[en] Over 80% of clearcutting operations in Canada involve whole-tree harvesting, in which non-merchantable components of tree biomass (slash) are removed from the forest. The removal of slash from the sites leads to a loss of nutrients and faster decomposition of soil organic matter. It sets up a chain reaction leading to increased nitrification due to warmer soil temperature, increased acidity build-up, and subsequent loss of base cations from the solum. The ultimate result is site deterioration and reduced timber yield. In 1989, a series of lysimeter studies was started on sites representing the major soil types in all three Maritime provinces and to including all the commercially important tree species. Whole- tree harvesting, conventional harvesting, and control constituted the three main treatments in each of the studies. Treatment responses in terms of soil temperature at three depths and the chemical composition of soil leachates were characterized. The diurnal fluctuations in the soil temperatures were most pronounced in the whole-tree harvested plots, followed by the conventional harvest plots. The largest difference in the temperature between the treatments consistently occurred immediately below the organic horizon in the mid-afternoon hours. At lower depths, the patterns were similar but the differential magnitudes were smaller. The temperatures in the whole-tree harvested plots were between 5-6 degrees C higher than those in the control and conventionally harvested plots during the first growing season after the treatments were implemented. During the spring and summer months, soil temperatures were warmer in the whole-tree harvested plots, but after September the trends reversed. The slash in the conventionally harvested plots acted as insulation to conserve heat. The calculated heat units accumulated were significantly higher in the whole-tree harvested plots over the growing season than in the other plots