Heat wave impacts on tree growth and recovery in temperate forests depend on leaf phenology

• We assessed how the 2022 heat wave impacted eight temperate tree species. • Early-leafing species showed the strongest growth loss after the heat wave. • Wood anatomy and δ 13 C did not show abrupt changes after the heat wave. • Acer pseudoplatanus showed a lower ray parenchyma fraction in 2022. • Fraxinus excelsior and A. pseudoplatanus were sensitive to heat stress. Climate change is leading to more frequent and severe extreme climate events, such as hot spells. However, we lack information on how trees recover after heat waves in terms of wood anatomy, radial growth (basal area increment, BAI), and wood δ 13 C, a proxy of intrinsic water-use efficiency (iWUE). This lack of information on recovery is notable in temperate forests, where heat waves reduce productivity and trigger canopy dieback. We filled this research gap by assessing the impacts of the 2022 heat wave on two temperate forests located at high (Cernobbio) and low elevation (Monza) sites in northern Italy. Eight winter-deciduous tree species were sampled with different leaf phenology (early leafing species, Betula pendula, Quercus robur ; intermediate leafing species, Fagus sylvatica, Acer pseudoplatanus ; and late leafing species, Tilia cordata, Castanea sativa, Fraxinus excelsior, Quercus pubescens ). Some species experienced a severe BAI reduction during 2022 ( B. pendula , -58%; Q. robur , -48 %), others showed a moderate drop ( A. pseudoplatanus , -5 %; F. excelsior , -5 to -34 %; T. cordata , -29 %; C. sativa , -25 %; Q. pubescens , -18 %), whereas F. sylvatica showed a slight increase (+ 3 %). Negative growth legacies were detected in F. excelsior at the low-elevation site. F. excelsior, A. pseudoplatanus and Q. pubescens were the most sensitive species to summer maximum temperatures and drought severity. In the case of A. pseudoplatanus , the ray parenchyma fraction declined in 2022, indicating lower C storage. A. pseudoplatanus (-26.1‰) and F. excelsior (-25.6 ‰) showed the highest wood δ 13 C values. Radial growth data indicate that the two early leafing species were the most negatively impacted by heat stress.