Geology‐Climate Interactions are Key Determinants of Climate‐Change Refugia in Japanese Mountain Streams

Abstract

Photo 1. Example of the confluence of a volcanic and nonvolcanic stream (left panel). The right panel is a thermal photograph of the confluence taken using a TVS-500 camera (Nippon Avionics Co., Ltd.) on September 17, 2019, where blue colors correspond to the cold water from the volcanic stream mixing with the warmer (orange) water from the nonvolcanic stream. Photo credit: Kenta Iwasaki. Photo 2. View of a volcanic stream, Ponnunobe stream, the Sorachi river, Hokkaido, Japan. The stream is located inside the University of Tokyo Hokkaido Forest. Many springs (top panels) occur in around the main channel (bottom panel). In this region, the mean summer water temperature of volcanic streams is 3°C colder than that of nonvolcanic streams on average. Photo credit: Yu Nagasaka. Photo 3. Wrinklehead sculpin (upper panel: Cottus nozawae) and Southern Asian Dolly Varden (lower panel: Salvelinus curilus) two major cold-water species in northern Japan. Their distribution is tightly restricted by summer water temperature. Photo credit: Yu Nagasaka (upper panel) and Chiharu Furusawa (lower panel). Photo 4. View of biotic and abiotic surveys in mountain streams, Japan. Macroinvertebrates (upper left panel) and fish (lower left panel) were collected once in each monitoring stream. Water loggers were installed with short sections of perforated PVC pipes to facilitate water exchange and shield them from sunlight (right panels). Photo credit: Jorge García Molinos. Photo 5. Dynamic changes in riverscapes at a monitoring site due to a large flood associated with Typhoon Hagibis, 2019 (before: upper panel, after: lower panel). Monitoring of water temperature in the Japanese archipelago is very challenging because of the many typhoons hitting the archipelago every summer season. Unfortunately, the temperature data of this site in 2019 was not available due to the loss of the logger. The yellow bridge at the upper-left corner of the picture offers a good visual reference to compare both pictures. Photo credit: Nobuo Ishiyama. These photographs illustrate the article “Underlying geology and climate interactively shape climate change refugia in mountain streams” by Ishiyama, N., Sueyoshi, M., García Molinos, J., Iwasaki, K., Negishi, J. N., Koizumi, I., Nagayama, S., Nagasaka, A., Nagasaka, Y. & Nakamura, F. published in Ecological Monographs. https://doi.org/10.1002/ecm.1566