IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 BOOK OF ABSTRACTS 92 Environment, Agriculture, and Forestry Tuesday, 25 August 2026 / Hall B+C SL42 Seasonal and Spatial Variations of Dissolved Organic Matter in Throughfall in CoolTemperate Birch Stands, Northern Japan Jun‘ichiro Ide1, Ryoei Kobayashi1, Masaharu Kato1, Ryo Oyamada1, Izuki Endo1,2,3 1 Department of Applied Chemistry and Bioscience, Chitose Institute of Science and Technology, 758-65 Bibi, Chitose 066-8655, Japan; E-mail: j-ide@photon.chitose.ac.jp 2 Forestry Research Institute, Hokkaido Research Organization, Bibai 079-0198, Japan 3 School of Human Science and Environment, University of Hyogo, Himeji 670-0092, Japan Forest fragmentation can change water and biogeochemical cycles especially in the boundary area of the forest (i.e., edge), such as increase in dry deposition of atmospheric pollutants, which is often known as „edge effect“ [1–3]. Yet it remains poorly constrained how the edges affect biogeochemical cycles depending on seasons via rainwater passing through the forest canopy in cool-temperate regions. In this study, we focused on dissolved organic matter (DOM), which plays a critical role in biogeochemical cycles, and aimed to examine how the quantity and quality of DOM differ depending on site conditions in a cool-temperate forest. To achieve this, throughfall (TF) water samples were collected twice a month at a 10 m-by10 m plot installed in each of the edge and interior of the silver birch (Betula platyphylla var. japonica) forest stands, located in Chitose, northern Japan, between May and Nov in 2024. The TF amounts and canopy openness were measured on site and dissolved organic carbon (DOC) content and specific ultraviolet absorbance (SUVA) of the samples were analyzed in the lab. DOC deposition during the observation period did not differ between the edge and interior of the forest. SUVA was significantly greater during the growing season (May–Aug) than during the dormant season (Sep–Nov) at a given DOC deposition. This suggests that DOM in TF water contained abundant aromatic compounds derived from plant tissues [4] during the growing season presumably because the tree metabolism was active, which in turn increased the leaf leachates. On the other hand, SUVA was slightly lower in the edge than in the interior during the dormant season. Since negative correlation was found between SUVA and the canopy openness and the canopy openness was slightly greater in the edge than in the interior, our results suggest that litterfall progresses earlier in the edge during the dormant season, which decreases the contact opportunity of rainwater and tree canopy and consequently affects the SUVA level. In the conference, we are also going to report the results regarding molecular composition of DOM detected by ultrahigh-resolution mass spectrometry.
RkJQdWJsaXNoZXIy NDA4Mjc=