Search

Frequency of storms and wind speeds in gusts had been increasing in Northern Europe in last decades, causing more damages to forest stands. Establishment of mixed stands had been suggested as one of the methods to reduce wind damages in future, however, empirical information on actual efficiency of this approach is still limited, especially in relation to summer storms. Therefore aim of our study was to assess summer storm damages in mixed birch spruce stands. Area influenced by the storm of June 2021 in Northern part of Latvia, where silver birch (Betula pendula Roth.) growth with admixture of conifers – Scots pine (Pinus sylvestris L.) and Norway spruce (Pice abies (L.) H. Karst.) had been selected and sample plots (500 m2 ) systematically placed. Tree heights, height of the green crown base and diameter at breast height (DBH) were measured for wind-affected and unaffected trees. For broken trees the damage height was measured, for tilted (bent or leaning) the angle from vertical position. Tree parameters influencing their wind resistance were assessed: higher proportion of birch were damaged than that of spruce and the most significant damages (snapping and uprooting) were characteristic to larger trees on average. Significant influence of summer storm on the birch spruce mixed stand was demonstrated. [ABSTRACT FROM AUTHOR] more...

Birch (Betula spp.) has a notable financial value and is less affected by most significant biotic factors than common coniferous tree species, however, still prone to wind and freezing rain damages. Main storms affect Northern Europe during winter (when trees are at leaf-less state), however it might change as the climate is warming and length of the vegetation period is increasing. Therefore information on wind damages in birch stands during this period is important. Aim of our study was to assess the damages caused by summer wind-storm in birch stands. Tree heights, height of the green crown base and diameter at breast height (DBH) were measured for wind-affected and unaffected trees of the same stands in area influenced by the storm of June 2021 in Northern part of Latvia. Sample plots (4-6, size 500 m²) were systematically placed in stands and the DBH range 6 to 30 cm covered. For broken trees the damage height was measured, for bent – the tilt angle. Tree parameters affecting probability and type of wind damages were assessed and compared to results of mechanical pulling tests. Most of the damaged trees (22% from total) had been tilted (bent or leaning at an angle <45º) or uprooted (7%); and only few trees snapped (2%). Financial influence of the storm to a large extent will be determined by the further development of the partly-affected trees. [ABSTRACT FROM AUTHOR] more...

European aspen (Populus tremula L.) is fast growing, almost exclusively naturally regenerated trees species, significant for biodiversity, but also with notable financial value. It is prone to browsing damages and rot. Limited information on traits important to wind resistance had been collected so far and used to adapt models predicting wind damages in stands of these tree species. Main storms affect Northern Europe during winter time (when trees are at leaf-less state), however, summer storms are becoming frequent common and, with climate change, the vegetation period is increasing. Therefore information on wind damages in such tree state are important. Aim of our study was to assess the damages caused by summer wind-storm in European aspen stands. Information of aspen with diameter at breast height (DBH) between 6 and 75 cm was collected in stands affected by storm of June 2021 in Northern part of Latvia. Tree heights, height of the green crown base and DBH were measured for wind-affected and unaffected trees. For broken trees the damage height was measured, for leaning or bent – the tilt angle. Tree-scale parameters affecting probability and type of wind damages were calculated and compared to the previous assessments from controlled tree pulling tests and primarily winter storms. The loss of financial value due to damaged assortments was calculated. [ABSTRACT FROM AUTHOR] more...

Naturally regenerated birch (Betula spp.) stands, to a large extent formed on abandoned agricultural lands, is a notable part of the privately owned forests in Latvia. Birch is fast growing and less frequently affected by abiotic and biotic factors (like dendrophagous insects, cervids, drought) than other main commercial tree species in Latvia. However, wind storms, predicted to increase in frequency in future, is an important risk in birch stands. Therefore, the aim of our study was to assess the snapping height of young birch stands in private forests and the financial losses caused by the damage. Information of the wind snapped trees was obtained from LSFRI Silava and height of damage was measured for 113 trees, with diameter at breast height (DBH) between 8 and 16 cm, in different private properties. Trees in naturally regenerated stands on relatively fertile (in comparison to other forest types) mineral soils with normal moisture regime or drained (corresponding to forest types Oxalidosa, Aegopodiosa and Myrtillosa mel., Mercurialiosa mel., respectively) were selected. Height of the damaged trees was measured as a sum of length of remaining high-stump and broken top, where possible, or estimated from the height curve of the specific stand. Value loss of the damaged wood was assessed as a difference in assortment price in comparison to timber from an undamaged tree of the same dimensions. Trees with DBH 8.1 to 12 cm had the mean snapping height at 5.3±1.0 m. For the larger trees significant differences between sites with normal moisture regime and drained soils were found and the height was 8.1±1.5 and 4.4±1.3 m, respectively, even so the mean DBH in both groups of trees was not significantly different. Consequently, higher financial damages were caused in stands on drained mineral soils, where the most valuable logs were affected. Overall, the wind damage caused value loss of 28 to 37% from the total stem value. Preventive measures to increase resistance of trees against wind damages can provide a notable financial benefit for the private forest owners. [ABSTRACT FROM AUTHOR] more...

Windstorms are one of the main factors causing damages in forest in Northern Europe. The damages are especially severe, if the ground during the storm is not frozen and is wet, therefore the trees are less stable. Cyclonic windstorms primarily happens during the winter, and there is a prediction of notable rise of temperature in this period of the year – thus we can expect more storm damages. It is known, that inside the forest stands specific microclimate exists, affecting also the soil temperature. However, there is lack on the specific of this impact at different depth of the soil in stand on organic soils. Therefore aim of the study was to assess the influence of presence of spruce stand on the peat soil temperature change in winter. Air (40 cm above ground) and soil (0 to 40 cm) temperature was monitored in open field (on peat soil) and middle age (40 years) and mature pure Norway spruce stands on deep peat soil in central part of Latvia. Observations were made in winter (December to February) and early spring (March) from December 2016 to March 2019 (three observation periods). Mean monthly air temperature in the observation period was from -6.1⁰C to +6.8⁰C. Air temperature during winter in mature stand was on average by 0 to 3.8⁰C lower than in open area on peat soil. In December and January there were minimal differences, but at the second part of winter the temperature differences reached on average 2.4⁰C. Similar trend had been observed, comparing the air temperature in open field and middle-age stand. In the soil temperature was notably higher, on average in December to February at the depth of 20 cm by +2.0⁰C (ranging from -0.1 to +4.6⁰C), in depth of 40 cm by 5.5⁰C (from 2 to 8.2⁰C). However, when the temperature raised in spring (in two out of the three observation years in March – the mean temperature was +6.8⁰C and +6⁰C) the temperature in soil was notably lower than in air: in depth of 20 cm by 5.7⁰C and 4.6⁰C, in depth of 40 cm by 3.3 and 1.9 C. Temperature on ground during the winter was by 0.5 to 1⁰C on average higher close to the spruce tree (1 m) than further away from it (3 m) in middle age stand, but there was much less influence of the distance from the tree in mature stand. Deeper in soil (20 cm) closeness to the tree did not made much difference in temperature (-0.2 cm). The influence of presence of forest stand was various – in milled age stand in 20 cm depth temperature during the winter was by was by 0.2⁰C higher in in another year by 1.2⁰C higher. Hoverer, overall, the temperature in peat soil was higher than in the air, and especially it was true in the Norway spruce stands. Thus, the effect predicted in the rise of air temperature will be even more pronounced for the soil temperature, thus influencing the probability of damages in forest stands. [ABSTRACT FROM AUTHOR] more...