Abstract. Trafficability in forest terrain is controlled by ground-bearing
capacity, which is crucial from the timber harvesting point of view. In winter, soil
frost affects the most the bearing capacity, especially on peatland soils
which have in general low bearing capacity. Ground frost similarly affects
the bearing capacity of forest truck roads. A 20 cm thick layer of
frozen soil or 40 cm thick layer of snow on the ground may already be sufficient for
heavy forest harvesters. In this work, we studied the impacts of climate
change on soil frost conditions and, consequently, on ground-bearing capacity
from the timber harvesting point of view. The number of days with good
wintertime bearing capacity was modelled by using a soil temperature model
with a snow accumulation model and wide set of downscaled climate model data
until the end of the 21st century. The model was calibrated for different
forest and soil types. The results show that by the mid-21st century, the
conditions with good bearing capacity will decrease in wintertime in Finland,
most likely by about 1 month. The decrease in soil frost and wintertime
bearing capacity will be more pronounced during the latter half of the
century, when drained peatlands may virtually lack soil frost in most of
winters in southern and western Finland. The projected decrease in the
bearing capacity, accompanied with increasing demand for wood harvesting from
drained peatlands, induces a clear need for the development of sustainable
and resource-efficient logging practices for drained peatlands. This is also
needed to avoid unnecessary harvesting damages, like rut formation on soils
and damage to tree roots and stems.
ASSESSMENT OF THE INTERACTION OF MELT WATER WITH FROZEN SOIL
