Causes of Alpine Timberline: A Review of the Hypotheses

Timberline, or the low-temperature limits of forest and tree growth, is one of the most fundamental ecological boundaries. Below timberline, foliage and reproductive structures are successfully produced at the height of tree canopies; above timberline, plants grow only in favoured environments close to the ground. Timberlines are also relatively well-defined, even where altitudinal environmental gradients are gradual. Most other sharp boundaries in nature reflect environmental discontinuities such as shore lines, or disturbances such as forest clearance.