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Climate change represents an important challenge for forest management and the silviculture of stands and it is known that climate change will have complex effects on cork oak forest ecosystems. North Africa and the Mediterranean basin are especially vulnerable to climate change. Under the effect of climate change, cork oak will disappear from a large area in the future, and the rest will migrate to higher altitudes and latitudes. This study aimed to evaluate the effect of climate change on the spatial distribution of Quercus suber L. and cork production in the Mediterranean area, and the risk of its exclusion by the Aleppo pine (Pinus halepensis Mill.) expansion. The literature review showed that up to 40% of current environmentally suitable areas for cork oak may be lost by 2070, mainly in northern Africa and the southern Iberian Peninsula. Temperature directly influences atmospheric evaporative demand and should affect cork productivity. Precipitation is the main factor that positively influences cork growth and several authors have confirmed the negative effect of drought on this growth. Currently, cork oak habitats are colonized in several places mainly by the Aleppo pine. Under climate change, Aleppo pine is projected to occupy higher altitude sites and several authors have predicted that current and future global warming will have a positive influence on Aleppo pine growth in wet sites. In the future and under climate change, there is a strong possibility that the Aleppo pine will colonize cork oak habitat. Finally, we proposed management practices to protect cork oak against climate change and Aleppo pine expansion.

Four Aleppo pine trees (Pinus halepensis Mill.) have been recorded in Miljakovac park in Belgrade. Aleppo pine is a xerothermic and oligotrophic species originating from the Mediterranean and very rarely cultivated in Serbia. Tree heights and diameters at breast height were measured, as well as the dimensions of needles. The trees are healthy, not attacked by diseases and pests, and are fruit-bearing. Given the climate changes that are causing an increasingly warmer climate in Serbia, xerothermic Mediterranean species that were not suited for cultivation in Serbia in the past could become a significant factor in dendroflora of green areas of urban districts.

This work was funded by the Spanish project FENOPIN (AGL2012-40151-C03-03). J.P.F. is supported by the Ram on y Cajal programme (RYC-2008-02050). An earlier version of this work was presented by D.L. to obtain an MSc degree in the Erasmus Mundus Programme MEDfOR. The authors acknowledge Mara Luc a and Pilar Sope~na for technical assistance and Javier Rodr ıguez and Marif e D ıaz for providing isotope data from the Red Espa~nola de Vigilancia de Is otopos en la Precipitaci on.

• Many ecologically important forest trees from dry areas have been insufficiently investigated for their ability to adapt to the challenges posed by climate change, which hampers the implementation of mitigation policies. We analyzed 14 common-garden experiments across the Mediterranean which studied the widespread thermophilic conifer Pinus halepensis and involved 157 populations categorized into five ecotypes. • Ecotype-specific tree height responses to climate were applied to projected climate change (2071–2100 AD), to project potential growth patterns both locally and across the species’ range. • We found contrasting ecotypic sensitivities to annual precipitation but comparatively uniform responses to mean temperature, while evidence of local adaptation for tree height was limited to mesic ecotypes. We projected intriguing patterns of response range-wide, implying either height inhibition or stimulation of up to 75%, and deduced that the ecotype currently experiencing more favorable (wetter) conditions will show the largest inhibition. Extensive height reductions can be expected for coastal areas of France, Greece, Spain and northern Africa. • Our findings underline the fact that intraspecific variations in sensitivity to precipitation must be considered when projecting tree height responses of dry forests to future climate. The ecotype-specific projected performances call for management activities to ensure forest resilience in the Mediterranean through, for example, tailored deployment strategies.

Key messageCompared to Pinus nigra, Pinus halepensis exhibited higher growth rate and drought tolerance, as well as higher resilience and resistance, making it a potential species to promote in similar sites.Due to climate change, trees are exposed to more frequent and longer periods of drought, which will inevitably change the composition of tree species in the forests of the future. To better understand the effects of site characteristics on species performance under future climate, tree species need to be compared in terms of their climate sensitivity and resilience to extreme events, giving guidelines to forest management. We therefore compared the climate–growth relationships and resilience indices of black pine (Pinus nigra) and Aleppo pine (Pinus halepensis) growing at a flysch site in the northern Adriatic coast. Compared to P. nigra, P. halepensis showed higher growth rates, lower correlations with precipitation, and higher resilience and resistance, and thus should be preferred when both species are considered for planting under similar site conditions.

Short-term, intense heat waves (hamsins) are common in the eastern Mediterranean region and provide an opportunity to study the resilience of forests to such events that are predicted to increase in frequency and intensity. * The response of a 50-yr-old Aleppo pine (Pinus halepensis) forest to hamsin events lasting 1–7 d was studied using 10 yr of eddy covariance and sap flow measurements. * The highest frequency of heat waves was c. four per month, coinciding with the peak productivity period (March–April). During these events, net ecosystem carbon exchange (NEE) and canopy conductance (gc) decreased by c. 60%, but evapotranspiration (ET) showed little change. Fast recovery was also observed with fluxes reaching pre-stress values within a day following the event. NEE and gc showed a strong response to vapor pressure deficit that weakened as soil moisture decreased, while sap flow was primarily responding to changes in soil moisture. On an annual scale, heat waves reduced NEE and gross primary productivity by c. 15% and 4%, respectively. * Forest resilience to short-term extreme events such as heat waves is probably a key to its survival and must be accounted for to better predict the increasing impact on productivity and survival of such events in future climates.

Understanding the physiological and molecular adjustments occurring during tree stress response is of great importance for forest management and breeding programs. Somatic embryogenesis has been used as a model system to analyze various processes occurring during embryo development, including stress response mechanisms. In addition, “priming” plants with heat stress during somatic embryogenesis seems to favor the acquisition of plant resilience to extreme temperature conditions. In this sense, Pinus halepensis somatic embryogenesis was induced under different heat stress treatments (40 °C for 4 h, 50 °C for 30 min, and 60 °C for 5 min) and its effects on the proteome and the relative concentration of soluble sugars, sugar alcohols and amino acids of the embryonal masses obtained were assessed. Heat severely affected the production of proteins, and 27 proteins related to heat stress response were identified; the majority of the proteins with increased amounts in embryonal masses induced at higher temperatures consisted of enzymes involved in the regulation of metabolism (glycolysis, the tricarboxylic acid cycle, amino acid biosynthesis and flavonoids formation), DNA binding, cell division, transcription regulation and the life-cycle of proteins. Finally, significant differences in the concentrations of sucrose and amino acids, such as glutamine, glycine and cysteine, were found.

The Mediterranean region is recognized as a global biodiversity hotspot. However, over the last decades, the cessation of traditional farming in the north part of the Mediterranean basin has given way to strong afforestation leading to occurrence of abandoned agricultural lands colonized by pioneer expansionist species like Pinus halepensis. This pine species is known to synthesize a wide range of secondary metabolites, and previous studies have demonstrated strong allelopathic potentialities of its needle and root leachates. Pinus halepensis is also recognized to release significant amounts of volatile organic compounds (VOC) with potential allelopathic effects that have never been investigated. In this context, the objectives of the present study were to improve our knowledge about the VOC released from P. halepensis needles and roots, determine if these VOC affect the seed germination and root growth of two herbaceous target species (Lactuca sativa and Linum strictum), and evaluate if soil microorganisms modulate the potential allelopathic effects of these VOC. Thirty terpenes were detected from both, needle and root emissions with β‐caryophyllene as the major volatile. Numerous terpenes, such as β‐caryophyllene, δ‐terpinene, or α‐pinene, showed higher headspace concentrations according to the gradient green needles < senescent needles < needle litter. Seed germination and root growth of the two target species were mainly reduced in presence of P. halepensis VOC. In strong contrast with the trend reported with needle leachates in literature, we observed an increasing inhibitory effect of P. halepensis VOC with the progress of needle physiological stages (i.e., green needle < senescent needle < needle litter). Surprisingly, several inhibitory effects observed on filter paper were also found or even amplified when natural soil was used as a substrate, highlighting that soil microorganisms do not necessarily limit the negative effects of VOC released by P. halepensis on herbaceous target species. We investigated the effects of the volatile organic compounds (VOC) released by Pinus halepensis needles and roots on seed germination and seedling growth of two herbaceous target species. Thirty terpenes were detected from both needle and root emissions with β‐caryophyllene as the major volatile. We confirmed the strong allelopathic potentialities of this pine species and demonstrated for the first time a clear increasing inhibitory effect of VOC according to the progress of needle physiological stage (green needle < senescent needle < needle litter). Finally, we pointed out that soil microorganisms are not necessarily able to limit the negative effect of pine VOC on target herbaceous species.

Climate change will impact forest productivity worldwide. Forecasting the magnitude of such impact, with multiple environmental stressors changing simultaneously, is only possible with the help of process-based models. In order to assess their performance, such models require careful evaluation against measurements. However, direct comparison of model outputs against observational data is often not reliable, as models may provide the right answers due to the wrong reasons. This would severely hinder forecasting abilities under unprecedented climate conditions. Here, we present a methodology for model assessment, which supplements the traditional output-to-observation model validation. It evaluates model performance through its ability to reproduce observed seasonal changes of the most limiting environmental driver (MLED) for a given process, here daily gross primary productivity (GPP). We analyzed seasonal changes of the MLED for GPP in two contrasting pine forests, the Mediterranean Pinus halepensis Mill. Yatir (Israel) and the boreal Pinus sylvestris L. Hyytiälä (Finland) from three years of eddy-covariance flux data. Then, we simulated the same period with a state-of-the-art process-based simulation model (LandscapeDNDC). Finally, we assessed if the model was able to reproduce both GPP observations and MLED seasonality. We found that the model reproduced the seasonality of GPP in both stands, but it was slightly overestimated without site-specific fine-tuning. Interestingly, although LandscapeDNDC properly captured the main MLED in Hyytiälä (temperature) and in Yatir (soil water availability), it failed to reproduce high-temperature and high-vapor pressure limitations of GPP in Yatir during spring and summer. We deduced that the most likely reason for this divergence is an incomplete description of stomatal behavior. In summary, this study validates the MLED approach as a model evaluation tool, and opens up new possibilities for model improvement

To understand better the adaptation strategies of intra-annual radial growth in and to local environmental conditions, we examined the seasonal rhythm of cambial activity and cell differentiation at tissue and cellular levels. Two contrasting sites differing in temperature and amount of precipitation were selected for each species, one typical for their growth and the other represented border climatic conditions, where the two species coexisted. Mature trees from Mediterranean (Spain) and sub-Mediterranean (Slovenia) sites, and from sub-Mediterranean (Slovenia) and temperate (Slovenia) sites were selected. Repeated sampling was performed throughout the year and samples were prepared for examination with light and transmission electron microscopes. We hypothesized that cambial rhythm in trees growing at the sub-Mediterranean site where the two species co-exist will be similar as at typical sites for their growth. Cambium in at the Mediterranean site was active throughout the year and was never truly dormant, whereas at the sub-Mediterranean site it appeared to be dormant during the winter months. In contrast, cambium in was clearly dormant at both sub-Mediterranean and temperate sites, although the dormant period seemed to be significantly longer at the temperate site. Thus, the hypothesis was only partly confirmed. Different cambial and cell differentiation rhythms of the two species at the site where both species co-exist and typical sites for their growth indicate their high but different adaptation strategies in terms of adjustment of radial growth to environmental heterogeneity, crucial for long-term tree performance and survival.