for Journals by Title or ISSN
for Articles by Keywords
help

Publisher: Elsevier   (Total: 3043 journals)

 A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z  

        1 2 3 4 5 6 7 8 | Last   [Sort by number of followers]   [Restore default list]

Showing 1 - 200 of 3043 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: 18, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 83, SJR: 1.109, h-index: 94)
Accounting Forum     Hybrid Journal   (Followers: 23, 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: 332, 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   (Followers: 1)
Acta de Investigación Psicológica     Open Access   (Followers: 2)
Acta Ecologica Sinica     Open Access   (Followers: 8, SJR: 0.172, h-index: 29)
Acta Haematologica Polonica     Free   (SJR: 0.123, h-index: 8)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.604, h-index: 38)
Acta Materialia     Hybrid Journal   (Followers: 211, 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: 23, SJR: 1.365, h-index: 73)
Acta Sociológica     Open Access  
Acta Tropica     Hybrid Journal   (Followers: 6, SJR: 1.059, h-index: 77)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 4)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 3)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 4, SJR: 0.383, h-index: 19)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 2)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 5, SJR: 0.141, h-index: 3)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 4, SJR: 0.112, h-index: 2)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 3)
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: 8, SJR: 1.039, h-index: 5)
Additives for Polymers     Full-text available via subscription   (Followers: 20)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 129, 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: 9, SJR: 0.299, h-index: 15)
Advances in Agronomy     Full-text available via subscription   (Followers: 15, SJR: 2.071, h-index: 82)
Advances in Anesthesia     Full-text available via subscription   (Followers: 25, 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: 22, 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: 25, 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: 10, 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: 41, 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: 40, 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: 47, SJR: 0.674, h-index: 38)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 15)
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: 21, 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: 25)
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: 35, 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: 5)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 4)
Advances in Life Course Research     Hybrid Journal   (Followers: 8, SJR: 0.764, h-index: 15)
Advances in Lipobiology     Full-text available via subscription   (Followers: 2)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 9)
Advances in Marine Biology     Full-text available via subscription   (Followers: 16, SJR: 1.645, h-index: 45)
Advances in Mathematics     Full-text available via subscription   (Followers: 10, SJR: 3.261, h-index: 65)
Advances in Medical Sciences     Hybrid Journal   (Followers: 6, SJR: 0.489, h-index: 25)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 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: 22)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 10)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 7, SJR: 0.324, h-index: 8)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 4)
Advances in Oncobiology     Full-text available via subscription   (Followers: 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: 24, SJR: 0.4, h-index: 28)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 13)
Advances in Pharmacology     Full-text available via subscription   (Followers: 15, 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: 19, SJR: 1.5, h-index: 62)
Advances in Psychology     Full-text available via subscription   (Followers: 60)
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: 2, SJR: 0.1, h-index: 2)
Advances in Space Research     Full-text available via subscription   (Followers: 345, SJR: 0.606, h-index: 65)
Advances in Structural Biology     Full-text available via subscription   (Followers: 8)
Advances in Surgery     Full-text available via subscription   (Followers: 7, SJR: 0.823, h-index: 27)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 30, SJR: 1.321, h-index: 56)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 15)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 13)
Advances in Virus Research     Full-text available via subscription   (Followers: 5, SJR: 1.878, h-index: 68)
Advances in Water Resources     Hybrid Journal   (Followers: 43, 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: 309, 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: 5, SJR: 0.344, h-index: 6)
Ageing Research Reviews     Hybrid Journal   (Followers: 8, SJR: 3.289, h-index: 78)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 405, 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: 30, SJR: 1.275, h-index: 74)
Agricultural Water Management     Hybrid Journal   (Followers: 38, 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: 53, SJR: 1.879, h-index: 120)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.434, h-index: 14)
Air Medical J.     Hybrid Journal   (Followers: 5, SJR: 0.234, h-index: 18)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.285, h-index: 3)
Alcohol     Hybrid Journal   (Followers: 9, SJR: 0.922, h-index: 66)
Alcoholism and Drug Addiction     Open Access   (Followers: 6)
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: 8, 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: 4, 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: 7, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 48, 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: 48, SJR: 3.157, h-index: 153)
American J. of Cardiology     Hybrid Journal   (Followers: 45, SJR: 2.063, h-index: 186)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 38, 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: 16, SJR: 1.653, h-index: 93)
American J. of Human Genetics     Hybrid Journal   (Followers: 31, SJR: 8.769, h-index: 256)
American J. of Infection Control     Hybrid Journal   (Followers: 24, SJR: 1.259, h-index: 81)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 33, SJR: 2.313, h-index: 172)
American J. of Medicine     Hybrid Journal   (Followers: 46, 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: 191, SJR: 2.255, h-index: 171)
American J. of Ophthalmology     Hybrid Journal   (Followers: 54, SJR: 2.803, h-index: 148)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 3)
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: 23, SJR: 0.59, h-index: 45)
American J. of Pathology     Hybrid Journal   (Followers: 26, 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: 34, SJR: 1.286, h-index: 125)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.653, h-index: 70)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 5)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.066, h-index: 51)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 55, SJR: 0.124, h-index: 9)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 10)
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: 162, SJR: 0.725, h-index: 154)
Analytical Chemistry Research     Open Access   (Followers: 8, SJR: 0.18, h-index: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 11)
Anesthésie & Réanimation     Full-text available via subscription   (Followers: 1)
Anesthesiology Clinics     Full-text available via subscription   (Followers: 22, SJR: 0.421, h-index: 40)
Angiología     Full-text available via subscription   (SJR: 0.124, h-index: 9)
Angiologia e Cirurgia Vascular     Open Access  
Animal Behaviour     Hybrid Journal   (Followers: 158, 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   (Followers: 1, 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)

        1 2 3 4 5 6 7 8 | Last   [Sort by number of followers]   [Restore default list]

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  [3043 journals]
  • Physical and biogeochemical controls on soil respiration along a
           topographical gradient in a semiarid forest
    • Authors: Wei-Yu Shi; Sheng Du; Joseph C. Morina; Jin-Hong Guan; Kai-Bo Wang; Ming-Guo Ma; Norikazu Yamanaka; Ryunosuke Tateno
      Pages: 1 - 11
      Abstract: Publication date: 15 December 2017
      Source:Agricultural and Forest Meteorology, Volume 247
      Author(s): Wei-Yu Shi, Sheng Du, Joseph C. Morina, Jin-Hong Guan, Kai-Bo Wang, Ming-Guo Ma, Norikazu Yamanaka, Ryunosuke Tateno
      Soil respiration is a dynamic and fundamental process across all terrestrial ecosystems. However, how physical and biogeochemical factors control seasonal variation and annual rates of soil respiration remains poorly understood. A topographical gradient in a semiarid forest was chosen as the study site to assess how both biogeochemical and physical factors control respiration rates. Parameters measured include soil respiration, litterfall, fine root biomass, soil physical and chemical properties, soil bacteria and archaea gene abundance, ectomycorrhizal fungi abundance and richness, and soil carbon isotope signatures. The results showed that increases in soil temperature and moisture exponentially and linearly promoted root activity, driving seasonal variation of total soil respiration. Seasonal variation of heterotrophic respiration was driven by soil moisture in a second-order polynomial pattern. Autotrophic respiration only contributed to 20% of the total soil respiration, and seasonal variation in the soil respiration rate was driven by heterotrophic respiration. Utilizing soil moisture as a scalar, the values of Q10 and R10 in different poisons on the slope indicated soil respiration was controlled by interaction of soil temperature and moisture, and a new transformation of the R10 function inducing soil moisture was proposed. Along the topographical gradient, the long-term average soil temperature and moisture significantly varied from the top to the bottom of a slope. This variation in physical processes induced differences in plant productivity and biomass accumulation, leading to varying organic matter accumulation across the gradient. The topographical position also induced differences in the size of the soil organic matter aggregates, archaea and bacteria gene abundances, and ectomycorrhizal fungi abundance and richness. The aforementioned parameters are interrelated due to their association with the long-term average soil temperature and moisture, and the interrelation of these parameters ultimately affects annual rates of soil respiration.

      PubDate: 2017-07-23T16:00:07Z
      DOI: 10.1016/j.agrformet.2017.07.006
      Issue No: Vol. 247 (2017)
       
  • Estimating wheat green area index from ground-based LiDAR measurement
           using a 3D canopy structure model
    • Authors: Shouyang Liu; Fred Baret; Mariem Abichou; Fred Boudon; Samuel Thomas; Kaiguang Zhao; Christian Fournier; Bruno Andrieu; Kamran Irfan; Matthieu Hemmerlé; Benoit de Solan
      Pages: 12 - 20
      Abstract: Publication date: 15 December 2017
      Source:Agricultural and Forest Meteorology, Volume 247
      Author(s): Shouyang Liu, Fred Baret, Mariem Abichou, Fred Boudon, Samuel Thomas, Kaiguang Zhao, Christian Fournier, Bruno Andrieu, Kamran Irfan, Matthieu Hemmerlé, Benoit de Solan
      The use of active remote sensing techniques based on light detection and ranging (LiDAR) was investigated here to estimate the green area index (GAI) of wheat crops. Emphasis was put on the maximum GAI development stage when saturation effects are known to limit the performances of standard indirect methods based either on the gap fraction or reflectance measurements. The LiDAR provides both the three dimensional (3D) point cloud from which the vertical distribution (Z profile) of the interception points is computed, as well as the intensity of the returned signal from which the green fraction (GF) is derived. The data were interpreted by exploiting the 3D ADEL-Wheat model that synthesizes the knowledge accumulated on wheat canopy structure. A LiDAR simulator that accounts for the specific observation configuration used was developed to mimic the actual LiDAR measurements. The in-silico experiments were conducted to generate training and validation dataset. Neural network were then used to estimate GAI from the Z profile and GF derived from the LiDAR measurements. Performances of GAI estimates by the several methods investigated were evaluated using either experimental data with 3<GAI<6 and data simulated with the 3D structure model with 1<GAI<7. Results confirm that using only the GF provides poor estimates of GAI (0.89<RMSE<1.28; 0.22<rRMSE<0.31), regardless of turbid medium or realistic assumptions on canopy 3D structure. The introduction of the Z profile information improved significantly the GAI estimation accuracy (0.48<RMSE<0.55; 0.12<rRMSE<0.13). This study demonstrates the interest of using the third dimension provided by LiDAR to better estimate GAI in crops under high GAI values. However, this requires the use of a realistic 3D structure crop model over which the LiDAR data could be simulated under the observational configuration used.
      Graphical abstract image

      PubDate: 2017-07-23T16:00:07Z
      DOI: 10.1016/j.agrformet.2017.07.007
      Issue No: Vol. 247 (2017)
       
  • 2D profiles of CO2, CH4, N2O and gas diffusivity in a well aerated soil:
           measurement and Finite Element Modeling
    • Authors: M. Maier; B. Longdoz; T. Laemmel; H. Schack-Kirchner; F. Lang
      Pages: 21 - 33
      Abstract: Publication date: 15 December 2017
      Source:Agricultural and Forest Meteorology, Volume 247
      Author(s): M. Maier, B. Longdoz, T. Laemmel, H. Schack-Kirchner, F. Lang
      Soil gas fluxes depend on soil gas concentrations and physical properties of a soil. Taking soil samples for physical analysis into the laboratory strongly modifies soil gas concentrations and also cuts roots that sustain the activity in the rhizosphere. Since microbial processes interact with gas concentrations in soil, we need to study gas transport and production in situ. We developed a method to monitor the transport and production and consumption of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) in soils in situ in a two dimensional (2D) profile using tetrafluoromethane (CF4) and sulfur hexafluoride (SF6) as tracer gases and Finite Element Modeling of soil gas transport. Continuous injection of the inert tracer gases and 2D gas sampling in a soil profile allowed for inverse modeling of the 2D profile of soil gas diffusivity. In a second step, the 2D profiles of the production and consumption of CO2, CH4, and N2O were inversely determined. Soil gas concentrations were monitored in a Scots pine stand in South-West Germany during a rain-free week in the fall. The 2D relative (so as to be independent of gas species) soil gas diffusivity profile showed large horizontal variability. Relative soil gas diffusivity was found to be anisotropic with the vertical direction greater by a factor of 1.26. Topsoil moisture decreased slowly over time resulting in an increase in relative soil gas diffusivity. The soil was found to be a source of CO2, and a net sink of CH4 and N2O, with the highest production (CO2) and consumption (CH4, N2O) occurring in the topsoil. The gas concentration and production profiles of CO2 were nearly horizontally homogenous, while those for CH4 showed larger horizontal differences. Net consumption of CH4 and net production of CO2 both increased as the soil dried. This occurred despite reverse trends for these variables in the topsoil (0–8cm depth) which were more than offset by the underlying soil becoming more active. Sensitivity tests showed that the determination of 2D profiles of soil gas diffusivity and production and consumption of CO2 and CH4 were more reliable than the estimates for N2O because the magnitudes of these for N2O were very low. Our method represents a useful tool for the analyses of soil gas flux heterogeneities and associated microbial processes within soil profiles.
      Graphical abstract image

      PubDate: 2017-08-03T10:06:27Z
      DOI: 10.1016/j.agrformet.2017.07.008
      Issue No: Vol. 247 (2017)
       
  • Shifts in cultivar and planting date have regulated rice growth duration
           under climate warming in China since the early 1980s
    • Authors: Xunyu Hu; Yao Huang; Wenjuan Sun; Lingfei Yu
      Pages: 34 - 41
      Abstract: Publication date: 15 December 2017
      Source:Agricultural and Forest Meteorology, Volume 247
      Author(s): Xunyu Hu, Yao Huang, Wenjuan Sun, Lingfei Yu
      Climate warming accelerates crop development and shortens growth duration. The adoption of new cultivars and changes in planting date may either retard or amplify this acceleration. However, the extent to which the cultivar and planting date shifts have impacted rice growth duration under climate warming remains largely unknown. Using an up-to-date data series from 82 agro-meteorological stations in China where rice phenology was observed from 1981 to 2012, we quantified the impacts of climate warming, cultivar and planting date shifts on rice growth duration based on a degree-days calculation. The results indicate that climate warming shortened the growth duration length (GDL) between emergence and maturity at rates of 4.2±0.7 (mean±SE), 1.8±0.3 and 3.9±0.5days 10-yr−1 for single, early and late rice. GDL shortening was more pronounced in the vegetative phase than in the reproductive phase for single and early rice, but it was opposite for late rice system. Cultivar shifts prolonged the GDL at rates of 6.1±1.0 and 1.7±0.6days 10-yr−1 for single and early rice but induced GDL shortening of 4.1±1.6days 10-yr−1 for late rice. The effect of planting date shifts (advanced or delayed) on GDL change was variable and depended on the rice cropping system. On average, climate warming accelerated crop development, with a relative contribution to GDL changes of −40% in single rice, −45% in early rice, and −35% in late rice. Cultivar shifts compensated for the GDL shortening induced by climate warming in single and early rice with the relative contribution of 58% and 44%, respectively, but accelerated crop development in late rice with a contribution of −37%. Nevertheless, the planting date at two-thirds of the late rice stations was significantly delayed, which retarded the acceleration by 29% in terms of GDL changes.

      PubDate: 2017-08-03T10:06:27Z
      DOI: 10.1016/j.agrformet.2017.07.014
      Issue No: Vol. 247 (2017)
       
  • Increasing moisture limitation of Norway spruce in Central Europe revealed
           by forward modelling of tree growth in tree-ring network
    • Authors: Jan Tumajer; Jan Altman; Petr Štěpánek; Václav Treml; Jiří Doležal; Emil Cienciala
      Pages: 56 - 64
      Abstract: Publication date: 15 December 2017
      Source:Agricultural and Forest Meteorology, Volume 247
      Author(s): Jan Tumajer, Jan Altman, Petr Štěpánek, Václav Treml, Jiří Doležal, Emil Cienciala
      Planted even-aged forests dominated by Norway spruce (Picea abies) progressively replaced mixed natural forests in large parts of Central Europe during past centuries due to the productivity-motivated preferences of forest owners. These managed forests have become vulnerable to climate change, specifically to increasingly severe drought. To evaluate the response of trees to warming, we collected samples from a randomized landscape inventory grid of 7×7km to account for spatial gradients in climate/growth interactions in the entire forested part of the Czech Republic. The purely climate-driven forward growth model − Vaganov-Shashkin “Lite” − was calibrated by real (observed) radial growth series to identify a course of climatic limiting factors on an intra-annual scale. Relative proportions of moisture and temperature limited parts of total tree-ring width were determined as well as trends in limiting conditions over the period 1940–2012 and along the elevation gradient. Significant match between modelled and observed growth was shown in 47% of the grid cells. The coherence between modelled and observed site series was significantly improved when individual grid cells were aggregated into elevation belts. In grid cells below 600m, from 51 to 58% of tree-ring width was formed under moisture-limited conditions, with the proportion of growth under optimal conditions being minimal. The effect of drought stress was outweighed by earlier spring onset of growth, resulting in positive trends in total tree-ring width above 500m. About 26% of tree-ring growth has occurred under optimal climatic conditions at elevations above 800m, where, moreover, 45% of total annual growth was temperature limited. Except for one medium-elevation belt, the proportion of growth under moisture-limited conditions significantly increased during the period analysed. Recent warming and increasing frequency of drought events deepened the divergence in growth trends between low-elevation areas and stands at medium and high elevations.

      PubDate: 2017-08-03T10:06:27Z
      DOI: 10.1016/j.agrformet.2017.07.015
      Issue No: Vol. 247 (2017)
       
  • Temporal variations and spatial differentiation in the black alder and
           silver birch pollination pattern-the impact of local climate or something
           more'
    • Authors: K. Borycka; B. Ortyl; I. Kasprzyk
      Pages: 65 - 78
      Abstract: Publication date: 15 December 2017
      Source:Agricultural and Forest Meteorology, Volume 247
      Author(s): K. Borycka, B. Ortyl, I. Kasprzyk
      Numerous abiotic factors have an important impact on the phenology of woody plants with temperature as the main driver of their development. Furthermore, the biological factors connected with phenotypic plasticity and genetic heterogeneity might be the cause of differentiation in phenological response to abiotic factors. As objects of our study, we chose black alder and silver birch trees. The main aims of the study were to demonstrate the spatial and temporal diversity in the timing of Alnus glutinosa and Betula pendula pollination as well as to identify factors affecting these variations. We focused on abiotic factors such as thermal conditions: air and surface temperatures, within and between population variability. Phenological observations were carried out in Rzeszów (SE Poland) in a period of four years at over a dozen locations. Stands differed in their thermal conditions and prevalent land use types. The pollination pattern in the study area was presented against the background of local thermal conditions which were described by Land Surface Temperature (LST) and maximum daily air temperature. LST was estimated with a single-channel algorithm using satellite images obtained from Landsat 7 and 8. Our results showed great spatial and temporal diversity in the pollination pattern in the study area. Year-to-year variations in the B. pendula pollination pattern were less pronounced than in the case of A. glutinosa. The pollination pattern was strongly influenced by temperature before and during pollination. In the study area, the variability of LST was greater than that of air temperature but the relationships between the timing of pollination phenophases and LST or land use types were weak. It was observed that the same sites were similar in their pollination pattern − the timing of phenophases was ‘accelerated’ or ‘delayed’ during the whole study period. The same individuals were the first or the last that began to pollinate independently of the year. We concluded that despite the impact of temperature on A. glutinosa and B. pendula development, the phenotype of an individual tree might be as important for phenological variability as local climate.

      PubDate: 2017-08-03T10:06:27Z
      DOI: 10.1016/j.agrformet.2017.07.017
      Issue No: Vol. 247 (2017)
       
  • Modeling forest above-ground biomass dynamics using multi-source data and
           incorporated models: A case study over the qilian mountains
    • Authors: Xin Tian; Min Yan; Christiaan van der Tol; Zengyuan Li; Zhongbo Su; Erxue Chen; Xin Li; Longhui Li; Xufeng Wang; Xiaoduo Pan; Lushuang Gao; Zongtao Han
      Pages: 1 - 14
      Abstract: Publication date: 15 November 2017
      Source:Agricultural and Forest Meteorology, Volume 246
      Author(s): Xin Tian, Min Yan, Christiaan van der Tol, Zengyuan Li, Zhongbo Su, Erxue Chen, Xin Li, Longhui Li, Xufeng Wang, Xiaoduo Pan, Lushuang Gao, Zongtao Han
      In this work, we present a strategy for obtaining forest above-ground biomass (AGB) dynamics at a fine spatial and temporal resolution. Our strategy rests on the assumption that combining estimates of both AGB and carbon fluxes results in a more accurate accounting for biomass than considering the terms separately, since the cumulative carbon flux should be consistent with AGB increments. Such a strategy was successfully applied to the Qilian Mountains, a cold arid region of northwest China. Based on Landsat Thematic Mapper 5 (TM) data and ASTER GDEM V2 products (GDEM), we first improved the efficiency of existing non-parametric methods for mapping regional forest AGB for 2009 by incorporating the Random Forest (RF) model with the k-Nearest Neighbor (k-NN). Validation using forest measurements from 159 plots and the leave-one-out (LOO) method indicated that the estimates were reasonable (R2 =0.70 and RMSE=24.52tonesha−1). We then obtained one seasonal cycle (2011) of GPP (R2 =0.88 and RMSE=5.02gCm−2 8d−1) using the MODIS MOD_17 GPP (MOD_17) model that was calibrated to Eddy Covariance (EC) flux tower data (2010). After that, we calibrated the ecological process model (Biome-BioGeochemical Cycles (Biome-BGC)) against above GPP estimates (for 2010) for 30 representative forest plots over an ecological gradient in order to simulate AGB changes over time. Biome-BGC outputs of GPP and net ecosystem exchange (NEE) were validated against EC data (R2 =0.75 and RMSE=1. 27gCm−2 d−1 for GPP, and R2 =0.61 and RMSE=1.17gCm−2 d−1 for NEE). The calibrated Biome-BGC was then applied to produce a longer time series for net primary productivity (NPP), which, after conversion into AGB increments according to site-calibrated coefficients, were compared to dendrochronological measurements (R2 =0.73 and RMSE=46.65gm−2 year−1). By combining these increments with the AGB map of 2009, we were able to model forest AGB dynamics. In the final step, we conducted a Monte Carlo analysis of uncertainties for interannual forest AGB estimates based on errors in the above forest AGB map, NPP estimates, and the conversion of NPP to an AGB increment.
      Graphical abstract image

      PubDate: 2017-06-11T22:21:41Z
      DOI: 10.1016/j.agrformet.2017.05.026
      Issue No: Vol. 246 (2017)
       
  • Snowpack enhanced dissolved organic carbon export during a variety of
           hydrologic of events in an agricultural landscape, Midwestern USA
    • Authors: Huijiao Qiao; Yong Q. Tian; Qian Yu; Hunter J. Carrick; Mark Francek; Jiwei Li
      Pages: 31 - 41
      Abstract: Publication date: 15 November 2017
      Source:Agricultural and Forest Meteorology, Volume 246
      Author(s): Huijiao Qiao, Yong Q. Tian, Qian Yu, Hunter J. Carrick, Mark Francek, Jiwei Li
      This study investigates the dynamics of riverine DOC concentrations during a series of stream discharge events (3–10days) following rainstorms of different intensity and duration. We examined six events, when high-frequency (hourly) water samples for DOC (n=321) were collected in spring (n=166) and autumn (n=155). Results identified three distinct water-mediated processes during stream discharges events that linked DOC source supply from agricultural land surfaces with sinks in a receiving river. These were as follows: 1) snowpack drives significant high DOC concentrations in base-flow during spring, 2) abundant organic matter in topsoil from crop residues determines a rapid DOC loading profile in the first flush, and 3) very large hydro-climatic events in snow-melting season over agricultural watersheds could increase the riverine DOC flux by 2.3 folds. These results revealed that ca. 76.5% of annual DOC was exported during a handful of storm-discharge events (78.9% for spring and 74.2% from autumn) over agricultural landscapes. Given the significant amount of riverine DOC exported from agricultural landscapes during severe weather events, our results suggest that changes in climate promote larger precipitation events that would likely enhance the export of terrestrial DOC to receiving water bodies. The study presents a semi-analytical model that is able to extrapolate the riverine DOC dynamics during storm discharge events of varying duration and intensity (R2 up to 0.9).

      PubDate: 2017-06-13T22:25:14Z
      DOI: 10.1016/j.agrformet.2017.06.002
      Issue No: Vol. 246 (2017)
       
  • A coupled hydrological-plant growth model for simulating the effect of
           elevated CO2 on a temperate grassland
    • Authors: Juliane Kellner; Sebastian Multsch; Tobias Houska; Philipp Kraft; Christoph Müller; Lutz Breuer
      Pages: 42 - 50
      Abstract: Publication date: 15 November 2017
      Source:Agricultural and Forest Meteorology, Volume 246
      Author(s): Juliane Kellner, Sebastian Multsch, Tobias Houska, Philipp Kraft, Christoph Müller, Lutz Breuer
      Elevated CO2 (eCO2) reduces transpiration at the leaf level by inducing stomatal closure. However, this water saving effect might be offset at the canopy level by increased leaf area as a consequence of eCO2 fertilization. To investigate this bi-directional effect, we coupled a plant growth and a soil hydrological model. The model performance and the uncertainty in model parameters were checked using a 13year data set of a Free Air Carbon dioxide Enrichment (FACE) experiment on grassland in Germany. We found a good agreement of simulated and observed data for soil moisture and total above-ground dry biomass (TAB) under ambient CO2 (∼395ppm) and eCO2 (∼480ppm). Optima for soil and plant growth model parameters were identified, which can be used in future studies. Our study presents a robust modelling approach for the investigation of effects of eCO2 on grassland biomass and water dynamics. We show an offset of the stomatal water saving effect at the canopy level because of a significant increase in TAB (6.5%, p< 0.001) leading to an increase in transpiration by +3.0±6.0mm, though insignificant (p =0.1). However, the increased water loss through transpiration was counteracted by a significant decrease in soil evaporation (−2.1±1.7mm, p < 0.01) as a consequence of higher TAB. Hence, evapotranspiration was not affected by the increased eCO2 (+0.9±4.9mm, p =0.5). This in turn led to a significantly better performance of the water use efficiency by 5.2% (p < 0.001). Our results indicate that mown, temperate grasslands can benefit from an increasing biomass production while maintaining water consumption at the +20% increase of eCO2 studied.

      PubDate: 2017-06-13T22:25:14Z
      DOI: 10.1016/j.agrformet.2017.05.017
      Issue No: Vol. 246 (2017)
       
  • Evaluating models of shortwave radiation below Eucalyptus canopies in SE
           Australia
    • Authors: Petter Nyman; Daniel Metzen; Sandra N.D. Hawthorne; Thomas J. Duff; Assaf Inbar; Patrick N.J. Lane; Gary J. Sheridan
      Pages: 51 - 63
      Abstract: Publication date: 15 November 2017
      Source:Agricultural and Forest Meteorology, Volume 246
      Author(s): Petter Nyman, Daniel Metzen, Sandra N.D. Hawthorne, Thomas J. Duff, Assaf Inbar, Patrick N.J. Lane, Gary J. Sheridan
      In this study we examine the performance of four models that simulate radiation under forest canopies. The models are different in terms of how transmittance of radiation is conceptualised and the data sources used to obtain parameters. Two models (PAIMS and PAINC models) use plant area index (PAI) to represent transmission. A third model (PL model) represents transmission as a function of the path length (L) of a directional beam as it crosses the canopy. The fourth model (LPI model) is based on a light penetration index obtained directly from lidar. The PAIMS and PL models were calibrated using 6 months of radiation data at 4 independent sites. The LPI and PAINC models are uncalibrated. Performance was assessed using sub-daily and daily radiation measurements during summer (December–March) at 10 sites in forests ranging from open dry forests (PAI =1.6) to tall temperate forests (PAI =4.6). Mean annual precipitation ranged from 760 to 1750mm across the domain. The PL model with a calibrated extinction coefficient (k 2 =0.033) was the most accurate model within sites (R-square=0.32–0.89 for sub-daily radiation) and across all sites (R-square=0.82 for daily and sub-daily radiation). The LPI model performed well at most sites, but displayed some systematic bias in dense forests resulting in lower performance (R-square=0.61 across all sites) while PAINC was negatively biased and a poor predictor across all sites (overall R-square=0). The PAIMS model, with a calibrated extinction coefficient (k 1 =0.48), produced good results, but inspection of sub-daily radiation patterns show that the model tends to underestimate (overestimate) sub-canopy radiation during times of high (low) radiation. This is because transmittance is highest when the sun elevation is high (i.e. short path length), resulting in sub-canopy radiation that varies non-linearly with the intensity of above canopy radiation. Models that explicitly include path length in the transmission term therefore provide more flexibility for capturing sub-daily, seasonal and latitudinal variation due to sun position and vegetation structure. Other advantages of the path length approach include i) simple parameterisation using tree height as input and ii) explicit representation of diffuse and direct radiation, which can be important when accounting for terrain-effects on energy balance at the forest floor. We therefore recommend path length based modelling approaches for investigating hydrological processes below the canopy in temperate Eucalyptus forests.

      PubDate: 2017-07-03T05:15:37Z
      DOI: 10.1016/j.agrformet.2017.05.025
      Issue No: Vol. 246 (2017)
       
  • Will nitrogen deposition mitigate warming-increased soil respiration in a
           young subtropical plantation'
    • Authors: Xiaofei Liu; Zhijie Yang; Chengfang Lin; Christian P. Giardina; Decheng Xiong; Weisheng Lin; Shidong Chen; Chao Xu; Guangshui Chen; Jinsheng Xie; Yiqing Li; Yusheng Yang
      Pages: 78 - 85
      Abstract: Publication date: 15 November 2017
      Source:Agricultural and Forest Meteorology, Volume 246
      Author(s): Xiaofei Liu, Zhijie Yang, Chengfang Lin, Christian P. Giardina, Decheng Xiong, Weisheng Lin, Shidong Chen, Chao Xu, Guangshui Chen, Jinsheng Xie, Yiqing Li, Yusheng Yang
      Global change such as climate warming and nitrogen (N) deposition is likely to alter terrestrial carbon (C) cycling, including soil respiration (Rs), the largest CO2 source from soils to the atmosphere. To examine the effects of warming, N addition and their interactions on Rs, we conducted a two-way factorial soil warming (control, 5°C warming) and N addition (control, 40 and 80kgNha−1 yr−1) mesocosm experiment in subtropical China. We measured Rs and nutrient availability. We found warming alone increased Rs by 15%, but warming plus high N addition treatment appeared to have offsetting effects as these plots were not significantly different from unheated and unfertilized controls. Warming alone increased soil available phosphorus (P) but availability declined in response to warming plus N additions. N additions alone had no effect on Rs in this study. Our results suggest that future increases in N deposition could mitigate warming-increased Rs in P-limited and relatively N-saturated subtropical forest ecosystems.

      PubDate: 2017-07-03T05:15:37Z
      DOI: 10.1016/j.agrformet.2017.06.010
      Issue No: Vol. 246 (2017)
       
  • A heat-pulse method for measuring sap flow in corn and sunflower using
           3D-printed sensor bodies and low-cost electronics
    • Authors: Grace Lloyd Miner; Jay M. Ham; Gerard J. Kluitenberg
      Pages: 86 - 97
      Abstract: Publication date: 15 November 2017
      Source:Agricultural and Forest Meteorology, Volume 246
      Author(s): Grace Lloyd Miner, Jay M. Ham, Gerard J. Kluitenberg
      Sap-flow (SF) measurements provide unique and valuable data for studying plant water relations and crop water use. In this study we utilize new developments in heat pulse theory, low-cost electronics, and 3D-printing to fabricate, calibrate, and field test an affordable research-grade sap flow instrument. Each gauge included three needle probes that were inserted into the stem. A central needle contained a resistance heater for applying the heat pulse, while two additional needles measured the resulting temperature increases at positions downstream and to the side of the heater. Time series data following a heat pulse were used to calculate heat velocity using two techniques. The Tmax method used the time to temperature maximum while a novel temperature ratio method (TmRatio) used the ratio of the temperature maxima at the downstream and side probes. Data acquisition systems were built from low-cost Arduino microcontrollers. Prototype SF gauges were tested and calibrated for corn and sunflower in the greenhouse. Once calibrated for a specific gauge design and species, the gauges tracked gravimetric measurements of transpiration rate to within 10%. The Tmax method performed well under high rates of sap flow (i.e., up to 300g hr−1) in both sunflower and corn, but overestimated flow at low transpiration rates. The new TmRatio method accurately tracked sap flow at rates near 150g hr−1 and also performed well during nighttime flows as low as 3g hr−1 in corn. However, both theory and observation suggest the TmRatio approach may fail at very high flow rates. The gauges and data acquisition systems were deployed in the field on irrigated corn. Sap flow was calculated using the Tmax method, the TmRatio method, and a hybrid approach that used the TmRatio method for flow rates <130g h−1 and the Tmax method for flow rates >130g h−1. Estimates of canopy transpiration over a two-week period were, on average, within 5% of calculated reference crop evapotranspiration. The do-it-yourself simplicity and low cost of the approach make it possible to deploy large numbers of gauges in the field to capture spatial variability, compare water use among agronomic plots, or scale-up sap flow to measure canopy transpiration.

      PubDate: 2017-07-03T05:15:37Z
      DOI: 10.1016/j.agrformet.2017.06.012
      Issue No: Vol. 246 (2017)
       
  • Climate-driven uncertainties in modeling terrestrial ecosystem net primary
           productivity in China
    • Authors: Fengxue Gu; Yuandong Zhang; Mei Huang; Bo Tao; Zhengjia Liu; Man Hao; Rui Guo
      Pages: 123 - 132
      Abstract: Publication date: 15 November 2017
      Source:Agricultural and Forest Meteorology, Volume 246
      Author(s): Fengxue Gu, Yuandong Zhang, Mei Huang, Bo Tao, Zhengjia Liu, Man Hao, Rui Guo
      Evaluating the uncertainties in regional/global carbon flux estimates is essential for better understanding of terrestrial carbon dynamics. At the regional scale, climate input data is an important source of model simulation uncertainty. In this study, a process-based ecosystem model, CEVSA, was run driven by four climate input datasets during 1980–2004, i.e., climate input datasets interpolated from 756 (756s) and 2400 weather stations (2400s), the NCEP/NCAR and Princeton reanalysis datasets. We used the 2400s dataset as the reference because it was derived from high density weather station interpolation. The simulated Net Primary Productivity (NPP) based on interpolated climate data from the 756s and the two reanalysis datasets were compared with that from the 2400s dataset. Then, we quantified the uncertainty of model simulations at regional-scale caused by climate input data, and evaluated the performance of different climate datasets across different eco-regions. Our results suggest that the 756s, Princeton and NCEP/NCAR reanalysis datasets overestimated the 25-year mean annual temperature by 7.66%–12.25% and the precipitation by 2.83%–8.43%, respectively; accordingly, the simulated NPP ranged from 3.53 to 3.96PgC, 6% to 12% higher than the reference over the entire China. The 756s and the two reanalysis datasets captured well the trend and interannual variations of annual NPP during the study period, but showed systematic errors in the total amount of NPP compared with the 2400s dataset. To increase the station density in the eco-regions with a station density greater than 1.0 station per 104 km2 (1.0s/104 km2) would not decrease the uncertainty for model simulation at a 0.1° spatial resolution. The NCEP/NCAR and Princeton reanalysis datasets showed larger uncertainties in most eco-regions compared with the interpolated datasets. Our results also suggest that the accuracy of the NCEP/NCAR reanalysis data should be further improved in most eco-regions. On Qinghai-Tibet Plateau and in northwestern China, all four climate input datasets had relatively lower accuracy due to the limited observation data available. Future work should further evaluate the simulated NPP against observations and quantify the accuracy of driving climate data to decrease the uncertainty of model simulations at the regional scale.

      PubDate: 2017-07-03T05:15:37Z
      DOI: 10.1016/j.agrformet.2017.06.011
      Issue No: Vol. 246 (2017)
       
  • Nitrous oxide emissions from different land uses affected by managements
           on the Qinghai-Tibetan Plateau
    • Authors: Zhenhua Zhang; Xiaoxue Zhu; Shiping Wang; Jichuang Duan; Xiaofeng Chang; Caiyun Luo; Jin-Sheng He; Andreas Wilkes
      Pages: 133 - 141
      Abstract: Publication date: 15 November 2017
      Source:Agricultural and Forest Meteorology, Volume 246
      Author(s): Zhenhua Zhang, Xiaoxue Zhu, Shiping Wang, Jichuang Duan, Xiaofeng Chang, Caiyun Luo, Jin-Sheng He, Andreas Wilkes
      We evaluated the N2O emissions from four land use types (a native alpine meadow with winter grazing (NAM), an abandoned pasture (APL), a perennial Elymus nutans Griseb. pasture (PEN) and an annual Avena sativa L. pasture (AAS)) with and without three management practices (nitrogen (N) fertilizer, sheep manure and no tillage (NT)) in a Gelic Cambisol soil underlying an alpine meadow on the Qinghai-Tibetan Plateau in 2009 and 2010. Our results show that, compared with NAM, APL had significantly higher cumulative-average seasonal N2O emissions. Converting unmanaged APL to PEN or AAS significantly increased cumulative-average seasonal N2O emissions by 35% and 75%, respectively. Sheep manure and N fertilizer application significantly increased N2O emissions due to increased soil inorganic N concentration. The effect of sheep manure addition on N2O emissions was lower than that of N fertilizer. For AAS, tillage significantly decreased the effect of sheep manure application on N2O emissions. Compared with tillage, NT significantly decreased N2O emissions from AAS. Therefore, our results suggest that cultivating natural grassland would increase N2O emissions, and fertilizer application would amplify the magnitude of emissions, whereas NT could mitigate the fertilizer impact on N2O emission. Furthermore, the structural equation analysis revealed that land use change affected N2O emissions directly by influencing the number of plant species and soil characteristics. There were two different underlying mechanisms regulating N2O emissions in response to N fertilizer and sheep manure addition.

      PubDate: 2017-07-03T05:15:37Z
      DOI: 10.1016/j.agrformet.2017.06.013
      Issue No: Vol. 246 (2017)
       
  • Experimental evaluation of flux footprint models
    • Authors: Katja Heidbach; Hans Peter Schmid; Matthias Mauder
      Pages: 142 - 153
      Abstract: Publication date: 15 November 2017
      Source:Agricultural and Forest Meteorology, Volume 246
      Author(s): Katja Heidbach, Hans Peter Schmid, Matthias Mauder
      In this study we experimentally evaluate analytical flux footprint models, as well as models based on Lagrangian stochastic particle dispersion. For this purpose, we conducted tracer experiments at a grassland site in southern Germany. An artificial tracer was released continuously over a number of flux-averaging intervals from a surface source. The flux contributions from the tracer source were measured by eddy covariance and compared to those predicted by footprint models. Furthermore, an additional eddy covariance measurement tower was used to evaluate the along-wind distribution of footprint models, as well as to analyze to what extent a forest edge upwind of the measurement tower affects model performance. Additionally, we quantify footprint model uncertainty resulting from the random error of input parameters. Our measurements show that all evaluated models match observations roughly, but tend to underestimate the value of the footprint maximum, and overestimate its distance. The analysis of stability dependence of model performances indicates that one model, based on simulation outputs of a Lagrangian stochastic model, clearly underestimates observations for near neutral to stable conditions, while no clear stability dependence could be identified for the performance of the other models. As expected, model performance is sensitive to an abrupt change in surface roughness and sensible heat flux at a forest edge in the near upwind fetch of the measurement tower. Using the local apparent roughness length (derived from measured wind speed and friction velocity) only slightly or negligibly improved model performance compared to the use of a constant local roughness length (determined from local surface characteristics). Thus we confirm experimentally that footprint estimates and related data quality assessments should be handled with care at sites with inhomogeneities in surface roughness.

      PubDate: 2017-07-03T05:15:37Z
      DOI: 10.1016/j.agrformet.2017.06.008
      Issue No: Vol. 246 (2017)
       
  • Reduction of fungal disease spread in cultivar mixtures: Impact of canopy
           architecture on rain-splash dispersal and on crop microclimate
    • Authors: Tiphaine Vidal; Anne-Lise Boixel; Brigitte Durand; Claude de Vallavieille-Pope; Laurent Huber; Sébastien Saint-Jean
      Pages: 154 - 161
      Abstract: Publication date: 15 November 2017
      Source:Agricultural and Forest Meteorology, Volume 246
      Author(s): Tiphaine Vidal, Anne-Lise Boixel, Brigitte Durand, Claude de Vallavieille-Pope, Laurent Huber, Sébastien Saint-Jean
      Mixtures of cultivars with different disease resistance levels make it possible to manage plant disease in a context of fungicide reduction. The cultivars composing a mixture are often chosen for their contrasted disease resistance levels, whereas their architecture is rarely taken into account. However, canopy architecture has an impact on spore dispersal and microclimate, both of which contribute to disease development. Disease spread by rain-splash occurs over short distances and is expected to be modulated by canopy structure. Our objective was to assess the impact of wheat cultivar mixtures that differ by their canopy architecture on crop microclimate, spore dispersal and the propagation of splash-dispersed disease, septoria tritici blotch, caused by Zymoseptoria tritici. Each cultivar mixture was composed of a susceptible and a resistant cultivar. A single, short susceptible cultivar was used. The resistant companion was either short (homogeneous) or tall (heterogeneous). Two proportions of resistant cultivar were tested in homogenous mixture. Mixtures were compared to pure stands of component cultivars. The level of resistance of each cultivar was assessed through disease measurements in pure stand. A diversity of canopy architecture was obtained at the flowering stage: the leaf area index ranged from 2.2 to 4.4m2/m2 and flag leaf insertion height from 0.65m (standard height) to 1.20m (tall plants). Spore fluxes were measured during two rain events and microclimate variables including air temperature, relative humidity and leaf wetness duration were recorded from the booting stage onwards. Disease assessments were carried out weekly in mixtures and pure stands. Disease on susceptible plants was significantly lower in heterogeneous mixtures than in pure stands. In homogeneous mixtures, a high proportion of resistant plants was associated with high canopy density, which led to a microclimate favorable to disease development. Leaf wetness duration was in fact longer in the pure stand constituted of standard height resistant plants, which had the densest canopy. In the two homogeneous mixtures that differed by the proportion of resistant plants, disease reduction was similar. On the other hand, heterogeneous mixtures had a lower canopy density and lower spore fluxes than homogeneous mixtures. Compared to the susceptible pure stand, the area under the disease progress curve of susceptible plants was reduced by 68% in the heterogeneous mixture and by 32% and 34% in the homogeneous mixtures with 75% and 25% of resistant plants, respectively. Our results suggest that the impact of canopy architecture on microclimate and spore dispersal can significantly contribute to the reduction of disease propagation in cultivar mixtures. We therefore suggest that taking cultivar architecture into account, in addition to the level of resistance to disease, could provide a strategy to enhance disease reduction in cultivar mixtures in the case of splash-dispersed diseases.

      PubDate: 2017-07-03T05:15:37Z
      DOI: 10.1016/j.agrformet.2017.06.014
      Issue No: Vol. 246 (2017)
       
  • Estimating structural parameters of agricultural crops from ground-based
           multi-angular digital images with a fractional model of sun and shade
           components
    • Authors: Xihan Mu; Ronghai Hu; Yelu Zeng; Tim R. McVicar; Huazhong Ren; Wanjuan Song; Yuanyuan Wang; Raffaele Casa; Jianbo Qi; Donghui Xie; Guangjian Yan
      Pages: 162 - 177
      Abstract: Publication date: 15 November 2017
      Source:Agricultural and Forest Meteorology, Volume 246
      Author(s): Xihan Mu, Ronghai Hu, Yelu Zeng, Tim R. McVicar, Huazhong Ren, Wanjuan Song, Yuanyuan Wang, Raffaele Casa, Jianbo Qi, Donghui Xie, Guangjian Yan
      Accurate and efficient in situ measurement methods of leaf area index (LAI) and leaf angle distribution (LAD) are needed to estimate the fluxes of water and energy in agricultural settings. However, available methods: to estimate these two parameters, especially LAD, are limited. In this study, we propose a field measurement method using multi-angular digital images to estimate LAI and LAD simultaneously from the area proportions of: (i) sunlit soil; (ii) sunlit leaves; (iii) shaded soil; and (iv) shaded leaves. A new expression of the fraction of sunlit leaves is developed based on the radiative transfer theory. Coupling the measured and modeled fractions with an optimization scheme, LAI and the LAD parameters are derived from inverting a fractional model of sunlit and shaded leaves and soil. Through four tests using simulated scenes and in situ measurements for row crops, it is determined that our method performs well. The absolute error of LAI estimation is less than 0.1 when LAI is low (i.e., <1.2), and the absolute deviations of LAI estimates are approximately 0.5 when the reference LAI is 3.5. The estimation errors of LAI and the G function (a representative of LAD which quantifies the projection of unit foliage area) for in situ measurements are respectively less than 0.2 and 0.06 in general. In addition, the accuracy of estimation is even higher when leaves are simulated as randomly distributed disks or observations from multiple azimuth planes are used. One of the most interesting features of this method is its ability to estimate reasonable LAD directly from the fractions of sunlit and shaded leaves, even when LAI is high (i.e., >3), so little background soil is seen. The sensitivity and uncertainty analysis is consistent with the estimation errors. Theoretically, the application of this method is not limited to row crops or to field measurement, as the derived formulae of sunlit and shaded components can be used for other types of vegetation by introducing the clumping index and can be used in the modeling of canopy vegetation parameters (e.g., canopy reflectance).
      Graphical abstract image

      PubDate: 2017-07-11T16:10:33Z
      DOI: 10.1016/j.agrformet.2017.06.009
      Issue No: Vol. 246 (2017)
       
  • Assimilation of the leaf area index and vegetation temperature condition
           index for winter wheat yield estimation using Landsat imagery and the
           CERES-Wheat model
    • Authors: Yi Xie; Pengxin Wang; Xuejiao Bai; Jahangir Khan; Shuyu Zhang; Li Li; Lei Wang
      Pages: 194 - 206
      Abstract: Publication date: 15 November 2017
      Source:Agricultural and Forest Meteorology, Volume 246
      Author(s): Yi Xie, Pengxin Wang, Xuejiao Bai, Jahangir Khan, Shuyu Zhang, Li Li, Lei Wang
      To improve the accuracy of regional winter wheat yield estimation in the Guanzhong Plain, China, the field-measured leaf area index (LAI) and soil moisture at the depth of 0–20cm (θ) and both Landsat-retrieved LAI and θ were assimilated into the CERES-Wheat model with an ensemble Kalman filter (EnKF) algorithm. The correlation between the assimilated LAI and the measured yield at each main wheat growth stage, including the green-up, jointing, heading-filling and milk stages, was compared with that between assimilated θ and yield. Then, five types of assimilation schemes were investigated to test the effects of assimilating different state variables at each wheat growth stage on wheat yield estimation. The results showed that the correlations between LAI and wheat yield at the jointing and heading-filling stages were higher than those between θ and wheat yield; moreover, the correlations between θ and wheat yield were higher at the green-up and milk stages. Among the five assimilation schemes, the accuracy of the yield estimation obtained by assimilating LAI at the jointing and heading-filling stages as well as by assimilating θ at the green-up and milk stages was the highest (R2 =0.76, root mean square error (RMSE)=548.97kgha−1), followed by the accuracy of the yield estimation obtained by assimilating LAI and θ simultaneously at each growth stage (R2 =0.67, RMSE=610.67kgha−1). Conversely, the accuracy of the yield estimation obtained by assimilating LAI at the green-up and milk stages as well as by assimilating θ at the jointing and heading-filling stages was the lowest (R2 =0.41, RMSE=928.95kgha−1). Thus, the assimilation of more yield-related state variables at each wheat growth stage in an agricultural data assimilation framework provides a reliable and promising method for improving wheat yield estimation.

      PubDate: 2017-07-11T16:10:33Z
      DOI: 10.1016/j.agrformet.2017.06.015
      Issue No: Vol. 246 (2017)
       
  • Evaluation of four long time-series global leaf area index products
    • Authors: Zhiqiang Xiao; Shunlin Liang; Bo Jiang
      Pages: 218 - 230
      Abstract: Publication date: 15 November 2017
      Source:Agricultural and Forest Meteorology, Volume 246
      Author(s): Zhiqiang Xiao, Shunlin Liang, Bo Jiang
      As an important vegetation biophysical variable, leaf area index (LAI) is a critical input parameter in many climate and ecological models. There exist four long time-series global LAI products since the 1980s, namely GLASS AVHRR, NCEI AVHRR, GIMMS3g and GLOBMAP. Currently, no inter-comparison studies exist to evaluate these LAI products and understand their differences for effective applications. In this study, the four long time-series global LAI products were inter-compared to evaluate their temporal and spatial discrepancies. These LAI products were also compared with MODIS LAI product and LAI values derived from high-resolution reference maps at VAlidation of Land European Remote sensing Instruments (VALERI) sites. The results show that the GLASS AVHRR and GLOBMAP LAI products are spatially complete, but the NCEI AVHRR and GIMMS3g LAI products contain many missing pixels, especially in rainforest regions. These LAI products reasonably represent the global vegetation characteristics and their seasonal variability. A relatively large discrepancy among these LAI products was observed in tropical forest regions, where the GLASS AVHRR and NCEI AVHRR LAI values achieved good agreement with the MODIS LAI values, but were between 0.5 and 1.0 LAI units lower than the GLOBMAP LAI values and higher than the GIMMS3g LAI values (more than 0.5 LAI units). Over the last three decades, the GLASS AVHRR, NCEI AVHRR, GIMMS3g LAI products show increasing trends for all biome types except evergreen needleleaf forests and deciduous needleleaf forests, but the GLOBMAP LAI product shows positive trends only for the grasses/cereal crops and shrubs. A comparison of these LAI products against the LAI values derived from high-resolution reference maps demonstrated that the GLASS AVHRR LAI values provided the better performance (RMSE=0.9014 and Bias=−0.1885) than the NCEI AVHRR LAI values (RMSE=1.0459 and Bias=−0.5695), the GIMMS3g LAI values (RMSE=1.0971 and Bias=−0.3904) and the GLOBMAP LAI values (RMSE=1.6145 and Bias=−0.9414).

      PubDate: 2017-07-11T16:10:33Z
      DOI: 10.1016/j.agrformet.2017.06.016
      Issue No: Vol. 246 (2017)
       
  • Biophysical controls of soil respiration in a wheat-maize rotation system
           in the North China Plain
    • Authors: Xiaojuan Tong; Jun Li; Rachael H. Nolan; Qiang Yu
      Pages: 231 - 240
      Abstract: Publication date: 15 November 2017
      Source:Agricultural and Forest Meteorology, Volume 246
      Author(s): Xiaojuan Tong, Jun Li, Rachael H. Nolan, Qiang Yu
      Croplands play a vital role in regional carbon budgets. We hypothesized that biophysical factors would be important for soil respiration in a wheat-maize rotation cropping system. Soil CO2 efflux was measured using the closed chamber method, and net CO2 exchange between the cropland and the atmosphere obtained by the eddy covariance technique in a winter wheat-summer maize double cropping system over four years (Oct 2002–Oct 2006). In addition to soil temperature, soil respiration was controlled by leaf area index and soil moisture in the wheat field and soil moisture in the maize field. Temperature sensitivity (Q 10) of soil respiration was 2.2 in the wheat and maize growing seasons. In the wheat field, the Q 10 value during the sowing–returning green period (4.9) was more than that during the returning green–ripening period (2.0). On a monthly time scale, soil respiration was controlled by gross primary productivity in the wheat field, indicating that soil respiration was coupled with ecosystem photosynthesis. Annual soil respiration was 825±73gCm−2 in the wheat–maize rotation system in 2003–2006. Over a 4–year average, soil respiration was 355±50gCm−2 in the wheat growing season and 470±67gCm−2 in the maize growing season, which accounted for 43% and 57% of the annual value respectively. At an annual time scale, soil respiration contributed to 72% of ecosystem respiration in the winter wheat–summer maize double cropping system.

      PubDate: 2017-07-23T16:00:07Z
      DOI: 10.1016/j.agrformet.2017.07.005
      Issue No: Vol. 246 (2017)
       
  • Water balance, surface conductance and water use efficiency of two young
           hybrid-poplar plantations in Canada’s aspen parkland
    • Authors: Hughie Jones; T. Andrew Black; Rachhpal S. Jassal; Zoran Nesic; Nick Grant; Jagtar S. Bhatti; Derek Sidders
      Pages: 256 - 271
      Abstract: Publication date: 15 November 2017
      Source:Agricultural and Forest Meteorology, Volume 246
      Author(s): Hughie Jones, T. Andrew Black, Rachhpal S. Jassal, Zoran Nesic, Nick Grant, Jagtar S. Bhatti, Derek Sidders
      Hybrid-poplar (HP) plantations have received considerable attention in the Canadian aspen parkland due to their fast growth and carbon (C) sequestration potential, but their high transpiration rates raise concerns due to the low annual precipitation (P) in this region. We quantified water and C balances of two HP plantations planted on high-productivity soils in the northwest (HP09) and southeast (HP11) aspen parkland for five and four years, respectively, using eddy-covariance (EC) measurements. A two-source evapotranspiration model, which estimates canopy transpiration (E cmod) and soil evaporation (E smod) separately, allowed us to study the dynamics of E cmod and E smod as the HP plantations aged. Plantation surface conductance obtained using the model agreed well with that calculated using EC-measured evapotranspiration (E EC) in the inverted form of the Penman-Monteith equation. We found that E smod accounted for 96% of total modelled evapotranspiration (E mod) in the 1st year of growth but quickly declined with HP canopy closure, as E cmod increasingly dominated E mod, to a maximum of 85% at HP09 in the 5th year of growth. Measurements of net ecosystem production (NEP) showed both HP09 and HP11 shifted from annual C sources to annual C sinks of 87±44 and 95±97gCm−2 yr−1, respectively, in the 3rd year of growth, as gross primary production (GPP) increased and exceeded ecosystem respiration (R e). The rapid increase in GPP at HP09 coincided with large increases in E EC, causing E EC to exceed P in the 3rd to 6th years of growth, partly due to low P during the 5th and 6th years of growth. Water use efficiency (WUE) increased with plantation age from 0.13 to 2.5gCkg−1 H2O in the 1st and 3rd year of growth at HP11, respectively, but at HP09, WUE plateaued during the 3rd to 5th years of growth (∼1.9gCkg−1 H2O) and declined slightly in the 6th year due to disturbance (drought, hail damage, and fungal infection). We show that, although these HP plantations quickly shifted from being C sources to being C sinks, E EC can increase rapidly and exceed P, which highlights the impact that fast-growing HP plantations, when established over a large area, could have on the local water balance.

      PubDate: 2017-08-03T10:06:27Z
      DOI: 10.1016/j.agrformet.2017.04.007
      Issue No: Vol. 246 (2017)
       
  • A binary mixing model for characterizing stony-soil water retention
    • Authors: Kshitij Parajuli; Morteza Sadeghi; Scott B. Jones
      Pages: 1 - 8
      Abstract: Publication date: 15 October 2017
      Source:Agricultural and Forest Meteorology, Volumes 244–245
      Author(s): Kshitij Parajuli, Morteza Sadeghi, Scott B. Jones
      A century of research focused primarily on agricultural soils has largely ignored stony soils, which dominate some forests and are poorly understood in terms of the stone influence on soil hydraulic properties. Motivated by this knowledge gap, we quantified the influence of soil-containing stone fragments on bulk soil hydraulic properties by determining the water retention curve (WRC) of soil, stone and stone-soil mixtures with varied volumetric stone content. The measured WRC for seven different stone types based on their composition showed maximum and minimum saturated water contents of 0.55m3 m−3 in pumice and 0.025m3 m−3 in fine sandstone, respectively. The stony soil water retention function was measured using the simplified evaporation method. Contrasting scenarios were studied considering a broad range of stone inclusions; (i) negligibly porous, (ii) significantly porous but less porous than the background soil, (iii) more porous than the background soil. An averaging scheme to describe the WRC of stony soil was proposed based on the individual WRC of the background and stone inclusion which was in good agreement with the experimental data. The HYDRUS-3D model was also employed to simulate the evaporation experiment used for the WRC measurements. The model simulations supported the basic assumptions of the proposed averaging scheme.

      PubDate: 2017-05-28T07:49:17Z
      DOI: 10.1016/j.agrformet.2017.05.013
      Issue No: Vol. 244-245 (2017)
       
  • Meteorological conditions during dust (PM10) emission from a tilled loam
           soil: Identifying variables and thresholds
    • Authors: Fernando Avecilla; Juan E. Panebianco; Daniel E. Buschiazzo
      Pages: 21 - 32
      Abstract: Publication date: 15 October 2017
      Source:Agricultural and Forest Meteorology, Volumes 244–245
      Author(s): Fernando Avecilla, Juan E. Panebianco, Daniel E. Buschiazzo
      Soil wind erosion and consequent PM10 emission is a complex process that has been related to surface properties and meteorological conditions. Most of the studies have emphasized on the relationship between the surface conditions and the dust emission, in general on deserts and dry lakes or playas. Little is known about the influence of meteorological variables on PM10 emission from agricultural soils. The objective of this study was to identify the most important meteorological variables involved in the emission of PM10, identify their threshold values, and to analyze their interaction with the soil surface conditions. Measurements were made on a loam soil (Entic Haplustoll) in the semiarid Argentinian Pampa. Horizontal mass transport (Q) and PM10 emission were measured during two years on a bare and flat surface that was tilled periodically. The meteorological variables measured were: average and maximum wind speed, wind direction, air temperature, relative humidity and soil temperature. In 30% of the events, the PM10 concentration at 1.8m height exceeded the average values allowed by the World Health Organization (50μgm−3 for a 24h period). Maximum values exceeded 1000μgm−3. The slope of the PM10 concentration gradient changed between spring − summer and autumn − winter periods. Threshold values of the studied variables were set when PM10 concentration values at 1.8m height were consistently above the 50μgm−3 limit. The highest PM10 emission rates were observed when relative humidity values were below 20% and the air temperature was higher than 30°C. In addition when the wind speed exceeded 8ms−1, dust emission increased significantly. From a multiple regression analysis, results indicated that PM10 emission was well correlated (p <0.001) with maximum wind speed, relative humidity, and air temperature. Maximum wind speed and relative humidity conditioned the PM10 emission in a synergistic way. However, the regression explained only 32% of the variability. Although higher average PM10 emission values were measured during events with a crusted surface, lower average values of Q were measured during events with a crust. Field observations indicated that the complex interaction between the weather conditions and soil surface properties such as soil crusts, aggregate size distribution, soil moisture and even the soil condition when the tilling is done, can produce a high variability and unpredictability, of the PM10 emission from bare agricultural soils.

      PubDate: 2017-06-01T16:31:40Z
      DOI: 10.1016/j.agrformet.2017.05.016
      Issue No: Vol. 244-245 (2017)
       
  • Carbon sources and sinks of North America as affected by major drought
           events during the past 30 years
    • Authors: Zelalem A. Mekonnen; Robert F. Grant; Christopher Schwalm
      Pages: 42 - 56
      Abstract: Publication date: 15 October 2017
      Source:Agricultural and Forest Meteorology, Volumes 244–245
      Author(s): Zelalem A. Mekonnen, Robert F. Grant, Christopher Schwalm
      The North American (NA) terrestrial biosphere has been a long-term carbon sink but impacts of climate extremes such as drought on ecosystem carbon exchange remain largely uncertain. Here, changes in biospheric carbon fluxes with recent climate change and impacts of the major droughts of the past 30 years on continental carbon cycle across NA were studied using a comprehensive mathematical process model, ecosys. In test of these model responses at continental scale, the spatial anomalies in modeled leaf area indices, fully prognostic in the model, from long-term (1980–2010) means during major drought events in 1988 and 2002 agreed well with those in AVHRR NDVI (R2 =0.84 in 1988, 0.71 in 2002). Net ecosystem productivity (NEP) modeled across NA declined by 92% (0.50PgC yr−1) and 90% (0.49PgC yr−1) from the long-term mean (+0.54PgC yr−1), in 1988 and 2002 respectively. These significant drops in NEP offset 28% of the carbon gains modeled over the last three decades. Although the long-term average modeled terrestrial carbon sink was estimated to offset ∼30% of the fossil fuel emissions of NA, only 0.03% and 3.2% were offset in 1988 and 2002 leaving almost all fossil fuel emissions to the atmosphere. These major drought events controlled much of the continental-scale interannual variability and mainly occurred in parts of the Great Plains, southwest US and northern Mexico. Although warming in northern ecosystems caused increasing carbon sinks to be modeled as a result of greater gross primary productivity with longer growing seasons, elsewhere in the continent frequent drought events of the past 30 years reduced carbon uptake and hence net carbon sinks of the NA.

      PubDate: 2017-06-06T16:31:50Z
      DOI: 10.1016/j.agrformet.2017.05.006
      Issue No: Vol. 244-245 (2017)
       
  • Comparison of different satellite bands and vegetation indices for
           estimation of soil organic matter based on simulated spectral
           configuration
    • Authors: Xiuliang Jin; Kaishan Song; Jia Du; Huanjun Liu; Zhidan Wen
      Pages: 57 - 71
      Abstract: Publication date: 15 October 2017
      Source:Agricultural and Forest Meteorology, Volumes 244–245
      Author(s): Xiuliang Jin, Kaishan Song, Jia Du, Huanjun Liu, Zhidan Wen
      Soil organic matter content (SOM) is an important indicator of soil productivity that governs biological, chemical, and physical processes in the soil environment. Previous studies have shown that remote sensing data provide useful information for SOM estimation in different soil types. However, no studies have estimated SOM based on simulated spectral configurations of different satellite sensors. Further study is required to investigate whether SOM estimation accuracy can be improved by combining data from different satellite sensors and developing appropriate algorithms. Therefore, this study investigated new methods for SOM estimation with the following three objectives: (1) analyze the reflectance changes of simulated bands for different SOMs using the spectral response function of various satellite sensors; (2) develop optimal difference index (ODI), optimal ratio index (ORI), optimal normalized vegetation difference index (ONDVI), and optimal enhanced vegetation index (OEVI) algorithms for estimating SOM based on simulated band reflectance; (3) evaluate all bands, ODI, ORI, ONDVI, and OEVI for all simulated bands derived from the data of each satellite, and then combine the simulated data to estimate SOM using the particle swarm optimization (PSO)-support vector machine (SVM) algorithm. The OEVI analysis of simulated WorldView-2 data provided the best SOM estimation accuracy (R2 =0.43 and RMSE=2.62%). The OEVI and ODI algorithms provided better estimation accuracy of SOM from the different simulated satellite data than the ORI and ONDVI algorithms. The best estimation accuracy of SOM was achieved using the PSO-SVM algorithm and simulated WorldView-2 data (R2 =0.77, RMSE=1.66%, and AIC=99.62). Combination of simulated bands 4–9 of ASTER data and all bands, ODI, ORI, ONDVI, and OEVI of WorldView-2 data provided optimum SOM estimation results (R2 =0.82, RMSE=1.41%, AIC=82.86). The results indicate that a combination of different satellite data and the PSO-SVM algorithm significantly improves the estimation accuracy of SOM.

      PubDate: 2017-06-06T16:31:50Z
      DOI: 10.1016/j.agrformet.2017.05.018
      Issue No: Vol. 244-245 (2017)
       
  • Monitoring succession after a non-cleared windthrow in a Norway spruce
           mountain forest using webcam, satellite vegetation indices and turbulent
           CO2 exchange
    • Authors: Michael Matiu; Ludwig Bothmann; Rainer Steinbrecher; Annette Menzel
      Pages: 72 - 81
      Abstract: Publication date: 15 October 2017
      Source:Agricultural and Forest Meteorology, Volumes 244–245
      Author(s): Michael Matiu, Ludwig Bothmann, Rainer Steinbrecher, Annette Menzel
      Forests cover approximately 30% of the world’s land area and are responsible for 75% of terrestrial gross primary production. Disturbances, such as fire, storm or insect outbreaks alter the dynamics and functioning of forest ecosystems with consequences, in terms of species distribution and/or gross primary production, not fully understood. Large forest areas are intensively managed and natural disturbances are yet rare events but expected to increase with climate change. Here, we used digital repeat photography to observe the ecological succession in a windthrow disturbed forest in the Bavarian Forest National Park (Germany) and compared it to satellite-derived vegetation indices (NDVI, EVI, and PPI) as well as turbulent CO2 exchange. A data-driven clustering of the webcam images identified three regions of interest: spruce, grass and a transition region that showed grass in the beginning and became successively overgrown by spruce. The succession was mirrored in trends of annual maxima of gross primary production (GPP), satellite vegetation indices and derived image greenness (green chromatic coordinate, GCC) in the transition region. These trends were also responsible for a positive link between seasonal GPP and proxies. Start and end of growing season were estimated from GCC, NDVI, EVI, PPI, and GPP, compared to each other, and were linked partly to climatological growing season indices and phenological observations. This study demonstrates the suitability and benefits of a webcam in monitoring forest recovery after a severe windthrow event, thus offering a versatile tool that helps to understand successional and phenological processes after a disturbance.

      PubDate: 2017-06-11T22:21:41Z
      DOI: 10.1016/j.agrformet.2017.05.020
      Issue No: Vol. 244-245 (2017)
       
  • Mapping daily evapotranspiration based on spatiotemporal fusion of ASTER
           and MODIS images over irrigated agricultural areas in the Heihe River
           Basin, Northwest China
    • Authors: Yan Li; Chunlin Huang; Jinliang Hou; Juan Gu; Gaofeng Zhu; Xin Li
      Pages: 82 - 97
      Abstract: Publication date: 15 October 2017
      Source:Agricultural and Forest Meteorology, Volumes 244–245
      Author(s): Yan Li, Chunlin Huang, Jinliang Hou, Juan Gu, Gaofeng Zhu, Xin Li
      Continuous monitoring of daily evapotranspiration (ET) is crucial for allocating and managing water resources in irrigated agricultural areas in arid regions. In this study, continuous daily ET at a 90-m spatial resolution was estimated using the Surface Energy Balance System (SEBS) by fusing Moderate Resolution Imaging Spectroradiometer (MODIS) images with high temporal resolution and Advanced Space-borne Thermal Emission Reflectance Radiometer (ASTER) images with high spatial resolution. The spatiotemporal characteristics of these sensors were obtained using the Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM). The performance of this approach was validated over a heterogeneous oasis-desert region covered by cropland, residential, woodland, water, Gobi desert, sandy desert, desert steppe, and wetland areas using in situ observations from automatic meteorological systems (AMS) and eddy covariance (EC) systems in the middle reaches of the Heihe River Basin in Northwest China. The error introduced during the data fusion process based on STARFM is within an acceptable range for predicted LST at a 90-m spatial resolution. The surface energy fluxes estimated using SEBS based on predicted remotely sensed data that combined the spatiotemporal characteristics of MODIS and ASTER agree well with the surface energy fluxes observed using EC systems for all land cover types, especially for vegetated area with MAP values range from 9% to 15%, which are less than the uncertainty (18%) of the observed λE in this study area. Time series of daily ET modelled from SEBS were compared to that modelled from PT-JPL (one of Satellite-based Priestley-Taylor ET model) and observations from EC systems. SEBS performed generally better than PT-JPL for vegetated area, especially irrigated cropland with bias, RMSE, and MAP values of 0.29mm/d, 0.75mm/d, 13% at maize site, −0.33mm/d, 0.81mm/d, and 14% at vegetable sites.

      PubDate: 2017-06-11T22:21:41Z
      DOI: 10.1016/j.agrformet.2017.05.023
      Issue No: Vol. 244-245 (2017)
       
  • Potential use of seasonal forecasts for operational planning of north
           European forest management
    • Authors: Anna Maria Jönsson; Fredrik Lagergren
      Pages: 122 - 135
      Abstract: Publication date: 15 October 2017
      Source:Agricultural and Forest Meteorology, Volumes 244–245
      Author(s): Anna Maria Jönsson, Fredrik Lagergren
      Weather and climate conditions can have large impacts on the outcome of forest management operations: Suboptimal conditions can increase the amount of driving damage to forest ground caused by the heavy machines used for harvesting, forwarding and soil scarification. Planting of tree seedlings is commonly practised after clear cutting, and drought in summer or soil frost uplifting in autumn reduces the likelihood of successful plant establishment. Weather and climate also influence the risk of forest fires and the occurrence and development of pest and pathogens, and thereby the timing suitable for surveillance and countermeasures. In this study, the potential use of seasonal forecasts to support the operational planning of forest management in northern Europe was assessed. The analysis was based on temperature and precipitation data from WFDEI System 4 with 15 ensemble members representing seasonal hindcasts (retrospective predictions) for the period of 1981–2010. The data was used directly and as input to a soil model from which monthly indices of frozen soil and plant water stress were calculated. Relatively low skills were found for most months, and in particular for longer lead times. Highest skill was found for bias corrected temperature of January to March, with one month lead time. The skill was higher for the soil model indices, in particular those related to soil frost, as they are influenced by cumulative processes and the initial model conditions contribute to the skill. Probabilistic forecasts on frozen soil can thus be valuable for planning of which areas to harvest, taking the risk of driving damage to forest soils and forest roads into account.

      PubDate: 2017-06-13T22:25:14Z
      DOI: 10.1016/j.agrformet.2017.06.001
      Issue No: Vol. 244-245 (2017)
       
  • Observations of microscale internal gravity waves in very stable
           atmospheric boundary layers over an orchard canopy
    • Authors: Shane D. Mayor
      Pages: 136 - 150
      Abstract: Publication date: 15 October 2017
      Source:Agricultural and Forest Meteorology, Volumes 244–245
      Author(s): Shane D. Mayor
      Fifty-three episodes of internal gravity waves, with horizontal wavelengths ranging from 30 to 100m, were identified in time-lapse animations of numerically filtered elastic backscatter lidar images collected during the Canopy Horizontal Array Turbulence Study (CHATS). The waves existed in and above a 10m tall walnut orchard and are also present in time-series data of meteorological variables such as wind and temperature as measured by in situ sensors at multiple heights on a 30m tower centrally located in the lidar scan area and inside the (1.6km)2 orchard. All of the episodes occurred at night in the presence of temperature inversions and light winds. Wave periods from time-series analysis of the in situ data range from 20 to 100s. Sequences of lidar images reveal that the waves propagate in the direction of and at phase speeds less than that of the mean wind. The in situ data indicate the presence of a wind shear maximum and an inflection point at the top of the canopy. Gradient Richardson numbers near that altitude range between 0 and 0.20 indicating hydrodynamic instability. Range versus height lidar images from one case show the wave structures tilting downstream with altitude. In some cases, horizontal scans reveal that the gradient of aerosol backscatter tends to be larger on the upwind side of the crests. The environment and observations are consistent with the prevailing theory that the waves are the result of inflection point instability and the lidar data suggest that in 42% of the episodes the waves may have begun, or be on the verge of, breaking.
      Graphical abstract image

      PubDate: 2017-07-03T05:15:37Z
      DOI: 10.1016/j.agrformet.2017.05.014
      Issue No: Vol. 244-245 (2017)
       
  • Calibration and comparison of thermal dissipation, heat ratio and heat
           field deformation sap flow probes for diffuse-porous trees
    • Authors: Sebastian Fuchs; Christoph Leuschner; Roman Link; Heinz Coners; Bernhard Schuldt
      Pages: 151 - 161
      Abstract: Publication date: 15 October 2017
      Source:Agricultural and Forest Meteorology, Volumes 244–245
      Author(s): Sebastian Fuchs, Christoph Leuschner, Roman Link, Heinz Coners, Bernhard Schuldt
      Sap flow probes are routinely used in forest and horticulture hydrology for estimating tree water use. This requires unbiased measurements when upscaling from tree to stand level, but accuracy and comparability of different thermometric methods have been questioned. Three sap flow measuring techniques were compared against gravimetric flow measurement in cut stem segments: ‘Granier-type’ thermal dissipation probes (TDP; three different sensor types), the heat field deformation method (HFD), and the heat ratio method (HRM). For the empirical methods (TDP and HFD), new calibration parameters were estimated using a nonlinear hierarchical modelling approach. 66 stem segments from five temperate, diffuse-porous tree species (9–16cm stem diameter, 100cm stem length) were exposed to a wide range of flux densities by applying subatmospheric pressure (−50 to −650hPa) analogous to natural flow conditions in the field. All TDP probes underestimated flux density by 23–45% when calculated with Granier's original calibration parameters, with the deviation increasing with flux rate. The accuracy was significantly improved by estimating new calibration parameters, especially for probes differing from Granier's original sensor design. Species-specific parameters further improved accuracy, although the species differences might partially be explained by variation in the observed ranges of sap flux. The HFD sensor overestimated gravimetric flow by ∼11%; empirical calibration did not improve its accuracy compared to the manufacturer's equation. At low to medium flow rates, the HRM system achieved higher accuracy than the other probes (0.8% underestimation), while performing poorly at high flux rates under our measurement settings (energy input of 25J). Both for TDP and HFD sensors, we observed a surprisingly large variability in calibration parameters between different stems of the same species. We conclude that (i) TDP and HFD sensors require species-specific calibration to measure sap flux with high accuracy, (ii) the original Granier equation cannot be used for TDP probes with deviating design, and (iii), at low to medium flow rates, the highest accuracy can be achieved with HRM sensors. Our results help to increase the accuracy of tree sap flow measurements with thermal dissipation probes, and to assess various levels of errors related to the different thermometric methods. This is important when synthesizing forest transpiration data on regional and global scales.

      PubDate: 2017-08-03T10:06:27Z
      DOI: 10.1016/j.agrformet.2017.04.003
      Issue No: Vol. 244-245 (2017)
       
  • Climate controls over the net carbon uptake period and amplitude of net
           ecosystem production in temperate and boreal ecosystems
    • Authors: Zheng Fu; Paul C. Stoy; Yiqi Luo; Jiquan Chen; Jian Sun; Leonardo Montagnani; Georg Wohlfahrt; Abdullah F. Rahman; Serge Rambal; Christian Bernhofer; Jinsong Wang; Gabriela Shirkey; Shuli Niu
      Pages: 9 - 18
      Abstract: Publication date: 15 September 2017
      Source:Agricultural and Forest Meteorology, Volume 243
      Author(s): Zheng Fu, Paul C. Stoy, Yiqi Luo, Jiquan Chen, Jian Sun, Leonardo Montagnani, Georg Wohlfahrt, Abdullah F. Rahman, Serge Rambal, Christian Bernhofer, Jinsong Wang, Gabriela Shirkey, Shuli Niu
      The seasonal and interannual variability of the terrestrial carbon cycle is regulated by the interactions of climate and ecosystem function. However, the key factors and processes determining the interannual variability of net ecosystem productivity (NEP) in different biomes are far from clear. Here, we quantified yearly anomalies of seasonal and annual NEP, net carbon uptake period (CUP), and the maximum daily NEP (NEPmax) in response to climatic variables in 24 deciduous broadleaf forest (DBF), evergreen forest (EF), and grassland (GRA) ecosystems that include at least eight years of eddy covariance observations. Over the 228 site-years studied, interannual variations in NEP were mostly explained by anomalies of CUP and NEPmax. CUP was determined by spring and autumn net carbon uptake phenology, which were sensitive to annual meteorological variability. Warmer spring temperatures led to an earlier start of net carbon uptake activity and higher spring and annual NEP values in DBF and EF, while warmer autumn temperatures in DBF, higher autumn radiation in EF, and more summer and autumn precipitation in GRA resulted in a later ending date of net carbon uptake and associated higher autumn and annual NEP. Anomalies in NEPmax s were determined by summer precipitation in DBF and GRA, and explained more than 50% of variation in summer NEP anomalies for all the three biomes. Results demonstrate the role of meteorological variability in controlling CUP and NEPmax, which in turn help describe the seasonal and interannual variability of NEP.

      PubDate: 2017-05-18T01:50:12Z
      DOI: 10.1016/j.agrformet.2017.05.009
      Issue No: Vol. 243 (2017)
       
  • Phenology and growth responses of Fraser fir (Abies fraseri) Christmas
           trees along an elevational gradient, southern Appalachian Mountains, USA
    • Authors: Scott T. Cory; Lauren K. Wood; Howard S. Neufeld
      Pages: 25 - 32
      Abstract: Publication date: 15 September 2017
      Source:Agricultural and Forest Meteorology, Volume 243
      Author(s): Scott T. Cory, Lauren K. Wood, Howard S. Neufeld
      Fraser fir (Abies fraseri) trees are endemic to locations above 1500m in the southern Appalachian Mountains, and are also grown commercially for Christmas trees well below their native range (down to 600m). To evaluate how phenology and growth of this species will respond to climate drivers associated with warming, we assessed the timing of bud-burst, shoot growth, trunk growth, as well as shoot- and leaf-level architecture, of Fraser fir Christmas trees along an elevational gradient from 664 to 1228m. Daytime maximum temperatures and evaporative demand were highest at low elevation and cloud events and higher wind speeds occurred more often at high elevations. Bud-burst occurred 6days sooner, new shoots ceased elongation 10days sooner, and radial trunk growth ended 8days later at low elevations than at high elevations, indicating a shift and lengthening of the growing season. Final shoot length did not vary among elevations, but the percent increase in trunk diameter was greatest at middle elevations. Architectural characteristics such as specific needle mass, needle packing density, and silhouette-to-projected area ratios generally did not vary with elevation. As climate change progresses, higher cloud ceilings, increased evaporative demand, and higher temperatures may further shift the timing of the growing season and reduce growth at low elevation Christmas tree farms, but farms at higher elevations may benefit from a longer growing season.

      PubDate: 2017-05-21T01:59:59Z
      DOI: 10.1016/j.agrformet.2017.05.003
      Issue No: Vol. 243 (2017)
       
  • Effects of jointing and booting low temperature stresses on grain yield
           and yield components in wheat
    • Authors: Hongting Ji; Liujun Xiao; Yumin Xia; Hang Song; Bing Liu; Liang Tang; Weixing Cao; Yan Zhu; Leilei Liu
      Pages: 33 - 42
      Abstract: Publication date: 15 September 2017
      Source:Agricultural and Forest Meteorology, Volume 243
      Author(s): Hongting Ji, Liujun Xiao, Yumin Xia, Hang Song, Bing Liu, Liang Tang, Weixing Cao, Yan Zhu, Leilei Liu
      Climate change has brought more low temperature events and posed an increasing risk to the global wheat production. In order to evaluate the effects of low temperature at jointing and booting stages on wheat grain yield and its components, two years of environment-controlled phytotron experiments were carried out with two wheat cultivars under different low temperature levels and durations. Low temperature level and its interaction with low temperature duration had negative effects on the observed grain yield in two cultivars. Moreover, wheat yield was more sensitive to low temperature at booting than at jointing stages. Compared with the control treatment (Tmin/Tmax/Tmean of 6°C/16°C/11°C, T1), 4.6%–56.4% and 3.1%–44.6% decreases of grain yield per plant (YPP) were observed under low temperature at jointing in Yangmai16 (spring wheat) and Xumai30 (semi-winter wheat), and 13.9%–85.2% and 3.2%–85.9% decreases under low temperature at booting in Yangmai16 and Xumai30, respectively. The spike number per plant (SNPP) and grain number per spike (GNPS) were more sensitive to low temperature at jointing and booting stages than 1000-grain weight (TGW). Furthermore, significant negative linear relationships were observed between the accumulated cold degree days (ACDD) and YPP, SNPP, GNPS and TGW in both cultivars. The contribution of GNPS to the variation of YPP was greater than SNPP and TGW at the mild low temperature level (Tmin/Tmax/Tmean of −2°C/8°C/3°C, T3) in both cultivars. However, at the extreme low temperature level (Tmin/Tmax/Tmean of −6°C/4°C/−1°C, T5), the major variation of YPP was caused by SNPP of Yangmai16 and GNPS of Xumai30. In general, the decreased YPP under low temperature condition was mainly from the decreased grain number per plant (GNPP=SNPP×GNPS) in both cultivars and treatment stages, thus maintaining a high GNPP is very important for compensating the yield losses caused by low temperature at jointing and booting stages.

      PubDate: 2017-05-21T01:59:59Z
      DOI: 10.1016/j.agrformet.2017.04.016
      Issue No: Vol. 243 (2017)
       
  • Aged but withstanding: Maintenance of growth rates in old pines is not
           related to enhanced water-use efficiency
    • Authors: Elena Granda; J. Julio Camarero; J. Diego Galván; Gabriel Sangüesa-Barreda; Arben Q. Alla; Emilia Gutierrez; Isabel Dorado-Liñán; Laia Andreu-Hayles; Inga Labuhn; Håkan Grudd; Jordi Voltas
      Pages: 43 - 54
      Abstract: Publication date: 15 September 2017
      Source:Agricultural and Forest Meteorology, Volume 243
      Author(s): Elena Granda, J. Julio Camarero, J. Diego Galván, Gabriel Sangüesa-Barreda, Arben Q. Alla, Emilia Gutierrez, Isabel Dorado-Liñán, Laia Andreu-Hayles, Inga Labuhn, Håkan Grudd, Jordi Voltas
      Growth of old trees in cold-limited forests may benefit from recent climate warming and rising atmospheric CO2 concentrations (ca ) if age-related constraints do not impair wood formation. To test this hypothesis, we studied old Mountain pine trees at three Pyrenean high-elevation forests subjected to cold-wet (ORD, AIG) or warmer-drier (PED) conditions. We analyzed long-term trends (1450–2008) in growth (BAI, basal area increment), maximum (MXD) and minimum (MID) wood density, and tree-ring carbon (δ13C) and oxygen (δ18O) isotope composition, which were used as proxies for intrinsic water-use efficiency (iWUE) and stomatal conductance (gs ), respectively. Old pines showed positive (AIG and ORD) or stable (PED) growth trends during the industrial period (since 1850) despite being older than 400 years. Growth and wood density covaried from 1850 onwards. In the cold-wet sites (AIG and ORD) enhanced photosynthesis through rising ca was likely responsible for the post-1850 iWUE improvement. However, uncoupling between BAI and iWUE indicated that increases in iWUE were not responsible for the higher growth but climate warming. A reduction in gs was inferred from increased δ18O for PED trees from 1960 onwards, the warmest site where the highest iWUE increase occurred (34%). This suggests that an emergent drought stress at warm-dry sites could trigger stomatal closure to avoid excessive transpiration. Overall, carbon acquisition as lasting woody pools is expected to be maintained in aged trees from cold and high-elevation sites where old forests constitute unique long-term carbon reservoirs.
      Graphical abstract image

      PubDate: 2017-05-21T01:59:59Z
      DOI: 10.1016/j.agrformet.2017.05.005
      Issue No: Vol. 243 (2017)
       
  • Inside Front Cover - Editorial Board Page
    • Abstract: Publication date: 15 October 2017
      Source:Agricultural and Forest Meteorology, Volumes 244–245


      PubDate: 2017-08-03T10:06:27Z
       
  • Inside Front Cover - Editorial Board Page/Cover image legend if applicable
    • Abstract: Publication date: 15 September 2017
      Source:Agricultural and Forest Meteorology, Volume 243


      PubDate: 2017-06-11T22:21:41Z
       
  • Integrating interactive effects of chilling and photoperiod in
           phenological process-based models. A case study with two European tree
           species: Fagus sylvatica and Quercus petraea
    • Authors: Gauzere Delzon; Davi Bonhomme Garcia Cortazar-Atauri Chuine
      Abstract: Publication date: 15 October 2017
      Source:Agricultural and Forest Meteorology, Volumes 244–245
      Author(s): J. Gauzere, S. Delzon, H. Davi, M. Bonhomme, I. Garcia de Cortazar-Atauri, I. Chuine
      Modeling studies predict that global warming might severely affect bud dormancy release. However, growing empirical evidences suggest that long photoperiod might compensate for a lack of chilling temperature in photosensitive species. For now, attempts to integrate this effect into models remain limited. Here, we used French budburst phenological records for two main European temperate tree species, Fagus sylvatica (n =136) and Quercus petraea (n =276), to compare four phenological models accounting for a photoperiod effect, two of them proposing a new formalism of the effect of photoperiod, and three classical thermal models. We also investigated the effect of a realistic photoperiod cue on budburst dates in future climatic conditions. Consistently with the empirical literature, we find that models integrating a photoperiod cue were more relevant to simulate budburst dates for beech than for oak. However, contrary to the recently debated expectation that photoperiod might mitigate the trend towards earlier budburst date, we find that the compensatory effect of photoperiod on a lack of chilling maintains a trend towards earlier dates up to the end of the 2100. Our results also suggest that phenological rank changes between photosensitive and photo-insensitive species may be more pronounced at cold than warm trailing edge.

      PubDate: 2017-05-28T07:49:17Z
       
 
 
JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
 
Home (Search)
Subjects A-Z
Publishers A-Z
Customise
APIs
Your IP address: 54.81.192.192
 
About JournalTOCs
API
Help
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2016