Abstract
Climate change poses major challenges to forest plantations by reducing wood biomass productivity, mainly through reduced water availability. This study compared aboveground biomass production and nutrient use efficiency of Corymbia and Eucalyptus species cultivated under contrasting water-deficit conditions. Differences in water availability strongly influenced biomass production, particularly in fast-growing species such as Corymbia henryi (CH) and Eucalyptus urophylla (UR). Eucalyptus longirostrata (EL) and Eucalyptus major (MJ) showed smaller declines in biomass under high water-deficit but had lower overall productivity, a pattern consistent with a drought-tolerant, slow-growing strategy. Biomass production was higher under low water-deficit, accompanied by greater nutrient stocks in the trees and higher nutrient use efficiency. Under high water-deficit, nutrient stocks in the trees were reduced and tended to converge among fast-growing species, suggesting similar constraints on nutrient uptake under water stress. In addition, UR and CH showed increased bark allocation under high water-deficit. Species from the spotted gum group (Corymbia citriodora subsp. citriodora, C. citriodora subsp. variegata, and C. henryi) maintained greater leaf allocation, possibly reflecting adaptive responses to water limitation. Most species also exhibited higher potassium (K) and boron (B) concentrations in stem wood under water-stress conditions. The ability of Corymbia species to maintain leaf biomass and relatively high potassium use efficiency highlights their potential for cultivation in regions prone to water-deficit. However, boron use efficiency decreased across all species under water-deficit conditions. These findings indicate that nutrient uptake strategies differ among species and support the development of site- and species-specific fertilization guidelines to sustain productivity under increasing water-deficit conditions.