Patterns of growth and nutrient accumulation in expanding leaves of Eucalyptus regnans (Myrtaceae)

Abstract

Patterns of leaf growth and nutrient accumulation were investigated in relation to leaf ontogeny in the tree species Eucalyptus regnans F.Muell. Newly emergent leaves were tagged in the field and collected every 14 days for measurement of leaf dimensions and nutrient concentrations over a 113-day period. Patterns of growth in area, length, width and mass of leaves followed sigmoid curves. An exponential rate of growth for all measures was observed up to 56 days after leaf emergence, after which there was little increase. Conversely, specific leaf area (leaf area/leaf mass) decreased from emergence to about Day 56 and then remained relatively constant. Contents of all nutrients (measured on a leaf basis) increased during leaf expansion. Concentrations of N, P and K decreased and Ca concentration increased, but there was no clear trend for Mg concentration with leaf development. In general, the results of the present study verify previously developed ‘idealised curves’ of changes in dry mass and nutrient concentrations with leaf age for eucalypts. Patterns of leaf growth and nutrient accumulation (particularly N) show that leaves had reached full expansion and physiological maturity by ~80–90 days after emergence.