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Showing 1 - 200 of 3042 Journals sorted alphabetically
AASRI Procedia     Open Access   (Followers: 15)
Academic Pediatrics     Hybrid Journal   (Followers: 19, SJR: 1.402, h-index: 51)
Academic Radiology     Hybrid Journal   (Followers: 16, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 81, 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: 326, SJR: 0.726, h-index: 43)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 3)
Acta Biomaterialia     Hybrid Journal   (Followers: 25, SJR: 2.02, h-index: 104)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription  
Acta de Investigación Psicológica     Open Access   (Followers: 2)
Acta Ecologica Sinica     Open Access   (Followers: 8, SJR: 0.172, h-index: 29)
Acta Haematologica Polonica     Free   (SJR: 0.123, h-index: 8)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.604, h-index: 38)
Acta Materialia     Hybrid Journal   (Followers: 203, 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: 22, SJR: 1.365, h-index: 73)
Acta Sociológica     Open Access  
Acta Tropica     Hybrid Journal   (Followers: 5, SJR: 1.059, h-index: 77)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 4)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 3)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 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: 7, SJR: 1.039, h-index: 5)
Additives for Polymers     Full-text available via subscription   (Followers: 20)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 124, 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: 24, SJR: 0.169, h-index: 4)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 3)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 6, SJR: 1.054, h-index: 35)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 10, SJR: 0.801, h-index: 26)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 21, SJR: 1.286, h-index: 49)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 16, SJR: 3.31, h-index: 42)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.277, h-index: 43)
Advances in Botanical Research     Full-text available via subscription   (Followers: 3, SJR: 0.619, h-index: 48)
Advances in Cancer Research     Full-text available via subscription   (Followers: 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: 8, SJR: 1.268, h-index: 45)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 28, SJR: 0.938, h-index: 33)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18, SJR: 2.314, h-index: 130)
Advances in Computers     Full-text available via subscription   (Followers: 16, SJR: 0.223, h-index: 22)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 11)
Advances in Digestive Medicine     Open Access   (Followers: 4)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 5)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Ecological Research     Full-text available via subscription   (Followers: 39, SJR: 3.25, h-index: 43)
Advances in Engineering Software     Hybrid Journal   (Followers: 25, SJR: 0.486, h-index: 10)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 7)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 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: 44, SJR: 0.674, h-index: 38)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 14)
Advances in Genetics     Full-text available via subscription   (Followers: 15, SJR: 2.558, h-index: 54)
Advances in Genome Biology     Full-text available via subscription   (Followers: 12)
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: 20, 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: 24)
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: 34, SJR: 4.152, h-index: 85)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 1.132, h-index: 42)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 3, SJR: 1.274, h-index: 27)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 4)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 4)
Advances in Life Course Research     Hybrid Journal   (Followers: 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: 5, SJR: 0.489, h-index: 25)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 4, SJR: 1.44, h-index: 51)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 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: 21, 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: 58)
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: 339, 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: 6, SJR: 0.823, h-index: 27)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 29, 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: 311, SJR: 0.816, h-index: 49)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.318, h-index: 36)
African J. of Emergency Medicine     Open Access   (Followers: 4, SJR: 0.344, h-index: 6)
Ageing Research Reviews     Hybrid Journal   (Followers: 7, SJR: 3.289, h-index: 78)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 398, 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: 50, 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: 5)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 1, SJR: 0.436, h-index: 12)
Alexandria J. of Medicine     Open Access  
Algal Research     Partially Free   (Followers: 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: 5, SJR: 0.776, h-index: 35)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 6, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 46, 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: 46, 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: 34, SJR: 0.574, h-index: 65)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 6, SJR: 1.091, h-index: 45)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 15, SJR: 1.653, h-index: 93)
American J. of Human Genetics     Hybrid Journal   (Followers: 30, 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: 32, SJR: 2.313, h-index: 172)
American J. of Medicine     Hybrid Journal   (Followers: 44, 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: 182, 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: 2)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.249, h-index: 88)
American J. of Otolaryngology     Hybrid Journal   (Followers: 23, SJR: 0.59, h-index: 45)
American J. of Pathology     Hybrid Journal   (Followers: 23, SJR: 2.653, h-index: 228)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 21, SJR: 2.764, h-index: 154)
American J. of Surgery     Hybrid Journal   (Followers: 33, 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: 52, SJR: 0.124, h-index: 9)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 4)
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: 161, 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: 10)
Anesthésie & Réanimation     Full-text available via subscription  
Anesthesiology Clinics     Full-text available via subscription   (Followers: 21, SJR: 0.421, h-index: 40)
Angiología     Full-text available via subscription   (SJR: 0.124, h-index: 9)
Angiologia e Cirurgia Vascular     Open Access  
Animal Behaviour     Hybrid Journal   (Followers: 153, SJR: 1.907, h-index: 126)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 5, SJR: 1.151, h-index: 83)
Animal Reproduction Science     Hybrid Journal   (Followers: 5, SJR: 0.711, h-index: 78)
Annales d'Endocrinologie     Full-text available via subscription   (SJR: 0.394, h-index: 30)
Annales d'Urologie     Full-text available via subscription  
Annales de Cardiologie et d'Angéiologie     Full-text available via subscription   (SJR: 0.177, h-index: 13)
Annales de Chirurgie de la Main et du Membre Supérieur     Full-text available via subscription  
Annales de Chirurgie Plastique Esthétique     Full-text available via subscription   (Followers: 2, SJR: 0.354, h-index: 22)
Annales de Chirurgie Vasculaire     Full-text available via subscription   (Followers: 1)

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Journal Cover Agricultural and Forest Meteorology
  [SJR: 2.18]   [H-I: 116]   [15 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0168-1923
   Published by Elsevier Homepage  [3042 journals]
  • 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)
  • 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
    • 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)
  • 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)
  • Interspecific and interannual variation in the duration of spring
           phenophases in a northern mixed forest
    • Authors: Alison Donnelly; Rong Yu; Amelia Caffarra; Jonathan Hanes; Liang Liang; Ankur R. Desai; Lingling Liu; Mark D. Schwartz
      Pages: 55 - 67
      Abstract: Publication date: 15 September 2017
      Source:Agricultural and Forest Meteorology, Volume 243
      Author(s): Alison Donnelly, Rong Yu, Amelia Caffarra, Jonathan Hanes, Liang Liang, Ankur R. Desai, Lingling Liu, Mark D. Schwartz
      A wide range of intra- and interspecific variation occurs in spring leaf phenology as a result of biotic factors such as, life strategy, ecological niche and genetic adaptation, and abiotic factors such as environmental condition. Whereas knowing when the start of bud-burst occurs is necessary for determining the beginning of the growing season, and the subsequent start of carbon uptake, the duration of phenophases is equally important (to estimate the rate of carbon uptake, for example), but rarely reported. Here, we investigate variation in the timing and duration of 3 key phenophase categories (bud-open, leaf-out, full-leaf unfolded) from a range of 8 broadleaf and 2 conifer species in a mixed forest in northern Wisconsin, USA over a 5-year period. As expected, the start of each phenophase category varied across species and years and an earlier start to one phenophase did not necessarily result in an earlier start to subsequent phenophases nor did it mean a faster or slower progression. Ecological niche was not always a useful predictor of the timing or duration of the spring phenology season. The spring phenology season from bud-burst to full leaf open for the entire forest community took an average of 13days ranging from 12 to 18days across species. Bud-open and leaf-out lasted an average of 4days whereas, full-leaf unfolding lasted 5 and again there were variations among species. Full leaf unfolded for A. incana lasted significantly (p<0.001) longer than other species. Variation in the duration of the spring phenology season among years closely tracked local seasonal air-temperature based on growing degree hours (GDH). These results could be used to help determine the relationship between phenology and the potential for carbon storage in early spring in a mixed forest and highlight the value of direct field observation data at species level, the detail of which cannot, at present, be captured by satellite remote sensing.

      PubDate: 2017-06-01T16:31:40Z
      DOI: 10.1016/j.agrformet.2017.05.007
      Issue No: Vol. 243 (2017)
  • Enhancing soil drought induced by climate change and agricultural
           practices: Observational and experimental evidence from the semiarid area
           of northern China
    • Authors: Jingting Zhang; Jia Yang; Pingli An; Wei Ren; Zhihua Pan; Zhiqiang Dong; Guolin Han; Yuying Pan; Shufen Pan; Hanqin Tian
      Pages: 74 - 83
      Abstract: Publication date: 15 September 2017
      Source:Agricultural and Forest Meteorology, Volume 243
      Author(s): Jingting Zhang, Jia Yang, Pingli An, Wei Ren, Zhihua Pan, Zhiqiang Dong, Guolin Han, Yuying Pan, Shufen Pan, Hanqin Tian
      Increased water scarcity has led to a decade-long soil drought in the semiarid area of northern China, which caused food insecurity in this region. However, there is a lack of sufficient observational evidence about how climate change and agricultural practices have interactively affected this soil drought. Long-term in situ soil moisture measurements collected in agricultural experimental plots indicate that the mean temperature and precipitation during the growing season have reduced soil moisture by 11.2%, and agricultural practices have aggravated the soil drying trend in the 0–100mm soil layer over the past three decades. Our results also show that planting water-expensive crops (e.g., potato and maize) may aggravate soil drought. Crop rotation increases soil water consumption by 8.9–12.6% over continuous cropping. Excessive fertilizer use increases water consumption by 25.4–46.9% and decreases the water use efficiency (WUE) by 14.6–35.3%, while tillage accounts for the consumption of 10.3% more soil moisture than no-tillage. Our results indicate that agricultural practices, including crop rotation, a high fertilizer input, and tillage, may increase water consumption and aggravate soil drying. Our findings call for effective strategies for mitigating soil drought in semiarid regions, such as an adjustment of the cropping system, reduced fertilizer use, and improved conservation tillage.

      PubDate: 2017-05-28T07:49:17Z
      DOI: 10.1016/j.agrformet.2017.05.008
      Issue No: Vol. 243 (2017)
  • Integrating growth stage deficit irrigation into a process based crop
    • Authors: Jose R. Lopez; Jonathan M. Winter; Joshua Elliott; Alex C. Ruane; Cheryl Porter; Gerrit Hoogenboom
      Pages: 84 - 92
      Abstract: Publication date: 15 September 2017
      Source:Agricultural and Forest Meteorology, Volume 243
      Author(s): Jose R. Lopez, Jonathan M. Winter, Joshua Elliott, Alex C. Ruane, Cheryl Porter, Gerrit Hoogenboom
      Current rates of agricultural water use are unsustainable in many regions, creating an urgent need to identify improved irrigation strategies for water limited areas. Crop models can be used to quantify plant water requirements, predict the impact of water shortages on yield, and calculate water productivity (WP) to link water availability and crop yields for economic analyses. Many simulations of crop growth and development, especially in regional and global assessments, rely on automatic irrigation algorithms to estimate irrigation dates and amounts. However, these algorithms are not well suited for water limited regions because they have simplistic irrigation rules, such as a single soil-moisture based threshold, and assume unlimited water. To address this constraint, a new modeling framework to simulate agricultural production in water limited areas was developed. The framework consists of a new automatic irrigation algorithm for the simulation of growth stage based deficit irrigation under limited seasonal water availability; and optimization of growth stage specific parameters. The new automatic irrigation algorithm was used to simulate maize and soybean in Gainesville, Florida, and first used to evaluate the sensitivity of maize and soybean simulations to irrigation at different growth stages and then to test the hypothesis that water productivity calculated using simplistic irrigation rules underestimates WP. In the first experiment, the effect of irrigating at specific growth stages on yield and irrigation water use efficiency (IWUE) in maize and soybean was evaluated. In the reproductive stages, IWUE tended to be higher than in the vegetative stages (e.g. IWUE was 18% higher than the well watered treatment when irrigating only during R3 in soybean), and when rainfall events were less frequent. In the second experiment, water productivity (WP) was significantly greater with optimized irrigation schedules compared to non-optimized irrigation schedules in water restricted scenarios. For example, the mean WP across 38 years of maize production was 1.1kgm−3 for non-optimized irrigation schedules with 50mm of seasonal available water and 2.1kgm−3 with optimized irrigation schedules, a 91% improvement in WP with optimized irrigation schedules. The framework described in this work could be used to estimate WP for regional to global assessments, as well as derive location specific irrigation guidance.

      PubDate: 2017-05-28T07:49:17Z
      DOI: 10.1016/j.agrformet.2017.05.001
      Issue No: Vol. 243 (2017)
  • Hourly fine fuel moisture model for Pinus halepensis (Mill.) litter
    • Authors: Nera Bakšić; Darko Bakšić; Anamarija Jazbec
      Pages: 93 - 99
      Abstract: Publication date: 15 September 2017
      Source:Agricultural and Forest Meteorology, Volume 243
      Author(s): Nera Bakšić, Darko Bakšić, Anamarija Jazbec
      Pinus halepensis (Mill.) is the most widely distributed and abundant Mediterranean pine, as well as one of the species most affected by wildfires in Europe. The objective of this study was to develop and test an operationally useful fine fuel moisture prediction model for P. halepensis needle litter below the fibre saturation point, where flammability increases rapidly with decreasing moisture content. The predictive ability of the hourly Fine Fuel Moisture Code (FFMC) was also evaluated. Even though the hourly FFMC model is designed for pine litter, it consistently over-predicted moisture content of P. halepensis needle litter and could not track the rapid moisture change during the day. Experimental measurements of equilibrium moisture content and response time of dead P. halepensis needles were used to modify the hourly FFMC model. The modified model performed better than the hourly FFMC model on all evaluation parameters, with a mean absolute error of 1% moisture content. Our results suggest that fine fuel moisture prediction models should be species-specific in order to achieve the accuracy needed for precise prediction of fire behaviour.

      PubDate: 2017-05-28T07:49:17Z
      DOI: 10.1016/j.agrformet.2017.04.014
      Issue No: Vol. 243 (2017)
  • Quantifying stand structural complexity and its relationship with forest
           management, tree species diversity and microclimate
    • Authors: Martin Ehbrecht; Peter Schall; Christian Ammer; Dominik Seidel
      Pages: 1 - 9
      Abstract: Publication date: 15 August 2017
      Source:Agricultural and Forest Meteorology, Volume 242
      Author(s): Martin Ehbrecht, Peter Schall, Christian Ammer, Dominik Seidel
      Measures to describe stand structural complexity efficiently and objectively are increasingly demanded to understand the relationship between forest management, stand structure, biodiversity and ecosystem functioning. Here, we present an approach to quantify stand structural complexity based on fractal dimension derived from single terrestrial laser scans (TLS) that were made on 126 permanent forest research plots in Germany, representing major stand and management types. The newly developed SSC-index (SSCI) was positively correlated to conventional tree-based measures of stand structural complexity, tree size differentiation, diversity of tree diameters and random tree spacing patterns. Beyond that, it successfully differentiated between stand types of different main tree species and management systems. SSCI increased from low to high tree species diversity and explained microclimatic fluctuations better than conventional, tree-based measures. Given the high efficiency during data collection, TLS can be used to assess stand structural complexity for large sample sizes to provide an explanatory variable for the effects of forest management on biodiversity, productivity and ecosystem processes.

      PubDate: 2017-05-03T08:50:55Z
      DOI: 10.1016/j.agrformet.2017.04.012
      Issue No: Vol. 242 (2017)
  • Assessment of random errors in multi-plot nitrous oxide flux gradient
    • Authors: Shannon E. Brown; Claudia Wagner-Riddle
      Pages: 10 - 20
      Abstract: Publication date: 15 August 2017
      Source:Agricultural and Forest Meteorology, Volume 242
      Author(s): Shannon E. Brown, Claudia Wagner-Riddle
      The multi-plot flux-gradient (FG) technique is well-suited for non-intrusive measurements of agricultural N2O emissions for individually-treated field-scale plots across growing seasons at high temporal and spatial resolution. The degree of random error associated with N2O flux measurements is unknown; knowledge of these errors will increase confidence in the flux measurements and strengthen comparisons of total N2O emissions between treatments. An error estimation routine was developed to determine the random error (σ) associated with FG-measured fluxes (σ F ). The combination of a moving-block bootstrapping technique and the filtering method of Salesky et al. (2012) estimated the σ values for each variable used in calculating individual 30-min FG-derived fluxes. This error analysis was applied to a year-long dataset where a four-plot FG system measured N2O fluxes semi-continuously in a soybean field in Southwestern Ontario, Canada, with each plot having different treatments affecting N2O emissions. Errors of the concentration differences contributed the largest proportion to the σ F values. The individual 30-min σ F values did not correlate with the magnitude of the flux but were positively correlated with turbulence conditions. Random errors of N2O fluxes greater than 45ngNm−2 s−1 had values representative of 9% of the measured flux, whereas error of fluxes close to zero frequently exceeded the value of the measured flux. Cumulating the errors over the experiment reduced the degree of error associated with the cumulated total N2O emissions with an average value of 31.5gNha−1, which represented on average ±5.5% of the total N2O emissions. The proposed framework is applicable to other scalar fluxes being determined by the flux-gradient method.

      PubDate: 2017-05-03T08:50:55Z
      DOI: 10.1016/j.agrformet.2017.04.005
      Issue No: Vol. 242 (2017)
  • Herbivore-induced BVOC emissions of Scots pine under warming, elevated
           ozone and increased nitrogen availability in an open-field exposure
    • Authors: Rajendra P. Ghimire; Minna Kivimäenpää; Anne Kasurinen; Elina Häikiö; Toini Holopainen; Jarmo K. Holopainen
      Pages: 21 - 32
      Abstract: Publication date: 15 August 2017
      Source:Agricultural and Forest Meteorology, Volume 242
      Author(s): Rajendra P. Ghimire, Minna Kivimäenpää, Anne Kasurinen, Elina Häikiö, Toini Holopainen, Jarmo K. Holopainen
      Climate change may promote the frequency of insect attacks such as outbreaks of the great web-spinning pine sawfly (Acantholyda posticalis) on Scots pine (Pinus sylvestris L.). We determined the emission rates of localized biogenic volatile organic compounds (BVOCs) from A. posticalis-fed branches, and systemic BVOCs from non-fed branches of Scots pine seedlings defoliated for two growing seasons by A. posticalis larvae. Seedlings were also exposed to warming, elevated ozone and higher nitrogen availability for three years in an open-field experiment. A. posticalis feeding increased localized emissions of total non-oxygenated monoterpenes 21-fold, total oxygenated monoterpenes 9.1-fold, total sesquiterpenes 11-fold and total green leaf volatiles 9.2-fold from insect-damaged shoots on the 7th day of feeding in June. Warming reduced the effects of herbivory on the emission rates of total non-oxygenated monoterpenes by 77%. However, the effect of herbivory on total sesquiterpene emissions was enhanced by 16-fold in combination with warming and elevated ozone. The localized emission rates of total BVOCs were linearly increased when feeding damage intensity by larvae exceeded 80%. After three weeks of continuous sawfly feeding, herbivory stress increased systemic emissions of total non-oxygenated monoterpenes 5.6-fold, total sesquiterpenes 5.6-fold and total green leaf volatiles 6.5-fold from the non-damaged branch of larvae-fed seedlings, and this effect on total non-oxygenated monoterpene emission was enhanced 8.6-fold with elevated ozone. Herbivory sporadically showed post-feeding effects still by the end of 12th week from the initiation of feeding, increasing total non-oxygenated monoterpene emissions 4.4-fold at elevated nitrogen level. Our results suggest that Scots pine, at least in seedling stage, will be a stronger source of BVOC emissions in future due to expected increase of sawfly outbreaks with climate warming and by increased herbivory interactions with abiotic climate change factors.
      Graphical abstract image

      PubDate: 2017-05-03T08:50:55Z
      DOI: 10.1016/j.agrformet.2017.04.008
      Issue No: Vol. 242 (2017)
  • Growth and cold hardening of European aspen seedlings in response to an
           altered temperature and soil moisture regime
    • Authors: Mārtiņš Zeps; Āris Jansons; Roberts Matisons; Niina Stenvall; Pertti Pulkkinen
      Pages: 47 - 54
      Abstract: Publication date: 15 August 2017
      Source:Agricultural and Forest Meteorology, Volume 242
      Author(s): Mārtiņš Zeps, Āris Jansons, Roberts Matisons, Niina Stenvall, Pertti Pulkkinen
      During the autumn, plants undergo a physiological process of cold hardening to limit damage caused by the low temperatures of winter. Under a warming climate, plants may be less cold hardened and hence more susceptible to the effects of a sudden temperature drop. During the growth season of 2010–2011, growth and cold hardening of European aspen (Populus tremula L.) seedlings from native wild populations were examined under ambient and projected climate scenarios in greenhouses at the Haapastensyrjä research station in Southern Finland. Using locally obtained seedlings, we manipulated temperature and soil moisture during the normal growth period and then subjected them to an artificial freezing treatment during September–November 2010. At the end of the experiment, we determined seedling height, survival and the extent of stem damage, and analysed their variation with mixed effect models. Among the treatments tested, temperature was the main factor affecting survival, cold hardening, and frost damage to seedlings. The higher temperature (4°C increase) of the 2100 future climate regime was associated with a 35% decrease in seedling survival (from 66 to 31%) during the growing period. Increased irrigation had a positive, but considerably weaker effect on seedling survival (improved survival by ca. 8%). Height of seedlings after the first growth season was enhanced by increased soil moisture and temperature, but these effects were negated the following spring by increased frost damage caused by warmer growth conditions. Although cold hardiness increased as the season progressed, increase of temperature by 1 and 4°C severely diminished it, and survival after the freezing dropped from 55% (control) to 48% and 14%, while stem damage increased from 58% (control) to 90% and 96%, respectively. These results suggest that regeneration of north European aspen might become burdened in a warmer climate. Although survival was clearly affected, several seedlings grown under the future climate regimes survived freezing and overwintered with negligible damage, suggesting an adaptive capacity of the local population. The intraspecific competition that occurred as a side effect of the experimental setup also affected cold hardening, suggesting that stand structure might be managed to improve the resilience of aspen to frost damage.

      PubDate: 2017-05-08T08:21:17Z
      DOI: 10.1016/j.agrformet.2017.04.015
      Issue No: Vol. 242 (2017)
  • Improving global terrestrial evapotranspiration estimation using support
           vector machine by integrating three process-based algorithms
    • Authors: Yunjun Yao; Shunlin Liang; Xianglan Li; Jiquan Chen; Shaomin Liu; Kun Jia; Xiaotong Zhang; Zhiqiang Xiao; Joshua B. Fisher; Qiaozhen Mu; Ming Pan; Meng Liu; Jie Cheng; Bo Jiang; Xianhong Xie; Thomas Grünwald; Christian Bernhofer; Olivier Roupsard
      Pages: 55 - 74
      Abstract: Publication date: 15 August 2017
      Source:Agricultural and Forest Meteorology, Volume 242
      Author(s): Yunjun Yao, Shunlin Liang, Xianglan Li, Jiquan Chen, Shaomin Liu, Kun Jia, Xiaotong Zhang, Zhiqiang Xiao, Joshua B. Fisher, Qiaozhen Mu, Ming Pan, Meng Liu, Jie Cheng, Bo Jiang, Xianhong Xie, Thomas Grünwald, Christian Bernhofer, Olivier Roupsard
      Terrestrial evapotranspiration (ET) for each plant functional type (PFT) is a key variable for linking the energy, water and carbon cycles of the atmosphere, hydrosphere and biosphere. Process-based algorithms have been widely used to estimate global terrestrial ET, yet each ET individual algorithm has exhibited large uncertainties. In this study, the support vector machine (SVM) method was introduced to improve global terrestrial ET estimation by integrating three process-based ET algorithms: MOD16, PT-JPL and SEMI-PM. At 200 FLUXNET flux tower sites, we evaluated the performance of the SVM method and others, including the Bayesian model averaging (BMA) method and the general regression neural networks (GRNNs) method together with three process-based ET algorithms. We found that the SVM method was superior to all other methods we evaluated. The validation results showed that compared with the individual algorithms, the SVM method driven by tower-specific (Modern Era Retrospective Analysis for Research and Applications, MERRA) meteorological data reduced the root mean square error (RMSE) by approximately 0.20 (0.15) mm/day for most forest sites and 0.30 (0.20) mm/day for most crop and grass sites and improved the squared correlation coefficient (R2 ) by approximately 0.10 (0.08) (95% confidence) for most flux tower sites. The water balance of basins and the global terrestrial ET calculation analysis also demonstrated that the regional and global estimates of the SVM-merged ET were reliable. The SVM method provides a powerful tool for improving global ET estimation to characterize the long-term spatiotemporal variations of the global terrestrial water budget.

      PubDate: 2017-05-08T08:21:17Z
      DOI: 10.1016/j.agrformet.2017.04.011
      Issue No: Vol. 242 (2017)
  • Experimental validation of footprint models for eddy covariance CO2 flux
           measurements above grassland by means of natural and artificial tracers
    • Authors: Nicola Arriga; Üllar Rannik; Marc Aubinet; Arnaud Carrara; Timo Vesala; Dario Papale
      Pages: 75 - 84
      Abstract: Publication date: 15 August 2017
      Source:Agricultural and Forest Meteorology, Volume 242
      Author(s): Nicola Arriga, Üllar Rannik, Marc Aubinet, Arnaud Carrara, Timo Vesala, Dario Papale
      Footprint models, which simulate source area for scalar fluxes, are fundamental tools for a correct interpretation of micromoeteorological flux measurements and ecosystem exchange inferred from such data. Over the last two decades models of varying complexity have been developed, but all of them suffer from a significant lack of experimental validation. In this study two different experimental tests have been conducted with the aim of offering validation: a manipulation of the vegetation cover and an artificial tracer emission. In the first case the extension of the flux source has been changed progressively by successive cuts of vegetation, while in the second case by varying the distance of a tracer emission line respect to the measurement point. Results have been used to validate two analytical and a numerical footprint models. The experimental data show a good agreement with footprint models and indicate a limited extension of the flux source area, with approximately 75% of the sources confined within a range of 10–20 times the effective measurement height, i.e. the measurement height above the zero plane displacement. Another interesting result was the strong dependence on the surface roughness of both experimental estimates and numerical simulations of footprint. The effect of surface roughness on experimental results and models outputs was comparable to the effect of atmospheric stability. This indicates that surface roughness and turbulence conditions may play a significant role in source area location, in particular above inhomogeneous surfaces with change in roughness, as in the case of the manipulation experiment. Consequently a careful site specific quantification of these parameters seems to be fundamental to obtain realistic footprint estimates and significantly improve eddy covariance flux interpretation at complex sites.

      PubDate: 2017-05-08T08:21:17Z
      DOI: 10.1016/j.agrformet.2017.04.006
      Issue No: Vol. 242 (2017)
  • Storms, temperature maxima and the Eurasian spruce bark beetle Ips
           typographus—An infernal trio in Norway spruce forests of the Central
           European High Tatra Mountains
    • Authors: Pavel Mezei; Rastislav Jakuš; Josef Pennerstorfer; Mária Havašová; Jaroslav Škvarenina; Ján Ferenčík; Ján Slivinský; Svetlana Bičárová; Dušan Bilčík; Miroslav Blaženec; Sigrid Netherer
      Pages: 85 - 95
      Abstract: Publication date: 15 August 2017
      Source:Agricultural and Forest Meteorology, Volume 242
      Author(s): Pavel Mezei, Rastislav Jakuš, Josef Pennerstorfer, Mária Havašová, Jaroslav Škvarenina, Ján Ferenčík, Ján Slivinský, Svetlana Bičárová, Dušan Bilčík, Miroslav Blaženec, Sigrid Netherer
      Norway spruce forests (Picea abies Karst.) of the Carpathian High Tatra Mountains have been subject to unprecedented tree mortality caused by attacks of the Eurasian spruce bark beetle (Ips typographus L.) in recent decades. The outbreaks were preceded and accompanied by wind throw events and periods of increased seasonal temperature. We obtained climatic data and data on tree mortality due to storm throw and bark beetles by using a combination of direct dead tree inventory and remote sensing techniques, and examined annual tree loss change over a 26-year period in a forest district of the Slovak High Tatra National Park. In particular, we found that the combination of the previous year’s maximum daily temperature sum, tree mortality caused by wind, and bark beetle-caused tree mortality best explained the annual tree loss change in nonlinear regression models. The number of trees infested by bark beetles clearly increased with maximum air temperature sums ranging from 2850 to 3150° days, but declined below or above this thermal optimum. Annual tree mortality clearly increased subsequent to years associated with seasonal temperature sums allowing for the development of sister broods. Given consistently favourable future climatic conditions for development of I. typographus populations in the study area, a possible shift from the now predominantly uni-voltine to multi-voltine bark beetle populations might increase attack pressure also at high elevation sites.

      PubDate: 2017-05-08T08:21:17Z
      DOI: 10.1016/j.agrformet.2017.04.004
      Issue No: Vol. 242 (2017)
  • Seasonal patterns of bole water content in old growth Douglas-fir
           (Pseudotsuga menziesii (Mirb.) Franco)
    • Authors: Peter A. Beedlow; Ronald S. Waschmann; E. Henry Lee; David T. Tingey
      Pages: 109 - 119
      Abstract: Publication date: 15 August 2017
      Source:Agricultural and Forest Meteorology, Volume 242
      Author(s): Peter A. Beedlow, Ronald S. Waschmann, E. Henry Lee, David T. Tingey
      Large conifer trees in the North American Pacific Northwest (PNW) use stored water to extend photosynthesis, both diurnally and seasonally. This is particularly important during the summer drought, which is characteristic of the region. In the PNW, climate change is predicted to result in hotter, drier summers and warmer, wetter winters with decreased snowpack by mid-century. Understanding seasonal bole water dynamics in relation to climate factors will enhance our ability to determine the vulnerability of forests to climate change. Seasonal patterns of bole water content in old-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees were studied in the Cascade Mountains of western Oregon, USA. Relative water content (RWC) was monitored hourly in three 400+ and three ∼150 years-old trees using permanently mounted dielectric devices for 10 years. RWC increased during the late spring and early summer to maximum levels in August then decreased into fall and remained low over winter. The difference between minimum RWC in the winter and maximum in mid-summer averaged 4.5 and 2.3% for the older and younger trees, respectively, across all years. RWC closely followed growth and was positively correlated with air and soil temperature, vapor pressure deficit and photosynthetically active radiation, but lagged plant available soil water. The progressive decrease in RWC seen each year from mid-summer through fall was attributed to net daily loss of water during the summer drought. The marked increase in RWC observed from spring to mid-summer each year was hypothesized to be the period of embolism repair and water recharge in elastic tissues. We conclude that bole water content is an integral part of tree water dynamics enabling trees to extend carbon assimilation into drought periods and during periods when cold soil inhibits water uptake by roots, an adaptation that could benefit the survival of large PNW trees under climate change.

      PubDate: 2017-05-18T01:50:12Z
      DOI: 10.1016/j.agrformet.2017.04.017
      Issue No: Vol. 242 (2017)
  • Aboveground net primary productivity and carbon balance remain stable
           under extreme precipitation events in a semiarid steppe ecosystem
    • Authors: Y.B. Hao; C.T. Zhou; W.J. Liu; L.F. Li; X.M. Kang; L.L. Jiang; X.Y. Cui; Y.F. Wang; X.Q. Zhou; C.Y. Xu
      Pages: 1 - 9
      Abstract: Publication date: 15 June 2017
      Source:Agricultural and Forest Meteorology, Volumes 240–241
      Author(s): Y.B. Hao, C.T. Zhou, W.J. Liu, L.F. Li, X.M. Kang, L.L. Jiang, X.Y. Cui, Y.F. Wang, X.Q. Zhou, C.Y. Xu
      Global climate change is projected to increase both the intensity and frequency of extreme precipitation events (EPEs), which are considered to have stronger impacts on ecosystem functions than gradual changes in mean precipitation conditions. In this study, a consecutive 20-day extreme precipitation event (282mm) was applied during the mid- and late-growing season periods in a semiarid steppe for three years to investigate the effects of extreme large precipitation events on aboveground net primary productivity (ANPP) and ecosystem carbon dioxide (CO2) fluxes, including net ecosystem carbon absorption (NEE), gross primary productivity (GPP) and ecosystem respiration (Re). Although soil moisture was significantly increased by extreme precipitation, and even exceeded field capacity during the treatment periods, ANPP remained stable across all the treatments. There was also little change in mean growing season ecosystem CO2 fluxes under the two precipitation treatments, despite GPP rates decreased by 34.4 and 26.3%, and NEE rates were suppressed by 77 and 68% during the mid- and late-season treatment periods, respectively. The stable CO2 fluxes could be attributed to the recovery of GPP and NEE in 7 and 12 days after the end of EPEs. Our study demonstrated that both ANPP and CO2 fluxes in this semiarid steppe were very stable in the face of extreme large precipitation events, regardless of the timing of events occur. Nevertheless, future, long-term studies need to investigate the potential tipping points or thresholds for ecosystem function shifts, as an increasing occurrence of EPEs has been forecasted in future climate change scenarios.

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

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

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

      PubDate: 2017-04-12T13:25:08Z
      DOI: 10.1016/j.agrformet.2017.03.019
      Issue No: Vol. 240-241 (2017)
  • Assessing the environmental controls on Scots pine transpiration and the
           implications for water partitioning in a boreal headwater catchment
    • Authors: Hailong Wang; Doerthe Tetzlaff; Jonathan J. Dick; Chris Soulsby
      Pages: 58 - 66
      Abstract: Publication date: 15 June 2017
      Source:Agricultural and Forest Meteorology, Volumes 240–241
      Author(s): Hailong Wang, Doerthe Tetzlaff, Jonathan J. Dick, Chris Soulsby
      Climate change projections indicate reduced summer precipitation and increased air temperature for the northern high latitudes. These climate changes are likely to alter forest water budgets of which plant transpiration (T) forms a significant component. Plant transpiration is regulated by stomata behavior of particular species, which is constrained by ambient air and soil conditions. Here, we measured sap flow in a Scots pine (Pinus Sylvestris) plantation in a low energy Scottish headwater catchment during the main summer growth period. Effects of rainfall on forest transpiration, as well as the response of T to four environmental variables were investigated at a daily scale. In this boreal environment, transpiration was mainly restricted by radiation and vapor pressure deficit. Air temperature was the least important controlling factor. Soil water became an important factor when rainfall was limited. Frequent but small rain events dictated that precipitation met short-term transpiration demand most of the time. The trees needed supplementary water from antecedent soil water stores when weekly rainfall was below ∼8mm, but such periods were rare. Water exchange mainly occurred in the canopy or upper 10cm of the soil, with 47% of rainfall transpired, 45% intercepted and <8% evaporated from the soil surface. Understanding interactions between forests and their hydroclimate, as well as the role of forests in water partitioning is crucial to assist a sustainable land and water management in a changing climate. Whilst such studies are common in semi-arid regions, they are limited in boreal zones, therefore, our findings are a valuable contribution to understanding plant-water relations in a changing environment.

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

      PubDate: 2017-04-12T13:25:08Z
      DOI: 10.1016/j.agrformet.2017.03.021
      Issue No: Vol. 240-241 (2017)
  • 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
  • Inside Front Cover - Editorial Board Page/Cover image legend if applicable
    • Abstract: Publication date: 15 August 2017
      Source:Agricultural and Forest Meteorology, Volume 242

      PubDate: 2017-06-11T22:21:41Z
  • Inter-annual variability of net and gross ecosystem carbon fluxes: A
    • Authors: Dennis Baldocchi; Housen Chu; Markus Reichstein
      Abstract: Publication date: Available online 7 June 2017
      Source:Agricultural and Forest Meteorology
      Author(s): Dennis Baldocchi, Housen Chu, Markus Reichstein
      As the lifetime of regional flux networks approach twenty years, there is a growing number of papers that have published long term records (5 years or more) of net carbon fluxes between ecosystems and the atmosphere. Unanswered questions from this body of work are: 1) how variable are carbon fluxes on a year to year basis?; 2) what are the biophysical factors that may cause interannual variability and/or temporal trends in carbon fluxes?; and 3) how does the biophysical control on this carbon flux variability differ by climate and ecological spaces? To address these questions, we surveyed published data from 59 sites that reported on five or more years of continuous measurements, yielding 544 site-years of data. We found that the standard deviation of the interannual variability in net ecosystem carbon exchange (162gCm−2 y−1) is large relative to its population mean (−200gCm−2 y−1). Broad-leaved evergreen forests and crops experienced the greatest absolute variability in interannual net carbon exchange (greater than ±300gCm−2 y−1) and boreal evergreen forests and maritime wetlands were among the least variable (less than  ±40 gCm−2 y−1). A disproportionate fraction of the yearly variability in net ecosystem exchange was associated with biophysical factors that modulated ecosystem photosynthesis rather than ecosystem respiration. Yet, there was appreciable and statistically significant covariance between ecosystem photosynthesis and respiration. Consequently, biophysical conditions that conspired to increase ecosystem photosynthesis to from one year to the next were associated with an increase in ecosystem respiration, and vice versa; on average, the year to year change in respiration was 40% as large as the year to year change in photosynthesis. The analysis also identified sets of ecosystems that are on the verge of switching from being carbon sinks to carbon sources. These include sites in the Arctic tundra, the evergreen forests in the Pacific northwest and some grasslands, where year to year changes in respiration are outpacing those in photosynthesis. While a select set of climatic and ecological factors (e.g. light, rainfall, temperature, phenology) played direct and indirect roles on this variability, their impact differed conditionally, as well as by climate and ecological spaces. For example, rainfall had both positive and negative effects. Deficient rainfall caused a physiological decline in photosynthesis in temperate and semi-arid regions. Too much rain, in the humid tropics, limited photosynthesis by limiting light. In peatlands and tundra, excess precipitation limited ecosystem respiration when it raised the water table to the surface. For deciduous forests, warmer temperatures lengthened the growing season, increasing photosynthesis, but this effect also increased soil respiration. Finally, statistical analysis was performed to evaluate the detection limit of trends; we computed the confidence intervals of trends in multi-year carbon fluxes that need to be resolved to conclude whether the differences are to be attributed to randomness or biophysical forcings. Future studies and reports on interannual variations need to consider the role of the duration of the time series on random errors when quantifying potential trends and extreme events.

      PubDate: 2017-06-11T22:21:41Z
      DOI: 10.1016/j.agrformet.2017.05.015
  • 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
  • Long-term UV dosimeter based on polyvinyl chloride for plant damage
           effective UV exposure measurements
    • Authors: Alfio Parisi; Abdurazaq Amar Damien Igoe
      Abstract: Publication date: 15 September 2017
      Source:Agricultural and Forest Meteorology, Volume 243
      Author(s): Alfio V. Parisi, Abdurazaq Amar, Damien P. Igoe
      Research on the influence of ultraviolet radiation (UV) on terrestrial plants and on its link with other influencing environmental factors requires information on UV exposures, both for a horizontal plane and specific portions of a plant, above and under the canopy. In this research, one set of UV dosimeters based on unstabilized polyvinyl chloride (PVC) were employed to measure the unweighted UVB (UVB) and the biologically effective UV radiation for plant damage (UVBEplant) incident on the leaves of a plant for a month, without having to change the dosimeters. The exposures were compared to the cumulative exposure concurrently measured with six sets of unstabilized polyphenylene oxide (PPO) dosimeters that required changing every four to six days. The difference in exposures between the two types of dosimeters was on average within 11%. The PVC dosimeter is the first reported polymer film dosimeter with a useable range of a month for measuring the plant damaging UV and the UVB exposures to specific parts of a plant. The exposure period of a month for the PVC dosimeter is an extension by a factor of four over the useable range of dosimeters previously reported in the literature for evaluation of the exposure of plants to UV radiation.
      Graphical abstract image

      PubDate: 2017-05-28T07:49:17Z
  • Inside Front Cover - Editorial Board Page/Cover image legend if applicable
    • Abstract: Publication date: 15 June 2017
      Source:Agricultural and Forest Meteorology, Volumes 240–241

      PubDate: 2017-05-28T07:49:17Z
  • Improved parameterization of the commonly used exponential equation for
           calculating soil-atmosphere exchange fluxes from closed-chamber
    • Authors: Antje Moffat; Christian
      Abstract: Publication date: 15 June 2017
      Source:Agricultural and Forest Meteorology, Volumes 240–241
      Author(s): Antje M. Moffat, Christian Brümmer
      The concentration change in a closed chamber derived from Fick’s law for a steady flux leads to a differential equation which describes an exponential curve of limited growth. Here we introduce and compare an alternative parameterization with those commonly used in the chamber flux community when investigating soil-atmosphere exchange of N2O, CH4, or CO2 using classical gas chromatography systems, infrared gas analyzers, or novel laser absorption spectrometers. This new parameterization has the advantages that the parameters are mathematically less dependent leading to a more stable regression and that all parameters are physically meaningful with one of them being the main quantity of interest, i.e. the initial flux at chamber closure.

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

      PubDate: 2017-04-12T13:25:08Z
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