Sammendrag
Insect herbivory is known to augment emissions of biogenic volatile organic compounds
(BVOCs). Yet few studies have quantified BVOC responses to insect herbivory in
natural populations in pan-Arctic regions. Here, we assess how quantitative and
qualitative BVOC emissions change with increasing herbivore feeding intensity in the
Subarctic mountain birch (Betula pubescens var pumila (L.)) forest. We conducted
three field experiments in which we manipulated the larval density of geometrid
moths (Operophtera brumata and Epirrita autumnata), on branches of mountain
birch and measured BVOC emissions using the branch enclosure method and gas
chromatography-mass spectrometry. Our study showed that herbivory significantly
increased BVOC emissions from the branches damaged by larvae. BVOC emissions
increased due to insect herbivory at relatively low larvae densities, causing up to 10%
of leaf area loss. Insect herbivory also changed the blend composition of BVOCs,
with damaged plants producing less intercorrelated BVOC blends than undamaged
ones. Our results provide a quantitative understanding of the relationship between
the severity of insect herbivore damage and emissions of BVOCs at larvae densities
corresponding to background herbivory levels in the Subarctic mountain birch. The
results have important and practical implications for modeling induced and constitutive
BVOC emissions and their feedbacks to atmospheric chemistry.
arctic, biotic stress, geometrid moth, insect herbivory, mountain birch, stress severity, volatile organic
compounds
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