Growth and photosynthetic responses following defoliation and bud removal in eucalypts



Growth and photosynthetic responses following defoliation and bud removal in eucalypts


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 pot-grown 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 above-ground, 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. (C) 2013 Elsevier B.V. All rights reserved.


K.M. Barry, E.A. Pinkard



Forest Ecology And Management