Predicting site index from climatic, edaphic, and stand structural properties for seven plantation-grown conifer species in Quebec

Models were built to relate site index to biophysical variables and stand structure for seven conifer species grown in plantation. Reduced models without stand structure were also derived to allow the prediction of site index even when information on the stand is unavailable. Biophysical variables tested were degree-days, aridity, summer precipitation, vapour pressure deficit, and soil water-holding capacity. The stand structure was accounted for using a Shannon evenness index of diameter at breast height distribution. Both full and reduced models had low to moderate R-2 values and were slightly biased for most of the species. The results indicate that while correlations between phytometric and biophysical site indices are rather weak, those between plantation yield predicted using both indices and volume observed in the field are reasonably high (above 0.80). The biophysical site index models derived in this study could be used for strategic planning to estimate plantation yield or allowable cut for each of the seven conifer species.