Editing Tree line (section)

{{Short description|Edge of the habitat at which trees are capable of growing}}
[[File:Tree line above St. Moritz.jpg|thumb|Tree line above [[St. Moritz, Switzerland]]. May 2009]]
[[File:Tree line.jpg|thumb|In this view of an alpine tree line, the distant line looks particularly sharp. The foreground shows the transition from trees to no trees. These trees are stunted in growth and one-sided because of cold and constant wind.]]

The '''tree line''' is the edge of a [[habitat]] at which [[tree]]s are capable of growing and beyond which they are not. It is found at high [[elevation]]s and high [[latitude]]s. Beyond the tree line, trees cannot tolerate the environmental conditions (usually low temperatures, extreme snowpack, or associated lack of available moisture).<ref name="taiga">{{Cite book |last=Elliott-Fisk |first=D.L. |title=North American Terrestrial Vegetation |publisher=[[Cambridge University Press]] |year=2000 |isbn=978-0-521-55986-7 |editor-last=Barbour |editor-first=M.G. |edition=2nd |chapter=The Taiga and Boreal Forest |editor-last2=Billings |editor-first2=M.D.}}</ref>{{rp|51}} The tree line is sometimes distinguished from a lower '''timberline''', which is the line below which trees form a forest with a closed [[Canopy (biology)|canopy]].<ref name="ecosystem">{{Cite book |last=Jørgensen |first=S.E. |title=Ecosystem Ecology |publisher=Academic Press |year=2009 |isbn=978-0-444-53466-8}}</ref>{{rp|151}}<ref>{{Cite book |last=Körner |first=C. |title=Alpine Treelines: Functional Ecology of the Global High Elevation Tree Limits |publisher=Springer |others=Illustrated by S. Riedl |year=2012 |isbn=978-3-0348-0396-0}}</ref>{{rp|18}}

At the tree line, tree growth is often sparse, stunted, and deformed by wind and cold. This is sometimes known as {{lang|de|[[krummholz]]}} (German for "crooked wood").<ref name="landabove">{{Cite book |last1=Zwinger |first1=A. |title=Land Above the Trees: A Guide to American Alpine Tundra |last2=Willard |first2=B.E. |publisher=Big Earth Publishing |year=1996 |isbn=978-1-55566-171-7}}</ref>{{rp|58}}

The tree line often appears well-defined, but it can be a more gradual transition. Trees grow shorter and often at lower densities as they approach the tree line, above which they are unable to grow at all.<ref name=landabove/>{{rp|55}} Given a certain latitude, the tree line is approximately 300 to 1000 meters below the permanent [[snow line]] and roughly parallel to it.<ref>{{Cite web |title=Why treelines? |url=https://www.geo.uzh.ch/microsite/alpecole/static/course/lessons/10/10c.htm}}</ref>