© 2005 Heron Publishing—Victoria, Canada
Photosynthetic capacity and foliar nitrogen distribution in Eucalyptus nitens is altered by high-intensity thinning
Jane L. Medhurst (1, 2) and Christopher L. Beadle (1, 3, 4)
1. Cooperative Research Centre for Sustainable Production Forestry, Private Bag 12, Hobart, Tasmania 7001, Australia / 2. School of Plant Science, University of Tasmania, GPO Box 252-55, Hobart, Tasmania 7001, Australia / 3. CSIRO Division of Forestry and Forest Products, Private Bag 12, Hobart, Tasmania 7001, Australia / Received May 5, 2004; accepted December 17, 2004; published online June 1, 2005
Summary
The changes in photosynthetic rates, light environment and foliar nutrient concentrations following thinning were examined
in an 8-year-old Eucalyptus nitens (Deane and Maiden) Maiden plantation. The objectives of the study were to: (1) determine the extent to which maximum photosynthetic
rates (Amax) of E. nitens are affected by stand thinning; (2) relate the spatial pattern of Amax within the crown to the changes in light environment caused by thinning; and (3) establish if the responses of Amax to thinning are driven by changes in area-based foliar nitrogen (Na) or phosphorus (Pa) concentrations.
Photosynthetic rates measured under saturating light availability increased throughout the crown after thinning. The greatest
increases were observed in the lower and middle crown zones. Photosynthetic rate was positively related to foliar N concentration.
Thinning increased Na and Pa because of a significant decrease in specific leaf area (SLA) after thinning. Changes in photosynthetic rates, SLA and foliar
nutrient distributions with thinning were well correlated with changes in incident solar irradiance throughout the tree crown.
Keywords:
foliar phosphorus, light attenuation, light-saturated photosynthetic rate, specific leaf area.
