In mountainous regions, global warming will likely affect the frequency and magnitude of geomorphic processes. This is also the case for rockfall, one of the most common mass movements on steep slopes. Rainfall, snowmelt, or freeze-thaw cycles are the main drivers of rockfall activity, rockfall hazards are thus generally thought to become more relevant in a context of climate change. At high elevations, unequivocal relationships have been found between increased rockfall activity, permafrost thawing and global warming. By contrast, below the permafrost limit, studies are scarcer. They mostly rely on short or incomplete rockfall records, and have so far failed to identify climatically induced trends in rockfall records. Here, using a dendrogeomorphic approach, we develop two continuous 60-year long chronologies of rockfall activity in the Vercors and Diois massifs (French Alps); both sites are located clearly below the permafrost limit. Uncertainties related to the decreasing number of trees available back in time were quantified based on a detailed mapping of trees covering the slope across time. Significant multiple regression models with reconstructed rockfalls as predictors and local changes in climatic conditions since 1959 extracted from the SAFRAN reanalysis dataset as predictants were fitted to investigate the potential impacts of global warming on rockfall activity at both sites. In the Vercors massif, the strong increase in reconstructed rockfall can be ascribed to the recolonization of the forest stand and the over-representation of young trees; changes that are observed should not therefore be ascribed to climatic fluctuations. In the Diois massif, we identify annual precipitation totals and mean temperatures as statistically significant drivers of rockfall activity but no significant increasing trend was identified in the reconstruction. All in all, despite the stringency of our approach, we cannot therefore confirm that rockfall hazard will increase as a result of global warming at our sites.

在山区，全球变暖可能会影响地貌过程的频率和幅度。落石也是如此，这是陡坡上最常见的群众运动之一。降雨、融雪或冻融循环是落石活动的主要驱动因素，因此通常认为落石危害在气候变化的背景下变得更加相关。在高海拔地区，已经发现落石活动增加、永久冻土融化和全球变暖之间存在明确的关系。相比之下，在永久冻土限制之下，研究较少。他们主要依靠简短或不完整的落石记录，迄今为止未能确定落石记录中气候诱发的趋势。在这里，使用树状形态方法，我们在 Vercors 和 Diois 地块（法国阿尔卑斯山）开发了两个连续 60 年的落石活动年表；这两个地点都明显低于永久冻土界限。基于随时间覆盖斜坡的树木的详细映射，量化了与过去可用的树木数量减少相关的不确定性。自 1959 年以来，从 SAFRAN 再分析数据集中提取的以重建的落石为预测因子和局部气候条件变化作为预测因子的显着多元回归模型被拟合用于研究全球变暖对两个地点落石活动的潜在影响。在 Vercors 地块中，重建落石量的大幅增加可归因于林分的重新定殖和幼树的过多；因此，观察到的变化不应归因于气候波动。在 Diois 地块中，我们将年降水总量和平均温度确定为落石活动的统计显着驱动因素，但在重建中没有发现显着的增加趋势。总而言之，尽管我们的方法很严格，但我们不能因此确认，由于我们现场的全球变暖，落石危险会增加。