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Forests are experiencing increasingly severe drought stress worldwide. Although most studies have quantified how tree growth was affected by extreme droughts, how trees recover from different drought intensities are still poorly understood for different species. We used a network of tree-ring data comprising 731 Quercus mongolica trees across 29 sites, 312 Larix olgensis Henry trees from 13 sites, and 818 Larix principis-rupprechtii trees from 34 sites, covering most of their distribution range in northern China, to compare the influences of drought intensity on post-drought recovery. The results showed that summer droughts had strong negative influences on tree growth. Post-drought growth varied with drought intensity for the three species. Larix species exhibited strong legacy effects after severe droughts, which is related to the lack of compensatory growth. In contrast, the compensatory growth of Q. mongolica reduced drought legacy effect. However, the compensatory growth of Q. mongolica gradually weaken with increasing drought intensity and disappeared during severe drought. Our findings indicated that influence of drought on Q. mongolica growth mainly shown in drought years, but Larix species suffered from long-term drought legacy effects, implying Q. mongolica rapidly recovered from droughts but Larix species need several years to recover from droughts, thus the two genera have different recovery strategy., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

• Drought reduced oak growth but no difference existed among mild to extreme droughts. • Drought intensity increased recovery, reduced resistance, and increased resilience. • Prolonged drought duration impaired the recovery and prevented compensatory growth. Global forests suffer from increasing drought pressure, as drought are more intense, and last for longer, and occur more frequently, but how drought intensity and duration affect post-drought growth recovery and compensatory growth is still poorly known. Understanding the immediate and subsequent impacts of drought on tree growth is key to predict future forest dynamics. Here, we used a network of tree-ring data of 735 Quercus mongolica trees from 27 sites of North China representing a large portion of its distribution to study the effects of drought intensity and duration on radial growth. We analyzed growth resistance, recovery, and resilience of Q. mongolica by linking it to drought intensity and duration, and further quantified the post-drought growth trajectories. Our results confirmed that current summer drought is a major influence on radial growth of Q. mongolica across its distribution. While drought occurrence was related to decreased growth even for incipient droughts, we found no differences in growth decline with drought severity. Although drought intensity did not alter growth decline in dry years, drought intensity was positively related to recovery and resilience indices. The damage of recovery is due to the extension of drought duration rather than drought intensity. However, post-drought growth was even more strongly related to drought duration and not intensity. Q. mongolica showed compensatory growth in the year following single-year droughts before returning to pre-drought growth-levels, while multi-year drought led to little to no compensatory growth and prolonged growth reductions. Hence, multi-year drought is the key to predict post-drought recovery of Q. mongolica including compensatory growth in an increasingly arid climate. [Display omitted] [ABSTRACT FROM AUTHOR]

l The Mongolia oak trees in drier portions grew slower than those in wetter portions l Drought restricted Mongolia oak tree growth in dry regions than in wetter regions l Dryness will reduce tree growth rate markedly in the period 2021-2100 l Drought suppression will increase in dry regions in the period 2021-2100 l Mongolian oak forests will likely shift towards wet regions with warmer climate [Display omitted] Mongolian oak is a widely distributed tree species in broadleaf forests of North China, which are susceptible to increasing drought. Expansion of oak species ranges has been reported in Europe, America, and Asia with drought and heat stress, and thus, oak species are often deemed to be drought-resistant. As an expanding species in our study region, the Mongolian oak (Quercus mongolica Fisch. ex Ledeb) was used to investigate how tree growth rate and drought resistance change along a moisture gradient. In this study, we used a network of Mongolian oak tree-ring samples across a wide range of moisture gradients in North China to assess oak tree growth and its response to drought under different moisture conditions. Our results revealed that spatial variation in tree radial growth rate was highly related to the regions' moisture index, an index indicating moisture condition. Oak trees in drier portions grew slower than those in wetter portions and their growth was more sensitive to drought events. We used an ensemble of climate projections from general circulation models to predict future changes in the Ivanov moisture index, and then estimated the tree growth rate and drought-growth correlation for the period 2021–2100. Increased dryness is likely to reduce tree average growth rate markedly and increase the drought sensitivity of radial growth in the expanding dry portions of our study region, leading to substantial overall drought suppression of growth. Our results suggest that dryness will present an increasing challenge for the continuing expansion of Mongolia oak in already dry areas of North China, whereas oak trees will thrive better in high moisture conditions. The distribution of Mongolia oak trees will likely shift to regions with increased moisture availability, especially under the increasing drought. [ABSTRACT FROM AUTHOR]