Seasonal changes in soil temperature and in the frost hardiness of Scots pine roots under subarctic conditions: comparison with soil temperature and snow-cover under different simulated winter conditions : 3rd EUROSILVA Workshop, Obergurgl, Austria, September, 10-14, 1998
Seasonal changes in soil temperature and in the frost hardiness of adult Scots pine (Pinus sylvestris L.) trees were studied between August 1991 and May 1993 in a pine forest growing on dry heathland soil (67 °N, 29 °E). The temperature in the humus layer varied between +21.2°C and -3.2°C and in the mineral soil (down to 10 cm) between +21.6°C. The temperature in the humus layer was continuously slightly colder than in the mineral soil from late August until May. The frost hardiness of the pine roots was lowest (about -5°C) in May and during the first week of September. Frost hardiness stayed at its maximum of about -20°C during November and December and slightly decreased in January and February. During most of the sampling time, the frost hardiness of the roots in the humus layer was greater than in the mineral soil. There was a clear relationship between the soil temperature and the frost hardiness of roots. Soil temperature and precipitation as snow in different winter conditions were simulated using the SOIL model. The simulations show that the insulating effect of the snow cover is crucial for the frost survival of Scots pine roots even during a moderate winter.
