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.
Windstorms are a significant disturbance in northern European Scots pine forests. Mechanistic models for assessment of their impact have been developed. The aim of our study was to assess the impact ...of windstorms on the financial value of Scots pine (Pinus sylvestris L.) stands. Wind damage probability in stands with certain dimensions (linked to age and site index) and the reduced value retrieved from salvage logging instead of planned harvest in undamaged stands were used for calculation. Equivalent annual annuity with interest rates of 3%, 4%, and 5%, three different commercial thinning regimes, and different planting densities were used to assess the mean influence. Wind damage risk had a notable and significant negative effect on the financial value of Scots pine forest stands. Equivalent annual annuity decreased sharply with stand age, especially in the most productive sites (SI 36). The negative financial impact could be reduced by selection of a lower initial planting density (1000–2000 trees ha−1 instead of 3000) and by reducing the rotation period, for example, by using target diameter as the criteria for the time of final harvest.
Wind is one of the major natural forest disturbances in Europe, and reduces the total economic (including carbon sequestration) value of forests. The aim of this study was to assess the financial ...benefit of silvicultural measures in young, pure, planted Norway spruce stands by reduction in the impact of wind damage over the rotation period. The analyzed measures are promptly applied precommercial thinning and low-density planting with improved plant material. Spatial information on factors affecting wind damage—wind climate and soil—were gathered and combined with the local growth model and empirical data from tree pulling experiments in Latvia to assess the economic value loss due to wind damage over a rotation period. Timely precommercial thinning and lower-density planting with improved plant material would ensure a positive net present value with an interest rate of 3%, using conservative estimates. The financial benefit is highest in windier (coastal) regions and for the planting, followed by moderate thinning. The results demonstrate that, even without changing the dominant tree species, a considerable reduction in wind-damage risk can be achieved.
Storms are the main abiotic disturbance in European forests, effects of which are expected to intensify in the future, hence the importance of forest stand stability is increasing. The predisposition ...of Norway spruce to wind damage appears to be enhanced by pathogens such as Heterobasidion spp., which reduce stability of individual trees. However, detailed information about the effects of the root rot on the stability of individual trees across diverse soil types is still lacking. The aim of the study was to assess the effect of root rot on the individual tree stability of Norway spruce growing on drained peat and mineral soils. In total, 77 Norway spruce trees (age 50–80 years) growing in four stands were tested under static loading. The presence of Heterobasidion spp. had a significant negative effect on the bending moment at primary and secondary failure of the tested trees irrespectively of soil type. This suggests increased legacy effects (e.g., susceptibility to pathogens and pests due to fractured roots and altered water uptake) of storms. Damaged trees act as weak spots increasing the susceptibility of stands to wind damage, thus forming a negative feedback loop and contributing to an ongoing decline in vitality of Norway spruce stands following storms in the study region in the future. Accordingly, the results support the importance of timely identification of the decayed trees, lowering stand density and/or shortening rotation period as the measures to counteract the increasing effects of storms on Norway spruce stands.
More than 280 trees were uprooted in winching tests monitored by high resolution inclinometers at the base of the trees and a forcemeter mounted in the winching line. The dataset comprises trees ...growing on different urban and forest sites in Europe and North America and mainly consists of fifteen widespread tree species. For the first time, a large number of trees were measured non-destructively prior to uprooting failure, as commonly practiced by consulting arborists in static load tests. With these tests, the bending moment required to cause 0.25° root plate inclination (rotational stiffness) was determined and used to predict the strength of the root system from equations described in two evaluation methods currently used in arboriculture. The predictions were tested against the measured anchorage strength, i.e., the maximum bending moment that was required to uproot the trees. Both methods delivered good estimates, which indicates that rotational stiffness at 0.25° inclination of the stem base is a suitable proxy for anchorage strength. Both equations can be considered valid for assessing the likelihood of uprooting failure, as they systematically underestimate and rarely overestimate the actual resistance to failure of a tree’s root system. As a trend, the differences between predicted and measured anchorage strength were larger for small trees, for which the resistance of the root system was overcome at larger inclination angles. While the quality of the predictions differed for species, it did not differ between sites. The angles of stem inclination at which the anchorage strength was overcome for all trees in our dataset support models for the mechanics involved in uprooting failure that previously have been described only for conifers with a shallow root system.
•Generalized additive model was used to analyse weather-growth relationships.•In the mid-part of species range, weather-growth responses were non-linear.•Growth showed generally positive response to ...winter temperature.•Responses to summer temperature mostly showed local optima.•Responses to the precipitation related variables showed thresholds of sensitivity.
Under changing climate, temporal and spatial stability (stationarity) of growth responses of trees to weather and climate, which has often been presumed without explicit testing, is crucial for prediction of productivity and sustainability of forests. However, considering evolutionary adaptation of tree populations to wide spatiotemporal ecological gradients, extrapolation of linear responses, which could be observed in limited parts of the gradients (certain locality), can result in biased results. Accordingly, the plasticity of responses of tree-ring width of the eastern Baltic populations of Scots pine (Pinus sylvestris L.) to meteorological conditions across the regional climatic gradient was assessed using a mixed generalized additive model. The linear responses were assessed using a bootstrapped correlation analysis for comparison. The radial growth responses of the eastern Baltic population of Scots pine showed explicit regional gradients according to the local climates, indicating gradual shifts in the effects of winter temperature and summer moisture regime. Accordingly, temperature in late-winter and summer, as well as summer water deficit were identified as the main regional drivers of tree-ring width. Their effects were generally non-linear, indicating explicit spatiotemporal gradients in growth responses in the mid-part of species distribution. This also implied limited efficiency of simple linear models for the assessment of radial growth under moderate conditions. The responses to summer temperature indicated local optima, while the responses to drought index showed threshold values. The responses to winter temperature indicated positive effect of warming on growth. In some stands, specific non-stationary responses though were evident, suggesting that trees have adapted (specialized) to certain local climatic conditions, which are changing and thus explaining temporal shifts in growth responses. Nevertheless, the estimated responses suggested phenotypical adaptability limits of the eastern Baltic populations of Scots pine in a longer term, supporting the necessity of climate-smart management for sustainability of forest in the region in the future.
•Competition among seedlings after germination was studied in a climate chamber.•Temperature increase differently affected growth of temperate tree species.•Species composition altered tradeoffs in ...competitiveness of seedlings.•European beech showed superior competitiveness northwards from its native range.
Mixed stands are advised for reduction of impacts of natural hazards, and species composition can largely affect sustainability and productivity of the stands. Early development of a stands after a stand-replacing disturbance can have considerable legacy effects on growth via alterations in the diversity-productivity relationships. Accordingly compatibility of growth and competitiveness of different species is one of the key issues for susceptibility of mixed stands. A two-year chamber experiment was conducted to assess early growth and intra- and inter-specific competition for light and soil resources among the seedlings of temperate tree species simulating the predicted effect of warming (presuming optimal moisture regime). Five species, which have high economic importance or potential to become so in the eastern Baltic region (Scots pine, Norway spruce, silver birch, red oak, and European beech) were studied. Among the studied species, European beech had the fastest height growth and competitiveness, suggesting ability to concur a stable niche outside its natural range, particularly under increased temperature. Beech also maintained high competitiveness despite the damages suffered during the overwintering, supporting legacy effects of early development and suggesting invasive properties. Among the studied, Norway spruce had the slowest growth and suffered the highest competition, which is in line with predicted changes in forest composition. Scots pine, silver birch, and red oak showed intermediate growth and competitiveness, particularly when growing together, suggesting balanced development and optimal productivity of such mixed stands. Nevertheless, growth and competitiveness of these species was reduced by increased temperature, indicating negative effects of warming.
•Wood anatomy of five Eastern European provenances of Scots pine was studied.•Tracheid proxies expressed significant provenance-by-trial interaction.•Top-performing provenances had tracheids with ...larger lumens and thinner walls.•Low-performing provenances formed smaller and thicker-walled tracheids.•Tracheids were affected by weather conditions prior and during their formation.
The efficiency of water use and transport are among the main factors affecting competitiveness, growth, and distribution of trees under warming climate. The phenotypical and genetic plasticity of tree populations is considered as an indicator of their adaptive capacity under changing environment. Climatic changes are expected to affect growth of Scots pine (Pinus sylvestris L.), and selection of reproductive material among the populations suitable for future climates has been advised for sustaining productivity of stands. In this regard, provenance trials can serve as source of comprehensive information about growth plasticity and climate-growth interactions of diverse populations. Quantitative wood anatomy can provide detailed information about xylogenesis and factors affecting it, which are crucial for long-term predictions. Wood anatomy of two top- (Gustrow and Rytel), two low-performing (Eibenstock and Dippoldiswalde), and one local (Kalsnava) provenances of Scots pine from the eastern Baltic region growing in three provenance trials in Latvia was studied using mixed models, accounting for the experimental design, as well as using the time-series approach. Provenance had a significant effect on the studied wood anatomical proxies, indicating genetic adaptation of xylogenesis. The top-performing provenances, which originated from warmer and drier conditions, had tracheids with larger lumens and thinner walls, thus indicating adaptation to water deficit. The top-performing Rytel provenance showed the highest phenotypical plasticity of lumen cross-section area and cell wall thickness of stemwood tracheids. The studied low-performing provenances, which originated from the Orr Mountains, had tracheids with thicker wall and smaller lumens, likely to ensure mechanical durability. The local provenance showed intermediate values of the studied wood anatomical proxies. The effect of provenance on wood anatomical proxies showed some variations among the trials, which differed by continentality, likely due to ecological transfer distance. The studied anatomical proxies were affected by weather conditions prior and during formation of a tree ring, yet these relationships differed by trial and provenance. In general, wood anatomy of earlywood was affected by temperature in the dormant period and beginning of summer, as well as precipitation in the end of the previous vegetation period. Proxies of latewood showed correlation with temperature (negative) and precipitation (positive) in summer, suggesting response to the availability of water. Considering the observed relationships, the top-performing provenances, particularly Rytel, have a high potential to sustain productivity of stands within the region in the future.
Climate change with more frequent extreme weather events and prolonged winter periods with un-frozen, wet soil is causing frequent wind damage events in forests. Trees with higher mass point and ...heavier weight are more prone to wind damage; however, limited information exists on distribution of biomass under naturally moist conditions. Such information is essential to improve models of wind damage prediction. Therefore, the aim of the present study was to assess the biomass distribution and the parameters important for wind-load of Norway spruce (Picea abies (L.) Karst.). Samples were collected in the year 2019 from 87 trees growing on two different sites, corresponding to freely drained mineral and peaty mineral soils at the age of 55 and 88 years, respectively. Tree diameters at breast height, height, and height of first living branch were measured. Tree stems were pruned and cut into 2-m-long fragments and weighed (fresh weight) afterwards. A biomass distribution model was developed to estimate fresh weight of the stem of Norway spruce using easy measurable tree variables. Relative height of the mass point and height of living branches were higher in peaty mineral soil than on freely drained mineral soil, which was an indicator for higher windthrow risks.
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.
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