Forecasted increase drought frequency and severity may drive worldwide declines in forest productivity. Species-level responses to a drier world are likely to be influenced by their functional traits. Here, we analyse forest resilience to drought using an extensive network of tree-ring width data and satellite imagery. We compiled proxies of forest growth and productivity (TRWi, absolutely dated ring-width indices; NDVI, Normalized Difference Vegetation Index) for 11 tree species and 502 forests in Spain corresponding to Mediterranean, temperate, and continental biomes. Four different components of forest resilience to drought were calculated based on TRWi and NDVI data before, during, and after four major droughts (1986, 1994-1995, 1999, and 2005), and pointed out that TRWi data were more sensitive metrics of forest resilience to drought than NDVI data. Resilience was related to both drought severity and forest composition. Evergreen gymnosperms dominating semi-arid Mediterranean forests showed the lowest resistance to drought, but higher recovery than deciduous angiosperms dominating humid temperate forests. Moreover, semi-arid gymnosperm forests presented a negative temporal trend in the resistance to drought, but this pattern was absent in continental and temperate forests. Although gymnosperms in dry Mediterranean forests showed a faster recovery after drought, their recovery potential could be constrained if droughts become more frequent. Conversely, angiosperms and gymnosperms inhabiting temperate and continental sites might have problems to recover after more intense droughts since they resist drought but are less able to recover afterwards.

Summary• Tree features may modulate the sensitivity of radial growth to climate, leading to a nonuniform response. Age-related increases in climatic sensitivity have been observed repeatedly. Sex-related climatic sensitivity is also possible because of the long-term differential reproductive cost between the sexes. This study analysed the simultaneous effects of age and sex on the sensitivity of tree-ring growth to climate.• Ring widths were measured from 50 female and 50 male Juniperus thurifera trees, 50-350 yr old, growing under a Mediterranean continental climate. Response functions were calculated based on tree-ring chronologies and monthly climatic records.• Climatic sensitivity decreased with increasing age. Young trees (50-100 yr) were the most climatically sensitive to June-July precipitation, which affected growth positively. We found a significant interaction between age and sex in the climatic response of J. thurifera, with young females the most sensitive to summer water stress.• Our results suggest that age-dependent climatic sensitivity can be determined by site-specific limiting environmental conditions and species-specific architectural and physiological adjustments during ontogeny. This study supports that the different ontogenetic stages of J. thurifera differ in their root structural traits and that sex-related sensitivity to summer drought may be attributable to less efficient water use by females.

-The influence of climate and disturbances on tree-ring widths of European beech and pedunculate oak were evaluated in a lowland forest of Northern Spain. From 1925 to 1980, 36% of the variance of beech ring-width and 29% of the oak one was explained by climate. The climatic models showed that low precipitation in July of the previous year limited the radial growth of beech, while oak one was instead restricted by water deficits in July of the current year. Ten main disturbance periods were identified from 1780 to 1997, among which the 1922-1935 one was the most important. Since beech trees showed suppressed growth from 1800 to 1920, probably the forest canopy became denser during this time. The disturbance periods identified in 1922-1935 and 1948-1953 contributed to both increase the growth of beech above the expected, and intensify its climatic response. On the other hand, deviations of oak growth from the expected without-disturbance indices agreed with the disturbance history up to 1850. From 1850 to 1997, oak growth became independent from disturbances sequence, yielding a constant climatic response in . The opposite effects of disturbances on both the radial growth and the climatic response of European beech and pedunculate oak are related to their different tolerance to shade. These results have relevant methodological implications on the analysis of climate-growth relationships, and on the reconstruction of past disturbance regimes by means of dendroecological techniques. dendroecology / ring width / response function / forest disturbance / Kalman filter Résumé -Effet du climat et des perturbations locales sur la croissance radiale de Fagus sylvatica L. et Quercus robur L. dans une forêt naturelle de Cantabria, Nord de l'Espagne. L'influence relative du climat et des perturbations locales sur la croissance radiale du hêtre et du chêne pédonculé a été analysée dans une vieille forêt naturelle du Nord de l'Espagne. Entre 1925 et 1980, 36 % de la variance des largeurs de cernes du hêtre et 29 % de celle du chêne s'expliquent par le climat. Les modèles climatiques élaborés montrent que la croissance radiale du hêtre est limitée par les précipitations du mois de juillet de l'année précédente, alors que celle du chêne l'est par le déficit hydrique du mois de juillet de l'année en cours. Dix périodes de perturbation de la croissance, d'origine non climatique, ont été identifiées entre 1780 et 1997, parmi lesquelles celle de 1922-1935 a été la plus importante. La croissance radiale des hêtres apparaît faible de 1800 à 1920 en raison de la fermeture du couvert forestier au cours de cette période. Puis des perturbations survenues en 1922-1935 et 1948-1953 entraînent une augmentation de la croissance, qui devient alors supérieure au signal commun. Conjointement, la réponse aux contraintes climatiques se renforce au cours des mêmes périodes. Chez le chêne, les dévia-tions de la croissance par rapport au signal commun sont en accord avec l'historique des perturbations locales jusqu'en 1850. Puis la croiss...

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The University of Chicago Press is collaborating with JSTOR to digitize, preserve and extend access to International Journal of Plant Sciences.A detailed understanding of how the climate models the hydraulic system of trees is still lacking, in spite of the need to understand tree response to the ongoing process of climatic change. A systematic correlation of tracheid anatomical features with climate has not been implemented in Mediterranean ecosystems, where climatic change is expected to be particularly intense. We measured ring width and cell number-in addition to intraring position, lumen size, and wall thickness of tracheids-in 10 Juniperus thurifera individuals from north-central Spain. We used this information to perform an exploratory analysis of how these parameters correlated with climatic variables in 1965-2004. Cell number and ring width shared a relatively similar climatic signal, whereas the anatomical variables provided differentiated and diverse signals about climatic conditions during their formation. Earlywood and latewood tracheids differed in controlling factors, with earlywood tracheid size and wall thickness being positively related to rainfall during early summer and latewood tracheid size being positively related to August temperature. Tracheid anatomical variables improved our understanding of climate effects on tree growth and wood formation under harsh environmental conditions, as those experienced in continental Mediterranean climates, where limiting factors show multiple shifts across the year.