2022 Fiscal Year Final Research Report

How does low phosphorus availability in volcanic soil affect the soil nitrogen distribution in a watershed?

Research Project

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Project/Area Number	19K15873
Research Category	Grant-in-Aid for Early-Career Scientists
Allocation Type	Multi-year Fund
Review Section	Basic Section 40010:Forest science-related
Research Institution	Forest Research and Management Organization (2021-2022) National Agriculture and Food Research Organization (2020) Akita Prefectural University (2019)
Principal Investigator	Hosokawa Nanae 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 (80821602)
Project Period (FY)	2019-04-01 – 2023-03-31
Keywords	連続リン抽出 / 活性アルミニウム / アルミニウム-腐植複合体 / 地形 / スギ林土壌
Outline of Final Research Achievements	The study clarified the effect of volcanic materials on the amount and dynamics of nutrients such as nitrogen and phosphorous in forest soil taking care of lithology, topography, and soil chemicals. First, some methods of phosphorous fraction were compared to explore the suitable method since the volcanic soils have distinct chemistry. Then, the modified fraction method was applied to the soil samples under cedar forests collected from multiple points in a watershed. Finally, the relationships among volcanic materials, soil phosphorous availability, and soil nitrogen mineralization indicators were analyzed by multivariable analyses. The results showed soil phosphorous and nitrogen dynamics were significantly affected by volcanic materials. Notably, lithology and topography affected phosphorous amounts, and volcanic materials influenced phosphorous availability.
Free Research Field	森林立地学
Academic Significance and Societal Importance of the Research Achievements	窒素やリンは森林生態系の一次生産や水質形成等に大きく関わる。火山灰由来物質はリン動態を大きく支配する一方で、リン利用性は窒素動態を制限すると言われているため、これら物質の密接な関係が予想されるが、その実態やメカニズムには不明な点が多い。本研究によって、森林土壌中のリンや窒素の動態は火山灰由来物質に大きく影響を受けることが明らかとなった。この成果は、森林の一次生産や水質形成等に関わる森林生態系の養分循環機能の基礎的知見となる。さらに、火山の多い日本では火山灰由来物質を含む土壌が広範囲に分布するため、本研究で得られた知見はより多くの地域で森林管理法の開発に役立つ。