Do artificial and natural defoliation have similar effects on physiology of Eucalyptus globulus Labill. seedlings?

Abstract

Abstract• Artificial defoliation is often used to simulate defoliation by herbivory and is usually considered a good indication of a plant's response to a given type of damage. However, the findings of studies directly comparing the two defoliation types are inconsistent.• Here, the short term effects of artificial and insect defoliation by larvae of Paropsisterna agricola on growth, biomass allocation and photosynthetic capacity of Eucalyptus globulus seedlings were compared in a glasshouse experiment. The artificial defoliation was carried out to closely resemble the spatial patterns observed for insect defoliation.• Height and diameter increments were reduced as a result of insect defoliation, whereas artificial defoliation had no significant effect on height. Increased photosynthetic capacity was observed in response to both treatments, but the magnitude of this increase was larger in insect-than in artificially-defoliated seedlings. Significant reductions in foliar carbohydrate content and total biomass were noticeable in artificially-defoliated seedlings. Although the foliar carbohydrate levels also decreased across the crown zones following insect defoliation treatment, seedlings allocated a large amount of their biomass in the branches of the damaged zone.• Despite our best endeavours to simulate insect defoliation in the artificial treatment, the latter may not reflect accurately the full strength of the effects. However, artificial and insect defoliation were similar in their direction of the responses they caused in E. globulus seedlings. Mots-clés :Paropsisterna agricola / croissance / allocation de la biomasse / capacité de la photosynthèse / glucides Résumé -Les défoliations artificielle et naturelle ont-elles des effets similaires sur la physiologie de jeune plants d'Eucalyptus globulus Labill. ?• La défoliation artificielle est couramment employée pour simuler la défoliation par les insectes herbivores et elle est généralement considérée comme un bon indicateur de la réponse des plantes pour un type de dommage donné. Cependant, les résultats d'études comparant directement les deux types de défoliation sont inconsistants.• Ici, les effets court terme des défoliations artificielles et naturelles par la larve de Paropsisterna agricola ont été comparés au plan de la croissance, de l'allocation de la biomasse et de la capacité de photosynthèse dans une expérimentation conduite en serre. La défoliation artificielle a été menée pour ressembler étroitement aux modèles spatiaux observés avec la défoliation par les insectes.• À la suite de la défoliation par les insectes, les accroissements en hauteur et en diamètre ont été ré-duits, alors que la défoliation artificielle n'a eu aucun effet significatif sur la hauteur. L'augmentation de la capacité de photosynthèse a été observée en réponses aux deux traitements, mais l'ampleur de cette augmentation a été plus forte pour les plants défoliés par les insectes que pour les plants artificiellement défoliés. Des réductions significatives de la teneur foliaire en...

Effects of partial defoliation on closed canopy Eucalyptus globulus Labilladière: Growth, biomass allocation and carbohydrates

“…The study carried out was designed to fit within these constraints and as a consequence limited the number of trees. Overall, four-year-old E. globulus were able to compensate for the partial defoliation in a similar way as younger E. globulus (Eyles et al, 2009;Quentin et al, 2010). Our results also suggest that the full impact of 45% leaf area removal on growth and resource allocation had been fully tolerated after 11 months recovery time, likely via activation of a number of physiological compensatory mechanisms which include: increase photosynthetic rate, improvement of tree's water relation and utilisation of carbon assimilates.…”

“…While artificial defoliation studies do not accurately mimic what occurs in the real world (e.g. Quentin et al, 2010), they can provide a sounder basis for understanding the effects of insect defoliation that can then be used to develop management strategies. We established a field experiment to examine the morphological and eco-physiological effects of artificial defoliation (45% leaf removal) on the growth and biomass allocation in 4-year-old, closed canopy stand of E. globulus trees.…”

Sex-specific responses of Populus deltoides to defoliation

“…Douglas fir under defoliation treatments had the significant decreases in height and diameter growth [37], while artificial defoliation of Eucalyptus globulus only negatively affected the diameter growth [38]. Our results showed that there were significant differences in height growth of P. deltoides males and females when exposed to defoliation.…”

ESTUDIOS SOBRE EL COMPORTAMIENTO DE FORRAJEO DE Acromyrmex lundi Guering (HYMENOPTERA, FORMICIDAE) Y SU EFECTO SOBRE EL CRECIMIENTO DE PROCEDENCIAS DE Eucalyptus globulus Labill. (Myrtaceae)

“…Sin embargo, Collett y Neumann (2002) efectuaron artificialmente distintos niveles de defoliación, encontrando que sólo el 100% redujo significativamente la altura y el diámetro basal del tallo de plantas de E. globulus durante la implantación, mientras que la defolición parcial no influyó sobre el crecimiento e incluso la remoción de las hojas inferiores favoreció el aumento de altura.En este trabajo la defoliación observada nunca alcanzó el 100% de las hojas (datos no presentados) y, sin embargo, las plantas con herbivoría redujeron, con respecto a las plantas control, en promedio un 10,3 % y un 26,5 % el diámetro final y el crecimiento en altura, respectivamente. Esto podría explicarse a través de las observaciones realizadas por Quentin et al (2010), quienes encontraron que la defoliación producidapor insectos en plantines de E. globulusde similar edad que los utilizados en este ensayo, redujo significativamente su altura y diámetro, mientras que la artificial sólo afectó el diámetro, concluyendo que las defoliaciones simuladas podrían subestimar el efecto de la herbivoría.…”

“…El distinto comportamiento de las plantas frente a la herbivoría podría ser una característica asociada al genotipo de cada procedencia. Se ha observado que las plantas de E. globulus sometidas a defoliación natural y artificial, aumentan la capacidad fotosintética del follaje remanente y modifican la partición de los asimilados (PIKARD et al, 2007;QUENTIN et al, 2010). Como en este trabajo todos los brotes axilares fueron removidos en cada observación, el principal órgano destino de los fotoasimilados fue el brote apical, cuyo desarrollo favorece el crecimiento en altura y la emisión de nuevas hojas, aumentando el área foliar.…”