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The impact of climate change on the physiological processes of Norway spruce in Central Europe is a significant concern. The increased temperature and evaporative demand associated with climate change may negatively affect its photosynthesis and carbon-water balance. This study tests the combined effect of branch position, temperature (T) and water vapour pressure deficit (VPD) on net photosynthetic rate (PN), water vapour stomatal conductance (gs), and intrinsic water-use efficiency (WUEi) of Norway spruce. More than 11 000 gas-exchange measurements during the summer of 2018 revealed that branch position significantly affects gas exchange and WUEi of juvenile Norway spruce trees. Northern branches showed on average 21% increased PN, 35% higher gs, and 8% lower WUEi compared to the southern branches (across T and VPD conditions). The PN and gs differences between the branches were temperatureand VPD-dependent. We observed the negative impact of raising temperature on gas exchange and WUEi for both treatments, with a 40°C threshold causing a rapid decline in WUEi. Variability of the southern branches' WUEi at 42°C was abruptly increased due to the decoupling of PN and gs (low PN, high gs). Surprisingly, raising VPD showed no significant impact on WUEi of Norway spruce. The results of this study provide necessary information for upscaling and process-based modelling of whole-crown gas exchange. Moreover, experimental studies of gas exchange should take into consideration the branch position effect to prevent possible bias errors. [ABSTRACT FROM AUTHOR]

The current projections of climate change might exceed the ability of European forest trees to adapt to upcoming environmental conditions. However, stomatal and leaf morphological traits could greatly influence the acclimation potential of forest tree species subjected to global warming, including the single most important forestry species in Europe, European beech.We analysed stomatal (guard cell length, stomatal density and potential conductance index) and leaf (leaf area, leaf dry weight and leaf mass per area) morphological traits of ten provenances from two provenance trials with contrasting climates between 2016 and 2020. The impact of meteorological conditions of the current and preceding year on stomatal and leaf traits was tested by linear and quadratic regressions. Ecodistance was used to capture the impact of adaptation after the transfer of provenances to new environments.Interactions of trial–provenance and trial–year factors were significant for all measured traits. Guard cell length was lowest and stomatal density was highest across beech provenances in the driest year, 2018. Adaptation was also reflected in a significant relationship between aridity ecodistance and measured traits. Moreover, the meteorological conditions of the preceding year affected the interannual variability of stomatal and leaf traits more than the meteorological conditions of the spring of the current year, suggesting the existence of plant stress memory.High intraspecific variability of stomatal and leaf traits controlled by the interaction of adaptation, acclimation and plant memory suggests a high acclimation potential of European beech provenances under future conditions of global climate change. [ABSTRACT FROM AUTHOR]

Understanding of the intraspecific variability in the physiological stress response of trees may enable to mitigate the impact of climate change on forest ecosystems in the future. We studied the photosynthetic performance of five silver fir (Abies alba Mill.) provenances originating from climatically distinct localities. The study was performed in the trial plot of the silver fir provenance experiment IUFRO 2005 on two dates: in the early summer and in the late summer. Heat waves and a decrease in water availability occurred between the two measurement dates, allowing us to study the response of the provenances to suboptimal growing conditions. The provenances were evaluated at the level of PSII photochemistry and CO2 assimilation by measuring photosynthesis-related pigment content, chlorophyll a fluorescence, and gas exchange parameters. Significant climatic clines were confirmed: the photosynthetic performance before and after the stress period increased with the increasing altitude and precipitation at the site of origin. In contrast, photosynthetic performance declined with the increasing temperature and Ellenberg's quotient of the origin site. We concluded that provenances originating from high altitudes, corresponding well with more humid and colder conditions in Central Europe, showed the greatest photosynthetic performance and were less responsive to moderate heat and drought. This documents inter-population variation in physiological traits, which needs to be considered in setting rules and recommendations for the transfer of forest reproductive materials. Is there any difference in photosynthesis among trees of different origin growing at the same plot? We found out that provenances of silver fir originating from high altitudes showed the greatest photosynthetic performance and were less responsive to moderate heat and drought stress. The knowledge about the physiology of trees with different origins can be used in forestry improvement programs. [ABSTRACT FROM AUTHOR]

• Colonization density of S. intricatus was analyzed on 150 trap trees over 3 years. • Temperature and host size drive S. intricatus colonization of trap trees. • An unusual second generation of S. intricatus was observed in Central Europe. • Highest S. intricatus populations occurred after warm and dry periods. The European oak bark beetle (Scolytus intricatus) has the potential to impact forest structures through its selection of certain trees. We investigated potential S. intricatus colonisation densities by setting up 150 trap trees and analysing them in 5-metre sections during a three-year period from 2014 to 2016 in a temperate forest in Slovakia, Central Europe. Understanding the population dynamics of S. intricatus and the drivers of its colonization density on trees is necessary if attempts to control or manage populations of S. intricatus in managed forests are to succeed. To explain the population dynamics of S. intricatus, ANOVA was used to assess the colonisation densities in the stem , and generalized linear mixed effect models (GLMMs) were used to analyse the main characteristics of the host trees and the meteorological variables. Structural equation modelling (SEM) was then used to explain the multitude of relationships among the predictor variables and bark beetle populations. Scolytus intricatus reached higher population levels under dry and warm conditions, when trees were prone to drought stress. The highest colonization densities at the trap trees occurred in May and June of 2014 and 2016; in 2015, the highest densities were reported in August and a second generation of S. intricatus was observed. This is unusual, as this species is usually univoltine, i.e. has one generation per year under Central European conditions. Population levels differed in different months during the 3-year study period, i.e. patterns of population dynamics and phenology are not repeating. The mixed-effects models demonstrated that the seasonal temperature influenced the occupation of trap trees by S. intricatus and that the lengths of the galleries were affected by the section surfaces. We conclude that environmental stress hastens the rate of drought stress in oak trees, resulting in faster population growth and higher survival of S. intricatus. [ABSTRACT FROM AUTHOR]

Climate change-induced elevated temperatures and drought are considered to be serious threats to forest ecosystems worldwide, negatively affecting tree growth and viability. We studied nine European beech (Fagus sylvatica L.) provenances located in two provenance trial plots with contrasting climates in Central Europe. Stomata play a vital role in the water balance of plants by regulating gaseous exchanges between plants and the atmosphere. Therefore, to explain the possible adaptation and acclimation of provenances to climate conditions, stomatal (stomatal density, the length of guard cells, and the potential conductance index) and leaf morphological traits (leaf size, leaf dry weight and specific leaf area) were assessed. The phenotypic plasticity index was calculated from the variability of provenances' stomatal and leaf traits between the provenance plots. We assessed the impact of various climatic characteristics and derived indices (e.g., ecodistance) on intraspecific differences in stomatal and leaf traits. Provenances transferred to drier and warmer conditions acclimated through a decrease in stomatal density, the length of guard cells, potential conductance index, leaf size and leaf dry weight. The reduction in stomatal density and the potential conductance index was proportional to the degree of aridity difference between the climate of origin and conditions of the new site. Moreover, we found that the climate heterogeneity and latitude of the original provenance sites influence the phenotypic plasticity of provenances. Provenances from lower latitudes and less heterogeneous climates showed higher values of phenotypic plasticity. Furthermore, we observed a positive correlation between phenotypic plasticity and mortality in the arid plot but not in the more humid plot. Based on these impacts of the climate on stomatal and leaf traits of transferred provenances, we can improve the predictions of provenance reactions for future scenarios of global climate change. [ABSTRACT FROM AUTHOR]