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Defoliation and nitrogen effects on photosynthesis and growth of Eucalyptus globulus


Pinkard, E and Battaglia, M and Mohammed, CL, Defoliation and nitrogen effects on photosynthesis and growth of Eucalyptus globulus, Tree Physiology, 27, (7) pp. 1053-1063. ISSN 0829-318X (2007) [Refereed Article]

DOI: doi:10.1093/treephys/27.7.1053


Plant responses to defoliation are complex. We established a field experiment in a nine-month-old Eucalyptus globulus Labill. plantation to examine the effects of pattern (upper crown versus lower crown removal), frequency (single, double or triple defoliation within a 12-month period) and severity (25 versus 38% of leaf area removed) of defoliation and the effect of soil nitrogen (N) on photosynthetic processes and stem growth. The photosynthetic responses observed following defoliation could be attributed to changes in source:sink ratios. Light-saturated CO2 uptake (Amax) increased with increasing severity and frequency of defoliation irrespective of defoliation pattern. Seedlings defoliated in autumn did not exhibit increases in A max until the following spring, whereas there was no such delay in photosynthetic responses associated with spring defoliation. Application of N before defoliation allowed trees to compensate for the effect of defoliation on stem diameter growth, which could not be explained simply in terms of increases in Amax. The observed increases in stem diameter increment following N fertilization of defoliated trees suggested increases in leaf area development, and there were changes in the leaf area: leaf dry mass ratio that may have increased light absorption by the crown. Nitrogen fertilization also increased partitioning of dry mass to branches at the expense of main stems, suggesting that N supply was important in rebuilding crowns following a defoliation event. © 2007 Heron Publishing.

Item Details

Item Type:Refereed Article
Research Division:Agricultural, Veterinary and Food Sciences
Research Group:Forestry sciences
Research Field:Forest health and pathology
Objective Division:Plant Production and Plant Primary Products
Objective Group:Other plant production and plant primary products
Objective Field:Other plant production and plant primary products not elsewhere classified
UTAS Author:Pinkard, E (Dr Elizabeth Pinkard)
UTAS Author:Battaglia, M (Dr Michael Battaglia)
UTAS Author:Mohammed, CL (Professor Caroline Mohammed)
ID Code:50782
Year Published:2007
Web of Science® Times Cited:59
Deposited By:Agricultural Science
Deposited On:2007-08-01
Last Modified:2009-11-05

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