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Quantifying stem growth loss at the tree-level in a Pinus radiata plantation to repeated attack by the aphid, Essigella californica


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Eyles, A, Robinson, AL, Smith, D, Carnegie, AJ and Smith, I 2010 , 'Quantifying stem growth loss at the tree-level in a Pinus radiata plantation to repeated attack by the aphid, Essigella californica' , Forest Ecology and Management, vol. 261 , pp. 120-127 , doi: 10.1016/j.foreco.2010.09.039.

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Since its detection in 1998, the exotic aphid pest, Essigella californica Essig (Hemiptera: Aphididae) has
caused extensive defoliation in commercial Pinus radiata plantations throughout Australia. A total of
one hundred and twenty plots encompassing thirty tree ages, and three thinning treatments were established
in September 2006 in southernNewSouth Wales, Australia to assess crown health and tree growth.
Assessments were carried out annually during 2006–2009 to quantify the relationship between natural
aphid-induced defoliation and growth loss at the individual tree level. Over the course of the four years,
particularly in 2006, trees were subjected to moisture stress, as indicated by average annual rainfalls
that were below the long-term average. In general, the diameter growth of individual trees appeared
unaffected by crown damage severity across most tree ages, indicating that the productivity in Green
Hills was limited by the interactive effects of climatic and biotic stressors (both cause premature loss
of foliage). Furthermore, the results from this four-year experiment demonstrated that both moisture
stress and aphid-induced defoliation constrained the growth response to thinning. However, thinning
may have assisted damaged trees to maintain growth rates similar to trees with little or no damage.
Understanding the impact of disturbances such as insect pest outbreaks on growth yield models is critical
for optimal modelling of long-term plantation growth and management. Our results highlight the
difficulty in quantifying the effect of aphid-induced defoliation when combined with chronic moisture

Item Type: Article
Authors/Creators:Eyles, A and Robinson, AL and Smith, D and Carnegie, AJ and Smith, I
Keywords: Defoliation Crown health Radiata pine Moisture stress Insect pest
Journal or Publication Title: Forest Ecology and Management
DOI / ID Number: 10.1016/j.foreco.2010.09.039
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