Robinia pseudoacacia is one of the most frequent non‐native species in Europe. It is a fast‐growing tree of high economic and cultural importance. On the other hand, it is an invasive species, ...causing changes in soil chemistry and light regime, and consequently altering the plant communities. Previously published models developed for the potential distribution of R. pseudoacacia concerned 2070, and were based mainly on data from Western and Central Europe; here we extended these findings and included additional data from Eastern Europe. To fill the gap in current knowledge of R. pseudoacacia distribution and improve the reliability of forecasts, we aimed to (i) determine the extent to which the outcome of range modeling will be affected by complementing R. pseudoacacia occurrence data with sites from Central, Southeastern, and Eastern Europe, (ii) identify and quantify the changes in the availability of climate niches for 2050 and 2070, and discuss their impacts on forest management and nature conservation. We showed that the majority of the range changes expected in 2070 will occur as early as 2050. In comparison to previous studies, we demonstrated a greater eastward shift of potential niches of this species and a greater decline of potential niches in Southern Europe. Consequently, future climatic conditions will likely favor the occurrence of R. pseudoacacia in Central and Northeastern Europe where this species is still absent or relatively rare. There, controlling the spread of R. pseudoacacia will require monitoring sources of invasion in the landscape and reducing the occurrence of this species. The expected effects of climate change will likely be observed 20 years earlier than previously forecasted. Hence we highlighted the urgent need for acceleration of policies aimed at climate change mitigation in Europe. Also, our results showed the need for using more complete distribution data to analyze potential niche models.
Previously published models of R. pseudoacacia 's potential distribution concerned 2070, and were based on data from Western and Central Europe; here we extended these findings using data from Eastern Europe and 2050. We demonstrated a greater eastward shift of potential niches of this species and a greater decline in Southern Europe. Future climatic conditions will likely favor the occurrence of R. pseudoacacia in Central and Northeastern Europe. The expected effects of climate change will likely be observed 20 years earlier than previously forecasted. Also, our results showed the need for using more complete distribution data to analyze potential niche models.
The role of future forests in global biogeochemical cycles will depend on how different tree species respond to climate. Interpreting the response of forest growth to climate change requires an ...understanding of the temporal and spatial patterns of seasonal climatic influences on the growth of common tree species. We constructed a new network of 310 tree‐ring width chronologies from three common tree species (Quercus robur, Pinus sylvestris and Fagus sylvatica) collected for different ecological, management and climate purposes in the south Baltic Sea region at the border of three bioclimatic zones (temperate continental, oceanic, southern boreal). The major climate factors (temperature, precipitation, drought) affecting tree growth at monthly and seasonal scales were identified. Our analysis documents that 20th century Scots pine and deciduous species growth is generally controlled by different climate parameters, and that summer moisture availability is increasingly important for the growth of deciduous species examined. We report changes in the influence of winter climate variables over the last decades, where a decreasing influence of late winter temperature on deciduous tree growth and an increasing influence of winter temperature on Scots pine growth was found. By comparing climate–growth responses for the 1943–1972 and 1973–2002 periods and characterizing site‐level growth response stability, a descriptive application of spatial segregation analysis distinguished sites with stable responses to dominant climate parameters (northeast of the study region), and sites that collectively showed unstable responses to winter climate (southeast of the study region). The findings presented here highlight the temporally unstable and nonuniform responses of tree growth to climate variability, and that there are geographical coherent regions where these changes are similar. Considering continued climate change in the future, our results provide important regional perspectives on recent broad‐scale climate–growth relationships for trees across the temperate to boreal forest transition around the south Baltic Sea.
A tree‐ring network from European beech, Scots pine and oak trees from around the south Baltic Sea was compiled to examine the relationship between tree growth and climate. Our findings indicate tree growth is influenced by warming winter climate and summer moisture availability in northern temperate forests. Furthermore, spatial analysis suggests that there are geographical patterns in similar growth responses to climate and that these responses can be unstable through time.
The expansion of European beech to northeastern regions due to climate change is anticipated, especially if assisted migration techniques are employed. Marginal populations of European beech are ...exposed to unfavorable growing conditions that are challenging for their survival and multifunctionality. Under such conditions, the structural complexity of stands is a critical factor that supports the sustainability of these populations. In this study, five stands of European beech in Latvia, which are currently the most northeastern stands in Europe, were investigated. In each of the stands, two sample plots (area 500 m2) were randomly established. The dimensions of trees, stem quality features, and spatial structure of the stands were assessed. The stands varied in density but were found to be productive as indicated by comparable tree dimensions to those in core populations. The studied beech stands displayed low species mingling and tended towards monospecies composition, with some structural diversification likely due to small-scale disturbances and varying stand densities, suggesting that spatial diversity was influenced by species composition and competition among trees. The analyzed European beech stands were in the maturing phase, but displayed diverse diameter and height structures, indicating that natural ecological processes were occurring, akin to those found in non-marginal regions. The stem quality of the trees was intermediate, with frequent occurrences of ramicorn, epicormic branches, and forking (41.8%, 53.5%, and 26.3%, respectively), while stem cracks were rare (4.6%). However, these features can provide crucial microhabitats for biodiversity. Therefore, European beech has the potential for diversification in forestry and ensuring sustainability at the edge of its range expansion. The main implications of this study highlight the diverse structural characteristics of the European beech stands, indicating the influence of species competition and small-scale disturbances, providing valuable insights for forest management and conservation strategies. Although, this study has a few potential limitations that should be considered, including the relatively small sample size and the absence of long-term data.
The dieback of common ash (Fraxinus excelsior L.) has dramatically decreased the abundance of the species in Europe; however, tolerance of trees varies regionally. The tolerance of trees is ...considered to be a result of synergy of genetic and environmental factors, suggesting an uneven future potential of populations. This also implies that wide extrapolations would be biased and local information is needed. Survival of ash during 2005–2020, as well as stand- and tree-level variables affecting them was assessed based on four surveys of 15 permanent sampling plots from an eastern Baltic region (Latvia) using an additive model. Although at the beginning of dieback a relatively low mortality rate was observed, it increased during the 2015–2020 period, which was caused by dying of the most tolerant trees, though single trees have survived. In the studied stands, ash has been gradually replaced by other local tree species, though some recruitment of ash was locally observed, implying formation of mixed broadleaved stands with slight ash admixture. The survival of trees was related to tree height and position within a stand (relative height and local density), though the relationships were nonlinear, indicating presence of critical conditions. Regarding temporal changes, survival rapidly dropped during the first 16 years, stabilizing at a relatively low level. Although low recruitment of ash still implies plummeting economic importance of the species, the observed responses of survival, as well as the recruitment, imply potential to locally improve the survival of ash via management (tending), hopefully providing time for natural resistance to develop.
The increasing effects of storms are considered the main abiotic disturbance affecting forest ecosystems. Bark-stripping damage from the growing ungulate populations, in turn, are among the main ...biotic risks, which might burden the stability of trees and stands. Therefore, the aim of our study is to estimate the effect of cervid bark-stripping on the mechanical stability of Norway spruce using a static tree-pulling test. For the test, eight damaged and 11 undamaged canopy trees were selected from a 40-year old stand (plantation with 1 × 3 m spacing) growing on mineral mesotrophic soil. The selected trees were bark-stripped 7–9 years prior to the experiment. Uprooting was the most frequent type of failure; only two trees broke at the stem. For the damaged trees, the resistance to pulling was significantly reduced (p-value < 0.001). Stem volume and presence of bark-stripping were the best linear predictors of the basal bending moment at the primary failure (irreversible deformation of wood structure) and secondary failure (collapse of the tree). A significant (p-value < 0.001) interaction between stem–wood volume and presence of bark-stripping was observed for primary failure, indicating a size-dependent reduction of stability of the damaged trees. Such interaction lacked significance (p-value = 0.43) for the secondary failure (mostly uprooting), indicating a decrease in stability irrespectively of tree size. Somewhat surprisingly, the decrease in the overall mechanical stability of the bark-stripped trees appeared not to be related to a direct reduction of the strength of the stems, but rather to physiological effects such as altered allocation of carbon, increased drought stress because of interfered hydraulic conductance of wood, or secondary infestation. The reduced stability also suggests that bark-stripped trees can act as the weak spots decreasing the collective stability of stands in the long term, thus increasing the susceptibility to storms.
In the Baltics, warming is expected to burden the growth of Norway spruce Picea abies, with weather anomalies/extremes having strong triggering effects, which can be mitigated by tree breeding. ...Within the region, breeding programmes have been aiming for productivity, yet being conservative, their sustainability depends on the adaptability of native genotypes, which is unclear. The adaptability of genotypes can be assessed through local adaptations and phenotypic plasticity, with the sensitivity of increment depicting the conformity of genotypes and environments. To assess the adaptability of native populations to anticipated climates, local genetic adaptation and phenotypic plasticity of the weather sensitivity of the radial increment were assessed by the methods of time series analysis and quantitative genetics based on three clonal trials (low-density single-tree plot plantations of grafted clones of native plus trees) representing the local climatic gradient in Latvia. The growth of trees was sensitive to the moisture availability in summer and the thermal regime in winter, yet coinciding anomalies in both were associated with abrupt changes in tree ring width. These environmental effects differed among the clones, indicating genetic controls over the sensitivity of increment, which, however, decreased under a warmer climate, suggesting a limited adaptability of local populations to warming. Still, the weather-growth relationships showed moderate phenotypic plasticity, suggesting some mid-term adaptability. Accordingly, supplementation of breeding populations via assisted gene transfer with the genotypes that are adapted to warmer and drier climates appears crucial.
This study examines microhabitat abundance and composition on retention trees in 20 young stands in Latvia that were clear-cut between 2002 and 2004. Retention trees play a vital role in sustaining ...biological diversity after clear-cutting, but their mortality rate is often high due to post-harvest environmental changes. This study compares tree-related microhabitat (TreM) abundance and composition on retention trees of different dimensions, species, and vitality. The tree height and diameter were measured, and the living status and position of each tree were determined. The research questions of the study were to assess the relationships between TreMs, tree dimensions, and species, as well as to compare the occurrence of TreMs on living and dead wood. The comprehensive analysis revealed that larger tree diameters and specific tree species (Populus tremula, Fraxinus excelsior, and Salix caprea) lead to a higher abundance of TreMs. The results also highlighted the importance of preserving deadwood within forest stands as it enhances the observed abundance of TreMs. This study provides the missing information on TreMs in Latvia, thus providing data for comparison in a wider region.
In the Eastern Baltic region, severe windstorms increase both in frequency and magnitude, particularly during the dormancy period, increasing wind damage risks even more for silver birch (Betula ...pendula Roth.), which is considered to be less vulnerable forest tree species. Tree anchorage, particularly the properties of soil–root plate, determines the type of fatal failures trees experience under extreme wind loads and, subsequently, the potential for timber recovery during salvage logging. The link between soil–root plate properties and fatal failure types was assessed by conducting destructive static pulling tests; trees on freely draining minerals and drained deep peat soils under frozen and non-frozen soil conditions were tested. The size of the root plate did not differ between trees experiencing uprooting or stem breakage but was largely affected by soil type. Frozen soil conditions increased soil–root anchorage (via binding between soil particles) and, hence, the frequency of stem breakage without changing the size of soil–root plate. However, the lack of frozen soil conditions is among the main climatic risks for forestry within the region. The differences in the properties of soil–root plate implies plasticity in adaptation to wind loadings relative to birch, suggesting a potential for managing different types of fatal failure of trees and, subsequently, the share of retrievable timber in cases of salvage logging.
The interactions between wind damage and biotic agents, such as root-rot and cervids (bark-stripping), amplify the effects of storms on forests in Europe and Norway spruce (Picea abies (L.) Karst.) ...stands, in the Eastern Baltic region in particular. Due to uneven manageability of the biotic agents, the information about their effects on susceptibility to wind damage can aid the prioritization of management for sustaining spruce stands. This study compared the effect of root-rot and bark-stripping on the mechanical stability of Norway spruce via mixed covariance analysis of basal bending moments, based on static tree-pulling test data of 87 trees from five stands in Latvia. Bark-stripping caused a significantly stronger reduction in resistance against the intrinsic wood damages (primary failure) compared to root-rot, while showing a similar effect on resistance to fatal (secondary) failure. This suggests that bark-stripping damage increases the susceptibility of spruce to storm legacy effects, and, hence, is a higher priority risk factor in Norway spruce stands under the climate-smart management approach.
PDF
