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Abstract: Wood formation and the anatomical characteristics of tree-rings play a decisive role in plant performance and survival due to the importance of water transport. Saplings may be especially vulnerable to water stress; however, the level of water stress that they can endure still remains largely unexamined. Thus, the general objective of our research is to determine the plasticity of wood formation in Pinus halepensis saplings. We evaluated cambial activity, xylem growth ring formation and its anatomical characteristics in different experimental irrigation conditions and tested for its influence on the success rate of sapling establishment. Our results demonstrate a high phenological plasticity in wood formation with juvenile P. halepensis saplings in relation to water availability. Dry conditions during spring and summer strongly limit their cambial activity, which is suggested to be linked to sapling survival during summer. Width and anatomical characteristics of tree-rings differ in saplings exposed to different irrigation conditions. Our results suggest that increasing water stress during spring and summer periods, as predicted by future climate change scenarios, may seriously affect the success of both natural regeneration and reforestation of P. halepensis, and this could severely modify potential distribution of the species. [Copyright &y& Elsevier]

The effects of short-term extreme events on tree functioning and physiology are still rather elusive. European beech is one of the most sensitive species to late frost and water shortage. We investigated the intra-annual C dynamics in stems under such conditions. Wood formation and stem CO 2 efflux were monitored in a Mediterranean beech forest for 3 years (2015-2017), including a late frost (2016) and a summer drought (2017). The late frost reduced radial growth and, consequently, the amount of carbon fixed in the stem biomass by 80%. Stem carbon dioxide efflux in 2016 was reduced by 25%, which can be attributed to the reduction of effluxes due to growth respiration. Counter to our expectations, we found no effects of the 2017 summer drought on radial growth and stem carbon efflux. The studied extreme weather events had various effects on tree growth. Even though late spring frost had a strong impact on beech radial growth in the current year, trees fully recovered in the following growing season, indicating high resilience of beech to this stressful event., (© 2020 John Wiley & Sons Ltd.)