Treeline Project

Definitions

What is the Arctic? The simple definition of the Arctic Circle is everything north of 66 degrees latitude. It can also be defined as the land above the treeline where there are arctic plants; arctic animals like the walrus and polar bear; permafrost; and cold temperature. Sometimes it is defined as the southern limit of pack ice during the winter.

Arctic treeline The furthest north in the Northern Hemisphere that trees can grow. Further north, it is too cold to sustain trees; this occurs for two main reasons.

  • Temperature: This region is so cold that the sap that feeds the trees freezes and cannot do its job. The trees will be stunted or die.
  • Permafrost  (frost that remains from one winter to the next) in the soil can prevent trees from getting their roots deep enough for the necessary structural support.

The treeline is not a fixed line, as it changes depending on weather conditions. In fact, one of the signs of global warming is that the treeline is moving more north over the years.

Factors that contribute to the Arctic Tree Lines

Polar treelines are heavily influenced by local variables such as:

  • Aspect of slope and degree of shelter, meaning the direction that the trees are facing: toward the wind, away from wind, towards a valley, over a lake, etc.
  • Permafrost (soil or rock that remains below 0°C or 32 °F  throughout the year, and forms when the ground cools sufficiently in winter to produce a frozen layer that persists throughout the following summer) has a major impact on the ability of trees to place roots into the ground. When roots are too shallow, trees are susceptible to windthrow and erosion.
  • River Valleys: Trees can often grow in river valleys at latitudes where they could not grow on a more exposed site.
  • Ocean currents: Maritime influences also play a major role in determining how far north trees can grow.

Vegetation: How Does Your Garden Grow?

To the north of the treeline, in the arctic tundra, numerous plants thrive such as:

  • Lichen: a special plant, made up of both algae and fungus; it can grow in very cold temperatures
  • Birch and willows shrubs: these trees do not grow very big, since it is too cold and the permafrost keeps them from putting down deep roots
  • Heath, lingonberries, bilberries, blueberries, alpine bearberries: these are found close to the treeline, where the caribou spend the winter
  • Bake-apples, also called cloudberries
  • Arctic poppies
  • Tundra grasses like cottongrass, and mosses.

Drunken Trees

Black Spruce grow at, or just below, the treeline. There trunks usually grow straight up, but with the continuous melting and freezing of the permafrost at the treeline, the Black Spruce is unable to develop a deep root system. This causes their trunks to tilt every which way. These trees are known as “drunken trees”.

Stunted Trees

Stunted Trees refer to stunted specimens of fir, larch, mountain ash, and birch trees, Because of cold temperatures and soil conditions, these trees are often stunted, looking more like shrubs.