© 1998 Heron Publishing—Victoria, Canada
Net primary production of forests: a constant fraction of gross primary production?
R. H. Waring (1), J. J. Landsberg (2) and M. Williams (3)
1. College of Forestry, Oregon State University, Corvallis, OR 97331-7501, USA (waring@ccmail.orst.edu) / 2. CSIRO Land and Water, Centre for Environmental Mechanics, GPO Box 821, Canberra, ACT 2601, Australia / 3. The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543, USA / Received April 24, 1997
Summary
Considerable progress has been made in our ability to model and measure annual gross primary production (GPP) by terrestrial
vegetation. But challenges remain in estimating maintenance respiration (Rm) and net primary production (NPP). To search for possible common relationships, we assembled annual carbon budgets from six
evergreen and one deciduous forest in Oregon, USA, three pine plantations in New South Wales, Australia, a deciduous forest
in Massachusetts, USA, and a Nothofagus forest on the South Island of New Zealand. At all 12 sites, a standard procedure was followed to estimate annual NPP of foliage,
branches, stems, and roots, the carbon expended in synthesis of these organs (Rg), their Rm, and that of previously produced foliage and sapwood in boles, branches, and large roots. In the survey, total NPP ranged
from 120 to 1660 g C m–2 year–1, whereas the calculated fraction allocated to roots varied from 0.22 to 0.63. Comparative analysis indicated that the total
NPP/GPP ratio was conservative (0.47 ± 0.04 SD). This finding supports the possibility of greatly simplifying forest growth
models. The constancy of the NPP/GPP ratio also provides an incentive to renew efforts to understand the environmental factors
affecting partitioning of NPP above and belowground.
Keywords:
forest growth models, forest productivity, growth respiration, maintenance respiration, NPP/GPP ratio.
