The spatial and temporal dynamics of soil temperature (T SOIL) strongly influence a wide range of biotic and abiotic processes in boreal forests. Relatively few spatial and temporal T SOIL measurements have been made in these systems; in addition, not all ecosystem models take into account the effect of changing stand structure during stand development on T SOIL dynamics. The goals of this study were to measure T SOIL and its spatiotemporal variability in a boreal forest chronosequence, develop and test a computationally simple empirical model to predict T SOIL, and quantify the effects of different approaches to deriving T SOIL on simulated ecosystem processes. T SOIL was measured hourly at six depths (0–100cm) for 3–4 years, and sampled in a spatial grid monthly during one growing season, in a black spruce (Picea mariana (Mill.) BSP)-dominated boreal forest chronosequence. We report annual and daily T SOIL patterns, air–soil hystereses, and T SOIL changes at the freeze-thaw transition. An empirical model predicting T SOIL as of the weighted sum of past air temperatures generally accounted for 90–95% of temporal T SOIL variability at shallow depths, and 77–83% at 50–100cm. A variety of stand structural characteristics affected the model parameters, with leaf area index (LAI) usually the most significant. Spatial T SOIL correlation, measured at depths of 2 and 10cm, was generally constant between 5 and 30m. The new empirical model that accounts for changes in canopy structure greatly improved the prediction of T SOIL for stands with high LAI in the Biome-BGC process model; the broader implications of this change are discussed. This model has simple data requirements – only air temperature and LAI – although the parameters given here should only be used for boreal stands with similar soil types.