Pine growth response to processionary moth defoliation across a 40-year chronosequence

► Pine processionary moth and artificial defoliations caused significant growth losses. ► Radial growth loss was proportional to defoliation intensity and lasted 2years. ► Old and highly defoliated trees were subsequently killed by bark beetles. ► Defoliation also affected carbon and nitrogen conten...

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Published in:Forest ecology and management Vol. 293; pp. 29 - 38
Main Authors: Jacquet, Jean-Sébastien, Bosc, Alexandre, O’Grady, Anthony P., Jactel, Hervé
Format: Journal Article
Language:English
Published: Kidlington Elsevier B.V 01-04-2013
Elsevier
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Summary:► Pine processionary moth and artificial defoliations caused significant growth losses. ► Radial growth loss was proportional to defoliation intensity and lasted 2years. ► Old and highly defoliated trees were subsequently killed by bark beetles. ► Defoliation also affected carbon and nitrogen contents in stem and needles. ► Defoliation is likely to affect stem growth through N and C resources limitation. Estimating the impact of pest insects on forest productivity requires a better understanding of host tree responses. While many studies have focused on juvenile trees, studying the impacts of defoliation on trees of increasing age helps to better characterize underlying mechanisms regulating growth responses to defoliation. During winter 2009–2010 a large outbreak of pine processionary moth occurred in Southwestern France. We established a field experiment to examine the effects of pine processionary moth defoliation varying from 25% to 100% on the growth of Pinus pinaster in stands ranging from 3 to 40years old. Our results showed that pine processionary moth defoliation resulted in significant loss of radial growth for at least two years following defoliation. Stem growth loss in the first and second years was proportional to defoliation intensity and ranged from 32% to 93% in year 1, and from 17% to 68% in year 2. Stem growth was most reduced in older trees. Carbohydrates and nitrogen contents in needles and stem sapwood were also affected by defoliation. Our results suggest that defoliation affects stem growth through nitrogen and carbon resource limitation and that stem growth would be a lower priority sink for resources than other physiological processes in pine trees.
Bibliography:http://dx.doi.org/10.1016/j.foreco.2012.12.003
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ISSN:0378-1127
1872-7042
DOI:10.1016/j.foreco.2012.12.003