Warming-induced shift in the climate response of Scotland’s temperate rainforests

Britain’s temperate rainforests contain rare plant communities of global conservation importance. Whilst climate models predict sustained biome suitability in Scotland, woodland-level vulnerabilities under current and projected regional warming remain unknown. Here, we present tree-ring width measurements from a network of 267 oaks ( Quercus spp. ), growing under extreme maritime conditions at ten sites across western Scotland. We investigate trends in climate-growth relationships and drivers of growth synchrony, and explore growth responses to extreme climate years. We also analyse observational phenology data to quantify growing season changes over past decades. Our regional master chronology exhibits pronounced temporal non-stationarity with major reductions in temperature sensitivity after North Atlantic warming shifts ( 1935 – 1980; r = 0.50, p < 0.001, 2004 – 2024; r = -0.01, p = 0.96 ), with evidence of corresponding increases in moisture sensitivity. This coincides with a modest increase in growth synchrony in response to increasingly frequent climate extremes. We further observe a reduction in the positive growth response during warm years from + 0.97 SD (1901–1980 CE) to insignificant (1901–2023 CE), whilst the negative growth response to dry years is prolonged though statistically insignificant. Finally, we observe both an advancement of the growing season by approximately one week, as well as a minor contraction, in the past three decades ( p < 0.001 ), likely impacting potential productivity gains. Despite the pronounced ecosystem changes, oak trees do not presently appear to show negative growth responses under regional warming. Yet, the shift towards moisture sensitivity will continue under climate change, with uncertain impacts on oak growth; thus adaptive management strategies will be necessary for long-term ecosystem restoration success. • We investigate the climate sensitivity of Scotland’s oak temperate rainforests. • Temperature (precipitation) sensitivity is decreasing (increasing) since the 1980s. • Higher temperatures do not result in higher growth rates of oaks. • Oak growing seasons have advanced by a week over the past decades. • Successful ecosystem restoration will require climate-adaptive management.