Dendrochronological assessment of drought resilience in Mediterranean shrub species near their xeric limits in Spain

Climate warming, drought stress and aridification impact shrub radial growth in drylands, but our knowledge on climate-growth relationships of these species is limited. To fill this research gap, we studied the age, growth patterns and year-to-year variability of five shrub species ( Rhamnus alaternus , Rhamnus lycioides , Rhamnus saxatilis , Berberis vulgaris , and Retama sphaerocarpa ) under semi-arid Mediterranean conditions in nine sites, located near the xeric distribution limits of the study species in Spain. Shrubs showed short ( R. sphaerocarpa and B. vulgaris , 14−20 years) to intermediate lifespans ( Rhamnus species, 25−46 years), albeit a R. lycioides individual reached an age of 144 years. Accordingly, ring-widths varied from 2.02 mm in R. sphaerocarpa to 0.40 mm in R. lycioides . Both R. alaternus and R. lycioides showed negative growth-lifespan trade-offs. The ring-width series showed common growth variability between coexisting species ( R. alaternus and R. lycioides ) and also between sites for the same species ( R. sphaerocarpa , B. vulgaris ). Growth was constrained by elevated temperatures in early spring and summer, and enhanced by wet winter-to-spring conditions. A negative water balance from the previous October up to July limited growth. Growth-drought correlations peaked in the most arid site. Resilience indices varied between species and years. In general, shrubs showed good post-drought recovery. Our findings indicate favorable prospects for the study shrubs under more arid climate scenarios. • We quantified age, growth and drought resilience of five shrubs in drylands. • Age and growth rates varied widely (14−144 years, 0.40−2.02 mm). • Rhamnus alaternus and Rhamnus lycioides showed negative growth-lifespan trade-offs. • Shrub growth was constrained by dry winter-spring and warm spring-summer conditions. • Shrubs showed good post-drought recovery.