[M-IS13] 生物地球化学

[MIS13-07] 超高分解能質量分析法を用いた温帯林における林外雨，林内雨および土壌水の溶存有機物の解析

*井手 淳一郎¹、山瀬 敬太郎²、Jeong Seonghun³、牧田 直樹⁴、西村 裕志⁵、福島 慶太郎⁶、大槻 恭一⁷、大橋 瑞江⁸ (1.九州大学　持続可能な社会のための決断科学センター、2.兵庫県立農林水産技術総合センター　森林林業技術センター、3.九州大学大学院　生物資源環境科学府、4.信州大学　理学部、5.京都大学　生存圏研究所、6.京都大学　生態学研究センター、7.九州大学　農学研究院、8.兵庫県立大学　環境人間学部)

キーワード：生体分子、炭素動態、林相、フーリエ変換イオンサイクロトロン共鳴型質量分析法、分子多様性

This study aimed to clarify alternations of the quality of dissolved organic matter (DOM) in rainwater moving through temperate forests. For this, we compared the molecular composition of dissolved organic matter (DOM) between bulk deposition (rainfall), throughfall and soil water in Japanese cypress (Cryptomeria japonica) and Japanese stone oak (Lithocarpus edulis) stands, which were regarded as coniferous and broad-leaved stands, respectively, during a rain event. Analyses of ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry revealed that the number of DOM molecular species detected was significantly greater in throughfall and soil water than in rainfall (p < 0.05). In contrast, the number of molecular species did not significantly differ between throughfall and soil water (p > 0.05). There were no significant differences in the number of molecular species in both throughfall and soil water between coniferous and broad-leaved stands (p > 0.05). These results suggest that a diverse array of DOM molecules are provided from the tree canopies and soils to the rainwater in both stands. Approximately 52%–59% of the total molecular species in throughfall samples (n = 6) were unique to throughfall. Additionally, approximately a half of the total molecular species in soil water samples (n = 5) were unique to soil water. The classification of molecular species into seven biomolecular classes using a van Krevelen diagram revealed that throughfall samples contained many of lipid and protein molecules compared to rainfall and soil water samples, whereas approximately 70% of the total molecular species in soil water were lignin-like molecules. The analysis of multidimensional scaling revealed that molecular species were significantly differentiated between rainfall, throughfall and soil water (p < 0.05). These results indicate that there are diverse molecules unique to throughfall and soil water and that the quality of DOM drastically changes in rainwater as it moves through temperate forests.