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1. The negative impacts of drought on forest growth and productivity last for several years generating legacies, although the factors that determine why such legacies vary across sites and tree species remain unclear. 2. We used an extensive network of tree-ring width (RWI, ring-width index) records of 16 tree species from 567 forests, and high-resolution climate and normalized difference vegetation index (NDVI) datasets across Spain during the common period 1982‒2008 to test the hypothesis that climate conditions and growth features modulate legacy effects of drought on forests. Legacy effects of drought were calculated as the differences between detrended-only RWI and NDVI series (i.e. after removing long-term growth trends) and pre-whitened RWI and NDVI series predicted by a model including drought intensity. Superposed Epoch Analysis (SEA) was used to estimate whether legacy effects differed from random. Finally, legacy effects were related to water balance, growth persistence and variability, and tree species identity. 3. We found a widespread occurrence of drought legacy effects on both RWI and NDVI, but they were seldom significant. According to SEA, first-year drought legacies were negative and different from random in 9% and 5% of the RWI and NDVI series respectively. The number of significant second- and third-year legacies was substantially lower. Differences between RWI and NDVI legacies indicate that canopy greenness and radial growth responses to drought are decoupled. We found variations in legacies between tree species with gymnosperms presenting larger first-year drought legacies than angiosperms, which were exposed to less severe droughts. Greater growth variability can explain the presence of first-year RWI legacies in gymnosperms from dry sites despite that the relationship between growth variability and legacies was complex. 4. Synthesis. Accounting for species and site responses to drought provides a better understanding of the magnitude and duration of drought legacies on forest growth and productivity. Despite the widespread occurrence of growth reductions in the years during and after drought occurrence, significant legacies were not very common, mostly lasted one year, and were more widespread in gymnosperms. These are relevant factors to be considered in the future when studying the consequences of drought on forest productivity and tree growth. ; This study was financially supported by: Xunta de Galicia, Grant/ Award Number: PGIDIT06PXIB502262PR, GRC GI-1809; INIA, Grant/Award Number: RTA2006-00117; CANOPEE, 2014-2020- FEDER funds; and Spanish Science Ministry: RTI2018-09688 4- B-C31, RTI2018-096884-B-C33, AGL2017-83828-C2-2R and ENV4-CT97-0641 projects. GSB was supported by a 'Juan de la Cierva Formación' grant from MINECO (FJCI 2016-30121). This re - search was supported by the BERC 2018-2021 program, and by the Spanish Ministry of Science, Innovation and Universities t hrough the BC3 María de Maeztu excellence accreditation (MDM-2017- 0714) and the IBERYCA (CGL2017-84723-P) project. R.S.S. was s up - ported by VULBOS project (UPO-1263216, FEDER Funds, And alusia Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014-2020), and A.H. by PinCaR pro ject (UHU-1266324, FEDER Funds, Andalusia Regional Government Consejería de Economía, Conocimiento, Empresas y Universidad 2014-2020). K.N. was supported by the Ministry of Educatio n, Science and Sports (Republic of Slovenia, Raziskovalci-2.1- UL-BF- C3330-19-952011). We sincerely thank the in-depth analyse s and comments provided by the reviewers.

Climate warming-related drought could become a major driver of large-scale forest dieback. However, little is known about how past management legacies modulate the climate-growth responses during recent dieback episodes in central European oak forests. Here, we examine the role played by past management –unmanaged old-growth vs. managed forests– in recent tree mortality events occurring in Quercus petraea (Matt.) Liebl. stands across large areas of western Romania. We analyze how stand structure (tree size, competition) and climatic factors (drought, temperature and precipitation) drive tree radial growth patterns in neighboring standing dead and living trees. We analyzed basal area increments (BAI) trends, past management legacies and climate- and drought-growth relationships during the 20th century to distinguish the roles and interactions on recent warming-induced dieback. We observed that temperature rises and changes in atmospheric water demand during growing season let to increasing drought stress during the late 20th century affecting both managed and unmanaged forests. Dead trees from old-growth and managed forests showed lower growth than living trees after dieback onset. In both forests, dead and living trees displayed divergent growth patterns after dry 1980s, indicating that dieback was triggered by severe extreme conditions. Dead trees from managed stands experienced significant stronger growth reductions after 1980s though they experienced less tree-to-tree competition than dead trees in old-growth forest. High stand density negatively drove growth and enhanced climate sensitivity in old-growth stands. Competition acted synergistically with climate warming and drought causing tree mortality regardless of the management legacies in of Q. petraea forests. Our retrospective assessment of growth rates in relation with climate and structure changes offers valuable information for further forest conservation and management decisions of Q. petraea forests. These findings highlight the importance of past uses legacies driving recent forest dieback in temperate oak forests, making them more vulnerable under forecasted climate-warming related droughts in central Europe. ; Nemoral Forests under Climate Extremes (NEMKLIM Project, grant number 3517861300), German Federal Agency for Nature Conservation (Bundesamt für Naturschutz,BfN), German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, Germany, project PN 19070506, Romanian National Authority from Scientific Research and Innovation, Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P4-ID-PCE-2020- 2696, within PNCDI III. projects VUL-BOS project (UPO-1263216 and PinCaR (UHU-1266324), FEDER Funds, Andalusia Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014-2020), project LESENS (RTI2018-096884-B-C33), Spanish Ministry of Science, Innovation and Universities. ; This work was supported by NEMKLIM project: Nemoral Forests under Climate Extremes (NEMKLIM Project, grant number 3517861300), financed by the German Federal Agency for Nature Conservation (Bundesamt für Naturschutz,BfN) and the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, Germany and by project PN 19070506 financed by Romanian National Authority from Scientific Research and Innovation. I.C. Petritan was supported by a grant of the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P4-ID-PCE-2020- 2696, within PNCDI III. R. S ´anchez-Salguero was supported by VUL-BOS project (UPO-1263216, FEDER Funds, Andalusia Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014-2020) and LESENS (RTI2018-096884-B-C33) project from the Spanish Ministry of Science, Innovation and Universities. A. Hevia was supported by PinCaR project (UHU-1266324, FEDER Funds, Andalusia Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014-2020). We are also grateful to Lucian Toiu, Nicu Tudose, George Sarbu and Gheorghe Stefan for help in collecting field data. We appreciate the permission and logistic support given by staff of the Barzava and Codrii Beiusului si Sfanta Maria Forest Districts, we are grateful especially to eng. Gheorghe Marc and eng. Jeno Ferko. The authors declare no conflicts of interest.

This is a pre-copyedit version of an article published in Annal of Forest Science. The final authenticated version is available online at: http://doi.org/10.1007/s13595-020-00956-y ; Context: It is essential to disentangle the influence of climate from the effect of provenance on inter- and intra-annual wood traits to identify populations' responses to climate changes. This will be even more relevant in the drought-prone Mediterranean region, where species have high genetic differentiation among populations. Aims: We investigated the effects of provenance and climate driving Pinus halepensis Mill. wood traits, as imprinted phenotypic adaptations to the Mediterranean climate. Methods: Inter- and intra-annual wood trait variation (ring-, early-, and latewood width, wood density) was studied by microdensitometry in 8 provenances from Spain, France, Greece, and Italy in a common-garden experiment. We related wood traits and density fluctuations with inter-annual climate variations at the trial site and the provenance origin. Results: Provenances showed distinct responses to climate regarding tree growth, wood density, and intra-annual fluctuations. Density fluctuations in latewood were more frequent than in earlywood. Climate at the provenance origin was a more important force for density fluctuations than climatic variations at the planting site, with different trends between coastal and inland provenances, and higher frequency of latewood fluctuations in provenances from arid and semiarid sites. Conclusion: Differences in P. halepensis wood density fluctuations confirmed the imprinted origin provenance control in response to climate variations and indicated a relation with local adaptation of these xylem anatomical features. Moreover, the position of these fluctuations in rings reflected the high plasticity of P. halepensis to cope with high intra-seasonal variability of climatic conditions. This underlines the importance of considering tree-ring features for the selection of provenances in reforestation material for conservation and silvicultural programs. ; PinCaR project (UHU-1266324, FEDER Funds, Andalusia Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014–2020); SFRH/BPD/105656/2015, (SFRH/ BPD/111307/2015), FCT with funds from POPH (Portuguese Operational Human Potential Program), QREN Portugal (Portuguese National Strategic Reference Framework), FSE (European Social Fund). Spanish Ministry of Economy, Industry and Competitiveness IJCI-2015-25845, MCIU funds, CoMo-ReAdapt (CGL2013-48843-C2-1-R) project, RTI2018-096884-B-C31 and RTI2018-096884-B-C33 Ministry of Science, Innovation and Universities, VULBOS project UPO-1263216, FEDER Funds, Andalusia Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014–2020.

The increase in frequency and intensity of droughts due to climate change might threaten forests under stress levels causing dieback and mortality episodes. Thus, deciphering how tree species from within a region respond to drought along environmental gradients should help us to understand forest vulnerability to climate change. To enlighten contrasting drought responses of dominant tree species, we reconstructed vegetation activity using Normalized Difference Vegetation Index (NDVI) and radial growth using tree-ring width series. We studied six tree species, three angiosperms (Fagus sylvatica, Quercus humilis, and Quercus ilex) and three gymnosperms (Pinus sylvestris, Pinus nigra, and Pinus halepensis), inhabiting a Mediterranean region in north-eastern Spain. We investigated if reduced growth resilience and increased growth synchrony after successive droughts (1986, 1989, 2005, and 2012): (i) were related to cumulative drought stress and (ii) preceded forest dieback in dry sites as compared to wet sites. In 2016, dieback affected Q. ilex and P. sylvestris stands in dry sites showing lower growth rates and NDVI. No dieback symptoms were observed in other species from dry (P. nigra, P. halepensis) or wet (F. sylvatica, Q. humilis, P. sylvestris) sites. Hot and dry summer conditions constrained growth and reduced NDVI. During 2005, a severe drought affected all species, but growth drops were more marked in dry places. All species were able to recover after extreme droughts, albeit angiosperms displayed lower than expected values of growth after the 2012 drought. Growth synchrony was higher in dry sites than in wet sites, and the differences were higher after the 2005 drought. This study reveals that the sensitivity of tree species to drought in species inhabiting the same region is species dependent, and it is contingent on local conditions with higher effects in dry sites than in wet sites. We describe how a cumulative impact of successive droughts increases growth synchrony and triggers the occurrence of dieback events in Mediterranean forests. ; JC, AG, and RS-S acknowledge the support of the FORMAL (RTI2018-096884-B-C31) and LESENS (RTI2018-096884-B-C33) projects from the Spanish Ministry of Science, Innovation and Universities; and VULBOS project (UPO-1263216) from the ERDF funds Andalusia regional government 2014-2020. GS-B was supported by Spanish Ministry of Economy, Industry and Competitiveness Postdoctoral grant (FJCI 2016-30121; FEDER funds) and from the European Union through the CANOPEE Interreg POCTEFA project.

Forests play a key role in the carbon balance of terrestrial ecosystems. One of the main uncertainties in global change predictions lies in how the spatiotemporal dynamics of forest productivity will be affected by climate warming. Here we show an increasing influence of climate on the spatial variability of tree growth during the last 120 y, ultimately leading to unprecedented temporal coherence in ring-width records over wide geographical scales (spatial synchrony). Synchrony in growth patterns across cold-constrained (central Siberia) and drought-constrained (Spain) Eurasian conifer forests have peaked in the early 21st century at subcontinental scales (∼1,000 km). Such enhanced synchrony is similar to that observed in trees co-occurring within a stand. In boreal forests, the combined effects of recent warming and increasing intensity of climate extremes are enhancing synchrony through an earlier start of wood formation and a stronger impact of year-to-year fluctuations of growing-season temperatures on growth. In Mediterranean forests, the impact of warming on synchrony is related mainly to an advanced onset of growth and the strengthening of drought-induced growth limitations. Spatial patterns of enhanced synchrony represent early warning signals of climate change impacts on forest ecosystems at subcontinental scales. ; T.A.S. is supported by ERANET-MUNDUS (Euro-Russian Academic Network-Mundus) (European Commission). V.R.d.D. is supported by the Ramón y Cajal Program (Contract RYC-2012-10970). Support for this work was provided by European Union projects ForMAT (Sensitivity of tree growth to climate change and growth modelling from past to future) (Contract ENV4-CT97-0641), ISONET (400 years of annual reconstructions of European climate variability using a high resolution isotopic network) (Contract EV K2-2001-00237), and MILLENNIUM (European climate of the last millennium) (Contract GOCE 017008); the Russian Science Foundation (Project 14-14-00295); the Catalan Government (Project 2014 SGR 1141); Studying Tree Responses to Extreme Events: A Synthesis (STReESS) COST (European Cooperation in Science and Technology) Action FP1106; and Spanish Projects CGL2011-26654 and CGL2013-48843-C2-1-R (Spanish Ministry of Economy and Competitiveness).

This study links tree-ring growth and gross primary production for a variety of forest types under different environmental conditions across Spain. NOAA-AVHRR satellite imagery data were combined with dendrochronological records and climate data at a fine spatial resolution (1.21 km2) to analyze the interannual variability of tree-ring growth and vegetation activity for different forest biomes from 1981 to 2015. Specifically, we assessed the links between tree-ring width indices (TRWi), the Normalized Difference Vegetation Index (NDVI) and a variety of environmental conditions, represented by climatic variables (air temperature, precipitation, evapotranspiration and water balance) and elevation. The impact of these variables on tree growth was assessed by means of the Predictive Discriminant Analysis (PDA). Results reveal a general positive and significant relationship between inter-annual variability of the NDVI at a high spatial resolution (1.21 km2) and tree-ring growth. Maximum correlations between NDVI and tree-ring growth were recorded when cumulative NDVI values were considered, in some cases covering long time periods (6–10 months), suggesting that tree growth is mainly related to Gross Primary Production (GPP) at annual scale. The relationship between tree-ring growth and inter-annual variability of the NDVI, however, strongly varies between forest types and environmental conditions. ; Research projects CGL2014-52135-C03-01, CGL2015-69186-C2-1-R, CGL2015-69985-R, CGL2013-48843-C2-1-R, AGL2014-53822-C2-1-R, (BFU2010-21451), PCIN-2015-220, CGL2016-81706-REDT, CGL2017-82216-R, Spanish Commission of Science and Technology and FEDER, 1560/2015: Herramientas de monitorización de la vegetación mediante modelización ecohidrológica en parques continentales financed by the Red de Parques Nacionales, IMDROFLOOD, Water Works 2014, co-funded call of the European Commission, CROSSDRO financed by the AXIS (Assessment of Cross(X) – sectorial climate Impacts and pathways for Sustainable transformation) JPI-Climate co-funded call of the European Commission and INDECIS, part of ERA4CS, an ERA-NET initiated by JPI Climate, FORMAS (SE), DLR (DE), BMWFW (AT), IFD (DK), MINECO (ES), ANR (FR), co-funding by the European Union (Grant 690462). Spanish Commission of Science and Technology and FEDER, and INDECIS, which is part of ERA4CS, an ERA-NET initiated by JPI Climate, and funded by FORMAS (SE), DLR (DE), BMWFW (AT), IFD (DK), MINECO (ES), ANR (FR) with co-funding by the European Union (Grant 690462), Aragon Regional Government, Spanish Ministry of Economy and Competitiveness, Spanish Ministry of Education, Culture and Sport, IJCI-2015-25845, MINECO-FPDI 2013-16600, FJCI 2016-30121, FEDER funds. Xunta de Galicia (PGIDIT06PXIB502262PR, GRC GI-1809, ROCLIGAL-10MDS291009PR), INIA (RTA2006-00117), and Interreg V-A POCTEFA (CANOPEE, 2014-2020-FEDER funds) projects.