Tree line
From Fiswiki
Tree line or timberline is the edge of the habitat at which trees are capable of growing.
Beyond the tree line, they are unable to grow because of inappropriate environmental conditions (usually cold temperatures, insufficient air pressure, or lack of moisture).
At the tree line, tree growth is often very stunted, with the last trees forming low, densely matted bushes. If it is caused by wind, it is known as krummholz formation, from the German for 'twisted wood'.
The alpine tree line at a location is dependent on local variables, such as aspect of slope, rain shadow and proximity to either geographical pole.
In addition, in some tropical or island localities, the lack of biogeographical access to species that have evolved in a sub-alpine environment, can result in lower tree lines than one might expect by climate alone.
Alpine tree line is the highest elevation that sustains trees; higher up, it is too cold or snow cover persists for too much of the year, to sustain trees.
Usually associated with mountains, the climate above the tree line is called an alpine climate, and the terrain can be described as alpine tundra.
Mountains of the Pacific Northwest of North America exhibit lower treelines on north-facing slopes than south-facing slopes, because increased shade means the deep snowpack takes longer to melt, which shortens the growing season for trees.
Given this caveat, here is a list of approximate tree lines from locations around the globe:
| Location | Approx. latitude | Approx. elevation of tree line | Notes | |
|---|---|---|---|---|
| (m) | (ft) | |||
| Sweden | 68°N | 800 | 2600 | |
| Norway | 61°N | 1100 | 3600 | Lower near the coast |
| Olympic Mountains WA, USA | 47°N | 1500 | 5000 | Heavy winter snowpack buries young trees until late summer |
| Mount Katahdin, Maine, USA | 46°N | 1158 | 3800 | |
| Swiss Alps | 46°N | 2100 | 7000 | Higher on the southern side of the Alps. |
| Alps of Piedmont, Northwestern Italy | 45°N | 2100 | 7000 | |
| New Hampshire, USA | 44°N | 1220 | 4000 | Some peaks have even lower treelines because of fire and subsequent loss of soil, such as Grand Monadnock and Mount Chocorua. |
| Wyoming, USA | 43°N | 3000 | 10000 | |
| Rila | 42°N | 2300 | 7700 | Mountain Pine is the most common tree line species |
| Pyrenees Spain, France, Andorra | 42°N | 2300 | 7700 | Mountain Pine is the tree line species |
| Wasatch Mountains, Utah, USA | 40°N | 2900 | 9500 | Higher (nearly 11,000 feet) in the Uintas |
| Rocky Mountain National Park|Rocky Mountain NP, USA | 40°N | 3500 | 11500 | On warm southwest slopes |
| 3250 | 10800 | On northeast slopes | ||
| Japanese Alps | 39°N | 2900 | 9500 | |
| Yosemite National Park|Yosemite, USA | 38°N | 3200 | 10500 | Sierra Nevada |
| 3600 | 11800 | East side of Sierra Nevada | ||
| Sierra Nevada, Spain | 37°N | 2400 | 8000 | Precipitation low in summer |
| Popocatepetl, Mexico | 28°N | 4000 | 13000 | |
| Himalaya | 28°N | 4400 | 14400 | |
| Hawaii, USA | 20°N | 2800 | 9000 | Precipitation low above the trade winds |
| Costa Rica | 9.5°N | 3400 | 11200 | |
| Mount Kilimanjaro, Tanzania | 3°S | 3000 | 10000 | Example of a tropical location lacking biogeographical access to species that are evolved for living in a subalpine environment. Thus, the tolerance of the indigenous species is lower and it results in a lower tree line |
| New Guinea | 6°S | 3900 | 13000 | |
| Andes, Peru | 11°S | 3900 | 13000 | East side; on west side tree growth is restricted by dryness |
| Andes, Bolivia | 18°S | 5200 | 17000 | Western Cordillera; highest treeline in the world on the slopes of Sajama Volcano (Polylepis tarapacana) |
| 4100 | 13000 | Eastern Cordillera; treeline is lower because of lower solar radiation (more humid climate) | ||
| Sierra de Córdoba, Argentina | 31°S | 2000 | 6500 | Precipitation low above trade winds, also high exposure |
| Australian Alps, Australia | 36°S | 2000 | 6500 | West side of Australian Alps |
| 1700 | 5500 | East side of Australian Alps | ||
| Tasmania, Australia | 41°S | 1200 | 4000 | Cold Winters, Strong Cold Winds and Cool Summers with occasional summer snow restrict tree growth |
| South Island, New Zealand | 43°S | 1200 | 4000 | Strong maritime influence serves to cool summer and restrict tree growth |
| Torres del Paine, Chile | 51°S | 950 | Strong influence from the Southern Patagonian Ice Field serves to cool summer and restrict tree growth | |
| Navarino Island, Chile | 55°S | 600 | Strong maritime influence serves to cool summer and restrict tree growth | |
[edit] Also See
- Mountain
- Snow line
- Physical Features of Mountains
- Defining Mountain Regions
- Snow and Weather Glossary
- Frozen Ground
- Cryosphere
- What Affects Frozen Ground
- What is the Cryosphere
- Snow
- Clouds
- Freezing Point / Freeze
- Moisture
- Rime
- Thaw depth
[edit] Reference
- Wikipedia Tree line [1]
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