CABALA, a productivity model for temperate plantation eucalypts, accounts for the impact of eucalypt defoliation on growth but does not yet account for differences in damage type. Consideration of both leaf and bud damage may result in a more realistic representation of growth outcomes for sites with different pest ecologies. We tested whether bud, as compared to leaf damage, elicited similar responses in two commercially important eucalypt species. Growth, biomass and physiological responses of young potgrown plants to artificial removal of approximately 40% of leaf area (L treatment) or both leaves and buds (LB treatment) was assessed over a 4 month period of recovery. We identified that responses to defoliation were similar between the two species (Eucalyptus globulus and Eucalyptus nitens). Time series analysis highlighted that growth (height and stem diameter) was significantly reduced by defoliation during the study, which was more pronounced following LB treatment than L alone. At the end of the study, leaf area, stem height and diameter increment were not significantly affected by treatment, but total aboveground, stem biomass and foliar N were. This suggests that changes in patterns of biomass allocation occurred to maintain leaf area and capacity for light interception. Increased photosynthetic rate, which occurred for plants of both defoliation treatments but to a greater extent for the LB than L treatment, also contributed to recovery following defoliation. There was no evidence that photosynthetic rate increase was driven by changes in foliar nitrogen or chlorophyll, as there was not a statistically significant and strong relationship between the two factors. These results give us confidence that the process-based models used to predict the impacts of defoliation on productivity (1) can assume similar responses to defoliation for E. globulus and E. nitens and (2) should account for differences in physiological responses to foliage and bud damage.

Item Type:	Refereed Article
Keywords:	defoliation, photosynthesis, chlorophyll, biomass
Research Division:	Agricultural, Veterinary and Food Sciences
Research Group:	Forestry sciences
Research Field:	Forest health and pathology
Objective Division:	Plant Production and Plant Primary Products
Objective Group:	Forestry
Objective Field:	Hardwood plantations
UTAS Author:	Barry, KM (Associate Professor Kara Barry)
UTAS Author:	Pinkard, E (Dr Elizabeth Pinkard)
ID Code:	78709
Year Published:	2013
Web of Science® Times Cited:	26
Deposited By:	Tasmanian Institute of Agriculture
Deposited On:	2012-07-22
Last Modified:	2014-04-03
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