timberline
noun
- line below which trees form a forest with a closed canopy
Wiktionary
Pronunciation: /ˈtɪmbɚˌlaɪn/
noun
Etymology: From timber + line.
- The height or limit beyond which trees do not grow in mountainous or Arctic regions.
“Most flocks in the Sierra and the Rocky Mountains live above the timber-line and at an altitude of twelve thousand feet.”