Tree Seedling Growth at Different Soil Temperatures

The effect of soil temperature on shoot and root development was investigated for three conifers and two broadleaved species. Plants were raised from seed through two 8-week stages in environmental chambers with soil temperatures controlled in constant-temperature water baths. Soil temperatures were 15, 19, 23, 27, and 31°C and soil moisture between 0.1 and 1.5 bars soil water suction. Other environmental factors were held constant at simulated natural levels. White spruce and tree-of-heaven had optimal shoot and root growth at 19°C. Jack pine growth was maximum at 27°C. Douglas-fir seedlings developed well between 15 and 27°C. Paper birch grew well between 19 and 31°C with best shoot development at 31°C, whereas root development was favored at 23°C. Forest Sci. 20:363-367.