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.
Increasing resistance against biotic and abiotic factors is an important goal of forest tree breeding. The aim of the present study was to develop a root rot resistance index for Scots pine breeding ...and evaluate its effectiveness. The productivity, branch diameter, branchiness, stem straightness, spike knots, and damage from natural infection of root rot in 154 Scots pine open-pollinated families from Latvia were evaluated through a progeny field trial at the age of 38 years. Trees with decline symptoms were sampled for fungal isolations. Based on this information and kriging estimates of root rot, 35 affected areas (average size: 108 m2; total 28% from the 1.5 ha trial) were delineated. Resistance index of a single tree was formed based on family adjusted proportion of live to infected trees and distance to the center of affected area. Heritability for resistance to root rot based on the value of this index, was high (0.37) and comparable to indices of growth traits. Correlations of family breeding estimates between resistance to root rot and the other traits were not significant, except for a weak, yet significant, positive correlation with diameter at breast height and branch diameter. Selection index including only growth traits (height and stem volume) had a negligible effect on damage by root rot. We detected a maximum genetic gain in resistance index of 33.7% when incorporating it into the selection index with positive gains for growth traits (6.5–11.0%). Two-stage selection with prior selection of the most resistant families was not superior to the use of selection index with only rot resistance included. Overall; rot resistance index appeared to be an effective tool in tree breeding for the selection of more resistant families, using the existing trials with natural (uncontrolled) infection
The ongoing shifts in natural vegetation zones predict the expansion of European beech (Fagus sylvatica L.) into the Eastern Baltic region, suggesting it will become a potential alternative to birch ...(Betula pendula Roth. and Betula pubescens Ehrh.) in forest regeneration. For a successful application of alternative forest regeneration material, an evaluation of susceptibility to natural disturbances (e.g., wind) is necessary for reliable projections of timber yield in the long term. This study compared the loading resistance of beech growing in the northeasternmost stands in Europe to local birch by applying the static tree-pulling test. Relationships between dimensions of aboveground parts and resistance against intrinsic wood damages (primary failure) and fatal (secondary) failure were similar between species. However, birch, which is more drought sensitive compared to beech, is suggested to have a higher susceptibility to post-storm legacy effects, supporting beech as a potential alternative to birch in terms of wind resistance.
Micropropagation has several advantages over conventional vegetative propagation methods, but it is limited by genotype responsiveness. We assessed the effect of age of the mother-tree and the time ...of explant collection on culture initiation, as well as the multiplication ability and effect of different nutrient media and plant growth regulators on silver birch genotypes. Explants collected from 1‐year‐old trees (66%) and explants collected in spring (64–67%) developed a significantly (both
p
< 0.001) higher proportion of shoots than those from 15‐year‐old trees (39%) and those collected in mid-summer (31%) and autumn (29%), respectively. In a stabilised culture, the length of the main shoot varied from 1.3 to 7.8 cm between genotypes, and the multiplication rate ranged from 1.0 to 6.8 shoots per explant. Hyperhydrated shoots were present in 17 out of 50 clones, and, among the clones, ranged from 14 to 50%. Cultures on the Murashige and Skoog basal medium had a higher multiplication rate than cultures on a Woody Plant Medium, and the application of zeatin provided better results than 6‐benzylaminopurine. The difference between cytokinin types was 11–29% for the multiplication rate and 21–29% for the length of the main stem. The highest multiplication rate was obtained using a zeatin concentration of 0.5 mg L
−1
. However, better shoot growth and proliferation had a significant positive relation to shoot hyperhydration (all
p
< 0.001). Therefore, a medium with an optimal balance between the multiplication rate and the number of hyperhydrated shoots should be carefully selected.
The increasing interest in carbon budget estimation and the growing use of woody biomass in bioenergy production raises the necessity for precise estimates of belowground biomass and soil carbon ...pools in forest ecosystems, particularly in terms of changes in the age structure of forests. The aim of this study was to estimate the belowground biomass of young (< 40 years) stands of Scots pine (Pinus sylvestris L.) in Latvia. The biomass of small roots (diameter 2-20 mm), coarse roots (diameter > 20 mm), and stumps of 39 trees from eight stands growing on dry, nutrient-poor mineral soils was measured and compared to the aboveground variables of sampled trees. The results revealed that stumps, small roots, and coarse roots comprised 43%, 35% and 22%, respectively, of the belowground biomass of young Scots pines. The proportion of belowground biomass over the total tree biomass was age-dependent, ranging from 33% to 17% for 8-year and 40-year old trees, respectively. Aboveground tree variables were significantly correlated with the belowground biomass, being stemwood volume and basal area the best predictors (R2 = 0.86-0.98, relative errors = 26-43%) of the belowground biomass components. Accordingly, the developed models produced more accurate estimates compared to previous models for the region, thus reducing the uncertainty in determining the carbon budget for belowground biomass. Still, an analysis of a more comprehensive dataset is needed to account for the effect of the social status of trees, as well as the within- and between-stand variation.
Fagus sylvatica L. is one of the most important commercial tree species in Europe and its natural distribution range is expected to shift northwards due to climatic changes. Detailed information of ...factors affecting its growth is crucial as a basis for recommendations of wider use of this tree species. Aim of the study was to characterize the changes of radial growth intensity of European beech during a vegetation season. In mature beech stand in northwest Latvia two sample trees (dominant (DT) and suppressed (ST)) were selected in Hylocomiosa forest type. Continuous measurements of changes of stem diameter and xylem sap fl ow as well as meteorological parameters were carried out. Stem cycle approach was applied to distinguish the duration of contraction, expansion and increment of the stem. Onset and cessation of growth of the ST tree was observed several days later compared with DT and mean growth intensity during the entire observation period was considerably lower (0.014 mm/day
for ST and 0.022 mm/day
for DT, respectively). Most intensive growth increment diurnally was observed in the early morning before sunrise, and seasonally till beginning of July. Positive effect of precipitation and low water pressure deficit (VPD) on growth was observed, while high VPD coincided with stem contraction. Results indicate the sensitivity of radial growth of European beech to water deficit and high atmospheric transpirational demand; therefore, future potential of cultivation of beech in Latvia depends on changes in moisture regime.
Cracks expose wood to fungal infections that significantly affects wood quality, while rapid wound occlusion decreases probability of infections. Assessment of scars was done at four grade scale in ...three adjacent hybrid aspen trials at the age of 8-10 years in central part of Latvia three years after bark crack occurrence. Occluded wounds were found for 95% of damaged trees, regardless of tree age. Among trees that had cracks wider than 1 cm, 42% had uniformly healed bark, but 7% still had open wounds. Wound development was significantly affected by crack width and length (both p < 0.001), but had no clear relation with tree DBH (diameter at breast height) and relative DBH increment (both p > 0.05). At clonal mean level, scar grade was significantly affected by grade of crack three years earlier and clone (both p < 0.001), but mean DBH of clone had no relation (p > 0.05) to proportion of trees evaluated by any of the scar grades. The results suggest that three years after the bark crack formation most of them had successfully occluded and selection of clones with better diameter growth has no influence on development of cracks.
In the eastern Baltic region, Norway spruce (Picea abies) is predicted to decrease in abundance, resulting in substantial economic consequences. Such predictions have been based on distribution, as ...well as the sensitivity of growth, largely neglecting the adaptive potential of local populations. Under such circumstances, information on growth sensitivity and its genetic control, as well as productivity-sensitivity relationships is necessary to evaluate the adaptability of populations. Radial increment, which is highly sensitive to local conditions has been mainly used for weather-growth analysis, while height increment, which is a better proxy of productivity due to lower dependence on local density, has been neglected due to laborious gathering of data. Long-term weather sensitivity of annual height increment to weather fluctuations and anomalies (extremes) was estimated by the time series decomposition and multiple regression techniques. Clones of plus-trees from a local population differing by productivity at the age of 55 years growing in an experimental plantation in Latvia were studied. Meteorological conditions prevailingly had carry-over effects on height increment. Thermal regime in winter was the primary driver of height increment with moisture availability in summer showing secondary effects, presuming a positive effect of warming on growth. Abrupt changes in annual increment were related to the co-occurrence of a few weather anomalies, suggesting robustness of height growth. Height increment showed explicit sensitivity-productivity relationships with more productive genotypes being more tolerant and resistant to weather fluctuations. Considering that narrow spatial scale and climatic gradient were analysed, linear and nonlinear responses to weather conditions were estimated implying local adaptation and varying phenotypic plasticity of the genotypes, thus suggesting the persistence of adaptive potential of the local non-marginal population.
•Long-term variability of height increment of Norway spruce genotypes was assessed.•Multiple regression was used to compare drivers of height growth of local genotypes.•Weather conditions had prevailingly carryover effects on height increment.•Winter temperature and summer moisture were the main drivers of increment.•Clonal differences and productivity-sensitivity relationships were explicit.
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