How does rain journey through the vertical structures of tree canopy? Development of physical model using chemical analysis

2022 Fiscal Year Final Research Report

• Project/Area Number: 17KK0159
• Research Category: Fund for the Promotion of Joint International Research (Fostering Joint International Research)
• Allocation Type: Multi-year Fund
• Research Field: Forest science
• Research Institution: Forest Research and Management Organization
• Principal Investigator: Nanko Kazuki 国立研究開発法人森林研究・整備機構, 森林総合研究所, 主任研究員 等 (40588951)
• Project Period (FY): 2018 – 2022
• Keywords: 樹冠遮断 / 樹冠通過雨 / 雨滴 / 濡れ / 撥水性 / 樹幹流

Outline of Final Research Achievements

Using raindrop data observed inside and outside the forest, we established a method to separate rainfall passing through the canopy into four components: direct throughfall, splash throughfall, canopy drip from leaves, and canopy drip from the bark surface. We clarified the differences in component ratios among evergreen conifers, foliated broadleaf trees, and unfoliated broadleaf trees. Field observations in an American beech forest showed variability within rainfall events and seasonal variation in the throughfall generation process. The study determined the effects of tree species, defoliation status, branch and leaf structure, and water repellency on the process of rainfall partitioning by the canopy.

Free Research Field

森林水文学

Academic Significance and Societal Importance of the Research Achievements

水循環に対する森林の影響評価に必要な樹冠による雨水分配プロセスについて、樹種、葉の有無、葉の量、葉や枝の表面の構造や撥水性が与える影響を解明した。本成果により、森林管理や樹種転換に伴う樹冠遮断損失量の変化を、仮想的に比較・予測することができるようになる。針広混交の育成複層林の造成等へ転換に対応するために、樹種による水源涵養機能の差異を評価するための基礎データとなり、森林の多面的機能に関わる様々な国の施策や社会的ニーズに合致している。