Data from: Underlying geology and climate interactively shape climate change refugia in mountain streams

Identifying climate-change refugia is a key adaptation strategy for
reducing global warming impacts. Knowledge of the effects of underlying
geology on thermal regime along climate gradients and the ecological
responses to the geology-controlled thermal regime is essential to plan
appropriate climate adaptation strategies. In the present study, the
dominance of volcanic rocks in the watershed is used as a landscape-scale
surrogate for cold groundwater inputs to clarify the importance of
underlying geology in stream ecosystems along climate gradients. First,
using hundreds of monitoring stations distributed across multiple
catchments, we explored the relationship between watershed geology and the
mean summer water temperature of mountain streams along climate gradients
in the Japanese archipelago. Mean summer water temperature was explained
by the interaction between the watershed geology and climate in addition
to independent effects. The cooling effect supported by volcanic rocks
reached up to 3.3°C among study regions, which was more pronounced in
streams with less summer precipitation or lower air temperatures. Next, we
examined the function of volcanic streams as cold refugia under
contemporary and future climatic conditions. Community composition
analyses revealed that volcanic streams hosted distinct stream communities
composed of more cold-water species compared with non-volcanic streams.
Scenario analyses based on multiple GCMs and RCPs revealed a
geology-related pattern of thermal habitat loss for cold-water species.
Non-volcanic streams rapidly declined in thermally suitable habitats for
lotic sculpins even under the lowest emission scenario (RCP 2.6). In
contrast, most volcanic streams will be sustained below the thermal
threshold, especially for low and mid-level emission scenarios (RCP 2.6,
4.5). However, the distinct stream community in volcanic streams and
geology-dependent habitat loss for lotic sculpins was not uniform and was
more pronounced in streams with less summer precipitation or lower air
temperatures. These findings highlight that underlying geology, climate
variability, and their interaction should be considered simultaneously for
effective management of climate-change refugia in mountain
streams.