Timberline, or tree line, is the point in any landscape beyond which trees will not grow. Typically it is affected by either altitude or latitude, although climatic and geographic factors can also influence tree growth.
The location of the timberline changes from region to region. Wherever it occurs, it is a rapid transition in landscape from forest to tundra.
In mountainous regions, the timberline is a result of elevation changes and steepness. It may be that at a certain slope, the soil is not strong enough to support large plant life.
In the polar regions, the timberline can be found at elevations as low as sea level. In such harsh climates, the resources to support large plant life are not present.
Trees near the timberline are often shaped by the weather conditions. A short, misshapen growth of trees is the result of high winds, cold temperatures and long winters that often occur in the poles and at high altitudes.
The reason for the timberline is still in debate. Different theories suggest various reasons for the sudden absence of trees, including lack of fire, harsh conditions, poor nutrient regeneration and limited drainage.