Morphological Variation in Absorptive Roots in Downy Birch (Betula pubescens) and Norway Spruce (Picea abies) Forests Growing on Drained Peat Soils

Peatland drainage based on ditch systems is a widely used forestry management practice in the boreal and hemiboreal forests to improve tree growth. This study investigated the morphological variation in absorptive roots (first- and second-order roots) across the distance gradient from the ditch with four sampling plots (5, 15, 40, and 80 m) in six drained peatland forests dominated by Downy birch and Norway spruce. The dominating tree species had a significant effect on the variation in absorptive root morphological traits. The absorptive roots of birch were thinner with a higher specific root area and length (SRA and SRL), higher branching intensity (BI), and lower root tissue density (RTD) than spruce. The distance from the ditch affected the absorptive root morphological traits (especially SRA and RTD), but this effect was not dependent on tree species and was directionally consistent between birch and spruce. With increased distance from the ditch (from plot 5 to plot 80), the mean SRA increased by about 10% in birch and 5% in spruce; by contrast, the mean RTD decreased by about 10% in both tree species, indicating a potential shift in nutrient foraging. However, soil physical and chemical properties were not dependent on the distance from the ditch. We found a species-specific response in absorptive root morphological traits to soil properties such as peat depth, pH, and temperature. Our results should be considered when evaluating the importance of morphological changes in absorptive roots when trees acclimate to a changing climate.

Tree line shifts, changing vegetation assemblages and permafrost dynamics on Galdhøpiggen (Jotunheimen, Norway) over the past ~4400 years

An environmental reconstruction based on palynological evidence preserved in peat was carried out to examine late-Holocene alpine tree line dynamics in the context of past climatic changes on Galdhøpiggen (Jotunheimen, southern Norway). We analysed a peat core taken from a mire at the present-day tree line (1000 m a.s.l.), c. 450 m downslope from the lower limit of sporadic permafrost. We adopted a combination of commonly used indicators of species’ local presence to reconstruct past vegetation assemblages, such as the relative pollen abundance (%), pollen accumulation rate (PAR), and presence of indicator species. Additionally, fossil pollen from the peat sequence was compared to modern pollen from a surface moss polster to establish a modern analogue. The results were compared with studies covering the late-Holocene climatic changes in the area. The reconstruction demonstrates that a pine-dominated woodland reached above the present-day tree line at c. 4300 cal. yr BP, suggesting a warmer climate suitable for Scots pine ( Pinus sylvestris) growth at this altitude. Scots pine retreated to lower altitudes between c. 3400 and 1700 cal. yr BP, accompanied by the descent of the low-alpine shrub-dominated belt, in response to cooling climatic conditions. The colder period covered c. 1700–170 cal. yr BP, and an open downy birch ( Betula pubescens) woodland became widespread at 1000 m a.s.l., whilst pine remained sparse at this altitude. From c. 170 cal. yr BP onwards, warming allowed pine to re-establish its local presence alongside downy birch at 1000 m a.s.l.

Cutlink Cleaning Head with a Spreading Feature for Biological Sprout Control

The ability of deciduous trees to sprout efficiently after cutting is problematic in young forests where the target is to cultivate coniferous trees for industry. Since the use of chemicals has been restricted, new alternatives are needed. One potential and environmentally friendly option is biological sprout control that is based on the use of a white-rot fungus, Chondrostereum purpureum (Pers. Ex Fr.) Pouzar. This method has been efficient in earlier investigations when performed manually, but efficient, fully mechanized devices which are able to cut and treat stumps with a fungus are still unavailable. Therefore, the efficacy of biological sprout control conducted with a Cutlink cleaning head equipped with a spreading feature was studied in two young Norway spruce (Picea abies (L.) H. Karst.) forests in central Finland.Sample plots for the control (cutting deciduous saplings only) and fungal treatment (cutting and spreading fungal inoculum on fresh stump surfaces) were established, and the ability of the Cutlink cleaning head in preventing sprouting of silver and downy birch (Betula pendula Roth and B. pubescens Ehrh., respectively) in the sample plots was investigated for two years.In the near vicinity of cultivated Norway spruce, the proportion of cut deciduous saplings varied from 50–60% after the Cutlink operation. The average mortality of silver and downy birch stumps in the fungal treatment plots was ca. 40%, while stump mortality in the control, i.e., cutting only, was only ca. 13%, after two years. Stump mortality increased up to 73% if the stumps did not include old branches, i.e., the stump was cut to a low enough height.These results confirmed that the Cutlink cleaning head is a potential tool in young stand management operation but further development will be needed in working methods in order to achieve lower stump heights (no branches on the stump) and also to increase the proportion of cut saplings.

Secondary metabolites of downy birch buds (Betula pubescens Erch.)

The subject of this study is the composition of low-molecular-weight metabolites in downy birch (Betula pubescens) buds and their participation in protection from various kinds of stress. Using the GC-MS, 640 compounds were detected, of which 314 were identified in downy birch buds for the first time. The volatile components detected using the SPME technique mainly consisted (about 70% of the total ionic current of the chromatogram, TIC) of mixtures of sesquiterpenoids. The exudate covering the buds, along with sesquiterpenoids (approximately 60% of TIC), included flavonoids (25% of TIC). The main part of the material extracted by supercritical carbon dioxide from buds comprised sesquiterpenoids and triterpenoids (47 and 28% of TIC, respectively). Via column chromatography, 25 known compounds (mainly flavonoids and triterpenoids) were isolated, most of which were first discovered in the buds of downy birch. Many compounds of these classes have strong biological activity and probably either directly or indirectly perform a protective function in birch buds. An assumption is made about the biological role of a number of secondary metabolites (such as volatile isomeric megastigmatriens and triterpene seco-acids) as well as about these compounds’ possible means of biosynthesis, which were first discovered in the buds of downy birch.

The effect of a single inbreeding on the growth and development of fast-growing tree species, Betula pendula and Betula pubescens

The aim of the research is to study parameters of seed reproduction systems in Betula pendula and B. pubescens, find possibilities for producing viable inbred plants, and analyze their growth and development and hybrid heterosis at crossing the selected forms in generations F1 and I1. Differentiation in deciduous trees by self-fertility level was established. By this feature the progeny of different tree groups have different genetic and selection value depending on pollination method of parent trees: at open pollination the progeny of self-sterile and transitional forms (cross-pollinating) are the most fast-growing and resistant to unfavorable environmental factors, whereas at self-pollination – the progeny of self-fertile forms. Accordingly parent trees were classified into three groups: self-fertile, self-sterile and transitional forms. Frequency of self-fertile forms and preservation of inbred plants in downy birch are higher than the similar indicators in silver birch. Thus an ambiguous effect of closely related crossing in tree species on the growth and development of their seed progeny was revealed. The effect of inbreeding on some trees is positive, on other negative, and there is the third group, in which the growth deflections caused by inbreeding are inessential. Such trees are suggested for use in various selection programs.

The impact of copper oxide and silver nanoparticles on woody plants obtained by in vitro method

The article substantiates the necessity of studying behaviour of copper oxide and silver nanoparticles on forest cultures (downy birch 29-58 (Betula pubescens Ehrh.) and poplar ‘Pyramidal-osokoreviy Kamyshinsky’ (Poplus pyramidalis Roz. x Poplus nigra L.) in in vitro as well as in ‘soil-plant-microbiota’ to ensure stability of forest cultures in forest regeneration. The impact of nanoparticles on shoot regeneration and propagation processes was evaluated by introducing nanoparticles into Woody Plant medium. Differences in the influence of nanoparticles on the life processes of plants depending on their concentration and the stage of clonal micropropagation have been established. The results are demonstrated by a 15-25% reduction in the frequency of infection of poplar and birch explants as well as by an increase in their regenerating potential at the stage of introduction in tissue culture. When the nanoparticle solution is used in the soil substrate, a decrease in the number of diseased plants and an increase in their survival rate of 30% can be observed. The inhibitory effect of silver nanoparticles on some ecological and trophic groups of microorganisms has been established. These results can be used in the application of CuO and Ag nanoparticles in the biotechnology of clonal micropropagation of forest crops.

Exploitative Competition between Mountain Hare and Moose—Qualitative Effects on Hare Winter Forage?

Mountain hares (Lepus timidus) in Scandinavia are classified as Near Threatened in the Norwegian and Swedish Redlists. This is due to a possible population decline witnessed during the last decades in Scandinavia. Competition between large herbivores and mountain hares is one of several hypotheses that has been put forward to explain this decline. In a cafeteria trial we investigate the effects of previous moose (Alces alces) winter browsing on the food selection (i.e., biomass consumed, bites per minute and bitediameter) of downy birch (Betula pubescens) and goat willow (Salix caprea) by captive mountain hares. We find that mountain hares do not differentiate among previous browsing levels of downy birch, but have larger bite diameters of goat willow earlier browsed by moose, compared to non-browsed plants. Thus, effects of moose on mountain hare winter food quality seem to be limited. We highlight the need for studies focusing on (1) qualitative effects of moose browsing using wild mountain hares in a natural experimental design, and (2) quantitative effects of moose browsing on available mountain hare forage at a landscape scale during winter.

Effect of Tree Density on Seed Production and Dispersal of Birch (Betula pendula Roth and Betula pubescens Ehrhs)

Silver and downy birch (Betula pendula Roth and B. pubescens Ehrhs) are pioneer species which play an important role in forest regeneration in disturbed areas. Knowledge of birch seed production and dispersal is key to making good predictions of the persistence and colonization of birch. Both processes can be affected by the density of trees in the neighbourhood. In this study, we studied the seed production and dispersal of birch trees in two plots in Wytham Woods, UK, in 2015, and investigated the potential effect of neighbourhood tree density. We applied inverse modelling to seed trap data, incorporating tree density around the source tree and on the seed path to estimate birch fecundity and the dispersal kernel of the seeds. We show that the pattern of dispersed seeds was best explained by a model that included an effect of tree density on seed dispersal. There was no strong evidence that conspecific or heterospecific tree density had an effect on birch fecundity in Wytham Woods. A birch with diameter at breast height (DBH) of 20 cm is estimated to have produced ~137,000 seeds in 2015. Mean dispersal distance in an open area is estimated to be 65 m but would be reduced to 38 m in a closed stand. Both the mean dispersal distance and the probability of long-distance dispersal of birch decreases in dense environments. Areas with higher tree density also would intercept more seeds. These results highlight the importance of considering tree density in the neighbourhood and in the overall landscape when predicting the colonization and recruitment of birch.

INFLUENCE OF GRAPHENE OXIDE ON MICROCLONES OF DOWNY BIRCH AT THE ADAPTATION STAGE

In this work, we studied the effect of graphene oxide on regenerants of downy birch when transferred to non-sterile greenhouse conditions (adaptation stage) during clonal micropropagation. During the experiment, it was found that a solution of graphene oxide at a concentration of 1.5 μg / l had a beneficial effect on the development of leaves and plant adaptability (+ 8%). However, with an increase in the concentration of nanomaterial to 3 μg / L, the survival rate decreased by 10% , the plant height - by 25%, and the number of adapted plants - by 35% relative to the control group. In addition, general condition of the seedlings of this group was assessed only by 3 points on a 5-point scale. The study of the content of graphene oxide in plant organs did not reveal pronounced foci of accumulation, which may indicate an indirect effect of nanomaterial on plants through changes in environmental conditions, for example, the availability of root nutrition or the composition of microbiota in the root zone. The mechanisms of ecological and biological impact of carbon nanomaterials on plants are not fully known and require further in-depth research

Titanium Trisulfide Nanoribbons Affect the Downy Birch and Poplar × Aspen Hybrid in Plant Tissue Culture via the Emission of Hydrogen Sulfide

Plant tissue culture is an important tool for accelerated vegetative reproduction of woody plants. To increase the efficiency of this method, it is necessary to search for new growth stimulators and protectors of microshoots. Two-dimensional (2D) nanomaterials are highly promising for applications in medicine and biotechnologies. We have studied the effects of TiS3 nanoribbons with the following mean dimensions: thickness less than 100 nm, length 1–10 μm and width 0.4–1 μm upon poplar × aspen hybrid and downy birch microclones in plant tissue culture. We have found the effectiveness of this particular nanomaterial as a sterilizing and stimulating agent in the initial growth stage and as a rhizogenesis-activating agent in the rooting stage. We analyzed a wide range of TiS3 concentrations in the nutrient media and identified 1.5 and 3 μg/L as optimal. However, concentration-dependent toxic effects manifesting themselves through microclones viability suppression have been discovered in the groups exposed to 6 and 15 μg/L TiS3. We have established that plant reaction to TiS3 treatment is specific for different plant species, i.e., downy birch is generally more tolerant than poplar × aspen hybrid. Here, we propose that the protective and stimulating effects of titanium trisulfide as well as its toxicity in high concentrations can be explained by the release of hydrogen sulfide as a result of aqueous hydrolysis of nanoribbons and its effect on plants. Additional studies are required in order to assess all biological effects produced by TiS3 nanoribbons at further stages of ontogenetic development and to identify the mechanisms of their action.