• Energy Research

Pinus sylvestris L. (Scots pine) is the conifer with widest natural distribution area. Portugal constitutes its westernmost limit of distribution. Most of the Portuguese populations were planted but two autochthonous populations were recently ascribed to 'Serra do Gerês' (NW Portugal), and seem to be well adapted to the temperate climate. However, the ongoing climate changes may compromise their survival. With this study we intend to evaluate the anatomic-physiological and genetic responses of Scots pine from five European provenances ('Gerês', 'Puebla de Lillo', 'Montes Universales', Germany and Sweden) to three water availability regimes, in order to determine which one(s) present higher resistance to drought. Individuals from 'Gerês' presented the highest stability in photosynthetic reactions as well as the better photochemical and metabolic behaviours under drought (T3). Hence, the relative expression ratio of three water stress-responsive genes during drought was lower and gradual in 'Gerês', compared to all other provenances, followed by Germany. The results achieved in 'Gerês' and Germany provenances are very interesting since they reflected that the native populations of 'Gerês' along with the Portuguese Scots pine planted populations with a probable German provenance, have ability and high adaptive potential to respond to situations of water deficit. Moreover, the present genetic and physiological data demonstrated the urgent demand for the conservation of Portuguese Scots pine genetic resources as well as its use in plantation/afforestation of areas where the warming and drought has been affecting the survival of this species.

Western Iberia has recently shown increasing frequency of drought conditions coupled with heatwave events, leading to exacerbated limiting climatic conditions for plant growth. It is not clear to what extent wood growth and density of agroforestry species have suffered from such changes or recent extreme climate events. To address this question, tree-ring width and density chronologies were built for a Pinus pinaster stand in southern Portugal and correlated with climate variables, including the minimum, mean and maximum temperatures and the number of cold days. Monthly and maximum daily precipitations were also analyzed as well as dry spells. The drought effect was assessed using the standardized precipitation-evapotranspiration (SPEI) multi-scalar drought index, between 1 to 24-months. The climate-growth/density relationships were evaluated for the period 1958-2011. We show that both wood radial growth and density highly benefit from the strong decay of cold days and the increase of minimum temperature. Yet the benefits are hindered by long-term water deficit, which results in different levels of impact on wood radial growth and density. Despite of the intensification of long-term water deficit, tree-ring width appears to benefit from the minimum temperature increase, whereas the effects of long-term droughts significantly prevail on tree-ring density. Our results further highlight the dependency of the species on deep water sources after the juvenile stage. The impact of climate changes on long-term droughts and their repercussion on the shallow groundwater table and P. pinaster's vulnerability are also discussed. This work provides relevant information for forest management in the semi-arid area of the Alentejo region of Portugal. It should ease the elaboration of mitigation strategies to assure P. pinaster's production capacity and quality in response to more arid conditions in the near future in the region.

Understanding the survival capacity of forest trees to periods of severe water stress could improve knowledge of the adaptive potential of different species under future climatic scenarios. In long lived organisms, like forest trees, the combination of induced osmotic stress treatments and field testing can elucidate the role of drought tolerance during the early stages of establishment, the most critical in the life of the species. We performed a Polyethylene glycol-osmotic induced stress experiment and evaluated two common garden experiments (xeric and mesic sites) to test for survival and growth of a wide range clonal collection of Maritime pine. This study demonstrates the importance of additive vs non additive effects for drought tolerance traits in Pinus pinaster, and shows differences in parameters determining the adaptive trajectories of populations and family and clones within populations. The results show that osmotic adjustment plays an important role in population variation, while biomass allocation and hydric content greatly influence survival at population level. Survival in the induced osmotic stress experiment presented significant correlations with survival in the xeric site, and height growth at the mesic site, at population level, indicating constraints of adaptation for those traits, while at the within population level no significant correlation existed. These results demonstrate that population differentiation and within population genetic variation for drought tolerance follow different patterns.

Abstractn‐Alkane and long‐chain alcohol (LCOH) profiles of needle cuticular waxes of nine provenances of three Pinus species (P. taeda. P. pinaster and P. pinea) were determined and their chemotaxonomic importance was studied. n‐Alkanes concentrations were very low in all Pinus spp. A lack of ability of these compounds to differentiate Pinus spp. and their provenances was observed. LCOH concentrations were much higher, being nonacosan‐10‐ol (10‐C29‐OH) the most abundant one in all Pinus spp. Total LCOH concentrations varied (P<0.001) between Pinus spp. with P. taeda presenting the highest (P<0.05) value and P. pinea the lowest one. Differences in LCOH profiles were large (P<0.001) and allowed separation of Pinus spp. in the Principal Component Analysis (PCA). Although a noticeable separation of individuals was not observed. cluster analysis on LCOH concentrations allowed a clear distinction between species, indicating their potential to be used as chemotaxonomic markers to differentiate provenances of different Pinus spp.