Height growth and site index models for trembling aspen (Populus tremuloides Michx) in northern British Columbia

To develop anamorphic height growth and site index models for trembling aspen (Populus tremuloides Michx.) stands in British Columbia, a total of 33 naturally established, fire-originated, unmanaged, and even-aged stands were located in the Boreal White and Black Spruce zone. The breast-height ages of dominant trees in these stands were older than 50 years. The height growth models developed from conditioned logistic, Chapman-Richards', and conditioned Chapman-Richards' functions were unbiased and provided an equally good fit. Similarly, the site index models constructed by conditioned logistic and Chapman-Richards' functions were unbiased and provided a similar fit, however, the precision of these models for predicting site index from young stands was low. The height growth models developed from aspen stands in Alberta and Ontario were significantly biased in estimating the aspen height growth in British Columbia, which may imply that the height growth pattern of aspen varies with climate. This finding suggest a low portability of height growth models between climatically different regions. (C) 1998 Elsevier Science B.V.