Silhouettes of wind sculpted Krumholz trees

''Krummholz'' (german: krumm, "crooked, bent, twisted" and ''Holz'', "wood") — also called ''knieholz'' ("knee timber") — is a type of stunted, deformed vegetation encountered in the

subarctic The subarctic zone is a region in the Northern Hemisphere immediately south of the true Arctic, north of humid continental regions and covering much of Alaska, Canada, Iceland, the north of Scandinavia, Siberia, and the Cairngorms. Generally, ...

and

subalpine Montane ecosystems are found on the slopes of mountains. The alpine climate in these regions strongly affects the ecosystem because temperatures fall as elevation increases, causing the ecosystem to stratify. This stratification is a crucial f ...

tree line The tree line is the edge of the habitat at which trees are capable of growing. It is found at high elevations and high latitudes. Beyond the tree line, trees cannot tolerate the environmental conditions (usually cold temperatures, extreme snowp ...

landscapes, shaped by continual exposure to fierce, freezing winds. Under these conditions, trees can only survive where they are sheltered by rock formations or

snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughout ...

cover. As the lower portion of these trees continues to grow, the coverage becomes extremely dense near the ground. In

Newfoundland and Labrador Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...

, the formation is known as tuckamore. ''Krummholz'' trees are also found on beaches such as the Oregon coast, where trees can become much taller than their subalpine cousins.

Species

Common trees showing ''krummholz'' formation include

European spruce ''Picea abies'', the Norway spruce or European spruce, is a species of spruce native to Northern, Central and Eastern Europe. It has branchlets that typically hang downwards, and the largest cones of any spruce, 9–17 cm long. It is very close ...

mountain pine ''Pinus mugo'', known as bog pine, creeping pine, dwarf mountain pine, mugo pine, mountain pine, scrub mountain pine, or Swiss mountain pine, is a species of conifer, native to high elevation habitats from southwestern to Central Europe and Sou ...

balsam fir ''Abies balsamea'' or balsam fir is a North American fir, native to most of eastern and central Canada (Newfoundland west to central Alberta) and the northeastern United States (Minnesota east to Maine, and south in the Appalachian Mountains to ...

red spruce ''Picea rubens'', commonly known as red spruce, is a species of spruce native to eastern North America, ranging from eastern Quebec and Nova Scotia, west to the Adirondack Mountains and south through New England along the Appalachians to western ...

black spruce ''Picea mariana'', the black spruce, is a North American species of spruce tree in the pine family. It is widespread across Canada, found in all 10 provinces and all 3 territories. It is the official tree of the province of Newfoundland and Labra ...

subalpine fir ''Abies lasiocarpa'', the subalpine fir or Rocky Mountain fir, is a western North American fir tree. Description ''Abies lasiocarpa'' is a medium-sized evergreen conifer with a very narrow conic crown, growing to tall, exceptionally , with a ...

subalpine larch ''Larix lyallii'', the subalpine larch, or simply alpine larch, is a deciduous, coniferous tree native to northwestern North America. It lives at high altitudes, from , in the Rocky Mountains of Idaho, Montana, British Columbia, and Alberta. Ther ...

Engelmann spruce ''Picea engelmannii'', with the common names Engelmann spruce, white spruce, mountain spruce, and silver spruce, is a species of spruce native to western North America. It is mostly a high-altitude mountain tree but also appears in watered canyon ...

whitebark pine ''Pinus albicaulis'', known by the common names whitebark pine, white bark pine, white pine, pitch pine, scrub pine, and creeping pine, is a conifer tree native to the mountains of the western United States and Canada, specifically subalpine ...

limber pine ''Pinus flexilis'', the limber pine, is a species of pine tree-the family Pinaceae that occurs in the mountains of the Western United States, Mexico, and Canada. It is also called Rocky Mountain white pine. A limber pine in Eagle Cap Wildernes ...

Bristlecone pine The term bristlecone pine covers three species of pine tree (family Pinaceae, genus ''Pinus A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. T ...

, and

lodgepole pine ''Pinus contorta'', with the common names lodgepole pine and shore pine, and also known as twisted pine, and contorta pine, is a common tree in western North America. It is common near the ocean shore and in dry montane forests to the subalpine, ...

. Instances of the ''krummholz'' form of black spruce, ''

Picea mariana ''Picea mariana'', the black spruce, is a North American species of spruce tree in the pine family. It is widespread across Canada, found in all 10 provinces and all 3 territories. It is the official tree of the province of Newfoundland and Labra ...

'', are found in the northern Canadian

boreal forest Taiga (; rus, тайга́, p=tɐjˈɡa; relates to Mongolic and Turkic languages), generally referred to in North America as a boreal forest or snow forest, is a biome characterized by coniferous forests consisting mostly of pines, spruces, ...

s.C. Michael Hogan. 2008
''Black Spruce: Picea mariana'', GlobalTwitcher.com, ed. N. Stromberg
''Krummholz''-form black spruce and balsam fir are abundant in the alpine transition zone of the White Mountains of Maine and New Hampshire and of the same zone in the

Green Mountains The Green Mountains are a mountain range in the U.S. state of Vermont. The range runs primarily south to north and extends approximately from the border with Massachusetts to the border with Quebec, Canada. The part of the same range that is in ...

Vermont Vermont () is a state in the northeast New England region of the United States. Vermont is bordered by the states of Massachusetts to the south, New Hampshire to the east, and New York to the west, and the Canadian province of Quebec to ...

Subalpine fir ''Abies lasiocarpa'', the subalpine fir or Rocky Mountain fir, is a western North American fir tree. Description ''Abies lasiocarpa'' is a medium-sized evergreen conifer with a very narrow conic crown, growing to tall, exceptionally , with a ...

is the most common associate of spruce in ''krummholz'' vegetation. Other associated

coniferous Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All extant ...

species include alpine larch (''

Larix lyallii ''Larix lyallii'', the subalpine larch, or simply alpine larch, is a deciduous, coniferous tree native to northwestern North America. It lives at high altitudes, from , in the Rocky Mountains of Idaho, Montana, British Columbia, and Alberta. Ther ...

''), whitebark pine (''

Pinus albicaulis ''Pinus albicaulis'', known by the common names whitebark pine, white bark pine, white pine, pitch pine, scrub pine, and creeping pine, is a conifer tree native to the mountains of the western United States and Canada, specifically subalpine ...

''), limber pine (''

Pinus flexilis ''Pinus flexilis'', the limber pine, is a species of pine tree-the family Pinaceae that occurs in the mountains of the Western United States, Mexico, and Canada. It is also called Rocky Mountain white pine. A limber pine in Eagle Cap Wilderness ...

''), and western white pine (''

Pinus monticola Western white pine (''Pinus monticola''), also called silver pine and California mountain pine, is a species of pine in the family Pinaceae. It occurs in mountain ranges of northwestern North America. It is the List of U.S. state trees, state tre ...

'') in southern British Columbia, and mountain hemlock (''

Tsuga mertensiana ''Tsuga mertensiana'', known as mountain hemlock, is a species of hemlock native to the west coast of North America, found between Southcentral Alaska and south-central California. Description ''Tsuga mertensiana'' is a large evergreen conifer ...

'') on the eastern slopes of the Coast Range and in the Revelstoke area of

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

. Lodgepole pine ( ''Pinus contorta'' var. ''contorta'') is a minor associate in most of the British Columbia interior, except in dry alpine areas of the southwest Cariboo/Chilcotin district where it is abundant (Pojar 1985).Pojar, J. 1985. Ecological classification of lodgepole pine in Canada. pp. 77–88 ''in'' D.M. Baumgartner, R.G. Krebill, J.T. Arnott and G.F. Weeman (compilers). Lodgepole pine the species and its management. Symp. Proc.. Cooperative Extension, Washington State University, Pullman, WA. Ericaceous species (''Vaccinium scoparium, V. membranaceum, V. caespitosum, Cassiope mertensiana, Phyllodoce empetriformis'') are common in the snow accumulation zone around the base of ''krummholz'' colonies.

Flag tree

A variation of ''krummholz'' formation is a flag tree or banner tree. Branches on the

windward Windward () and leeward () are terms used to describe the direction of the wind. Windward is ''upwind'' from the point of reference, i.e. towards the direction from which the wind is coming; leeward is ''downwind'' from the point of reference ...

side are killed or deformed by the almost constant strong winds, giving the tree a characteristic flag-like appearance. Where the lower portion of the tree is protected by snow cover or rocks, only the exposed upper portion may have this appearance. This is a rather common occurrence in red spruce trees of the highest peaks of the central and even the southern

Appalachian Mountains The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They ...

, and is most often seen in the windswept high peaks and plateaus of the

Allegheny Mountains The Allegheny Mountain Range (; also spelled Alleghany or Allegany), informally the Alleghenies, is part of the vast Appalachian Mountain Range of the Eastern United States and Canada and posed a significant barrier to land travel in less devel ...

. This formation most notably occurs with high frequency in the

Dolly Sods The Dolly Sods Wilderness – originally simply Dolly Sods – is a U.S. Wilderness Area in the Allegheny Mountains of eastern West Virginia, US, and is part of the Monongahela National Forest (MNF) of the U.S. Forest Service (USFS). Dolly Sods ...

and

Roaring Plains West Wilderness The Roaring Plains West Wilderness is a U.S. Wilderness Area in the Allegheny Mountains of eastern West Virginia, USA. It is part of the Monongahela National Forest and includes Mount Porte Crayon, the sixth highest point in the state. Known as "R ...

areas along the

Allegheny Front The Allegheny Front is the major southeast- or east-facing escarpment in the Allegheny Mountains in southern Pennsylvania, western Maryland, eastern West Virginia, and western Virginia, USA. The Allegheny Front forms the boundary between the Rid ...

in eastern

West Virginia West Virginia is a state in the Appalachian, Mid-Atlantic and Southeastern regions of the United States.The Census Bureau and the Association of American Geographers classify West Virginia as part of the Southern United States while the Bur ...

, typically occurring at elevations of and higher.

Trade wind The trade winds or easterlies are the permanent east-to-west prevailing winds that flow in the Earth's equatorial region. The trade winds blow mainly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisph ...

s in tropical regions near the equator can also shape trees in a similar manner. The southernmost reaches of the

Magellanic subpolar forests The Magellanic subpolar forests () are a terrestrial ecoregion of southernmost South America, covering parts of southern Chile and Argentina, and are part of the Neotropical realm. It is a temperate broadleaf and mixed forests ecoregion, and ...

of Chile contain many flag trees also.

References

External links

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Trees Conifers Forest ecology Montane ecology

Species

Flag tree

See also

References

Further reading

External links