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Tree physiological monitoring of the 2018 larch budmoth outbreak: preference for leaf recovery and carbon storage over stem wood formation in Larix decidua.

  • Peters, Richard L1, 2
  • Miranda, Jose Carlos1, 3
  • Schönbeck, Leonie1
  • Nievergelt, Daniel1
  • Fonti, Marina V1, 4
  • Saurer, Matthias1
  • Stritih, Ana5, 6
  • Fonti, Patrick1
  • Wermelinger, Beat7
  • von Arx, Georg1
  • Lehmann, Marco M1
  • 1 Forest Dynamics, Swiss Federal Research Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, Birmensdorf CH-8903, Switzerland. , (Switzerland)
  • 2 Department of Plants and Crops, Faculty of Bioscience Engineering, Laboratory of Plant Ecology, Ghent University, Coupure links 653, Ghent B-9000, Belgium. , (Belgium)
  • 3 Forest Genetics and Ecophysiology Research Group, School of Forestry Engineering, Universidad Politécnica de Madrid, Ciudad Universitaria s/n, Madrid 28040, Spain. , (Spain)
  • 4 Institute of Ecology and Geography, Siberian Federal University, 79 Svobodny pr., Krasnoyarsk 660041, Russia.
  • 5 ETH Zurich, Institute for Landscape and Spatial Development, Planning of Landscape and Urban Systems (PLUS), Stefano-Franscini Platz 5, Zürich 8093, Switzerland. , (Switzerland)
  • 6 WSL Institute for Snow and Avalanche Research SLF, Flüelastrasse 11, Davos Dorf 7260, Switzerland. , (Switzerland)
  • 7 Forest Health and Biotic Interactions, Swiss Federal Research Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, Birmensdorf CH-8903, Switzerland. , (Switzerland)
Published Article
Tree Physiology
Oxford University Press
Publication Date
Dec 05, 2020
DOI: 10.1093/treephys/tpaa087
PMID: 32722795


Insect defoliation impacts forest productivity worldwide, highlighting the relevance of plant-insect interactions. The larch budmoth (Zeiraphera griseana Hübner) is one of the most extensively studied defoliators, where numerous tree ring-based analyses on its host (Larix decidua Mill.) have aided in identifying outbreak dynamics over the past millennia. Yet, outbreaks have been widely absent after the early 1980s, and little is known about the in situ tree physiological responses and the allocation of carbon resources during and after defoliation. In summer 2018, we tracked an ongoing larch budmoth outbreak in a well-studied larch forest in the Swiss Alps. We performed biweekly monitoring on an affected and unaffected site using a unique combination of xylogenesis observations, measurements of non-structural carbohydrates, isotopic analysis of needle assimilates and ground-based and remote-sensed leaf trait observations. The budmoth induced a defoliation that lasted 40 days and could be detected by satellite observations. Soluble sugars significantly decreased in needles and stem phloem of the defoliated trees, while starch levels remained stable in the stem and root xylem compared to the control. Carbon and oxygen isotope ratios in needle assimilates indicated that neither photosynthetic assimilation rates nor stomatal conductance was different between sites before, during and after the outbreak. Defoliated trees ceased cell wall thickening 17 days earlier than unaffected trees, showing the earliest halt of ring formation recorded from 2007 untill 2013 and causing significant thinner cell walls, particularly in the latewood. No significant differences were found for cell enlargement rates and ring width. Our study revealed that an outbreak causes a downregulation of cell wall thickening first, while no starch is mobilized or leaf physiology is adjusted to compensate for the reduced carbon source due to defoliation. Our observations suggest that affected larch trees prioritize leaf recovery and carbon storage over wood biomass development. © The Author(s) 2020. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: [email protected]

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