Until when will the enhancement of biodiversity and ecosystem function through intensive thinning be sustained?

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K06143
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 40010:Forest science-related
• Research Institution: Shinshu University
• Principal Investigator: Shirota Tetsuoh 信州大学, 学術研究院農学系, 助教 (10374711)
• Co-Investigator(Kenkyū-buntansha): 岡野 哲郎 信州大学, 学術研究院農学系, 教授 (00194374)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 強度間伐 / 生物多様性 / 生態系機能 / 有効期間

Outline of Final Research Achievements

A study was conducted on the biodiversity of a Hinoki cypress plantation 20 years after intensive thinning, analyzing the data along with previous monitoring data. The light environment on the forest floor deteriorated rapidly from the 14th year, leading to a decline in species diversity, population numbers, tree form development, and productivity. Most of the remaining species were understory species, and the conversion to a mixed forest of conifers and broadleaf trees, along with the associated increase in biodiversity, seems not to be possible. Additionally, a large portion of the photosynthetic assimilation was allocated to stem production of the Hinoki cypress. In other words, it took more work for the ecosystem functions to be expressed by the broadleaf trees in the understory. From this, the effects of intensive thinning last for about 15 to 20 years.

Free Research Field

森林科学

Academic Significance and Societal Importance of the Research Achievements

強度間伐の生物多様性向上に対する顕著な効果は最初の５年間に留まった。その後，１５年までは低木層としての発達および多くの葉量を蓄えかつ土壌へ供給することで，土壌の改善を通じた生態系機能の向上に寄与すると考えられた。しかし，林冠が閉鎖すると低木層の機能が大きく損なわれる。そのため，強度間伐による生態系機能の改善には１５～２０年間という効果の”持続期限”が存在する。今回明らかにされた”有効期限”を念頭に置いた森林施業計画を策定することで，引き続き生物多様性と生態系機能を向上させることが可能となる。