Altitude above which there are only smaller plants

Wikipedia Word definitions in Wikipedia
The tree line is the edge of the habitat at which trees are capable of growing. It is found at high elevations and in frigid environments. Beyond the tree line, trees cannot tolerate the environmental conditions (usually cold temperatures or lack of moisture). ...

Longman Dictionary of Contemporary English Word definitions in Longman Dictionary of Contemporary English
noun EXAMPLES FROM CORPUS ▪ Adam landed in the clearing between the tree line and the wall. ▪ After a thirty-second pause to let us load up, Shaker took off over the forward tree line . ▪ I could see the muzzle flashes in the tree line fifty yards away, ...

WordNet Word definitions in WordNet
n. line marking the upper limit of tree growth in mountains or northern latitudes [syn: timber line , timberline ]

Wiktionary Word definitions in Wiktionary
n. 1 A division in altitude above which trees tend not to grow on mountains. 2 A division in latitude where latitudes higher than that do not tend to grow trees (this line is not a constant latitude)