© 1996 Heron Publishing—Victoria, Canada
Sustainable stemwood yield in relation to the nitrogen balance of forest plantations: a model analysis
Roderick C. Dewar and Ross E. McMurtrie
School of Biological Science, University of New South Wales, Sydney NSW 2052, Australia / Received March 2, 1995
Summary
We used an existing analytical model of stemwood growth in relation to nitrogen supply, which we describe in an accompanying
paper, to examine the long-term effects of harvesting and fire on tree growth. Our analysis takes into account the balance
between nitrogen additions from deposition, fixation, and fertilizer applications, and nitrogen losses from stemwood harvesting,
regeneration burning, leaching and gaseous emissions. Using a plausible set of parameter values for Eucalyptus, we conclude that nitrogen loss through fire is the main factor limiting sustainable yield, defined as the maximum mean annual
stemwood volume increment obtained in the steady state, if management practices are continued indefinitely. The sustainable
yield is 30 m3 ha–1 year–1 with harvesting only, 15 m3 ha–1 year–1 with harvesting and regeneration burning, and 13 m3 ha–1 year–1 with harvesting, fire, leaching and gaseous emissions combined.
Our approach uses a simple graphical analysis that provides a useful framework for examining the factors affecting sustainable
yield. The graphical analysis is also useful for extending the application of the present model to the effects of climate
change on sustainable yield, or for interpreting the behavior of other models of sustainable forest growth.
Keywords:
fire, growth, harvesting, mean annual increment, sustainability.
