Influence of volcanic ash in soils on Ca cycling in forest ecosystems

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K07788
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Forest science
• Research Institution: National Institute for Environmental Studies
• Principal Investigator: KOSHIKAWA Masami (金尾昌美) 国立研究開発法人国立環境研究所, 地域環境研究センター, 主任研究員 (80291045)
• Co-Investigator(Kenkyū-buntansha): 渡邊 未来 国立研究開発法人国立環境研究所, 地域環境研究センター, 主任研究員 (50455250)
• Research Collaborator: SASE Hiroyuki ; SHIN Ki-Cheol ; MIURA Shingo ; MURATA Tomoyoshi ; TAKAMATSU Takejiro ; NAKANO Takanori
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 火山灰 / ストロンチウム同位体比 / カルシウム供給源 / 渓流水 / チャート

Outline of Final Research Achievements

The sources of Ca in forest ecosystems in Japan have been considered to be sea salt, bedrock, and Asian dust. However, we believe that volcanic ash in soil also is an important source of Ca in areas with volcanic ash soil, especially in the areas where the Ca supply from bedrock is low. We reported the significant contribution of volcanic ash in soil to Ca in stream waters in a granite watershed of Tsukuba area, using stable isotope of Sr, a good proxy of Ca. To evaluate the contribution of volcanic substances to ecosystems, we conducted a similar study at the forest on Mount Amamaki where similar volcanic ash is distributed in soil and chert with high resistance to chemical weathering are widely distributed. We determined the concentrations of Sr and Ca and the isotope ratio of Sr in the 42 stream waters, and those of precipitation, bedrock and volcanic ash which are considered to be the end component, and estimated the contribution of volcanic ash to Sr and Ca in stream waters.

Free Research Field

分析化学、土壌化学、陸水化学

Academic Significance and Societal Importance of the Research Achievements

これまで、土壌中における火山灰の機能に関する研究は、有機物やイオウに対する吸着保持作用を調べたものに限られている。これに対し本研究は、全く異なる視点からCa 供給源として火山灰に着目しており、森林土壌における火山灰の機能研究のみならず、Ca 循環研究にも新展開をもたらすことが期待できる。さらに、本研究で確立するCa 起源解析手法が広く実施されれば、「日本の多くの土壌が欧米の土壌よりも酸耐性が高いのは火山灰の効果である」という基礎的かつ未解明な問題を明らかにすることが出来る。