How does the winter weather cutting on both sides of zero affect trees, berries and animals?

In winter the temperature can fluctuate between zero and zero. Continuous melting and freezing is characterized as winter sawing.

Then the snow cover condenses into a hard ice crust or disappears completely. Researcher at the Center for Natural Resources Timo Domisch tells how it affects plants and animals.

Does the temperature drop more in winter than before?

The winter heat periods have clearly increased. Long and severe periods of frost have decreased. Warming causes cycles that cut across zero on both sides.

How does this variation affect trees?

It depends on when and how long the temperature drops. Finnish forest trees are quite well adapted to changing conditions, and they usually do not suffer much from temperature fluctuations.

In winter, the trees are dormant. During the heat period, the trees’ cellular respiration increases, which means they begin to consume energy.

However, the trees cannot communicate in the winter. When the energy reserves are used up, the sugar content of the cells decreases and the antifreeze that protects the cells from freezing is diluted.

Then the plant is no longer as cold-resistant. If there is a period of severe frost, the tree may suffer damage. Large trees are more often affected by this than sensitive seedlings.

Does snow matter?

The roots of even a large tree can be damaged if there is no protective snow cover on the ground. The roots are less resistant to frost than the above-ground parts of the tree. The tree can die if the early winter is snowless and the frost is severe.

For example, a cherry tree in my yard died because of the snowless early winter. Of course, it is much more sensitive than pine or birch, and will not survive in the wild in Finland. Mechanical damage can also occur to the roots of Finnish forest trees if there is a sudden freeze after a rainy warm period.

How are the other plants doing?

Sparrow plants such as blueberry and lingonberry have adapted to wintering in a thick snow cover. Under the snow, the temperature of the ground can be around zero, even if it would otherwise be over ten degrees below zero.

As a result of the temperature drop, the snow cover can become denser, and then it no longer insulates as well. If it rains in winter, the entire snow cover can flatten or melt. Then the insulation is missing and the toes can dry out or suffer from frostbite. This can reduce the next summer’s berry harvest.

Does the timing of the sawing period matter?

In autumn, temperature fluctuations are common. However, the northern plants’ preparation for winter rest is not disturbed by the autumn heat cycle, as they still perceive the continuous decrease in light.

During an unusually warm autumn, plants prepare for winter more slowly, and they may be less resistant to frost.

If the heat cycle comes at the end of winter, the winter dormancy of a single tree may break too early. For example, a conifer may try to start bonding due to a heat cycle.

However, there will be problems if the ground is still frozen and the tree cannot get water taken up by its roots. Then there is a risk of dehydration. For this reason, it is customary to protect the starlings, for example, familiar from the garden with a cover during the spring and winter. For the same reason, the evergreen rhododendron can dry out in spring and winter.

Desiccation does not necessarily kill the entire plant. Some part of it may die, but otherwise it will continue to grow.

How does the change in winter temperature affect animals?

Small mammals such as moles clearly suffer from the harsh winter. They would need an insulating snow cover for protection.

Snow cover is also important for many hens, as they burrow into snowdrifts for shelter. If the snow cover does not insulate, small mammals can freeze to death.

If ice forms on the ground, many invertebrates that winter on the ground will also suffer. The mound ants, on the other hand, have burrowed to a depth of many tens of centimeters in the lower parts of the mound, and they are protected from the frost. The nest may be damaged, but the ants will repair it in the spring.

Deer, on the other hand, can benefit if there is less snow. A thick layer of snow makes it harder for them to move.

What kind of winter is ideal for Finnish nature?

Last winter was quite good from nature’s point of view. Then the first snows came at the end of October and the snow cover remained on the ground for about half a year. The temperature didn’t drop much.

The best thing would be if a blanket of snow fell on the slightly melted ground. Then it would protect the roots of the plants from rotting. It would be good for the snow cover to stay long enough that spring has properly started.