Recent world‐wide episodes of tree dieback have been attributed to increasing temperatures and associated drought. Because these events are likely to become more common, improved knowledge of their cumulative effects on resilience and the ability to recover pre‐disturbance conditions is important for forest management. Here we propose several indices to examine components of individual tree resilience based on tree ring growth: resistance (inverse of growth reduction during the episode), recovery (growth increase relative to the minimum growth during the episode), resilience (capacity to reach pre‐episode growth levels) and relative resilience (resilience weighted by the damage incurred during the episode). Based on tree ring analyses, we analyzed historical patterns of tree resilience to successive drought‐induced low growth periods in ponderosa pine trees growing in unmanaged, remote forests of the Rocky Mountains. Low‐growth periods registered in tree rings were related to anomalies in the Palmer drought severity index (PDSI) and were attributed to drought. Independently of the impact of a specific event, subsequent growth after a single low‐growth episode was related to the growth prior to the event. Growth performance differed with tree age: young trees were overall more resistant to low‐growth periods, but older trees recovered better from more recent events. Regardless of tree age, recently burned sites exhibited lower post‐episode growth and lower resistance and resilience than unburned ones. We found mixed evidence for the cumulative effect of past low‐growth episodes: overall, greater impacts of a prior event and greater cumulative effects of past low‐growth periods caused a decrease in resistance. However, we did not find a progressive decrease in resilience over time in old trees. Our results highlight the value of using a combination of estimators to evaluate the different components of resilience. Specifically, while tree responses to disturbance depend on past disturbance episodes, the response is context‐specific and depends on the impact the capacity to recover after disturbance. This suggests that recent increases in forest mortality under current climate trends could relate to thresholds on specific components of resilience (resistance, recovery, resilience itself) rather than to an overall loss of resilience over time. Identifying such thresholds and their underlying mechanisms is a promising area of research with important implications for forest management.

Current climatic trends involve both increasing temperatures and climatic variability, with extreme events becoming more frequent. Increasing concern on extreme climatic events has triggered research on vegetation shifts. However, evidences of vegetation shifts resulting from these events are still relatively rare. Empirical evidence supports the existence of stabilizing processes minimizing and counteracting the effects of these events, reinforcing community resilience. We propose a demographic framework to understand this inertia to change based on the balance between adult mortality induced by the event and enhanced recruitment or adult survival after the event. The stabilizing processes potentially contributing to this compensation include attenuation of the adult mortality caused by the event, due to site quality variability, to tolerance, phenotypic variability, and plasticity at population level, and to facilitative interactions. Mortality compensation may also occur by increasing future survival due to beneficial effect on growth and survival of the new conditions derived from global warming and increased climatic variability, to lowered competition resulting from reduced density in affected stands, or to antagonistic release when pathogens or predators are vulnerable to the event or the ongoing climatic conditions. Finally, mortality compensation may appear by enhanced recruitment due to release of competition with established vegetation, for instance as a consequence of gap openings after event-caused mortality, or to the new conditions, which may be more favorable for seedling establishment, or to enhanced mutualistic interactions (pollination, dispersal). There are important challenges imposed by the need of long-term studies, but a research agenda focused on potentially stabilizing processes is well suited to understand the variety of responses, including lack of sudden changes and community inertia that are frequently observed in vegetation under extreme events. This understanding is crucial for the establishment of sound management strategies and actions addressed to improve ecosystem resilience under climate change scenarios.

Drought events are increasing globally, and reports of consequent forest mortality are widespread. However, due to a lack of a quantitative global synthesis, it is still not clear whether droughtinduced mortality rates differ among global biomes and whether functional traits influence the risk of drought-induced mortality. To address these uncertainties, we performed a global metaanalysis of 58 studies of drought-induced forest mortality. Mortality rates were modelled as a function of drought, temperature, biomes, phylogenetic and functional groups and functional traits. We identified a consistent global-scale response, where mortality increased with drought severity [log mortality (trees trees À1 year À1 ) increased 0.46 (95% CI = 0.2-0.7) with one SPEI unit drought intensity]. We found no significant differences in the magnitude of the response depending on forest biomes or between angiosperms and gymnosperms or evergreen and deciduous tree species. Functional traits explained some of the variation in drought responses between species (i.e. increased from 30 to 37% when wood density and specific leaf area were included). Tree species with denser wood and lower specific leaf area showed lower mortality responses. Our results illustrate the value of functional traits for understanding patterns of drought-induced tree mortality and suggest that mortality could become increasingly widespread in the future.

Summary Severe drought may increase physiological stress on long‐lived woody vegetation, occasionally leading to mortality of overstory trees. Little is known about the factors determining tree survival and subsequent recovery after drought. We used structural equation modeling to analyse the recovery of Scots pine (Pinus sylvestris) trees 4 yr after an extreme drought episode occurred in 2004–2005 in north‐east Spain. Measured variables included the amount of green foliage, carbon reserves in the stem, mistletoe (Viscum album) infection, needle physiological performance and stem radial growth before, during and after the drought event. The amount of green leaves and the levels of carbon reserves were related to the impact of drought on radial growth, and mutually correlated. However, our most likely path model indicated that current depletion of carbon reserves was a result of reduced photosynthetic tissue. This relationship potentially constitutes a feedback limiting tree recovery. In addition, mistletoe infection reduced leaf nitrogen content, negatively affecting growth. Finally, successive surveys in 2009–2010 showed a direct association between carbon reserves depletion and drought‐induced mortality. Severe drought events may induce long‐term physiological disorders associated with canopy defoliation and depletion of carbon reserves, leading to prolonged recovery of surviving individuals and, eventually, to delayed tree death.

Summary• Climatic warming produces significant gradual alterations in the timing of lifecycle events , and here we study the phenological effects of rainfall-pattern changes.• We conducted ecosystem field experiments that partially excluded rain and runoff during the growing season in a Mediterranean forest and in a mediterranean shrubland. Studies of time-series of leaf-unfolding, flowering and fruiting over the last 50 yr in central Catalonia were carried out, and greenup onset in the Iberian Peninsula was monitored by satellite images.• Experimental, historical and geographical changes in rainfall produced significant, complex and strongly species-specific, as well as spatially and temporally variable, phenological effects. Among these changes, it was found that in the Iberian Peninsula, greenup onset changes from spring (triggered by rising temperatures) in the northern cool-wet regions to autumn (triggered by the arrival of autumn rainfalls) in the southern warm-dry regions. Even in the mesic Mediterranean central Catalonia (NE of the peninsula) rainfall had a stronger relative influence than temperature on fruiting phenology.• The results show that changes in rainfall and water availability, an important driver of climate change, can cause complex phenological changes with likely far-reaching consequences for ecosystem and biosphere functioning and structure. The seasonal shift in the Iberian Peninsula further highlights this importance and indicates that vegetation may respond to climate change not only with gradual, but also with abrupt temporal and spatial, changes in the timing of greenup onset.

Summary1 Species attributes have been used to explain invasion patterns assuming the prevalence of biological mechanisms, although this approach often suffers several methodological and conceptual limitations, such as local idiosyncrasies, differences among habitats, phylogenetic constraints and insufficient sample size. 2 The relative importance of 15 species traits for explaining the abundance over 350 naturalized alien plant species was assessed across five Mediterranean islands (Corsica, Crete, Majorca, Malta and Sardinia). A comparative analysis accounting for phylogeny was used to examine variation in semi-quantitative estimates of species abundance in comparable habitats across the five island floras. 3 Species were divided into those with affinity for semi-natural, agricultural and ruderal habitats. Both vegetative and reproductive attributes were evaluated for individual islands and averaged across all islands. 4 Vegetative propagation, large leaf size, summer flowering, long flowering period and dispersal by wind or vertebrates were positively associated with average alien abundance across all five islands. Fewer significant trends were found in island-specific patterns. 5 The relative importance of a few reproductive traits is reflected in over-representation of Caryophyllales, Asterales and Poales (late flowering, large seed size and anemochory). Although significant covariation in traits was found there was no evidence for welldefined invasive syndromes. 6 Succulence was important in ruderal habitats, long flowering period in agricultural habitats and vertebrate seed dispersal in semi-natural habitats, suggesting that empty niches, avoidance of competitors and exploitation of mutualists, respectively, are important. 7 The study highlights the importance of estimating invasion success across a wide region, but analyses of specific invasion stages are also needed. Reproductive traits, which may be more relevant for long-distance colonization, and vegetative traits, which determine local dominance and persistence, were, nevertheless, both related to abundance within islands.

. The values of the slope (reduced-majoraxis regression), regression coefficient and its significance are given inside the respective plots. Root allocation was estimated as the slope of the function root biomass = a + b log shoot biomass.

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