Canadian Forest Service Publications

Models of the Vertical Distribution of Sapwood Area for Lodgepole Pine and Western Hemlock in Western Canada. 2015. Cruickshank, M.G.; Cameron, I.R.; Groot, A.; Stewart, J.D.; Goudie, J.W. For. Sci. 61(6):973–987.

Year: 2015

Available from: Pacific Forestry Centre

Catalog ID: 36511

Language: English

CFS Availability: PDF (download)

Available from the Journal's Web site.
DOI: 10.5849/forsci.14-206

† This site may require a fee.

Abstract

Mixed-effects models described sapwood area distribution along stems of 60 lodgepole pine and 124 western hemlock trees. The Gallant-Fuller (GF) segmented polynomial model for stem taper equations comprising three joined polynomial segments and a functional components (FC) model derived from pipe model theory containing three additive components were compared. A fixed-effects model was constructed, and then random tree effects were added. Random-effect variability was highest at the tree base for both models and species. Random variation was regressed against tree-level measurements to identify additional fixed-effects crown or height variables. All models fit well, but root mean square error was lower for pine than for hemlock and lower for the FC than the GF final fixed-effects model. Sapwood area conformed to pipe model theory assuming variable stem permeability that was associated with tree crown and total height. Pine validation data from four Alberta and two British Columbia sites showed that the FC model underpredicted (9%) and the GF model overpredicted (7%) sapwood area, mainly in the lower stem. Reasonable predictions of sapwood area could be derived from ground-based or remote sensing methods, allowing classification of sites, trees, and logs based on this wood quality characteristic.

Plain Language Summary

The differing characteristics of sapwood and heartwood affect the processing and value of forest products that are desirable to predict before harvesting. Sapwood area distribution along stems of 60 lodgepole pine and 124 western hemlock trees was described by regression models. Two models, one modified from tree stem taper equations (GF), and one a functional components model (FC) derived from pipe model theory, each containing three segments, were used to describe the sapwood. Sapwood could be predicted using tree height and crown width and length and distance along the stem. Unexplained variability was highest at the tree base for both models and species. All models fit well, but error was lower for pine than hemlock, and lower for the FC than GF final model. Sapwood area conformed to pipe model theory assuming variable stem permeability that was associated with tree crown and total height. To validate the models, geographically separate new data sets from four Alberta and two British Columbia sites were input into both models that showed the FC model underpredicted (9%) and the GF model overpredicted (7%) sapwood area mainly in the lower stem. Reasonable predictions of sapwood area along stems could be derived from ground-based or remote sensing methods capturing tree and crown data, and allowing prediction of sites, trees, and logs based on the wood quality characteristic sapwood.

Date modified: