Mathias Herbst, Furong Niu, Frank Tiedemann, Tania June, Abdul Rauf, Dirk Hölscher, Alexander Knohl
      Oil palm is rapidly expanding, particularly in Indonesia, but there is still very limited information on water and energy fluxes in oil palm plantations, and on how those are affected by varying environmental conditions or plantation age. In our study, we measured turbulent fluxes of sensible (H) and latent (LE) heat and gross primary productivity (GPP) with the eddy covariance technique for 8 months each in a young oil palm plantation (1-year old) and subsequently in a mature plantation (12-year old) in Jambi Province, Sumatra, Indonesia. Simultaneous measurements of transpiration (T) were performed using the sap flux technique. We additionally estimated albedo, the maximum rate of carboxylation (Vcmax), the maximum rate of photosynthetic electron transport (Jmax) and water use efficiency (WUE). LE dominated the energy budget in both plantations, particularly in the mature one, where it accounted for up to 70% of the available energy. In the young oil palm plantation, evapotranspiration (ET) was significantly reduced and H fluxes were higher. The Bowen ratio was higher in the 1-year old plantation (0.67±0.33), where it remained constant during the day, than in the mature plantation (0.14±0.09), where it varied considerably over the day, suggesting the existence of water sources inside the canopy which evaporated during the day. Albedo was similar in both plantations (0.16±0.02 and 0.14±0.01 for the 1 and 12-year old plantation, respectively), while WUE differed with plantation age. Annual T estimates for oil palm were 64±3 and 826±34mmyr−1 for the 1 and 12-year old plantation, respectively. The corresponding annual ET was 918±46 and 1216±34mmyr−1, respectively. The Community Land Model (CLM), a process based land surface model that has been adapted to oil palm functional traits (i.e. CLM-Palm), was used to investigate the contribution of different water sources to the measured fluxes. CLM-Palm differentiates leaf and stem surfaces in modelling water interception and thus is able to diagnose the fraction of dry foliage that contributes to T and the wet fraction of all vegetation surfaces (leaf and stem) that contributes to evaporation. The results of the simulations performed are consistent with the storage of water within the canopy in the mature plantation, and suggest that oil palm trunk surfaces including epiphytes provide water reservoirs for intercepted rain which significantly contribute to ET. The decoupling between GPP and T in the morning and the early decreases of both fluxes at midday point to internal water storage mechanisms in oil palms both in the leaves and in the stem, which delayed the detection of water movement at the leaf petioles. Our measured data combined with the model simulations therefore suggest the existence of both external and internal trunk water storage mechanisms in mature oil palms contributing to ecosystem water fluxes. Oil palm plantations can lead to surface warming at early stages of development, but further assessments should be performed at landscape level. Our study provides data relevant for the parametrization of larger-scale models, which can contribute to understanding the climatic feedbacks of oil palm expansion.

      PubDate: 2017-03-17T09:04:59Z
      DOI: 10.1016/j.agrformet.2017.02.034
      Issue No: Vol. 239 (2017)
       
  • Large-scale atmospheric circulation enhances the Mediterranean East-West
           tree growth contrast at rear-edge deciduous forests
    • Authors: Isabel Dorado-Liñán; Eduardo Zorita; Elisabet Martínez-Sancho; Guillermo Gea-Izquierdo; Alfredo Di Filippo; Emilia Gutiérrez; Tom Levanic; Gianluca Piovesan; Giorgio Vacchiano; Christian Zang; Tzvetan Zlatanov; Annette Menzel
      Pages: 86 - 95
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Isabel Dorado-Liñán, Eduardo Zorita, Elisabet Martínez-Sancho, Guillermo Gea-Izquierdo, Alfredo Di Filippo, Emilia Gutiérrez, Tom Levanic, Gianluca Piovesan, Giorgio Vacchiano, Christian Zang, Tzvetan Zlatanov, Annette Menzel
      Overlaid to a general reduction of European beech and sessile oak tree growth over the recent decades in the Mediterranean Basin, tree-ring records from western Mediterranean populations display a stronger growth decrease than eastern populations. We investigate here to what extent the impact of sustained atmospheric circulation patterns in summertime can explain the observed spatial patterns of tree growth. We use Canonical Correlation Analysis, a statistical method that identifies the coupled patterns that are optimally correlated between two multivariate data sets. A general change in growth trends, shifting from a general increase during the period 1950–1981 to a decrease during the last three decades (1982–2012), can be attributed to increasing summer temperatures, which exert a dominant and negative influence on growth in both tree species across sites. However, summer precipitation has gained importance for growth, coinciding with the intensification of the geographical polarity in climate conditions across the Mediterranean Basin. This intensification during the last three decades can be traced back to a strengthening of the Summer North Atlantic Oscillation (SNAO), which imparts an east-west dipole to summer climate in this region. Under predicted persistent stronger SNAO in the future, western populations would face harsher summer conditions than central and eastern rear-edge populations, due to decreasing precipitation and increasing temperatures in the western Mediterranean Basin. These results evidence the determinant role that changes in the atmospheric circulation patterns may play in the persistence of rear-edge temperate deciduous forests in the near future.

      PubDate: 2017-03-17T09:04:59Z
      DOI: 10.1016/j.agrformet.2017.02.029
      Issue No: Vol. 239 (2017)
       
  • Estimating maize yield potential and yield gap with agro-climatic zones in
           China—Distinguish irrigated and rainfed conditions
    • Authors: Baohua Liu; Xinping Chen; Qingfeng Meng; Haishun Yang; Justin van Wart
      Pages: 108 - 117
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Baohua Liu, Xinping Chen, Qingfeng Meng, Haishun Yang, Justin van Wart
      Understanding yield potential (Yp) and yield gap (Yg) in current intensive maize (Zea mays L.) production is essential to meet future food demand with the limited resources. In this study, we used the agro-climatic zones (CZs) and the reference weather stations (RWS) buffer zones, together with the Hybird-Maize model to estimate maize Yp in the four maize-growing-regions of China under both irrigated and rainfed conditions. In irrigated maize areas, we got 70 RWS buffer zones, and total maize area in the RWS buffer zones covered 67% of the whole irrigated maize area. In rainfed maize areas, we got 106 RWS buffer zones, which covered 51% of the whole rainfed maize area. As a result, the average Yp was 14.2tha−1 and farmers have achieved 58% of Yp. The average water-limited yield potential (Yw) was 10.7tha−1 and farmers have achieved 65% of Yw. Further analysis for four maize-growing-regions showed that precipitation was a limiting factor for Yw to fully achieve Yp except in Southwest China (SW), whereas the average precipitation was more than 653mm during maize growing season. The ratio between Yw and Yp (Yw/Yp) was 51% in Northwest China (NW), and around 80% in both Northeast China (NE) and North China Plain (NCP). The comparison of Yp in different regions showed the low Yp in NE was due to low temperature while Yp in both NCP and SW were limited by low solar radiation. In conclusion, our findings highlight the efficiency and importance to estimate Yp, Yw and Yg by the upscaling method with CZs and RWS buffer zones. Meanwhile, the comparison of Yp, Yw and Yg in different regions was important to improve maize production in future in China.

      PubDate: 2017-03-17T09:04:59Z
      DOI: 10.1016/j.agrformet.2017.02.035
      Issue No: Vol. 239 (2017)
       
  • Analyzing the hydrological impact of afforestation and tree species in two
           catchments with contrasting soil properties using the spatially
           distributed model MIKE SHE SWET
    • Authors: Torben O. Sonnenborg; Jesper R. Christiansen; Bo Pang; Antoine Bruge; Simon Stisen; Per Gundersen
      Pages: 118 - 133
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Torben O. Sonnenborg, Jesper R. Christiansen, Bo Pang, Antoine Bruge, Simon Stisen, Per Gundersen
      Groundwater depletion occurs at a global scale but requires regional strategies for sustainable management of freshwater resources. In Denmark the groundwater quantity and quality is under pressure, and forested areas are considered to protect groundwater reservoirs. However, little is known on how afforestation or forest conversion impacts the water resource at the catchment scale. We hypothesize that the groundwater formation and streamflow is increased when water consuming conifers are replaced with the less consumptive broadleaf tree species. To test this a distributed hydrological model with an energy-based description of evaporation and transpiration processes (MIKE SHE SWET) was used. Large scale hydrological models were established for two geologically (sandy/clayey) contrasting catchments in Denmark; Skjern and Lejre catchments. Land use scenarios were defined with forest vegetation (conifer/broadleaf) and agricultural crops (grass, maize, wheat and barley) in different areal combinations. Initially, the SWET component was calibrated against plot scale field data from two forest sites to obtain vegetation parameter estimates for conifers and broadleaves. Subsequently, the catchment models were run for 10 years with predefined land use scenarios. MIKE SHE SWET simulated canopy interception and throughfall for conifers and broadleaf forests satisfactorily. The catchment simulations showed that replacing current conifer forests with broadleaves, resulted in a significant increase in groundwater recharge and groundwater level, especially in the Skjern catchment with predominantly sandy soils. Also, doubling the forest area, as intended by national legislations, using only broadleaves did not negatively affect the groundwater generation or minimum stream discharge compared to current conditions at Skjern. However, because the shallow geology in the Lejre catchment are dominated by clayey glacial moraine deposits with low hydraulic conductivity, increased net precipitation in areas covered by broadleaf forests would primarily discharge as overland flow or drainage flow rather than contributing to groundwater formation.

      PubDate: 2017-03-17T09:04:59Z
      DOI: 10.1016/j.agrformet.2017.03.001
      Issue No: Vol. 239 (2017)
       
  • Developing a growing degree day model for North Dakota and Northern
           Minnesota soybean
    • Authors: Fikri Adnan Akyuz; Hans Kandel; Dallas Morlock
      Pages: 134 - 140
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Fikri Adnan Akyuz, Hans Kandel, Dallas Morlock
      Farmers in North Dakota and Northern Minnesota did not have a model to predict when their soybean (Glycine max L. Merr.) crop will be mature. Soybean plants need to be mature before the first fall freeze. The objectives of this study were to estimate needed accumulated growing degree days (AGDD) for adapted soybean maturity groups (MG) to reach maturity (R8). Research was conducted during 2007–2012 at northern, central, and southern North Dakota, to develop a model to predict the soybean maturity date based on accumulated GDDs and to verify the model using field research data from 2013 to 2015. Based on 1816 data points a regression analysis was performed which predicted that 1666, 1862, 2030 AGDD (with a 50°F base temperature) were needed to reach maturity for 00.7, 0.4, and 1.0 MG soybean cultivars, respectively. The predicted values were used to create a model that allows producers to select the MG of their cultivar, date of planting, and the nearest North Dakota Agricultural Weather Network (NDAWN) station. The output provides the predicted maturity date, as well as the average first day of occurrence of select threshold temperatures (36°, 32° and 28°F) at 50% probability level. This model will help growers to judge the risks of certain frost occurring before the selected cultivar's projected maturity date. The projected maturity date is based on two parts. The first part is the observed period from the planting date to the date the model is queried and is based on daily maximum and minimum temperatures. The second part is the forecast period that is based on normal (1981–2010 average) daily maximum and minimum temperatures from the queried date through the end of the select growing season. The growing degree days (GDD) values are accumulated from the planting date through the end of season based on these daily maximum and minimum temperatures. Input into the model should be for adapted MG soybean for the region and for planting dates between May 15 and 31. Farmers and agriculturist in North Dakota and northwest Minnesota can use the model before planting to determine if a MG would mature before the frost with varying temperature thresholds and monitor the accumulation of GDD and development of the crop during the season and estimated date of maturity.

      PubDate: 2017-03-17T09:04:59Z
      DOI: 10.1016/j.agrformet.2017.02.027
      Issue No: Vol. 239 (2017)
       
  • Poor acclimation to current drier climate of the long-lived tree species
           Fitzroya cupressoides in the temperate rainforest of southern Chile
    • Authors: J. Julio Camarero; Alex Fajardo
      Pages: 141 - 150
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): J. Julio Camarero, Alex Fajardo
      Climate change and rising atmospheric CO2 concentrations (c a ) are expected to affect forests worldwide. The effects of climate change, however, have not been deeply assessed in humid forest biomes from the southern Hemisphere where climate is not warming but drying. This is the case of the temperate rainforest in southern Chile, where the endemic and threatened long-living gymnosperm Fitzroya cupressoides occurs. We assessed how radial growth, intrinsic water-use efficiency (iWUE) and tree-ring δ18O responded to increasing c a and decreasing precipitation in F. cupressoides and companion species. We hypothesized that F. cupressoides, a long-lived and probably less plastic species, will show less acclimation to global-change effects than co-occurring Nothofagus species which show broader climatic niche. Thus, F. cupressoides should display iWUE increases different from the c i /c a constant scenario, which represents an active mechanism to increase intercellular CO2 concentrations (c i ) as c a rises. Although cool and wet conditions during the growing season enhanced growth of all species, particularly in F. cupressoides, growth of F. cupressoides declined noticeably since the 1980s in response to a decrease in precipitation. Current drier conditions led to increased iWUE in Nothofagus species. According to δ18O values, this increased in iWUE should be due to a decrease in stomatal conductance. Fitzroya cupressoides, however, displayed a decrease in iWUE in response to drier conditions, shifting from an active c i /c a scenario to a more passive c i /c a scenario, and maintaining a relatively constant stomatal conductance. Using multiple bodies of evidence, our findings indicate a poor adaptability of the long-lived F. cupessoides to drier conditions despite rising c a . Thus, not all species are having similar and expected responses to increasing c a , which should be a call of attention in the case of long-lived, endangered and narrow-distributed species, like F. cupressoides.

      PubDate: 2017-03-21T21:05:11Z
      DOI: 10.1016/j.agrformet.2017.03.003
      Issue No: Vol. 239 (2017)
       
  • Crop production variability in North and South America forced by
           life-cycles of the El Niño Southern Oscillation
    • Authors: Weston Anderson; Richard Seager; Walter Baethgen; Mark Cane
      Pages: 151 - 165
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Weston Anderson, Richard Seager, Walter Baethgen, Mark Cane
      In this analysis we show how globally coherent teleconnections from life-cycles of the El Niño Southern Oscillation (ENSO) lead to correlated crop production anomalies in North and South America. We estimate the magnitude of ENSO-induced Pan-American production anomalies and discuss how increasing crop harvesting frequency may affect Pan-American production variability. We find that ENSO accounts for ∼72%, 30% and 57% of Pan-American maize, soybean and wheat production variability, respectively. ENSO-induced production anomalies are greatest for maize, with median anomalies of ∼5% of Pan-American production. ENSO-induced yield anomalies for maize and soybeans tend to be of the same sign in North America and southeast South America but of an opposite sign in northeast Brazil. Teleconnections for wheat are more complicated because ENSO affects wheat yields via lagged soil moisture teleconnections in the US and an increased probability of disease in South America, but anomalies tend to be of the same sign in North America and southeast South America. After broadly characterizing ENSO-induced production anomalies, we demonstrate that they are not static in time. Increasing crop harvesting frequency has affected the correlated risks posed by ENSO. We use a soil water balance to show that in Brazil changing to a safrinha cropping cycle increases both the mean water stress and the ENSO-induced soil water content anomalies during flowering in both the maize and soybean seasons, which is a result of increasing evaporative demand during times of lower precipitation and moving the flowering seasons into months with strong ENSO teleconnections. Increasing crop harvesting frequency in Brazil has therefore increased ENSO-induced production variability of soybeans and maize.

      PubDate: 2017-03-21T21:05:11Z
      DOI: 10.1016/j.agrformet.2017.03.008
      Issue No: Vol. 239 (2017)
       
  • Divergent shifts and responses of plant autumn phenology to climate change
           on the Qinghai-Tibetan Plateau
    • Authors: Wenquan Zhu; Nan Jiang; Guangsheng Chen; Donghai Zhang; Zhoutao Zheng; Deqin Fan
      Pages: 166 - 175
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Wenquan Zhu, Nan Jiang, Guangsheng Chen, Donghai Zhang, Zhoutao Zheng, Deqin Fan
      Autumn phenology along with spring/summer phenology controls the length of the vegetation growing season and significantly influences ecosystem biogeochemical cycles. Many previous studies have focused on spring/summer phenology. However, fewer studies have addressed autumn phenology because of no available or insufficient observations. Based on a series of long-term and continuous observations of autumn phenological events (8000+ records) on the Qinghai-Tibetan Plateau (QTP), we made a comprehensive assessment of autumn phenological shifts and their responses to climate change during the period from 1981 to 2011. Although a significantly delayed overall trend in autumn phenology was observed across the QTP from 1981 to 2011, the autumn phenologies showed divergent shifting trends and responses to climate change among plant species, phenological events, study periods and thermal conditions. Larger variations were observed for the occurrence dates of fruit-related events than foliar events. Significantly advanced shifts in autumn phenology were observed for woody plants (mostly owing to fruit-related phenological events), while significantly delayed shifts were observed for herbaceous plants (mostly owing to foliar events). The autumn phenology of woody plants varied little among plant species, recording periods and thermal conditions but varied greatly under different temperature change trends. The autumn phenology of herbaceous plants varied greatly among plant species, recording periods, thermal conditions and sites with different temperature change trends. The occurrence dates of most phenological events for herbaceous plants were positively correlated with the preseason temperature and negatively correlated with the preseason precipitation, while opposite relationships were observed for woody plants. Our results provide new field evidence for the dispersive changes in autumn phenology on the QTP and suggest that the dispersive shifts in autumn phenology and their different responses to climate warming should be considered when assessing the impacts of climate change on vegetation dynamics and ecosystem biogeochemical cycles.

      PubDate: 2017-03-28T21:15:46Z
      DOI: 10.1016/j.agrformet.2017.03.013
      Issue No: Vol. 239 (2017)
       
  • Which plant traits respond to aridity? A critical step to assess
           functional diversity in Mediterranean drylands
    • Authors: Alice Nunes; Melanie Köbel; Pedro Pinho; Paula Matos; Francesco de Bello; Otília Correia; Cristina Branquinho
      Pages: 176 - 184
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Alice Nunes, Melanie Köbel, Pedro Pinho, Paula Matos, Francesco de Bello, Otília Correia, Cristina Branquinho
      Aridity acts as a strong environmental filter to plants, limiting major ecosystem processes. Climate change models predict an overall increase of aridity in drylands. This could lead to changes in plant communities, particularly in the dominance and range of plant functional traits, which largely determine ecosystem functioning. However, to study how changes in aridity may affect plant functional metrics, a critical decision needs to be taken: the choice of the functional traits to be studied. Previous studies related plant functional traits and aridity, however mostly focusing on a single facet of functional diversity and primarily on perennial species. Hence, the response of plant traits to aridity quantifying different functional metrics at the whole-community level (considering also annual species) is not well established in drylands. Here, we use a high-resolution aridity gradient along a Mediterranean dryland ecosystem of Holm-oak woodlands to identify plant functional traits responding to aridity at the community-level (comprising annual and perennial species). We studied how the community-weighted-mean and functional dispersion of 13 traits related to plant establishment, growth, reproduction, dispersal and persistence changed with aridity. Nine plant functional traits varied with aridity. Aridity acted as an environmental filter on community-weighted-means, increasing the dominance of annual species, particularly rosettes, and plants with lower maximum height, shorter flowering duration, and increased anemochorous dispersal. Higher aridity was associated to an overall decrease in functional dispersion, particularly for life cycle, specific leaf area, onset of flowering, dispersal strategy and seed persistence traits, probably due to a lower niche differentiation under more arid conditions. The changes in community-weighted-means and in functional dispersion due to aridity are likely to negatively affect major ecosystem functions such as biomass production and nutrient cycling. Our results fill an important knowledge gap by quantifying how the functional structure and dispersion of 13 plant traits change with aridity at the whole-community level, providing an important basis for the selection of key functional traits to be used in trait-based studies in drylands.

      PubDate: 2017-03-28T21:15:46Z
      DOI: 10.1016/j.agrformet.2017.03.007
      Issue No: Vol. 239 (2017)
       
  • Circadian rhythms regulate the environmental responses of net CO2 exchange
           in bean and cotton canopies
    • Authors: Víctor Resco de Dios; Arthur Gessler; Juan Pedro Ferrio; Josu G. Alday; Michael Bahn; Jorge del Castillo; Sébastien Devidal; Sonia García-Muñoz; Zachary Kayler; Damien Landais; Paula Martín-Gómez; Alexandru Milcu; Clément Piel; Karin Pirhofer-Walzl; Olivier Ravel; Serajis Salekin; David T. Tissue; Mark G. Tjoelker; Jordi Voltas; Jacques Roy
      Pages: 185 - 191
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Víctor Resco de Dios, Arthur Gessler, Juan Pedro Ferrio, Josu G. Alday, Michael Bahn, Jorge del Castillo, Sébastien Devidal, Sonia García-Muñoz, Zachary Kayler, Damien Landais, Paula Martín-Gómez, Alexandru Milcu, Clément Piel, Karin Pirhofer-Walzl, Olivier Ravel, Serajis Salekin, David T. Tissue, Mark G. Tjoelker, Jordi Voltas, Jacques Roy
      Studies on the dependence of the rates of ecosystem gas exchange on environmental parameters often rely on the up-scaling of leaf-level response curves (‘bottom-up’ approach), and/or the down-scaling of ecosystem fluxes (‘top-down’ approach), where one takes advantage of the natural diurnal covariation between the parameter of interest and photosynthesis rates. Partly independent from environmental variation, molecular circadian clocks drive ∼24h oscillations in leaf-level photosynthesis, stomatal conductance and other physiological processes in plants under controlled laboratory conditions. If present and of sufficient magnitude at ecosystem scales, circadian regulation could lead to different results when using the bottom-up approach (where circadian regulation exerts a negligible influence over fluxes because the environment is modified rapidly) relative to the top-down approach (where circadian regulation could affect fluxes as it requires the passage of a few hours). Here we dissected the drivers of diurnal net CO2 exchange in canopies of an annual herb (bean) and of a perennial shrub (cotton) through a set of experimental manipulations to test for the importance of circadian regulation of net canopy CO2 exchange, relative to that of temperature and vapor pressure deficit, and to understand whether circadian regulation could affect the derivation of environmental flux dependencies. Contrary to conventional wisdom, we observed how circadian regulation exerted controls over net CO2 exchange that were of similar magnitude to the controls exerted by direct physiological responses to temperature and vapor pressure deficit. Diurnal patterns of net CO2 exchange could only be explained by considering effects of environmental responses combined with circadian effects. Consequently, we observed significantly different results when inferring the dependence of photosynthesis over temperature and vapor pressure deficit when using the top-down and the bottom up approaches.

      PubDate: 2017-03-28T21:15:46Z
      DOI: 10.1016/j.agrformet.2017.03.014
      Issue No: Vol. 239 (2017)
       
  • Field responses of potato to increased temperature during tuber bulking:
           Projection for climate change scenarios, at high-yield environments of
           Southern Chile
    • Authors: X. Carolina Lizana; Andrea Avila; Alejandro Tolaba; Juan Pablo Martinez
      Pages: 192 - 201
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): X. Carolina Lizana, Andrea Avila, Alejandro Tolaba, Juan Pablo Martinez
      Potato is considered a key crop for food security, mainly in developing countries. Increased temperature in future climate scenarios could be a significant constraint for potato productivity in tropical regions, while favorable for temperate regions. Global warming in the range of moderately high temperatures (15–32°C) is projected for temperate areas of southern Chile, which is a high potential environment for potato. The present study assessed the impact of moderately high temperatures on yield and physiological traits, during tuber bulking (TB) of two native Chilean varieties and three commercial varieties. Experiments were carried out under field conditions during two growing seasons. Three thermal regimes were applied: (i) ambient temperature (T0), and increased temperature (2.3–5.3°C) for 20days (ii) from the beginning to middle of TB (T1) and (iii) from the middle of TB until the beginning of leaf yellowing (T2). Effect of temperature on yield and physiological performance of genotypes were dependent on the timing of heat treatments. T1 increased tuber yield by 11–59%, but T2 did not modify tuber yield. Yield sensitivity was highly dependent on genotype. Harvest index was the most sensitive trait to increase temperature at T1, decreasing in the range of temperatures evaluated without reduction for tuber yield. Increased tuber yield at T1 was associated with higher intercepted radiation between flowering and 50% of leaf brownship, explained in part by elongation of this period and stomatal conductance of leaves.

      PubDate: 2017-03-28T21:15:46Z
      DOI: 10.1016/j.agrformet.2017.03.012
      Issue No: Vol. 239 (2017)
       
  • Season-long ammonia flux measurements above fertilized corn in central
           Illinois, USA, using relaxed eddy accumulation
    • Authors: Andrew J. Nelson; Sotiria Koloutsou-Vakakis; Mark J. Rood; LaToya Myles; Christopher Lehmann; Carl Bernacchi; Srinidhi Balasubramanian; Eva Joo; Mark Heuer; Marcelo Vieira-Filho; Jie Lin
      Pages: 202 - 212
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Andrew J. Nelson, Sotiria Koloutsou-Vakakis, Mark J. Rood, LaToya Myles, Christopher Lehmann, Carl Bernacchi, Srinidhi Balasubramanian, Eva Joo, Mark Heuer, Marcelo Vieira-Filho, Jie Lin
      The objective of this research is to quantify NH3 flux above an intensively managed cornfield in the Midwestern United States to improve understanding of NH3 emissions and evaluations of new and existing emission models. A relaxed eddy accumulation (REA) system was deployed above a corn canopy in central Illinois, USA (40°3′46.209″N, 88° 11′46.0212″W) from May through September 2014 (day of year 115–273) to measure NH3 fluxes due to chemical fertilizer application. NH3 flux was measured in four-hour periods during mornings and afternoons. Mean atmospheric NH3 concentration during the complete measurement period was 2.6±2.0μgm−3. Larger upward fluxes of gaseous NH3 were measured during the first 30days after fertilization, with variations observed throughout the field campaign. Measured NH3 fluxes ranged from −246.0ngm−2 s−1 during wintertime background measurements to 799.6ngm−2 s−1 within two weeks of fertilization (where negative flux indicates deposition). Mean positive flux was 233.3±203.0ngm−2 s−1 in the morning and 260.0±253.3ngm−2 s−1 in the afternoon while mean negative flux was −45.3±38.6ngm−2 s−1 in the morning and −78.35±74.9ngm−2 s−1 in the afternoon. NH3 volatilization during the first 21days after fertilization accounted for 79% of total nitrogen loss during the growing season. Such measurements are critical to improve understanding of agricultural NH3 emissions in managed agricultural ecosystems dominated by rotations of highly fertilized corn and moderately to lightly fertilized soybeans, such as the plot studied herein. These measurements are also important to improve understanding of how managed agricultural ecosystems impact air quality, and contribute to the global nitrogen cycle, and to evaluate current NH3 emission models.

      PubDate: 2017-03-28T21:15:46Z
      DOI: 10.1016/j.agrformet.2017.03.010
      Issue No: Vol. 239 (2017)
       
  • Flux-variance and flux-gradient relationships in the roughness sublayer
           over the Amazon forest
    • Authors: Tomás L. Chor; Nelson L. Dias; Alessandro Araújo; Stefan Wolff; Einara Zahn; Antônio Manzi; Ivonne Trebs; Marta O. Sá; Paulo R. Teixeira; Matthias Sörgel
      Pages: 213 - 222
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Tomás L. Chor, Nelson L. Dias, Alessandro Araújo, Stefan Wolff, Einara Zahn, Antônio Manzi, Ivonne Trebs, Marta O. Sá, Paulo R. Teixeira, Matthias Sörgel
      The failure of the Monin–Obukhov Similarity Theory (MOST) in the roughness sublayer is a major problem for the estimation of fluxes over tall forests, whenever indirect methods that rely on MOST, such as flux-gradient or the variance method, are involved. While much research focuses on micrometeorological measurements over temperate-climate forests, very few studies deal with such measurements over tropical forests. In this paper, we show evidence that some similarity functions over the Amazon forest are somewhat different from temperate forests. Comparison of the nondimensional scalar gradients canonical values for the inertial sublayer with our measurements in the roughness sublayer showed smaller deviations than what is usually reported for temperate forests. Although the fluxes of water vapor and CO2 derived from mean profiles show considerable scatter when compared with the eddy covariance measurements, using calibrated dimensionless gradients it is possible to estimate their mean daily cycle during the period of measurement (36 days in May and June, transition between rainy and dry season). Moreover, since mean ozone profiles were available, although without the corresponding eddy covariance measurements, mean daily ozone fluxes were calculated with the flux-gradient method, yielding a nighttime value of −0.05 and a daily peak of −0.45μgm−2 s−1 (−1.04 and −9.37nmolm−2 s−1, respectively). These values are comparable to previously measured fluxes in the literature for the Amazon forest.

      PubDate: 2017-04-05T10:50:37Z
      DOI: 10.1016/j.agrformet.2017.03.009
      Issue No: Vol. 239 (2017)
       
  • Temporal scale influence on multifractal properties of agro-meteorological
           time series
    • Authors: Jaromir Krzyszczak; Piotr Baranowski; Monika Zubik; Holger Hoffmann
      Pages: 223 - 235
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Jaromir Krzyszczak, Piotr Baranowski, Monika Zubik, Holger Hoffmann
      Scale issues become very important when applying weather time series. We address problems associated with transferring meteorological data across time scales by comparing multifractal properties of hourly and daily meteorological time series. The multifractal detrended fluctuation approach revealed that temporal aggregation of agro-meteorological time series can impact on their multifractal properties. The most apparent evidence of changing the time scale on multifractal properties was found for precipitation. It was the least noticeable for the wind speed time series. The change from hourly to daily time scale had an effect on the long-range correlations and the broadness of the probability density function. The contribution of these two components to series multifractality was smaller than before data aggregation. Our results confirm the loss of unique multifractal features at daily time scale as compared to hourly time series.

      PubDate: 2017-04-05T10:50:37Z
      DOI: 10.1016/j.agrformet.2017.03.015
      Issue No: Vol. 239 (2017)
       
  • Partitioning of net ecosystem exchange using chamber measurements data
           from bare soil and vegetated sites
    • Authors: Egor A. Dyukarev
      Pages: 236 - 248
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Egor A. Dyukarev
      A model of net ecosystem exchange (NEE) was suggested to study the influence of different environmental factors and to calculate daily and annual carbon budget. The model uses air temperature, incoming photosynthetically active radiation, vapor pressure deficit, and leaf area index as the explanatory factors for gross primary production, heterotrophic and autotrophic respiration. The model coefficients were calibrated using data collected by automated soil carbon dioxide (CO2) flux system with clear long-term chamber at an urban grassland in Tomsk, Russia. Observation results obtained at two sites (bare soil and vegetated) allows to calculate the temperature sensitivity for soil and plant respiration. Revealed fast and slow responses of soil respiration to temperature contribute together to the pulsed behavior of heterotrophic respiration. The total annual NEE resulted in 163.5gCm−2. Growing plants accumulate 522.7gCm−2 in total, but the net annual release of CO2 is higher (686.2gCm−2). The studied ecosystem is a source of carbon according to modelling and observation results. Results indicate that the suggested model is a promising tool for a better understanding of ecosystem biogeochemical processes.

      PubDate: 2017-04-05T10:50:37Z
      DOI: 10.1016/j.agrformet.2017.03.011
      Issue No: Vol. 239 (2017)
       
  • The rainfall factor in lightning-ignited wildfires in Catalonia
    • Authors: Nicolau Pineda; Tomeu Rigo
      Pages: 249 - 263
      Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Nicolau Pineda, Tomeu Rigo
      Wildland fires originated by lightning in Catalonia (NE Spain) are systematically examined through the use of lightning and precipitation data. The region of study, with a Mediterranean climate, is prone to summer wildfires. Despite being mainly anthropogenic, lightning-ignited fires (10%) are relevant as they can trigger large fires. Given that the lightning efficiency in Catalonia is of 1/1400 fires per lightning, the ability to identify potential ignition candidates among the whole lightning population would be of great value to forest protection agencies. Literature reveals that lightning characteristics such as polarity or multiplicity has proven to be of limited value as predictors. Therefore, another approach is necessary to set a probability of wildfire ignition to each lightning. In this regard, the aim of this study was to explore the relationship between lightning-ignited wildfires and precipitation, as lightning-ignited wildfires in the region are often attributed to ‘dry’ lightning (lightning accompanied with little or no precipitation). Results revealed that 25% of the lightning strokes related to wildfire ignitions had no associated precipitation at all, 40% had less than 2mm of precipitation and 90% had less than 10mm. Results also revealed that holdover fires (ignitions with delayed arrivals) are rare in the region. Finally, results suggest that there is no apparent link between the amount of precipitation and the holdover duration, indicating that the survival phase of lightning-ignitions is mainly driven by the daily cycle of solar heating. All in all, adding information on the precipitation associated to each lightning may help focusing attention on a reduced sample of strokes and provide fire managers with valuable information about potential lightning-caused wildfires.

      PubDate: 2017-04-05T10:50:37Z
      DOI: 10.1016/j.agrformet.2017.03.016
      Issue No: Vol. 239 (2017)
       
  • Drying models to estimate moisture change in switchgrass and corn stover
           based on weather conditions and swath density
    • Authors: A. Khanchi; S. Birrell
      Pages: 1 - 8
      Abstract: Publication date: 1 May 2017
      Source:Agricultural and Forest Meteorology, Volumes 237–238
      Author(s): A. Khanchi, S. Birrell
      An environmental chamber was built to evaluate the effect of weather parameters and swath density that affect the drying rate of crops during field drying. A series of 52 drying experiments was conducted on corn stover (CS) of which 27 were used for model development and 25 were used for model validation. Similarly, 80 experiments were performed on switchgrass of which 72 were used for model development and eight were used for model validation. Regression models were developed for switchgrass and CS that predicted the drying rate based on environmental conditions and swath density. During the day, radiation was found to be the most significant variable that affected the drying rate of switchgrass with a correlation coefficient (r) of 0.5 and 0.49 during different maturity stages. During the night, VPD was the most significant variable that affected the drying rate with r of 0.69 for corn stover (CS) and 0.83–0.85 for switchgrass. The effect of wind speed was variable and was found to be dependent on solar radiation. During the day time, an increase in wind speed removed the heat produced by radiation and thus decreased the drying rate. However, at night, the wind speed was positively correlated with drying rate. Swath density was negatively correlated (r=−0.38) with the drying rate of switchgrass which suggested that biomass should be dried in wide swaths if possible. The model should be a useful tool for planning field logistics and transportation operations for biomass supply.

      PubDate: 2017-02-05T08:14:19Z
      DOI: 10.1016/j.agrformet.2017.01.019
      Issue No: Vol. 237-238 (2017)
       
  • Above and below-ground environmental changes associated with the use of
           photoselective protective netting to reduce sunburn in apple
    • Authors: Lee Kalcsits; Stefano Musacchi; Desmond R. Layne; Tory Schmidt; Giverson Mupambi; Sara Serra; Manoella Mendoza; Laura Asteggiano; Sanaz Jarolmasjed; Sindhuja Sankaran; Lav R. Khot; Carlos Zúñiga Espinoza
      Pages: 9 - 17
      Abstract: Publication date: 1 May 2017
      Source:Agricultural and Forest Meteorology, Volumes 237–238
      Author(s): Lee Kalcsits, Stefano Musacchi, Desmond R. Layne, Tory Schmidt, Giverson Mupambi, Sara Serra, Manoella Mendoza, Laura Asteggiano, Sanaz Jarolmasjed, Sindhuja Sankaran, Lav R. Khot, Carlos Zúñiga Espinoza
      Anti-hail (protective) netting was originally developed to protect horticultural crops from hail damage. Netting reduces the amount and modifies the light reaching the orchard canopy. It also has the potential to optimize conditions for canopy and fruit growth and mitigate abiotic stress as climate change leads to increased temperatures. This study measured the effect of different colors of netting on the above and below-ground environment and apple sunburn incidence in a 3-year-old ‘Honeycrisp’ apple orchard growing in an irrigated desert climate in comparison to a traditional uncovered control. Netting did not affect air temperature or relative humidity within the orchard canopy, but reduced wind speed by 40% compared to the uncovered control. Netting reduced soil temperature and improved soil moisture at 20 and 40cm depths throughout the study period compared to the uncovered control. Amongst different colors of netting tested in this study, pearl and blue netting significantly reduced soil temperature compared to red netting. Netting also reduced photosynthetically active radiation (PAR) by approximately 20% and strongly reduced fruit surface temperature during hot periods. During full sunlight, differences in maximum fruit surface temperature between the uncovered control and the protective netting were 2.6–4.3°C under full sun conditions and reduced the incidence and severity of sunburn measured at harvest. As temperatures warm in the future, netting provides a viable option to mitigate some of the negative effects of excessive temperature and light on apple production in hot, dry growing regions.

      PubDate: 2017-03-03T21:33:36Z
      DOI: 10.1016/j.agrformet.2017.01.016
      Issue No: Vol. 237-238 (2017)
       
  • Influence of regional nighttime atmospheric regimes on canopy turbulence
           and gradients at a closed and open forest in mountain-valley terrain
    • Authors: S. Wharton; S. Ma; D.D. Baldocchi; M. Falk; J.F. Newman; J.L. Osuna; K. Bible
      Pages: 18 - 29
      Abstract: Publication date: 1 May 2017
      Source:Agricultural and Forest Meteorology, Volumes 237–238
      Author(s): S. Wharton, S. Ma, D.D. Baldocchi, M. Falk, J.F. Newman, J.L. Osuna, K. Bible
      Stable stratification of the nocturnal lower boundary layer inhibits convective turbulence, such that turbulent vertical transfer of ecosystem carbon dioxide (CO2), water vapor (H2O) and energy is driven by mechanically forced turbulence, either from frictional forces near the ground or top of a plant canopy, or from shear generated aloft. The significance of this last source of turbulence on canopy flow characteristics in a closed and open forest canopy is addressed in this paper. We present micrometeorological observations of the lower boundary layer and canopy air space collected on nearly 200 nights using a combination of atmospheric laser detection and ranging (lidar), eddy covariance (EC), and tower profiling instrumentation. Two AmeriFlux/Fluxnet sites in mountain-valley terrain in the Western U.S. are investigated: Wind River, a tall, dense conifer canopy, and Tonzi Ranch, a short, open oak canopy. On roughly 40% of nights lidar detected down-valley or downslope flows above the canopy at both sites. Nights with intermittent strong bursts of “top-down” forced turbulence were also observed above both canopies. The strongest of these bursts increased sub-canopy turbulence and reduced canopy virtual potential temperature (θv) gradient at Tonzi, but did not appear to change the flow characteristics within the dense Wind River canopy. At Tonzi we observed other times when high turbulence (via friction velocity, u* ) was found just above the trees, yet CO2 and θv gradients remained large and suggested flow decoupling. These events were triggered by regional downslope flow. Lastly, a set of turbulence parameters is evaluated for estimating canopy turbulence mixing strength. The relationship between turbulence parameters and canopy θv gradients was found to be complex, although better agreement between the canopy θv gradient and turbulence was found for parameters based on the standard deviation of vertical velocity, or ratios of 3-D turbulence to mean flow, than for u* . These findings add evidence that the relationship between canopy turbulence, static stability, and canopy mixing is far from straightforward even within an open canopy.

      PubDate: 2017-02-12T08:17:59Z
      DOI: 10.1016/j.agrformet.2017.01.020
      Issue No: Vol. 237-238 (2017)
       
  • A dendroclimatological assessment of shelterbelt trees in a moisture
           limited environment
    • Authors: Jason Maillet; Colin Laroque; Barrie Bonsal
      Pages: 30 - 38
      Abstract: Publication date: 1 May 2017
      Source:Agricultural and Forest Meteorology, Volumes 237–238
      Author(s): Jason Maillet, Colin Laroque, Barrie Bonsal
      The goal of this paper is to apply dendroclimatological methods to the analysis of two commonly planted shelterbelt tree species, Fraxinus pennsylvanica (green ash), and Picea glauca (white spruce), to assess their current relationship with climate and determine how their growth may be affected by climate change in the moisture limited region of southeastern Saskatchewan. Spring precipitation and more importantly spring drought, as represented by the standardized precipitation evapotranspiration index (SPEI), were found to be the most important factors controlling the growth of green ash and white spruce in southeastern Saskatchewan. Furthermore, a breakdown in the radial growth-climate relationship was observed in individuals planted far from their typical native ranges, a potential indication of climate induced stress. Considering these findings, and projections of future climate, it is suggested that conditions beyond the northern limit of the artificial green ash range, and into the boreal forest, may become more suitable for green ash growth, while the southern limit of the artificial white spruce range is expected to recede northward. This information can help guide the management of shelterbelt systems in the Canadian Prairies to ensure they provide maximum practical and ecological benefits for now and into the future.

      PubDate: 2017-02-12T08:17:59Z
      DOI: 10.1016/j.agrformet.2017.02.003
      Issue No: Vol. 237-238 (2017)
       
  • Enhanced water use efficiency in global terrestrial ecosystems under
           increasing aerosol loadings
    • Authors: Xiaoliang Lu; Min Chen; Yaling Liu; Diego G. Miralles; Faming Wang
      Pages: 39 - 49
      Abstract: Publication date: 1 May 2017
      Source:Agricultural and Forest Meteorology, Volumes 237–238
      Author(s): Xiaoliang Lu, Min Chen, Yaling Liu, Diego G. Miralles, Faming Wang
      Aerosols play a crucial role in the climate system, affecting incoming radiation and cloud formation. Based on a modelling framework that couples ecosystem processes with the atmospheric transfer of radiation, we analyze the effect of aerosols on surface incoming radiation, gross primary productivity (GPP), water losses from ecosystems through evapotranspiration (ET) and ecosystem water use efficiency (WUE, defined as GPP/ET) for 2003–2010 and validate them at global FLUXNET sites. The total diffuse radiation increases under relatively low or intermediate aerosol loadings, but decreases under more polluted conditions. We find that aerosol-induced changes in GPP depend on leaf area index, aerosol loading and cloudiness. Specifically, low and moderate aerosol loadings cause increases in GPP for all plant types, while heavy aerosol loadings result in enhancement (decrease) in GPP for dense (sparse) vegetation. On the other hand, ET is mainly negatively affected by aerosol loadings due to the reduction in total incoming radiation. Finally, WUE shows a consistent rise in all plant types under increasing aerosol loadings. Overall, the simulated daily WUE compares well with observations at 43 eddy-covariance tower sites (R2 =0.84 and RMSE=0.01gC (kg H2O)−1) with better performance at forest sites. In addition to the increasing portions of diffuse light, the rise in WUE is also favored by the reduction in radiation- and heat-stress caused by the aerosols, especially for wet and hot climates.

      PubDate: 2017-02-12T08:17:59Z
      DOI: 10.1016/j.agrformet.2017.02.002
      Issue No: Vol. 237-238 (2017)
       
  • Assessing the role of drought events on wildfires in the Iberian Peninsula
    • Authors: Ana Russo; Célia M. Gouveia; Patrícia Páscoa; Carlos C. DaCamara; Pedro M. Sousa; Ricardo M. Trigo
      Pages: 50 - 59
      Abstract: Publication date: 1 May 2017
      Source:Agricultural and Forest Meteorology, Volumes 237–238
      Author(s): Ana Russo, Célia M. Gouveia, Patrícia Páscoa, Carlos C. DaCamara, Pedro M. Sousa, Ricardo M. Trigo
      Southern European countries are particularly affected by summer wildfires and drought events. The occurrence of extreme meteorological conditions during preceding and contemporaneous months amplifies the risk of summer wildfires. The main scope of this study was to investigate the impact of drought periods on burned areas in the Iberian Peninsula. This will be achieved through the comparison of time series of two widely used multi-scalar drought indices (SPI and SPEI) calculated for each province and then associated with the time series of the standardized logarithm of normalized burned areas during the fire summer season. The SPI and SPEI were both calculated for the time scales spanning between 2 to 12 months and for each month from January to August, between 1980 and 2005. Based on the regression analysis between drought indicators and burned areas, the months that present lowest errors were identified for each province. From the obtained results two main conclusions were reached: (i) the association between drought and fires is a local scale process and should be analyzed at the province or sub-province level rather than at the country or continental level; (ii) the relation between wildfires and drought is better explained by the influence of the spring precipitation on the central sector and by the influence of temperature and precipitation during summer on most of the Portuguese provinces.

      PubDate: 2017-02-12T08:17:59Z
      DOI: 10.1016/j.agrformet.2017.01.021
      Issue No: Vol. 237-238 (2017)
       
  • Examining the short-term impacts of diverse management practices on plant
           phenology and carbon fluxes of Old World bluestems pasture
    • Authors: Yuting Zhou; Xiangming Xiao; Pradeep Wagle; Rajen Bajgain; Hayden Mahan; Jeffrey B. Basara; Jinwei Dong; Yuanwei Qin; Geli Zhang; Yiqi Luo; Prasanna H. Gowda; James P.S. Neel; Patrick J. Starks; Jean L. Steiner
      Pages: 60 - 70
      Abstract: Publication date: 1 May 2017
      Source:Agricultural and Forest Meteorology, Volumes 237–238
      Author(s): Yuting Zhou, Xiangming Xiao, Pradeep Wagle, Rajen Bajgain, Hayden Mahan, Jeffrey B. Basara, Jinwei Dong, Yuanwei Qin, Geli Zhang, Yiqi Luo, Prasanna H. Gowda, James P.S. Neel, Patrick J. Starks, Jean L. Steiner
      Burning, grazing, and baling (hay harvesting) are common management practices in grassland. To develop and adopt sustainable management practices, it is essential to better understand and quantify the impacts of management practices on plant phenology and carbon fluxes. In this study, we combined multiple data sources, including in-situ PhenoCam digital images, eddy covariance data, and satellite data (Landsat and Moderate Resolution Imaging Spectroradiometer (MODIS)) to examine the impacts of burning, baling, and grazing on canopy dynamics, plant phenology, and carbon fluxes in a pasture in El Reno, Oklahoma in 2014. Landsat images were used to assess the baling area and the trajectory of vegetation recovery. MODIS vegetation indices (VIs) were used in the Vegetation Photosynthesis Model (VPM) to estimate gross primary production (GPPVPM) at a MODIS pixel for the flux tower (baled) site. For comparison between baled and unbaled conditions, we used MODIS VIs for a neighbor MODIS pixel (unbaled) and ran VPM. Daily PhenoCam images and green chromatic coordinate (GCC) tracked canopy dynamics and plant phenology well. The grassland greened up immediately after burning in April. GCC values showed two peaks with the similar magnitude because of quick recovery of grassland after baling. Satellite-derived VIs and GPPVPM showed that the pasture recovered in one month after baling. The GPPVPM matched well (R2 =0.89) with the eddy covariance-derived GPP (GPPEC). Grazing in the late growing season did not influence plant phenology (VIs and GCC) and carbon uptake (GPP) as plants were in the late growing stage. Neither did it affect GPP differently in those two conditions because of even grazing intensity. The reduction in GPP after baling was compensated by higher GPP after large rain events in late July and early September, causing little seasonal differences in GPP (-0.002gCm−2 day−1) between the baled and unbaled conditions. Interactions of different management practices with climate make it complicated to understand the impacts of different management practices on carbon dynamics and plant phenology. Thus, it is necessary to further investigate the responses of pastures to different management practices under different climate regimes at multiple temporal and spatial scales.

      PubDate: 2017-02-12T08:17:59Z
      DOI: 10.1016/j.agrformet.2017.01.018
      Issue No: Vol. 237-238 (2017)
       
  • Impact of tree canopy on thermal and radiative microclimates in a mixed
           temperate forest: A new statistical method to analyse hourly temporal
           dynamics
    • Authors: Noémie Gaudio; Xavier Gendre; Marc Saudreau; Vincent Seigner; Philippe Balandier
      Pages: 71 - 79
      Abstract: Publication date: 1 May 2017
      Source:Agricultural and Forest Meteorology, Volumes 237–238
      Author(s): Noémie Gaudio, Xavier Gendre, Marc Saudreau, Vincent Seigner, Philippe Balandier
      Forest shelter buffers microclimate, decreasing daily ranges of solar radiation and temperature, yielding higher minimum and lower maximum temperatures than those of open field. The most common way to analyse sets of these data is to compare mean, maximum and minimum values of climate parameters of open field and understorey conditions at daily, monthly or seasonal scales; however, this approach loses information about temporal dynamics. This study developed a statistical method to analyse hourly dynamics of temperature (T) and radiation (Rad) together and quantify effects of canopy openness and seasonality on these dynamics. Eight experimental sites were chosen in small gaps located in a temperate oak-pine forest (France), and five plots were established in each along a light gradient (i.e. a total of 40 plots), which delimited a transect along which T and Rad were measured hourly at a height of 200cm from May 2009 to March 2010. T and Rad were also measured in open field. A specific Principal Component Analysis (PCA) with an innovative graphical representation was performed on this dataset. This statistical method allowed hourly temporal dynamics of all data recorded to be analysed and included a chart to interpret the distribution of the data in the principal plane defined by the PCA. Except in winter, results demonstrate the well-documented buffering effect of the tree canopy on T, with higher minimum and lower maximum values in the forest understorey. This effect was especially pronounced for minimum T and increased as canopy grew denser. In summer, T remained higher than expected in the understorey and was lower than expected in the open field, indicating thermal inertia in the understorey and an a priori cooling effect linked to wind or radiative losses during the night in the open field. The newly developed statistical method offers an innovative approach to better understand the tree canopy’s buffering effect on temporal dynamics.

      PubDate: 2017-02-12T08:17:59Z
      DOI: 10.1016/j.agrformet.2017.02.010
      Issue No: Vol. 237-238 (2017)
       
  • Investigating sources of measured forest-atmosphere ammonia fluxes using
           two-layer bi-directional modelling
    • Authors: K. Hansen; E. Personne; C.A. Skjøth; B. Loubet; A. Ibrom; R. Jensen; L.L. Sørensen; E. Boegh
      Pages: 80 - 94
      Abstract: Publication date: 1 May 2017
      Source:Agricultural and Forest Meteorology, Volumes 237–238
      Author(s): K. Hansen, E. Personne, C.A. Skjøth, B. Loubet, A. Ibrom, R. Jensen, L.L. Sørensen, E. Boegh
      Understanding and predicting the ammonia (NH3) exchange between the biosphere and the atmosphere is important due to the environmental consequences of the presence of reactive nitrogen (Nr) in the environment. The dynamics of the natural sources are, however, not well understood, especially not for forest ecosystems due to the complex nature of this soil-vegetation-atmosphere system. Furthermore, the high reactivity of NH3 makes it technically complex and expensive to measure and understand the forest-atmospheric NH3 exchange. The aim of this study is to investigate the NH3 flux partitioning between the ground layer, cuticle and stomata compartments for two temperate deciduous forest ecosystems located in Midwestern, USA (MMSF) and in Denmark (DK-Sor). This study is based on measurements and simulations of the surface energy balance, fluxes of CO2 and NH3 during two contrasted periods of the forest ecosystems, a period with full developed canopy (MMSF) and a senescent period for the DK-Sor site, with leaf fall and leaf litter build-up. Both datasets indicate emissions of NH3 from the forest to the atmosphere. The two-layer NH3 compensation point model SURFATM-NH3 was used in combination with a coupled photosynthesis-stomatal conductance model to represent seasonal variation in canopy physiological activity for simulating both net ecosystem CO2 exchange rates (R2 =0.77 for MMSF and R2 =0.84 for DK-Sor) and atmospheric NH3 fluxes (R2 =0.43 for MMSF and R2 =0.60 for DK-Sor). A scaling of the ground layer NH3 emission potential (Г g) was successfully applied using the plant area index (PAI) to represent the build-up of a litter layer in the leaf fall period. For a closed green forest canopy (MMSF), unaffected by agricultural NH3 sources, NH3 was emitted with daytime fluxes up to 50ng NH3-N m−2 s−1 and nighttime fluxes up to 30ng NH3-N m−2 s−1. For a senescing forest (DK-Sor), located in an agricultural region, deposition rates of 250ng NH3-N m−2 s−1 were measured prior to leaf fall, and emission rates up to 670ng NH3-N m−2 s−1 were measured following leaf fall. For MMSF, simulated stomatal NH3 emissions explain the daytime flux observations well, and it is hypothesized that cuticular desorption is responsible for the observed NH3 emissions at night. During leaf fall in DK-Sor, ground fluxes dominate the NH3 flux with a mean emission rate of 150ng NH3-N m−2 s−1. This study shows that forests potentially comprise a natural source of NH3 to the atmosphere, and that it is crucial to take into account the bi-directional exchange processes related to both the stomatal, cuticular and ground layer pathways in order to realistically simulate forest–atmosphere fluxes of NH3.

      PubDate: 2017-02-12T08:17:59Z
      DOI: 10.1016/j.agrformet.2017.02.008
      Issue No: Vol. 237-238 (2017)
       
  • Site index changes of Scots pine, Norway spruce and larch stands in
           southern and central Finland
    • Authors: Harri Mäkinen; Chaofang Yue; Ulrich Kohnle
      Pages: 95 - 104
      Abstract: Publication date: 1 May 2017
      Source:Agricultural and Forest Meteorology, Volumes 237–238
      Author(s): Harri Mäkinen, Chaofang Yue, Ulrich Kohnle
      The annual growth of the Finnish forests has doubled in less than a century but the reasons for the increase have been a subject of much debate. Site index aggregates the mid- to long-term impacts of variable edaphic and climatic factors on site productivity and is an important characteristic with regard to the ongoing environmental changes. We quantified changes of site index in Finland over time by applying a new approach developed in our previous study in Germany. A large data base for Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.) and larch (Larix spp.) was available from the network of long-term growth and yield experiments in southern and central Finland. For all tree species, site indices fluctuated over time, i.e. they slightly decreased in the 1970s, followed by an increasing trend in the 1980s and a decline again in the 1990s. Apparently, the only significant change was a change point indicated for Scots pine around the year 1944; however, indication was weak due to notable limitations of the database during the respective period. Interestingly, the result of this study in Finland differs from central Europe, where Norway spruce site productivity has displayed a considerable increase since the 1950s. Potentially, the low nitrogen deposition in Finland may be of major importance accounting for the divergent changes in site productivity between Finland and central Europe. Thus, the results indicate that a large share of the growth increase in the Finnish forests might actually be due to altered management.

      PubDate: 2017-02-12T08:17:59Z
      DOI: 10.1016/j.agrformet.2017.01.017
      Issue No: Vol. 237-238 (2017)
       
  • Meteorological drought forecasting for ungauged areas based on machine
           learning: Using long-range climate forecast and remote sensing data
    • Authors: Jinyoung Rhee; Jungho Im
      Pages: 105 - 122
      Abstract: Publication date: 1 May 2017
      Source:Agricultural and Forest Meteorology, Volumes 237–238
      Author(s): Jinyoung Rhee, Jungho Im
      A high-resolution drought forecast model for ungauged areas was developed in this study. The Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) with 3-, 6-, 9-, and 12-month time scales were forecasted with 1–6-month lead times at 0.05×0.05° resolution. The use of long-range climate forecast data was compared to the use of climatological data for periods with no observation data. Machine learning models utilizing drought-related variables based on remote sensing data were compared to the spatial interpolation of Kriging. Two performance measures were used; one is producer’s drought accuracy, defined as the number of correctly classified samples in extreme, severe, and moderate drought classes over the total number of samples in those classes, and the other is user’s drought accuracy, defined as the number of correctly classified samples in drought classes over the total number of samples classified to those classes. One of the machine learning models, extremely randomized trees, performed the best in most cases in terms of producer’s accuracy reaching up to 64%, while spatial interpolation performed better in terms of user’s accuracy up to 44%. The contribution of long-range climate forecast data was not significant under the conditions used in this study, but further improvement is expected if forecast skill is improved or a more sophisticated downscaling method is used. Simulated decreases of forecast error in precipitation and mean temperature were tested: the simulated decrease of forecast error in precipitation improves drought forecast while the decrease of forecast error in mean temperature does not contribute much. Although there is still some room for improvement, the developed model can be used for drought-related decision making in ungauged areas.

      PubDate: 2017-02-12T08:17:59Z
      DOI: 10.1016/j.agrformet.2017.02.011
      Issue No: Vol. 237-238 (2017)
       
  • Evaluation of DeNitrification DeComposition model for estimating ammonia
           fluxes from chemical fertilizer application
    • Authors: Srinidhi Balasubramanian; Andrew Nelson; Sotiria Koloutsou-Vakakis; Jie Lin; Mark J. Rood; LaToya Myles; Carl Bernacchi
      Pages: 123 - 134
      Abstract: Publication date: 1 May 2017
      Source:Agricultural and Forest Meteorology, Volumes 237–238
      Author(s): Srinidhi Balasubramanian, Andrew Nelson, Sotiria Koloutsou-Vakakis, Jie Lin, Mark J. Rood, LaToya Myles, Carl Bernacchi
      DeNitrification DeComposition (DNDC) model predictions of NH3 fluxes following chemical fertilizer application were evaluated by comparison to relaxed eddy accumulation (REA) measurements, in Central Illinois, United States, over the 2014 growing season of corn. Practical issues for evaluating closure were addressed by accounting for fluxes outside the measurement site and differences in temporal resolution. DNDC modeled NH3 fluxes showed no significant differences in magnitude (at p=0.05) compared to measurements and replicated trends satisfactorily (ra 2 >0.74), during the initial 33days after fertilizer application, when measured fluxes were to the atmosphere, compared to later time periods when depositional fluxes were measured (ra 2 <0.52). Among the model input parameters, NH3 fluxes were most sensitive to air temperature, precipitation, soil organic carbon, field capacity, pH, and fertilizer application rate, timing, and depth. By constraining these inputs for conditions in Central Illinois, uncertainty in daily NH3 fluxes was estimated to vary from 0% to 70% on a daily basis, during the corn growing season, with the highest uncertainty values estimated for the period of highest positive NH3 fluxes. These results can guide future improvements in DNDC, which is a valuable tool to assist (1) in the development of NH3 emission inventories with high spatial (constrained by the spatial resolution of input parameters) and temporal resolution (daily) and (2) in upscaling emissions from the site (farm) to the regional scale.

      PubDate: 2017-02-12T08:17:59Z
      DOI: 10.1016/j.agrformet.2017.02.006
      Issue No: Vol. 237-238 (2017)
       
  • Revisiting the choice of the driving temperature for eddy covariance CO2
           flux partitioning
    • Authors: Georg Wohlfahrt; Marta Galvagno
      Pages: 135 - 142
      Abstract: Publication date: 1 May 2017
      Source:Agricultural and Forest Meteorology, Volumes 237–238
      Author(s): Georg Wohlfahrt, Marta Galvagno
      So-called CO2 flux partitioning algorithms are widely used to partition the net ecosystem CO2 exchange into the two component fluxes, gross primary productivity and ecosystem respiration. Common CO2 flux partitioning algorithms conceptualise ecosystem respiration to originate from a single source, requiring the choice of a corresponding driving temperature. Using a conceptual dual-source respiration model, consisting of an above- and a below-ground respiration source each driven by a corresponding temperature, we demonstrate that the typical phase shift between air and soil temperature gives rise to a hysteresis relationship between ecosystem respiration and temperature. The hysteresis proceeds in a clockwise fashion if soil temperature is used to drive ecosystem respiration, while a counter-clockwise response is observed when ecosystem respiration is related to air temperature. As a consequence, nighttime ecosystem respiration is smaller than daytime ecosystem respiration when referenced to soil temperature, while the reverse is true for air temperature. We confirm these qualitative modelling results using measurements of day and night ecosystem respiration made with opaque chambers in a short-statured mountain grassland. Inferring daytime from nighttime ecosystem respiration or vice versa, as attempted by CO2 flux partitioning algorithms, using a single-source respiration model is thus an oversimplification resulting in biased estimates of ecosystem respiration. We discuss the likely magnitude of the bias, options for minimizing it and conclude by emphasizing that the systematic uncertainty of gross primary productivity and ecosystem respiration inferred through CO2 flux partitioning needs to be better quantified and reported.
      Graphical abstract image

      PubDate: 2017-02-18T08:25:32Z
      DOI: 10.1016/j.agrformet.2017.02.012
      Issue No: Vol. 237-238 (2017)
       
  • Influence of levelling technique on the retrieval of canopy structural
           parameters from digital hemispherical photography
    • Authors: Niall Origo; Kim Calders; Joanne Nightingale; Mathias Disney
      Pages: 143 - 149
      Abstract: Publication date: 1 May 2017
      Source:Agricultural and Forest Meteorology, Volumes 237–238
      Author(s): Niall Origo, Kim Calders, Joanne Nightingale, Mathias Disney
      Digital hemispherical photography is a simple, non-destructive method for estimating canopy biophysical parameters for ecological applications and validation of remote sensing products. Determination of optimum and repeatable acquisition procedures is well documented in the literature but so far this has not focused on evaluating the levelling procedure used to align the camera. In this paper, the standard recommendation that tripod levelling is a necessity is tested by comparing it with a hand-levelled procedure. The results show that the average difference between the two procedures is <2% for effective plant area index and <1% for gap fraction at the VALERI plot scale, which generally falls within the variance. Users implementing the hand-levelled technique can expect large reductions in data acquisition time, allowing many more samples to be collected without compromising the overall quality of the data retrieved.

      PubDate: 2017-02-18T08:25:32Z
      DOI: 10.1016/j.agrformet.2017.02.004
      Issue No: Vol. 237-238 (2017)
       
  • Springtime ecosystem-scale monoterpene fluxes from Mediterranean pine
           forests across a precipitation gradient
    • Authors: Roger Seco; Thomas Karl; Andrew Turnipseed; Jim Greenberg; Alex Guenther; Joan Llusia; Josep Peñuelas; Uri Dicken; Eyal Rotenberg; Saewung Kim; Dan Yakir
      Pages: 150 - 159
      Abstract: Publication date: 1 May 2017
      Source:Agricultural and Forest Meteorology, Volumes 237–238
      Author(s): Roger Seco, Thomas Karl, Andrew Turnipseed, Jim Greenberg, Alex Guenther, Joan Llusia, Josep Peñuelas, Uri Dicken, Eyal Rotenberg, Saewung Kim, Dan Yakir
      We quantified springtime ecosystem-scale monoterpene fluxes from two similar Aleppo pine (Pinus halepensis Mill.) forests, located in Israel, that differed in the amount of received precipitation: Yatir in the arid south and Birya in the northern part of Israel (291 and 755mm annual average rainfall, respectively). In addition to the lower water availability, during our measurement campaign the Yatir site suffered from a heat wave with temperatures up to 35°C, which made the campaign-average net CO2 assimilation to occur in the morning (1μmolm−2 s−1), with the rest of the daytime hours mainly dominated by net release of CO2. The milder conditions at Birya favored a higher net CO2 assimilation during all daytime hours (with average peaks higher than 10μmolm−2 s−1). Despite these large differences in ambient conditions and CO2 net assimilation, daytime monoterpene emission capacities at both sites were comparable. While observed monoterpene fluxes were lower at Yatir than at Birya (hourly averages up to 0.4 and 1mgm−2 h−1, respectively), the standardized hourly fluxes, after accounting for the differences in light, temperature and stand density between both sites, were comparable (0–1.3mgm−2 h−1). The approach typically used by biogenic emission models overestimated monoterpene fluxes at Yatir when temperatures rose during the heat wave. This result, together with complementary leaf-level measurements showing that summertime monoterpene fluxes almost completely ceased at Yatir while being enhanced at Birya, highlight the interaction of water scarcity and high temperatures that drive monoterpene emissions from vegetation in such extreme climate zones and the need to further improve model performance.

      PubDate: 2017-02-24T16:16:02Z
      DOI: 10.1016/j.agrformet.2017.02.007
      Issue No: Vol. 237-238 (2017)
       
  • Combining eddy-covariance and chamber measurements to determine the
           methane budget from a small, heterogeneous urban floodplain wetland park
    • Authors: T.H. Morin; G. Bohrer; K.C. Stefanik; A.C. Rey-Sanchez; A.M. Matheny; W.J. Mitsch
      Pages: 160 - 170
      Abstract: Publication date: 1 May 2017
      Source:Agricultural and Forest Meteorology, Volumes 237–238
      Author(s): T.H. Morin, G. Bohrer, K.C. Stefanik, A.C. Rey-Sanchez, A.M. Matheny, W.J. Mitsch
      Methane (CH4) emissions and carbon uptake in temperate freshwater wetlands act in opposing directions in the context of global radiative forcing. Large uncertainties exist for the rates of CH4 emissions making it difficult to determine the extent that CH4 emissions counteract the carbon sequestration of wetlands. Urban temperate wetlands are typically small and feature highly heterogeneous land cover, posing an additional challenge to determining their CH4 budget. The data analysis approach we introduce here combines two different CH4 flux measurement techniques to overcome scale and heterogeneity problems and determine the overall CH4 budget of a small, heterogeneous, urban wetland landscape. Temporally intermittent point measurements from non-steady-state chambers provided information about patch-level heterogeneity of fluxes, while continuous, high temporal resolution flux measurements using the eddy-covariance (EC) technique provided information about the temporal dynamics of the fluxes. Patch-level scaling parameterization was developed from the chamber data to scale eddy covariance data to a ‘fixed-frame’, which corrects for variability in the spatial coverage of the eddy covariance observation footprint at any single point in time. By combining two measurement techniques at different scales, we addressed shortcomings of both techniques with respect to heterogeneous wetland sites. We determined that fluxes observed by the two methods are statistically similar in magnitude when brought to the same temporal and spatial scale. We also found that open-water and macrophyte-covered areas of the wetland followed similar phenological cycles and emitted nearly equivalent levels of CH4 for much of the year. However, vegetated wetland areas regularly exhibited a stronger late-summer emission peak, possibly due to CH4 transport through mature vegetation vascular systems. Normalizing the eddy covariance data to a fixed-frame allowed us to determine the seasonal CH4 budget of each patch and the overall site. Overall, the macrophyte areas had the largest CH4 fluxes followed by the open water areas. Uncertainties in the final CH4 budget included spatial heterogeneity of CH4 fluxes, the tower footprint, measurement in the data to be scaled, and gap-filling. Of these, the spatial placement of the chambers provided the largest source of uncertainty in CH4 estimates. This reinforces the need to utilize site-level measurements when estimating CH4 fluxes from wetlands as opposed to using only up-scaled point measurements.

      PubDate: 2017-02-18T08:25:32Z
      DOI: 10.1016/j.agrformet.2017.01.022
      Issue No: Vol. 237-238 (2017)
       
  • Quantum sensors for accurate and stable long-term photosynthetically
           active radiation observations
    • Authors: Tomoko Akitsu; Kenlo Nishida Nasahara; Yasuo Hirose; Osamu Ijima; Atsushi Kume
      Pages: 171 - 183
      Abstract: Publication date: 1 May 2017
      Source:Agricultural and Forest Meteorology, Volumes 237–238
      Author(s): Tomoko Akitsu, Kenlo Nishida Nasahara, Yasuo Hirose, Osamu Ijima, Atsushi Kume
      Long-term accurate data of photosynthetically active radiation (PAR) are needed because PAR is one of the standard environmental statistics needed to evaluate plant photosynthesis. Therefore, PAR observation sites are globally distributed, particularly in flux observation sites. Quantum sensors have been used for half a century to observe PAR; however, their accuracy is still uncertain. This study evaluates the accuracies of nine quantum sensor products by examining their spectral and cosine responses. On the basis of these data as well as reference spectrum data provided by our standard spectrometric measurement, we performed the following analyses: (1) a simulation of errors caused by the sensors’ non-ideal spectral response in three types of radiation inputs (open sky, forest canopy transmission, and forest canopy reflection), (2) a simulation of the errors caused by a complex combination of the sensors’ non-ideal spectral and cosine responses in three diurnal variation types of incident radiation (clear sky, partial clouds, and an overcast sky), and (3) an observation of the sensors’ long-term sensitivity degradation outdoors. Based on the results, we recommend two quantum sensors with minimal errors, LI-COR LI-190 encased in a weather-proof external housing with a glass dome and PREDE PAR-02D. The findings of this study contribute in establishing a long-term PAR observation protocol and should become a basis for quality checks and controls of PAR observation values that have previously been obtained worldwide.

      PubDate: 2017-02-18T08:25:32Z
      DOI: 10.1016/j.agrformet.2017.01.011
      Issue No: Vol. 237-238 (2017)
       
  • A simple parameterisation of windbreak effects on wind speed reduction and
           resulting thermal benefits to sheep
    • Abstract: Publication date: 28 May 2017
      Source:Agricultural and Forest Meteorology, Volume 239
      Author(s): Yufeng He, Pippa J. Jones, Mark Rayment
      It is well known that windbreaks can provide favourable conditions for livestock. Determining the benefit of any given windbreak system first requires that the impact of the windbreak on the wind microclimate is characterised, but in practice, modelling wind flow around obstacles is complex and computationally intensive. We report a simple parameterised model to estimate the wind speed reduction around a windbreak. Analytically, model parameters showed close links to the real-world attributes that characterise windbreaks. The model was validated with field measurements on a farmland in the UK; a Monte Carlo simulation was used to measure model parameter uncertainties. Results showed that the model produced an excellent fit to the relative wind speed (i.e. normalized by ambient wind speed) with root-mean-square error of 4%±0.5%. The model was further applied to literature data to characterise the dependence of the relative wind speed on windbreak porosity. A field-scale simulation of a sheep grazing system, including an explicit description of wind-chill effects, was conducted to estimate the net gain associated with including a windbreak in sheep productivity. The maximum productivity gain (27%) was found at a porosity of 0.5 and a wind speed of 12m/s. Wind-chill effects were further simulated for lowland and upland environments, and related to ovine-specific thermal tolerance limits. Results showed a distinct response to reduced wind speeds between sites, indicating different levels of thermal risk to livestock and different, microclimate-specific, windbreak benefits for each location. The simplified models proposed in this study provides a generic framework for an efficient and precise quantification of windbreak effects and optimising the design of windbreak systems.

      PubDate: 2017-04-26T14:30:57Z
       
  • Improved parameterization of the commonly used exponential equation for
           calculating soil-atmosphere exchange fluxes from closed-chamber
           measurements
    • Authors: Antje Moffat; Christian
      Abstract: Publication date: 15 June 2017
      Source:Agricultural and Forest Meteorology, Volumes 240–241
      Author(s): Antje M. Moffat, Christian Brümmer
      The concentration change in a closed chamber derived from Fick’s law for a steady flux leads to a differential equation which describes an exponential curve of limited growth. Here we introduce and compare an alternative parameterization with those commonly used in the chamber flux community when investigating soil-atmosphere exchange of N2O, CH4, or CO2 using classical gas chromatography systems, infrared gas analyzers, or novel laser absorption spectrometers. This new parameterization has the advantages that the parameters are mathematically less dependent leading to a more stable regression and that all parameters are physically meaningful with one of them being the main quantity of interest, i.e. the initial flux at chamber closure.

      PubDate: 2017-04-12T13:25:08Z
       
  • Timing of cherry tree blooming: Contrasting effects of rising winter low
           temperatures and early spring temperatures
    • Authors: Peijian Shi; Zhenghong Chen Gadi V.P. Reddy Cang Hui Jianguo
      Abstract: Publication date: 15 June 2017
      Source:Agricultural and Forest Meteorology, Volumes 240–241
      Author(s): Peijian Shi, Zhenghong Chen, Gadi V.P. Reddy, Cang Hui, Jianguo Huang, Mei Xiao
      Phenology reflects the interplay of climate and biological development. Early spring phenological phenomena are particularly important because the end of diapause or dormancy is related not only to heat accumulation in the early spring but also probably to winter low temperatures. Although a warmer winter can reduce overwintering mortality in many insects and plants, it also reduces the accumulation of chilling time that often triggers the end of diapause or dormancy. We examined a continuous 67-year time series of the first flowering date of cherry trees and compared three phenological models based on the temperature-dependent developmental rate: (i) the accumulated degree days (ADD) method, (ii) the number of days transferred to a standardized temperature (DTS) method, and (iii) the accumulated developmental progress (ADP) method. The ADP method performed the best but only slightly better than the DTS method. We further explained the residuals from the ADP method by an additive model using the mean winter minimum daily temperatures, the number of days with low temperatures (represented by daily minimum temperature) below a critical low temperature, and the minimum annual extreme temperature. These three temperature variables explained more than 57.5% deviance of the ADP model residuals. Increased mean winter low temperatures can delay the blooming of cherry trees by reducing the accumulation of chilling time, whereas reduced numbers of cold days can shift the blooming to become earlier. Overall, rising winter low temperatures will delay the flowering time, while rising early spring temperatures directly shift earlier the flowering time. The flowering time has been shifted to earlier, and the balance from the opposing effects of rising winter low temperatures and early spring temperatures explains this shift.

      PubDate: 2017-04-12T13:25:08Z
       
  • Inside Front Cover (Editorial Board)
    • Abstract: Publication date: 1 May 2017
      Source:Agricultural and Forest Meteorology, Volumes 237–238


      PubDate: 2017-04-05T10:50:37Z
       
 
 
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