Summary Seasonal radial‐increment and xylogenesis data can help to elucidate how climate modulates wood formation in conifers. Few xylogenesis studies have assessed how plastic xylogenesis is in sympatric conifer species from continental Mediterranean areas, where low winter temperatures and summer drought constrain growth. Here, we analysed intra‐annual patterns of secondary growth in sympatric conifer species (Juniperus thurifera, Pinus halepensis and Pinus sylvestris). Two field sites (xeric and mesic) were evaluated using dendrometers, microcores and climatic data. A bimodal pattern of xylogenesis characterized by spring and autumn precipitation and subsequent cambial reactivation was detected in J. thurifera at both study sites and in P. halepensis at the xeric site, but was absent in P. sylvestris where growth was largely controlled by day length. In the xeric site J. thurifera exhibited an increased response to water availability in autumn relative to P. halepensis and summer cambial suppression was more marked in J. thurifera than in P. halepensis. Juniperus thurifera exhibited increased plasticity in its xylogenesis pattern compared with sympatric pines, enabling this species to occupy sites with more variable climatic conditions. The plastic xylogenesis patterns of junipers in drought‐stressed areas may also provide them with a competitive advantage against co‐occurring pines.

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 0The restriction of some vascular plants to soils high in gypsum under arid or semi! arid climates has been reported by many authors in di}erent parts of the world[ Factors controlling the presence of gypsophytes on these soils are far from being de_nitively explained[ 1 The establishment of Helianthemum squamatum\ an Iberian gypsophyte\ was inves! tigated during a 1!year period in a typical semi!arid gypsum gradient landscape in central Spain that included the three community belts where this plant can grow[ 2 More than 499 seedlings were tagged[ Their growth and survival were monitored periodically "12 census dates#[ Over 79) of the recorded seedlings emerged during the _rst year\ which followed a severe and long drought period[ Germination occurred principally in winter "over 74)#\ although seeds germinated sporadically even in late May[ Emergence was clearly spatially con_ned\ with seedlings appearing only in the summit area\ which was characterized by gypsum outcrops "059 per m 1 #\ and at the boundary between gypsum slope and alluvial piedmont "162 per m 1 #[ Seedlings were very scarce in lower areas "Ly`eum spartum and Artemisia herba!alba communities# and absent from the steeper gypsum slope[ 3 Survival was size!dependent] larger plants had a better chance of surviving the _rst summer\ which is the bottle!neck for recruitment[ We detected few di}erences in the _nal survival percentage after the _rst year for cohorts or zones\ and survival curves were also similar\ except at the boundary between gypsum slope and piedmont[ However\ seedlings emerging in 0886 had a higher survival percentage than those emerging in 0885[ 4 Proximity to a seed source was the most relevant predictor of emergence[ This may be related to the presence of mucilaginous coats in H[ squamatum seeds\ which may enable plants to become established on crusted soils[ 5 Our results seem to link gypsophily with some properties of the surface crust\ which is thought to contribute to the restrictive behaviour of such soils [

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.

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