Alpine plants - alpine plants

It refers to plants that grow in the alpine zone, the highest vertical distribution zone, but in Japan it is used in a very broad sense to include plants from the coniferous forest zone and above.

Many alpine plants originate from plants in the cold zone, but there are also species that have developed locally in lowlands that have adapted to the alpine zone in each region. The closer the mountain is to the cold zone, the more frequent and dense the exchange of plants between the cold zone and the alpine zone during the glacial period, so there are many species in common with the cold zone, but the further away from the cold zone, the higher the degree of independence of the flora, and the more species that have developed locally. In addition, plants that originated in the cold zone often undergo differentiation due to isolation, changing into different taxa. The high mountains from the Himalayas to western China have little contact with the cold zone of the circumpolar (Arctic) even during the glacial period, so their alpine flora is quite unique. Tropical high mountains such as Mount Kilimanjaro in Africa are in a special environment where temperature changes are repeated throughout the day and night rather than throughout the year, and because the high mountains are highly independent of each other, the flora varies greatly from mountain to mountain. The highlands of the Andes also have unique floras, and many species of tropical rainforests, such as the Viola genus, have risen to the mountains and changed. New Zealand and Australia also have alpine flora, and it is noteworthy that their flora has many species and genera in common with the cold regions and alpine mountains of the Northern Hemisphere, such as Ranunculaceae and Gentianaceae. Several species and genera are known from the tropics to the Southern Hemisphere, such as Festuca, which is thought to have originated in the cold regions of the Northern Hemisphere. When considering the distribution and spread of alpine plants, it is necessary to consider not only their continuous distribution during the glacial period, but also their distribution by wind, birds, etc.

Many alpine plants have large flowers despite their short height, but wind-pollinated graminoid plants (plants with thin, hard grass-like leaves) such as those from the Poaceae, Cyperaceae, and Juncaceae families also play an important role, and in terms of quantity, mosses and lichens cannot be ignored. Also, like plants in the cold zone, many alpine plants have high chromosome ploidy and many species reproduce asexually by producing bulbils (embryos).

In high mountains, the distribution of snow has an important effect on the distribution of plants. In the Northern Hemisphere, snow accumulates more on the northeastern side and less on the southwestern side. For this reason, the southwestern side and ridges are less protected by snow in winter and are exposed to the cold, but the snow melts early in summer, and plants grow there for the longest period of time among high mountains. However, because they receive a lot of sunlight and are constantly exposed to the westerly winds, they tend to be dry and are strongly affected by the wind. On the northeastern side, they are protected by snow and are protected to a large extent from the cold in winter, but the snow melts slowly, which shortens the growing period, and at the bottom of the snowfields, it may only be one to two weeks between the thaw and the first snow. In years with heavy snowfall, the snow may not melt and plants may be trapped under snow for two years. However, once the snow melts, there is generally enough moisture and water, and they are not exposed to the strong westerly winds.

In addition to the large contrasting environmental divisions caused by snow accumulation, elements such as running water, rocky areas, structured soil, and landslides combine to form various ecological spaces in high mountains, where the environmental changes per unit area are remarkable, resulting in a wide variety of plant communities and a rich flora. The important environmental spaces of Japan's high mountains and the plant communities that occur there are as follows:

[1] Low grasslands in windswept areas These occur in the windiest areas of southwestern slopes and ridges, and are a mixture of graminoid plants such as Carex gracilis and Carex nigricans, herbaceous plants such as Lilium longiflorum, Amana nigricans, and Siberian sedge, and small shrubs such as Scutellaria baicalensis and Scutellaria baicalensis, as well as lichens such as Polytrichum communes, Polytrichum formosum, and Pectinifera fasciata, and bryophytes such as Sphaerotheca spp. and Sphaerotheca pallidum.

[2] Dwarf shrub communities in windswept areas These occur in the same environment as low grasslands, but at slightly lower altitudes or in areas with weaker winds. There are communities with a high concentration of evergreen dwarf shrubs such as the Japanese laurel, the Japanese hemlock, and the Japanese crowberry, and communities with a high concentration of summer-green dwarf shrubs such as the Japanese black laurel and the Urashima azalea, and sometimes a mixture of both. Mosses and lichens are abundant, just like in low grasslands. From the Tohoku region to Hokkaido, the Tsugazakura is added.

[3] Plant communities on structured gravel Soils move due to freezing and thawing, and gravel is sorted and moved according to particle size, arranging in polygonal shapes on flat ground and in stepped or linear shapes on slopes. In the fine particles, which are the most susceptible to movement, communities of dicentra, alpine viola, and other plants grow.

[4] Plant communities in collapsed areas In places where gravel moves due to gravity, plants such as rock clover and rock sedge grow sparsely. This is an environment with many alpine plants that have formed locally, and the representative species is the mountain bellflower of central Honshu.

[5] Snowfield plant communities (snowfield communities) In areas that remain moist after the snow melts, the soil develops well and plants such as Hakusan kozakura, Hakusan plantain, and Iwaichou grow. In the convex areas that dry out after the snow melts, communities of dwarf shrubs such as Aonotsugazakura and Aentroma chinensis form.

[6] Plant communities around springs and flowing water include many bryophytes such as Korean moss, as well as white plovers and alpine hawkweed.

[7] Rocky plant communities: In the shady rock crevices, plants such as Blue Fern and Japanese Fern grow, while in the sun, plants such as Spider Fern and Rhodiola Rosea grow.

It is possible to divide the environment of alpine mountains in temperate zones in the same way as alpine mountains in Japan, and even if the species are different, related plants are usually found in similar environmental spaces. Alpine mountains around the world are almost without exception subject to grazing, and this has a strong influence on alpine plant communities, but the alpine zone in Japan is a rare example that has been spared from grazing since recorded history.

Among Japan's high mountains, Mount Kitadake and Mount Higashidake in the Akaishi mountain range, Mount Shirouma in the Hida mountain range, and Mount Daisetsu in Hokkaido have the richest variety of alpine plants, but other mountains made of ultramafic rocks such as Mount Hayachine (Iwate Prefecture), Mount Yubari (Hokkaido), and Mount Shibutsu (Gunma Prefecture) also have unique flora, where alpine vegetation descends to a much lower altitude than usual.

Japan's alpine plants can be divided into three regions in terms of their genealogy: (1) the mountains of central Honshu, (2) the mountains of the Tohoku region from Mt. Iide to Mt. Hakkoda, and (3) the high mountains of Hokkaido. However, their flora has two sources, one in the northeastern Pacific region such as Alaska, and the other in eastern Siberia.

[Tatsuyuki Ohba]

"Oba Tatsuyuki and Takahashi Hideo, 'Universal Guide Series 33: Flowers of the Japanese Alps' (1985, Shogakukan)" ▽ "Takahashi Hideo, 'JTB Books: Alpine Plants' (1985, Japan Travel Bureau)" ▽ "Yamazaki Kei (ed.), 'Field Edition: Japanese Alpine Plants' (1985, Heibonsha)" ▽ "Aoyama Fujio, 'Nature Observation Series 21: Alpine Flowers' (1984, Shogakukan)" ▽ "Shimizu Takemi, 'New Illustrated Guide to Japanese Alpine Plants I and II in Primary Colors' (1982, 1983, Hoikusha)" ▽ "Oba Tatsuyuki and Kihara Hiroshi, 'Field Hundred Flowers: Mountain Flowers 2 and 3' (1982, Yama-to-Keikoku-sha)" ▽ "Oba Tatsuyuki and Takahashi Hideo, 'Japanese Plant Illustrated Guide 8: Alpine and Subalpine Flowers' (1978, Shakaishisosha)"

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

垂直分布帯でもっとも高い高山帯に生える植物をいうが、日本では針葉林（針葉樹林）帯から上の植物をも含めて、きわめて広義に使われている。

　高山植物は寒帯の植物に由来するものが多いが、低地の植物が、それぞれの地域で高山帯に適応するようになった現地形成の種類もある。寒帯に近い高山ほど、氷期に寒帯と植物の交流が頻繁、かつ高密度に行われるので、寒帯との共通の種類が多いが、寒帯から離れるにつれて植物相の独立の程度が高くなり、現地形成の種類が多くなる。また、寒帯に由来した植物も隔離のために分化が進行して、別の分類群に変化していることが多い。ヒマラヤから中国西部にかけての高山は、氷期にも周北極（北極周辺）の寒帯との連絡が少なく、その高山植物相はかなり独自である。アフリカのキリマンジャロなどの熱帯の高山は、気温の変化が年間ではなく、1日のうちの昼夜で繰り返されるという特殊な環境下にあり、また、高山相互の独立性が強いために、その植物相は山ごとに大きく違っている。アンデス山脈の高地も独特の植物相をもち、スミレ属のように、熱帯降雨林の構成種が山地に上昇し、変化したものも少なくない。ニュージーランド、オーストラリアにも高山があるが、その植物相はキンポウゲ科、リンドウ科などの北半球の寒帯や高山と共通する種属の多いことが注目される。熱帯から南半球にわたっては、北半球の寒冷地に起源すると考えられるウシノケグサ属など、いくつかの種属も知られている。高山植物の分布拡散には、氷期の地続き分布のほか、風、鳥などによる分布もあわせ考える必要がある。

　高山植物には、丈の低いわりに大きな花をつけるものが多いが、イネ科、カヤツリグサ科、イグサ科などの風媒花のグラミノイド植物（イネ科植物状の葉が細くて硬い植物）も重要な役割を果たしており、量的には蘚苔(せんたい)、地衣も無視することができない。また、高山植物には寒帯の植物と同じく、染色体の倍数性の高いものが多く、むかご（胎芽(たいが)）などによる無性生殖を行う種類が多い。

　高山では積雪の配分状態が植物の配分に重要な影響をもっている。北半球では、積雪は北東面により多く積もり、南西面は少ない。このため、南西面や尾根筋(すじ)では冬に積雪で保護されることが少なく、寒気にさらされるが、夏にはいち早く雪が消えて、高山のなかでは植物の生育期間がもっとも長い。しかし、日射量が多く、偏西風を常時受けるので、乾燥に傾き、風の影響が強く現れる。北東面では雪のために保護されて、冬の寒気からはかなりの程度に守られるが、融雪が遅く、そのために生育期間は短縮し、雪田の底では、雪解けから初雪まで1～2週間しかないこともある。降雪の多い年には雪が解けず、2年にわたって雪の下に閉じ込められる場合もある。しかし、雪が解ければ水湿は一般に十分で、強い偏西風にさらされることもない。

　この積雪による対照的な環境の大区分に加えて、流水、岩場、構造土、崩壊などの要素が複合して、さまざまな生態空間が形成されている高山は、単位面積当りの環境変化が著しく、それが多彩な植物群落と豊かな植物相を演出している。日本の高山の重要な環境空間と、そこに生ずる植物群落は次のようになる。

〔1〕風衝地の低小草原　南西斜面や尾根筋のもっとも風当りの強い所に生じ、ヒゲハリスゲ、オノエスゲなどのグラミノイド植物とミヤマシオガマ、チシマアマナ、チシマゼキショウなどの草本、チョウノスケソウ、オヤマノエンドウなどの小低木が混合し、さらにハナゴケ類、エイランタイ類、ムシゴケなどの地衣とシモフリゴケ、フトゴケなどの蘚苔類が複合する。

〔2〕風衝地の矮性(わいせい)低木群落　低小草原と同様の環境だが、それよりやや低い所、あるいはやや風の弱い所に生ずる。ミネズオウ、コメバツガザクラ、ガンコウランなどの常緑性の矮性低木の多い群落と、クロマメノキ、ウラシマツツジなどの夏緑性の矮性低木の多い群落とがあり、また、両者が混合している場合もある。蘚苔、地衣は低小草原と同様に多い。東北地方から北海道にかけてはチシマツガザクラが加わる。

〔3〕構造土礫地(れきち)の植物群落　氷結融解によって土壌が動き、砂礫が粒径別に選別移動して平坦(へいたん)地では多角形に、斜面では階段状または線状に配列する環境で、そのもっとも動きやすい細粒部には、コマクサ、タカネスミレなどの群落が生ずる。

〔4〕崩壊地の植物群落　重力によって砂礫が移動する所で、イワツメクサ、イワスゲなどがまばらに生える。現地形成の高山植物の多い環境で、本州中部のヤマホタルブクロなどがこの代表種である。

〔5〕雪田の植物群落（雪田群落）　融雪後も湿っている所で、土壌がよく発達し、ハクサンコザクラ、ハクサンオオバコ、イワイチョウなどが生え、融雪後に乾く凸状の所では、アオノツガザクラ、チングルマなどの矮性低木の群落となる。

〔6〕湧水(ゆうすい)地、流水縁の植物群落　チョウセンハリガネゴケなどの蘚苔類が多いほか、シロウマチドリ、タカネイなどがみられる。

〔7〕岩場の植物群落　日陰の岩隙(がんげき)ではアオチャセンシダ、トガクシデンダなどが、日なたにはクモマナズナ、イワベンケイなどがつく。

　温帯の高山は、どこでも日本の高山と同じような環境区分が可能で、種は違っても同じような環境空間には、類縁の植物がみられるのが普通である。世界各地の高山はほとんど例外なく放牧され、高山植物群落にその影響が強く現れているが、日本の高山帯は有史以来放牧を免れてきた希少な例である。

　日本の高山では、赤石山系の北岳(きただけ)や東岳、飛騨(ひだ)山系の白馬(しろうま)岳、北海道の大雪山(たいせつざん)がもっとも高山植物の種類に富んでいるが、ほかに早池峰山(はやちねさん)（岩手県）、夕張(ゆうばり)岳（北海道）、至仏(しぶつ)山（群馬県）などの超塩基性岩の山も特異な植物相を示し、そこでは高山帯的な植生が通常よりずっと低位置に降りている。

　日本の高山植物は、区系的にみると、(1)本州中部山岳、(2)飯豊(いいで)山から八甲田(はっこうだ)山までの東北地方の山、(3)北海道の高山の3地域に区画できるが、その植物相には、アラスカなどの周北太平洋地域と東シベリア方面の二つの源流が認められる。

［大場達之］

『大場達之・高橋秀男著『万有ガイド・シリーズ33　日本アルプスの花』（1985・小学館）』▽『高橋秀男著『JTBブックス　高山植物』（1985・日本交通公社）』▽『山崎敬編『フィールド版　日本の高山植物』（1985・平凡社）』▽『青山富士夫著『自然観察シリーズ21　高山の花』（1984・小学館）』▽『清水建美著『原色新日本高山植物図鑑Ⅰ・Ⅱ』（1982、1983・保育社）』▽『大場達之・木原浩著『フィールド百花　山の花2・3』（1982・山と渓谷社）』▽『大場達之・高橋秀男著『日本植物図鑑8　高山と亜高山の花』（1978・社会思想社）』

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