In the near future, it is predicted that the natural distribution range of forest tree species will be reshaped due to the rapid changes in climate conditions. The assisted migration of species in favorable environmental conditions, as future solutions for sustainable forest management, could be supported by genetic tests. This study aims to evaluate the adaptive potential of European beech (Fagus sylvatica L.) and the opportunities for applying assisted migration practices in the Carpathian region of Romania. Growth and stability performances, as well as phenotypic plasticity of 31 international beech provenances, were assessed in two common garden experiments located in optimum growing conditions and at the eastern margin of the beech distribution range, respectively. For all analyses, trees height, breast height diameter, and survival were determined. Survival and growth traits were higher by 6–8% in the ecological optimum for beech. The highest mean plasticity was obtained by three provenances from France and one from Denmark. Three provenances performed better in both trials. Increasing the management sustainability of beech forests in a changing climate might be possible by using assisted migration practices, which include the promotion of the highest adapted and productive provenances only in the provenance region where they performed.

Swiss stone pine (Pinus cembra L.) may represent a vital species for afforestation at the upper altitudinal limits of forests due to its adaptability to challenging environmental conditions. In this study, we aimed to analyze the variability in ring width (radial growth, RW, earlywood, EW, latewood, LW, and latewood proportion, LWP) and the influence of different sites on the climatic resilience of twelve European provenances of Swiss stone pine to identify the best-adapted provenances. Five provenances from the Alps and seven from the Carpathians were tested across two 27-year-old field trials conducted in the Eastern and Southern Carpathians. Moderate genetic differentiation among the provenances was noted, which could ensure the success of breeding programs. Based on ring width and latewood proportion, we successfully selected the 25% best-performing provenances and recommend them for use in the provenance regions where have performed. The significant influence of the testing site and the different outcomes of the provenances necessitate extreme attention during the transfer of forest reproductive materials. Additionally, the breeding strategies applied in the two trials differed, consisting in individual selection in the Cugir trial and provenance selection in the Cârlibaba trial. The low resistance of all provenances shown in both trials, particularly in the Cugir trial, is worrying in the context of global warming.

Swiss stone pine (Pinus cembra) is a viable solution for afforestation in the high mountain zone, at the upper limit of the forests, due to the species adaptation ability to the limiting climatic conditions. The aim of this study was to analyse the genetic variability, inheritance rate and juvenile-adult correlations, in a 26 years full-sib (10x10 complete mating design) trial, in order to predict the genetic gain of forward selection. In the spring of 2023, measurements and evaluations were carried out for all the existing trees, for Survival rate (Sr), growth (Diameter as breast height- Dbh, Trees' height- Th, Trees' volume- Tv) and quality traits (Forks, stem slenderness- Ss, branches' diameter- Bd, branches' finesse- Bf, defoliation- Def). The 90 cross-pollinated (CP) families registered 50% of Sr whereas the other 10 selfcross-pollinated (consanguineous) registered just 11% of Sr, and the majority of those trees are dominated and face extinction in the next years. Juvenile-adult correlations were highly significant (p<0.001), indicating that early selection (at the age of 14 years) might be efficient. At the trial age, based on the medium to high heritabilities, the forward selection of the best 10% individual trees from the top 20 of the 90 CP families, for Dbh, could be applied, which ensure at least 9.2% of genetic gain.

Phenology is considered an indicator of environmental changes, with direct implications in the length of the growing season; therefore, it offers essential information for a better understanding of the tree–environment relationships that could lead to the right decisions for forests’ sustainable use and conservation. A better understanding of how European beech (Fagus sylvatica) phenology responds to predicted climate change effects is important for forest management. This study aimed to assess bud burst and senescence among and within beech populations located along a steep elevational gradient. Phenological observations were carried out on 150 beech individuals along an altitudinal transect in the south-eastern Carpathian Mountains, from 550 to 1450 m, in five study sites in two consecutive years. The start of the bud burst, of senescence, and the duration of the growing season varied inversely proportionally to the elevational gradient in both monitored years. Individuals located at the highest altitude need 28 more days to start the growing season than those at the lowest altitude. There is an average difference of 14 days at the start of the growing season in the same beech populations between the two consecutive years. The first stage of senescence (yellowing of leaves) lasted longer in 2021 (21–32 days) than in 2022 (18–25 days), with a difference of 16%–28%, proportional to the increase in altitude. The association of field phenological data with meteorological data indicates that the start of the growing season occurs when the thermal threshold of 10 °C is exceeded, with an accumulation of a least 60 GDD (growing degree days) with a threshold of 0 °C in the last 7 days as a complementary condition. The appearance of the first stage of senescence, the yellowing of the leaves, was also influenced by the temperature and the accumulation of at least 72 SDD (senescence degree days) with a threshold of 0 °C in the last 7 days. Our results confirm that the temperature is the triggering meteorological factor for the onset of bud burst and leaf senescence in European beech.

In a changing climate, forest managers need to select productive and climate-change-resilient tree species and provenances. Therefore, assessing the growth response of provenances growing in field trials to climate provides useful information for identifying the more appropriate provenance or variety. To determine the genetic gain through selection of the most productive and resilient families and to decipher the role of crown forms of Norway spruces (Picea abies (L.) Karst.), we used 24 families with a classical crown (pyramidalis) and 24 with a narrow crown (pendula) from eight provenances, growing in a 25-year-old comparative trial. The annual wood characteristics (ring width and early- and latewood), the wood resistance (expressed by latewood proportion (LWP)), and the growth response to climate of the two spruce crown forms were investigated. No significant differences between the two spruce forms were found regarding the ring width characteristics. However, three pendula families of Stâna de Vale I provenance exhibited the highest LWP and could be included in a future selection strategy, the respective trait having also high heritability. Radial growth was positively and significantly correlated with previous September and current July precipitation and negatively with current June temperature. Both spruce forms showed good recovery capacity after a drought event.

The genetic inheritance of a tree species is fully expressed in the phenotype only when its ecological requirements are accomplished. Therefore, genetic tests provide the opportunity to simulate the change in the environment and determine the most suitable site conditions for specific populations. In light of the unpredictable climate conditions resulting from rapid environmental changes, the current study investigated possible signs of adaptation and productivity of European beech in the Romanian Carpathian region. For this purpose, the tree growth and stability performances, as well as the transfer effect, were examined in 17 international beech provenances tested in two different environments for 27 years. Growth and stability performances were evaluated using tree height (Th), breast height diameter (DBH), and survival (S). In the case of the transfer analyses, the ecodistance approach was applied. According to the results, the average of S was 13% higher in the Carbunari provenance trial, and DBH was higher in the Sacele trial by 15%, while no noticeable differences were registered for Th. The best-performing provenances were those originating from similar site conditions to the Romanian test sites, and the transfer function detected the sensitivity of beech provenances to increasing temperature. The general transfer response of provenances revealed a similar performance across sites and suggested that provenances exhibited adaptation and acclimation to the test environments from Romanian Carpathians.