Site regions revisited: a climatic analysis of Hills' site regions for the province of Ontario using a parametric method

A climatic analysis was conducted` of Hills' site regions for Ontario using spatially distributed models of long-term, mean monthly climate data. Gridded estimates of eight climatic variables were generated by coupling thin-plate smoothing spline surfaces (fitted as a trivariate function of longitude, latitude, and elevation) to a 1-km resolution digital elevation model of Ontario. The gridded climate estimates were used to characterize the climate of each site region. New climatic classifications for the province were calculated from these data using a clustering algorithm. They were also compared with the existing site region boundaries. The analyses confirm many of the general climatic gradients established by Hills, but also suggest where major revisions should be made. The climatic models present new analytical opportunities for mapping plant–climate response in the context of forest planning and management.