Krummholz#Flag tree

{{Short description|Type of stunted, deformed vegetation encountered in subarctic and subalpine tree line landscapes}}

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{{for|the American actor|David Krumholtz}}

{{Globalize|1=article|2=North America|date=April 2023}}

{{use mdy dates |date=June 2019}}

File:Pinus albicaulis 7872.JPG in Wenatchee National Forest]]

File:Silhouettes of wind sculpted Krumholz trees.jpg

Krummholz ({{langx|de|krumm}}, "crooked, bent, twisted" and Holz, "wood") — also called knieholz ("knee timber") — is a type of stunted, deformed vegetation encountered in the subarctic and subalpine tree line landscapes, shaped by continual exposure to fierce, freezing winds. Under these conditions, trees can survive only where they are sheltered by rock formations or snow cover. As the lower portion of these trees continues to grow, the coverage becomes extremely dense near the ground.{{cite web |url=http://www.nps.gov/archive/romo/resources/plantsandanimals/ecosystem/subalpine.html |title=The subalpine ecosystem |access-date=2009-01-29 |publisher=National Park Service |archive-url=https://web.archive.org/web/20070809001440/http://www.nps.gov/archive/romo/resources/plantsandanimals/ecosystem/subalpine.html |archive-date=2007-08-09}} In Newfoundland and Labrador, the formation is known as tuckamore.{{cite book |url=https://books.google.com/books?id=XVP0BwAAQBAJ&pg=PA212 |title=Forest Development in Cold Climates |last1=Alden |first1=John |last2=Mastrantonio |first2=J. Louise |last3=Ødum |first3=Soren |date=2013-06-29 |publisher=Springer Science & Business Media |isbn=9781489916006 |language=en}}{{cite book |url=https://books.google.com/books?id=GqhqZ3rM7eMC&pg=PA86 |title=Gros Morne National Park |last=Burzynski |first=Michael |date=1999 |publisher=Breakwater Books |isbn=9781550811353 |language=en}}{{cite news |url=http://www.capebretonpost.com/opinion/columnists/2014/6/19/tuckamore-the-little-tree-growth-that-c-3769304.html |title=Tuckamore: The little tree growth that could |last=Gouthro |first=Jen |date=2014-06-21 |work=Cape Breton Post |access-date=2017-07-23 }} Krummholz trees are also found on beaches, such as the Oregon coast, where trees can become much taller than their subalpine cousins.

The labeling of diverse sets of tree species in different ecological contexts may be problematic. The ecological requirements of krummholz trees in the Alps, for example, are different from those in the Rockies. The terms scrub or shrubland may be more appropriate for some communities with krummholz trees.{{Cite journal |last=Holtmeier |first=Friedrich-Karl |date=1981 |title=What Does the Term "Krummholz" Really Mean? Observations with Special Reference to the Alps and the Colorado Front Range |url=https://www.jstor.org/stable/3673062 |journal=Mountain Research and Development |volume=1 |issue=3/4 |pages=253–260 |doi=10.2307/3673062 |jstor=3673062 |issn=0276-4741|url-access=subscription }}

Krummholz trees can cover nearly all of the area in which they inhabit, with only patches of moss and flowers in between. Frequent fog and cloudy conditions, along with cool weather, create a rather moist microclimate around the shrubs.{{Cite web |title=Maine Natural Areas Program, Natural Community Fact Sheet for Spruce - Fir Krummholz |url=https://www.maine.gov/dacf/mnap/features/communities/sprucefirkrummholz.htm |access-date=2023-10-31 |website=www.maine.gov}} Krummholz might depend on less acidic soil to survive. This means that they are threatened by acid rain. The thin soils that cover mountaintops have low buffering capacity, that is the capacity to resist changes in acidity.{{Cite web |title=Alpine Krummholz Guide - New York Natural Heritage Program |url=https://guides.nynhp.org/alpine-krummholz/ |access-date=2023-10-31 |website=guides.nynhp.org}} These trees are also endangered by the use of them as timber for fires, and other human activity.