報告書番号

V08021

タイトル（和文）

自然の再生力を活用した森林管理手法の提案―赤城山南麓のアカマツ林をケーススタディーとして―

タイトル（英文）

Application of natural regeneration for forest management-A case study for the Japanese red pine forest on the south slope of Mt. Akagi-

概要 （図表や脚注は「報告書全文」に掲載しております）

自然の再生力を活用した森林の効率的な管理手法を検討するために，GISデータを用いた目標とすべき森林像の設定と，管理実験によるモニタリング調査を行った．植生と立地環境の解析から，対象地域で成立可能な自然林はコナラ林であることが推定された．目標とすべき森林の代表樹種であるコナラの稚樹は，過去の林床管理によって定着が困難となっていた．そこで管理を停止した実験区を設置したところ多数の稚樹が発生したものの，4年間で約90％が死亡した．稚樹の生存に影響を与える要因を解析したところ，アズマネザサの被度が大きな影響を与えていることが明らかとなった．アズマネザサの被度の4年間の被度は，管理停止実験区で増大していたが，管理継続区では抑制されていた．実験データにもとづく推移確率行列によるシミュレーションの結果，アズマネザサの被度は2～3年おきの下草刈りによって抑制できることが推定された．自然の再生力を活用した森林管理の適用に際しては，周辺環境の分析にもとづく明確な管理目標の設定と，モニタリングによる効果の検証が必要である．

概要 （英文）

Natural regeneration is expected to be a low-cost end ecologically-sound forest management approach. Previous studies suggested that restorations of disturbed site by natural regeneration were successful in some human-disturbed sites. However, potentials and limitations of application of natural regeneration for secondary and artificial forest management have been unknown. In this study, we decided the target-forest by vegetation and environment database and monitored the understory vegetation to examine effectiveness of natural regeneration for forest management.
First, we collected GIS data from the study area and its surroundings for deciding target forest type. Quercus serrata forest was extracted as a target forest based on analyses of the vegetation and the environmental relationships. Many adult individuals of Quercus serrata were growing on the middle layer of the study forest, but few juveniles were growing on the understory. Discontinuation of understory mowing would be expected to accelerate seedling establishment. Thus we placed forest experiment sites protected from understory managements and monitored the tree seedlings and the understory vegetations.
In the first year, 191 seedlings of Quercus serrata were emerged. However, 90 % of seedlings had died during four years. The result of statistical analysis suggested that dwarf bamboo prevented establishment and survival of natural Quercus seedlings.
In order to clarify effective understory management for seedling establishment of Quercus serrata, we analyzed the dynamics of dwarf bamboo for four years. The result of Markov chain modeling suggested that two or three interval mowing is most effective for dwarf bamboo control and facilitation of Quercus seedling establishment.
Natural regeneration is considered to be an efficient approach for forest management but its success is uncertain. Adaptive management based on target-setting and vegetation monitoring will be needed for broad application of this approach.

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