Natural forest - Tennenrin

A general term for forests that have naturally regenerated without human intervention. Natural forest is a forestry statistical term established from the perspective of timber production, and does not include bamboo forests and bare timber land (logged areas, grass areas) that are not subject to timber production. From the perspective of nature conservation and environmental conservation, natural forests are divided into secondary forests (naturally regenerated forests on logged areas) and virgin forests. As of 2007, the area of ​​natural forests in Japan was 13.38 million hectares, accounting for 53% of the total forest area. Bamboo forests and bare timber land accounted for 1.37 million hectares, or 5%, (Forest and Forestry White Paper 2012 edition). Most natural forests are broadleaf forests, but there are also natural coniferous forests that produce fine cedar and cypress trees. The natural Akita cedar forests found in the northern part of Akita Prefecture, the natural Kiso cypress forests found in the Kiso Valley of Nagano Prefecture, and the Yaku cedar forests in Kyushu are representative natural coniferous forests in Japan. During the period of "high economic growth," large-scale felling of natural coniferous forests has led to a situation in which the survival of the ecosystem as a species is in jeopardy. Furthermore, natural broadleaf forests were used as household fuel such as charcoal and firewood until the 1950s, and from the 1960s they were widely used as raw materials for paper, pulp, and chips, but since the 1970s, imports of chips have increased sharply, and the use of natural broadleaf forest chips has declined significantly. Natural broadleaf forests were also widely used as furniture materials, but this furniture use has also been replaced by imported wood products. Natural red pine and black pine forests were also distributed throughout the country, but since the 1970s, damage caused by pine bark beetles has spread nationwide, and many natural pine forests have been lost. The Great East Japan Earthquake of March 11, 2011 also caused widespread loss of natural pine forests along the coast. Natural forests are forests that have remained almost untouched by human intervention, and are an indispensable and valuable resource for studying the ecology of Japan's ancient forest vegetation, elucidating the mechanisms of the public functions of forests, such as land conservation and water source conservation, and even developing medicinal products.

[Yamagishi Kiyotaka]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

人の手が入らずに自然更新で成林した森林の総称。天然林は、木材生産の観点から設けられた林業統計用語であり、木材生産の対象とならない竹林、無立木地（伐採跡地、草生地）は天然林に含まれない。自然保護や環境保全の観点からは、天然林は二次林（伐採跡地の自然更新林）と原生林に区分される。2007年（平成19）時点の日本の天然林面積は1338万ヘクタール、全森林面積の53％を占める。竹林、無立木地は137万ヘクタール、5％となっている（『森林・林業白書』2012年版）。天然林の大半は広葉樹林からなるが、スギ、ヒノキの銘木を生み出す天然の針葉樹林も存在する。秋田県の北部地域に分布する天然秋田スギ林、長野県の木曽谷に分布する天然木曽ヒノキ林、九州の屋久スギ林などは、日本を代表する天然針葉樹林である。天然針葉樹林は「高度経済成長」の過程で大規模伐採が繰り返され、種としての生態系の存続が危ぶまれる事態になっている。また、広葉樹天然林は、1950年代までは木炭、薪(まき)などの家庭用燃料として利用され、1960年代からは紙・パルプ・チップ原料として多く利用されてきたが、1970年代からチップ輸入が急増し、広葉樹天然林のチップ利用が大きく後退している。この他、広葉樹天然林は、家具材としても多く使用されてきたが、その家具用利用も外材製品によって置き換わられている。天然のアカマツ林やクロマツ林も各地に分布していたが、1970年代ごろから松くい虫の被害が全国的に広がり、天然マツ林の多くが失われている。2011年3月11日の東日本大震災でも、沿岸部の天然マツ林が広範に失われた。天然林は、人手がほとんど加わっていない森林であり、日本古来の森林植生の生態学的な解明や、森林のもつ国土保全機能や水源涵養(かんよう)機能などの公益的機能のメカニズムの解明、さらには薬用品開発などを行ううえで、欠くことのできない貴重な資源でもある。

［山岸清隆］

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