Coops, N.C. (corresponding author, email@example.com) & Gaulton, R. (firstname.lastname@example.org): Department of Forest Resource Management, 2424 Main Mall, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4 Waring, R.H. (Richard.Waring@oregonstate.edu): College of Forestry, Oregon State University, Corvallis, OR 97331, USA
Mapping site indices for five Pacific Northwest conifers using a physiologically based model
Article first published online: 28 OCT 2010
© 2010 International Association for Vegetation Science
Applied Vegetation Science
Volume 14, Issue 2, pages 268–276, April 2011
How to Cite
Coops, N. C., Gaulton, R. and Waring, R. H. (2011), Mapping site indices for five Pacific Northwest conifers using a physiologically based model. Applied Vegetation Science, 14: 268–276. doi: 10.1111/j.1654-109X.2010.01109.x
Co-ordinating Editor: Geoffrey Henebry
- Issue published online: 1 MAR 2011
- Article first published online: 28 OCT 2010
- Received 17 March 2010 Accepted 31 August 2010
- 3-PG model;
- British Columbia;
- Forest Productivity;
- Physiological modelling;
- Picea glauca;
- Pinus contorta;
- Pseudotsuga menziesii;
- Thuja plicata;
- Tsuga heterophylla;
Questions: How well can we predict tree growth potential (site index) of five, locally dominant tree species in reference to estimates made with a detailed vegetation classification?
Location: The forested region of the Pacific Northwest, USA and Canada.
Methods: We employed a physiologically based process model (3-PG, Physiological Processes to Predict Growth) to generate estimates of site index under averaged climatic conditions (1971–2000) generated from hundreds of weather stations and extrapolated, with adjustments for topography, across the region at 1-km resolution. The model was parameterized from published information, but we had to assume fixed values of soil water storage capacity at 200 mm and soil fertility at 70% of maximum across the region. Field estimates of site index for the five dominant species were derived from published correlations with detailed mapping of vegetation provided by The British Columbia Ministry of Forests and Range.
Results: The site indices projected with the 3-PG model for the five species combined, when compared with those produced by the Ministry of Forests and Range, produced an r2 averaging ∼0.5 with a standard error of 2.8 m at 50 yr, equivalent to 10% of the mean. Some of the variation may be attributed to inadequate information on soil properties. Importantly, the relationship between the two estimates was not significantly different from a 1:1 line, with an intercept of zero.
Conclusions: The 3-PG modelling approach offers a means of predicting spatial variation in site indices across the Pacific Northwest and provides a basis for predicting future site indices under a changing climate.