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 nonvolcanic streams. Scenario analyses based on multiple global climate models and Representative Concentration Pathways (RCPs) revealed a geology-related pattern of thermal habitat loss for cold-water species. Nonvolcanic 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 were 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 the effective management of climate-change refugia in mountain streams.

中文翻译：

---

底层地质和气候相互作用塑造山区溪流中的气候变化避难所

确定气候变化避难所是减少全球变暖影响的关键适应战略。了解基础地质对沿气候梯度的热状况的影响以及对地质控制的热状况的生态响应对于规划适当的气候适应战略至关重要。在本研究中，火山岩在流域中的主导地位被用作冷地下水输入的景观尺度替代品，以阐明潜在地质在沿气候梯度的河流生态系统中的重要性。首先，我们利用分布在多个流域的数百个监测站，探索了日本列岛气候梯度沿线的流域地质与山间溪流夏季平均水温之间的关系。除了独立影响外，夏季平均水温还可以通过流域地质和气候之间的相互作用来解释。在研究区域中，火山岩支持的降温效果高达 3.3°C，这在夏季降水较少或气温较低的溪流中更为明显。接下来，我们研究了火山流在当代和未来气候条件下作为寒冷避难所的功能。群落组成分析表明，与非火山溪流相比，火山溪流拥有由更多冷水物种组成的独特溪流群落。基于多个全球气候模型和代表性浓度路径 (RCP) 的情景分析揭示了冷水物种热栖息地丧失的地质相关模式。即使在最低排放情景 (RCP 2.6) 下，非火山溪流在热适宜的栖息地也迅速减少，适合 lotic sculpins。相比之下，大多数火山流将持续低于热阈值，特别是对于中低排放情景（RCP 2.6、4.5）。然而，火山溪流中独特的溪流群落和依赖于地质条件的多头杜鹃栖息地丧失并不统一，并且在夏季降水较少或气温较低的溪流中更为明显。这些发现强调，为了有效管理山区溪流中的气候变化避难所，应同时考虑潜在的地质学、气候变率及其相互作用。大多数火山流将持续低于热阈值，特别是对于中低排放情景（RCP 2.6、4.5）。然而，火山溪流中独特的溪流群落和依赖于地质条件的多头杜鹃栖息地丧失并不统一，并且在夏季降水较少或气温较低的溪流中更为明显。这些发现强调，为了有效管理山区溪流中的气候变化避难所，应同时考虑潜在的地质学、气候变率及其相互作用。大多数火山流将持续低于热阈值，特别是对于中低排放情景（RCP 2.6、4.5）。然而，火山溪流中独特的溪流群落和依赖于地质条件的多头杜鹃栖息地丧失并不统一，并且在夏季降水较少或气温较低的溪流中更为明显。这些发现强调，为了有效管理山区溪流中的气候变化避难所，应同时考虑潜在的地质学、气候变率及其相互作用。火山溪流中独特的溪流群落和 lotic sculpins 的依赖于地质的栖息地丧失并不统一，并且在夏季降水较少或气温较低的溪流中更为明显。这些发现强调，为了有效管理山区溪流中的气候变化避难所，应同时考虑潜在的地质学、气候变率及其相互作用。火山溪流中独特的溪流群落和 lotic sculpins 的依赖于地质的栖息地丧失并不统一，并且在夏季降水较少或气温较低的溪流中更为明显。这些发现强调，为了有效管理山区溪流中的气候变化避难所，应同时考虑潜在的地质学、气候变率及其相互作用。