Specific leaf weight as an indicator of juvenile leaf toughness in Tasmanian bluegum (Eucalyptus globulusssp.globulus): implications for insect defoliation

Summary The influence of watering regime, provenance and leaf-age were studied in relation to specific leaf weight (abbreviated SLW; inversely correlated with percentage leaf water) of juvenile leaves of Eucalyptus globulus subspecies globulus. SLW provides a physiological estimate of leaf “toughness” relevant to studies of insect herbivory. Leaves from saplings given continuous access to water had lower SLWs and higher water contents than leaves from saplings that were drip irrigated. Saplings of the King Island provenance produced leaves of consistently lower SLW compared with leaves from saplings of the Geeveston provenance irrespective of watering regime. Furthermore, leaves from the King Island provenance saplings exhibited less variation with respect to water content than leaves from the Geeveston saplings irrespective of watering regime. Generally, new leaves exhibited lower SLWs and higher water contents than old leaves irrespective of watering regime or provenance. The importance of leaf “toughness” (as indicated by SLW) to insect herbivory, and therefore its relevance to plantation managers, is discussed.