Growth of plantation eucalypts responds strongly to applied nitrogen (N). Above-ground biomass accumulation, gas exchange and foliar N per unit leaf area (Narea) along vertical and lateral gradients within a canopy were assessed in Eucalyptus nitens (Deane & Maiden) Maiden cuttings in a glasshouse experiment ( E. nitens glasshouse cuttings) and E. globulus Labill. saplings in a field trial ( E. globulus field saplings) under varying levels of applied N. A large range of maximum net photosynthesis ( A max) and Narea was observed among different leaf-age classes (apical, expanding, mature and old) within vertical and lateral gradients in both E. nitens glasshouse cuttings and E. globulus field saplings. In both experiments, Narea was generally positively correlated with levels of applied N but A max was not. There was generally no relationship between A max and Narea in either E. nitens glasshouse cuttings or E. globulus field saplings, except in expanding and mature leaves within the vertical gradient of E. nitens glasshouse cuttings. These results contribute to the emerging consensus among workers that within species, poor correlation between A max and Narea is often observed. Biomass data indicate that increased N application significantly increased growth in both experiments. Overall, the results of these experiments provide information that will further resolve the predictive strength of process-based models that describe growth of E. nitens and E. globulus in plantations.
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Close et al. (2004) studied this question.