Quercus robur and Q. petraea responses to hydroclimatic changes and extremes in the Loire River valley, central France

With more frequent and severe droughts under ongoing global warming impacting European forests, major components of French forest ecosystems, such as oak woodlands, are at increasing risk of decline. Tree-ring width (TRW) records provide valuable insights into both short- and long-term drought impacts on tree growth and have been widely used to improve our understanding of the spatial and temporal patterns of drought effects on forest ecosystems. However, such data are still lacking for oaks in central France over the past decade, and no high-resolution studies have yet explored oak responses to drought in French floodplain environments. Here, we investigated the climatic sensitivity, long-term growth response, and drought impact on TRW over the last century in two oak species from the Loire River basin in central France: riparian Quercus robur and non-riparian Q. petraea . Tree growth in both species was positively correlated with growing season SPEI and precipitation, and negatively with summer maximum temperature. Growth of riparian oaks was additionally influenced by summer river discharge and exhibited higher and more stable sensitivity to hydroclimatic variability than Q. petraea , reflecting species-specific traits and local site conditions. Despite these differences, both species showed consistent growth reductions during drought years, with full recovery to pre-drought growth levels not always achieved in the following year. Nevertheless, similar long-term growth patterns, with no overall decline over the last century, suggest a certain capacity of oaks to buffer drought impacts. These findings highlight the importance of continued monitoring of drought effects across contrasting ecological contexts and have direct management implications, particularly for Loire River riparian forests protected under the Natura 2000 network and encompassing national nature reserves.