Search

Platforms mounted in rope parks cause injuries to trees. A new method for mounting platforms uses clamps, which are theoretically less damaging to trees. The aim of the study was to determine changes in the vitality of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) in response to both old and new platform mounting systems. In the old system, wooden brackets are embedded in the cut fragments of tree trunks. The new system utilizes clamps that hug the trunks. A vitality assessment was carried out for control trees and trees with platforms on the basis of changes in the assimilation apparatus and the degree of thinning of the outer parts of the tree crowns. The visual assessments differentiated between four classes 0–3. We conducted the visual assessment of tree vitality four years after the installation of the platforms. The level of trunk circumference damaged at the platform attachment point was determined using photogrammetric measurements and laser scanning technology. The obtained results were compared to the vitality recorded for the control trees. Trees that initially had better vitality showed a clear decrease in vitality of ~0.5 class. Trees that initially had worse vitality showed a clear increase in vitality, ranging from 0.25 class for pines to 1 class for beeches. Pine and beech trees reacted differently to injuries caused by platform installations. Pine trees responded with a slight increase in vitality, while beech trees experienced a decrease of over a hundred percent. The reactions were more pronounced for the new type of platform. Although the new method of platform installation caused more damage to the surface of tree trunks, its impact on tree vitality was not significantly greater than that of the old system. Since the new system allows, in the long term, to change the position on the tree and adjust the clamping force to the trunk, it can be recommended for use in practice despite the overall slightly worse state of the trees when compared to trees with the old mounting system. [ABSTRACT FROM AUTHOR]

Common beech is a shade-tolerant tree species that can adapt to varying light intensities at the level of whole plants, crown fragments, and individual leaves. The acclimation abilities of the morphological, physiological, and biochemical characteristics of beech leaves were experimentally determined in tree crowns for different levels of light availability. About 24% higher length, width, and area and about 35% higher thickness were recorded in the sun leaves compared with shade leaves. Lower and earlier maximum leaf pigment levels, a faster degradation of leaf pigments during senescence, and a higher chlorophyll a/b ratio were observed in fully sun-grown leaves compared with leaves growing deeper in the canopy. Changes in the intensity of oxidative stress and the differential ability of developing and senescing leaves to defend against this effect under different light conditions were determined. This resulted in a higher redox imbalance and faster senescence in the outer parts of the tree crowns. Due to higher ascorbic acid and glutathione content and slower activity loss of antioxidative enzymes involved in superoxide anion and hydrogen peroxide decomposition, better control over the redox balance, oxidative stress, and senescence induction was noted in the sun leaves. [ABSTRACT FROM AUTHOR]

Girdling was applied to 5-year-old potted beech individuals of early, intermediate and late phenological forms to block assimilate export from leaves. Phloem severance caused accumulation of soluble carbohydrates and starch in leaves and increased the C/N ratio. While the hexose content increased continuously until the end of the experiment, the sucrose and starch contents peaked earlier, depending on the plant’s phenological features. Different rates of chlorophyll degradation and H2O2 and TBARS (thiobarbituric acid-reactive substances) production in different phenological forms implied that phloem girdling was the source of oxidative stress and, depending on the phenological form, accelerated leaf senescence to different degrees. The variable rate of the increase in soluble carbohydrate and starch content, characteristic of the different phenological forms, had different modifying effects on the antioxidant activity in leaves. Compared with the early phenological form, the late form was characterized by a smaller increase in H2O2 and TBARS content and delayed and slowed chlorophyll and carotenoid degradation. In conjunction with the larger increase in the activity of antioxidant enzymes (catalase, ascorbate peroxidase and superoxide dismutase) induced by carbohydrate accumulation and slower carotenoid degradation, these changes led to the late form having greater resistance to oxidative stress and slower senescence. [ABSTRACT FROM AUTHOR]

High-altitude tree populations are exposed to severe natural environmental conditions. Among abiotic factors, variable temperatures, early frosts, and high radiation are the factors affecting tree growth at high altitudes. Fagus sylvatica L. exhibits a variety of physiological and genetic traits that allow it to adapt to different forest habitats. This study examines the differences in the biochemical properties of senescing beech leaves between populations originating from different altitudes using a common-garden experiment. Leaves were collected from five-year-old plants from the beginning of August to the end of October for two years. Based on the changes in senescence marker levels the genetic differences and significant correlations between populations' altitude origin and their biochemical characteristics were identified. According to the free radical theory of leaf senescence, reactive oxygen species (ROS) and senescence markers were highly correlated. In this study, populations from higher altitudes were characterized by earlier and greater increases in ROS content and oxidative stress, which resulted in higher antioxidative system activity. Increases in ROS in high-altitude populations play a controlling role to initiate earlier senescence processes that allow the trees to adapt to harsh climatic conditions. Earlier senescence allows beech trees to maintain a balance between nitrogen metabolism and photosynthetic activity. It allows for remobilization of nitrogen compounds more efficiently and protects the trees from nitrogen loss and prepares them for winter dormancy. [ABSTRACT FROM AUTHOR]