Retranslocation of foliar nutrients in evergreen tree species planted in a Mediterranean environment
D. N. Fife (1), E. K. S. Nambiar (2, 3) and E. Saur (4)
1. Ensis, CSIRO Plantation Forest Research Centre, P.O. Box 946, Mount Gambier, SA 5290, Australia / 2. Ensis, CSIRO Forestry and Forest Products, P.O. Box E4008, Kingston, ACT 2604, Australia / 3. Corresponding author () / 4. École Nationale d’Ingénieurs des Travaux Agricoles de Bordeaux, 1, cours du Général de Gaulle, CS 4021, F. 33175 Grandigan
Cedex, France / Received November 23, 2006; accepted September 3, 2007; published online December 3, 2007
Summary
Internal nutrient recycling through retranslocation (resorption) is important for meeting the nutrient demands of new tissue
production in trees. We conducted a comparative study of nutrient retranslocation from leaves of five tree species from three
genera grown in plantation forests for commercial or environmental purposes in southern Australia—Acacia mearnsii De Wild., Eucalyptus globulus Labill., E. fraxinoides H. Deane & Maiden, E. grandis W. Hill ex Maiden and Pinus radiata D. Don. Significant amounts of nitrogen, phosphorus and potassium were retranslocated during three phases of leaf life. In
the first phase, retranslocation occurred from young leaves beginning 6 months after leaf initiation, even when leaves were
physiologically most active. In the second phase, retranslocation occurred from mature green leaves during their second year,
and in the third phase, retranslocation occurred during senescence before leaf fall. Nutrient retranslocation occurred mainly
in response to new shoot production. The pattern of retranslocation was remarkably similar in the leaves of all study species
(and in the phyllodes of Casuarina glauca Sieber ex Spreng.), despite their diverse genetics, leaf forms and growth rates. There was no net retranslocation of calcium
in any of the species. The amounts of nutrients at the start of each pre-retranslocation phase had a strong positive relationship
with the amounts subsequently retranslocated, and all species fitted a common relationship. The percentage reduction in concentration
or content (retranslocation efficiency) at a particular growth phase is subject to many variables, even within a species,
and is therefore not a meaningful measure of interspecific variation. It is proposed that the pattern of retranslocation and
its governing factors are similar among species in the absence of interspecies competition for growth and crown structure
which occurs in mixed species stands.
