Editing Geography of Norway (section)

====North Boreal====
[[File:Sand with pines.jpg|thumb|Road in the pine forest in [[Karasjok Municipality]]. The climate here has the greatest continentality and the coldest winters in Norway; north boreal zone.]]
[[File:Övre dividal anjajohka.jpg|thumb|North boreal forest in [[Øvre Dividal National Park]]; the autumn colored leaves of the mountain birch, which continue upslope, pine having reached its limit.]]

The North Boreal (NB) zone, (also known as open or sparse taiga) is the zone closest to the [[tree line]], bordering the alpine or polar area, and dominated by a harsh subarctic climate. There are at least 30 summer days with a mean temperature of {{convert|10|C}} or more, up to about two months. The trees grow very slowly and generally do not get very large. The forest is not as dense as further south or at lower altitudes and is known as the mountain forest (''Fjellskog''). The NB zone covers a total of 28% of the total land area of Norway, including almost half of Finnmark, where the mountain birch grows down to sea level. The lower part of this zone also has conifers, but the tree line in Norway is mostly formed by mountain birch, a subspecies of downy birch (subspecies ''czerepanovii''),<ref>{{cite journal |last=Taulavuori |first=K.M.J. |display-authors=etal |title=Dehardening of mountain birch (Betula pubescens ssp. czerepanovii) ecotypes at elevated winter temperatures |url=http://www.skogoglandskap.no/publikasjon/SF_3230_2800 |date=2004 |archive-url=https://web.archive.org/web/20110720024233/http://www.skogoglandskap.no/publikasjon/SF_3230_2800 |journal=[[New Phytologist]] |volume=162 |issue=2 |pages=427–436 |doi=10.1111/j.1469-8137.2004.01042.x |archive-date=20 July 2011 |via=[[Norwegian Forest and Landscape Institute]] |access-date=25 December 2019|doi-access=free }}</ref> which is not to be confused with [[dwarf birch]]). Spruce and pine make up the tree line in some mountain areas with a more continental climate. Alpine plants are common in this zone. The birch forest {{convert|1320|m}} above sea level at Sikilsdalshorn is the highest tree line in Norway, while a birch at 1,404 m ASL in Veodal, Jotunheimen, is the highest growing single tree.<ref>{{Cite web|url=https://www.nrk.no/innlandet/norges-hoyestvoksende-tre-skaper-bekymring-blant-forskere-1.14653798|title = Norges høyestvoksende tre skaper bekymring blant forskere|date = 18 August 2019}}</ref> The tree line is lower closer to the coast and in areas with lower mountains, due to cooler summers, more wind near mountain summits, and more snow in the winter (coastal mountains) leading to later snowmelt. The NB zone covers large areas at {{convert|750–950|m}} altitude in the interior of Østlandet; is {{convert|800–1200|m}} in the central mountain areas; but at the western coast the tree line is down to about {{convert|500|m}} above sea level, increasing significantly in the long fjords ({{convert|1100|m}} at the head of [[Sognefjord]]). Further north, large areas in the interior highlands or uplands of Trøndelag and North Norway are dominated by the NB zone, with the tree line at about {{convert|800|m}} amsl in the interior of Trøndelag, {{convert|600|m}} in [[Rana Municipality]], {{convert|500|m}} at Narvik, {{convert|400|m}} at Tromsø, {{convert|200|m}} at Kirkenes and {{convert|100|m}} at [[Hammerfest (town)|Hammerfest]] (only pockets in sheltered areas). The large [[Finnmarksvidda]] plateau is at an altitude placing it almost exactly at the tree line. The last patch of NB zone gives way to tundra at sea level about {{convert|10|km}} south of the [[North Cape, Norway|North Cape]] plateau (near [[Skarsvåg]]). Areas south of this line are tundra-like with scattered patches of mountain birch woodland (forest tundra) and become alpine tundra even at minor elevations. The trees near the tree line are often bent by snow, wind, and growing-season frost; and their height is only {{convert|2–4|m}}. Outside Norway (and adjacent areas in Sweden), the only other areas in the world with the tree line mostly made up by a small-leaved deciduous tree such as birch—in contrast to conifers—are [[Iceland]] and the [[Kamtschatka peninsula]].

The presence of a [[conifer]] tree line is sometimes used (''Barskoggrense'') to divide this zone into two subzones, as the conifers will usually not grow as high up as the mountain birch. Spruce and pine grow at nearly {{convert|1100|m}} above sea level in some areas of Jotunheimen, down to {{Convert|400|m|feet}} in Bergen ({{Convert|900|m}} at the head of Sognefjord), {{Convert|900|m}} at Lillehammer (mountains near Oslo are too low to have a tree line), {{Convert|500|m}} at Trondheim ({{Convert|750|m}} at Oppdal), {{Convert|350|m}} at Narvik, {{Convert|200|m}} at Harstad, {{Convert|250|m|feet}} at Alta; and the most northerly pine forest in the world is in [[Stabbursdalen National Park]] in [[Porsanger Municipality]]. There are some forests in this part of the NB zone; and some conifers can grow quite large even if growth is slow.