Methane Exchange and Microbial Functional Potential in Forest Tree Tissues

Appreciation for the influence of plant metabolism on the hydrogen isotope composition (δ2H) of plant compounds has increased in recent years, adding new opportunities to understand how plants respond to environmental change. In general, where carbon supply is limited (e.g. at the beginning of the growth season, in darkness, under low CO2), the resulting δ2H of newly produced plant compounds tends to be 2H-enriched. The source of the 2H-enrichment has yet to be identified but hypotheses include: 1) a direct effect of reduced photosynthesis; 2) change in the partitioning of photoassimilates to sucrose/transitory starch; 3) use of longer-term starch reserves; and/or, 4) increased isotopic exchange with water suggesting increased metabolite cycling. To test these ideas, we utilised samples collected from a study which grew tree saplings under 100% and 6% of ambient sunlight in the field (Weber et al. 2018, New Phytologist, 222: 171-182).  In general, relative growth rate was attenuated by a species-specific amount that ensured homeostasis of non-structural carbohydrate (NSC) concentrations; however, not before an initial two-fold reduction in NSC levels – the time period the current study focussed on. Cellulose was purified and n-alkanes extracted from leaves of six deciduous species (Betula pendula, Carpinus betulus, Fagus sylvatica, Prunus avium, Quercus petraea and Tilia platyphyllos) in July 2016, around one year after the shade treatment began. The isotopic difference of cellulose between shaded and full sunlit grown leaves (εshade-sun) was significantly different from zero, with species-specific offsets ranging between 20 to 70‰. In comparison, the treatment effect was minimal for the C-chain length concentration weighted δ2H values of n-alkanes, ranging between -7 to +10‰. To narrow down the source of 2H-enrichment in leaf cellulose, the δ2H of sucrose and starch are currently being analysed in samples collected from stem wood (without bark) before bud-break in March 2016, and in leaf and stem material sampled after leaf-out in July 2016. An increase in sucrose δ2H values from shade leaves relative to controls would support Hypothesis 1 and 2; 2H-enriched storage starch relative to leaf sucrose would support Hypothesis 3; and an increase in the δ2H of sucrose in stem wood relative to storage starch (before bud-break), would support Hypothesis 4. Our study has important implications for interpreting 2H-enrichment of plant compounds with respect to reduced C supply.

ContextForest harvest removal may cause nutrient depletion of soils, when removal of essential nutrients, including nitrogen (N), phosphorus (P), sulphur (S), calcium (Ca), potassium (K) and magnesium (Mg) exceeds their net input by deposition and weImpacts of acid atmospheric deposition on woodland athering minus leaching. Nutrient removal by harvest depends on tree species and the harvesting method, i.e. whole-tree harvesting (removal of stems and branches) versus stem wood removal only.AimThe aim of this study was to assess the impacts of these two harvesting methods on nutrient removal in Dutch forests exposed to high-nitrogen deposition.MethodsTo assess those impacts, we measured nutrient concentrations in stem wood and branch wood of seven major tree species in the Netherlands, i.e. Japanese larch (Larix kaempferi Lamb.), Norway spruce (Picea abies L. Karst.), Douglas fir (Pseudotsuga menziesii Mirb.), Scots pine (Pinus sylvestris L.), silver birch (Betula pendula Roth), beech (Fagus sylvatica L.) and common oak (Quercus robur L.). Average nutrient concentrations in stems were based on measured concentrations in heartwood, sapwood and bark and estimated volumes and densities of these compartments. Similarly, average nutrient concentrations in branches were based on measured concentrations in coarse branches, fine branches and the bark of coarse branches and estimated volumes and densities of these compartments. Removal was assessed by using the average growth rates of these tree species on nutrient poor sandy soils in the Netherlands.ResultsCompared to other countries, N concentrations in the Netherlands were higher in stems, while phosphorus, Ca, K and Mg concentrations in both stems and branches were nearly always lower. The elevated long-term N deposition levels in the Netherlands most likely contribute to this finding, since N deposition causes soil acidification reducing the availability of Ca, K, Mg and P, that could become limiting to growth. Limits for sustainable harvest, above which outputs exceed inputs of nutrients, depend on nutrient, soil type and tree species and are mostly determined by K and P and sometimes Ca, which may already be depleted at relatively low harvest levels on poor sandy soils, in particular for broadleaved species, while depletion of Mg is not likely. Nevertheless, the average growth of forests in the Netherlands appears to be slightly higher than in most other countries in Europe.ConclusionOverall, we thus conclude that limited P, Ca, Mg and K availability in response to elevated N deposition is reflected in reduced contents of these nutrients in stem wood and branch wood but not in growth.Key messageNutrient concentrations in tree compartments were assessed for seven major tree species in the Netherlands. Concentrations of phosphorus, calcium, potassium and magnesium (base cations) in stems and branches are mostly lower compared to those in other countries, while nitrogen concentrations are higher. A long-term nitrogen deposition has likely contributed to these differences. The average growth has not declined, despite the low availability of phosphorus and base cations. Limiting the harvest of branch wood is suggested on nutrient poor soils to avoid depletion of phosphorus and base cations.

Boreal peatlands emit a substantial amount of CH4, a potent greenhouse gas, to the atmosphere. Despite decades of effort made on studying CH4 efflux to the atmosphere, understanding the dynamics of the different co-occurring processes underlying CH4 emission remains a challenge in peatland CH4 modeling, especially during the non-growing seasons. Stable isotope signatures of the soil pore water and emitted CH4 can provide information on these processes. To this end, we conducted a first systematic study using stable isotope methods on in-situ major CH4 turnover processes along a peat profile in a typical boreal peatland (Siikaneva fen) in Southern Finland.We run a cavity ring-down spectrometer continuously in 2022 to capture the dynamics of belowground dissolved CH4 and CO2 concentrations and their δ13C natural abundance signatures at 10, 30 and 50cm. Same variables were measured at 40cm above peatland surface to estimate ecosystem-scale average δ13C value of the emitted CH4 using nocturnal boundary-layer accumulation approach. These data were used to indicate CH4 production pathways, in-situ CH4 oxidation and transport pathways on an annual basis. Additionally, 13C pulse labelling experiments targeting acetoclastic methanogenesis, hydrogenotrophic methanogenesis and methanotrophy were performed both in-situ and in the lab condition to trace all these processes which cannot be separated by the isotope natural abundance approach alone.Preliminary results indicated a successful implementation of these novel methods. Continuous measurement of soil gas showed systematic differences in the vertical profile of soil pore water isotopes between winter and summer. δ13C-CH4 values were highest in the deepest layer during winter but they were the lowest in summer. As expected, CH4 production pathway moved towards acetoclastic methanogenesis through winter-summer transition. In winter, the δ13C-CH4 values from emitted CH4 was higher than those from the soil which indicating CH4 oxidation, while in summer the opposite was found due to CH4 diffusive plant transport. CH4 concentrations were higher in summer than in winter from all the depths, while at -30cm had the highest concentration. In-situ labelling experiments showed a higher rate of acetoclastic methanogenesis at -30cm than at -50cm, while hydrogenotrophic methanogenesis was similar at both depths. Experiments also demostrated that there was substantial methanotrophy in the soil as deep as 50cm belowground. 

In Central Europe, forest grazing was probably the main way of providing winter feeding for livestock in prehistory; the main components of this diet most likely included annual twigs of woody species ( Acer platanoides, Betula pendula, Carpinus betulus, Corylus avellana, Fagus sylvatica, Fraxinus excelsior, Picea abies, Pinus sylvestris, Populus tremula, Quercus robur, Salix caprea, Tilia cordata and Ulmus glabra), Hedera helix, Viscum album and senescent grassland biomass; however, their nutritive value has never been compared. Biomass samples were collected in the Czech Republic in February 2013 and analysed for concentration of nitrogen, phosphorus, potassium, calcium, magnesium, fibre and lignin. With the help of a recent analogy from the Altai Mountains (Russia), possible consequences of winter grazing on the development of forest vegetation and cattle breeds in prehistory were assessed. Hedera and Viscum were the best forage available in winter, and their nutritive value, according to the highest N and lowest fibre and lignin concentrations, was higher than the nutritive value of all winter-collected annual twigs of woody species. Nutritive value of annual twigs of all woody species was very low, especially compared with the quality of meadow hay, leaf-fodder or senescent steppe grassland biomass. Therefore, Hedera and Viscum might have been preferentially grazed by livestock and collected by ancient farmers for the supplementary feeding of privileged animals. According to recent analogy, annual twigs of woody species were browsed by livestock. Their insufficient quality could be one of the reasons for the low body size of cattle recorded in prehistory. The most realistic model of livestock breeding in prehistory seems to be year-round grazing, opening forests and causing deforestation in the surroundings of prehistoric settlements.

Site details Mire Kupena is a former lake (41◦ 59′ 07.5′′ N, 24◦ 19′ 05.1′′ E; 1356 m above sea level (a.s.l.)) located on the territory of the Biosphere Reserve Kupena, Western Rhodopes Mountains, Bulgaria. The reserve is located between 600 and 1400 m a.s.l. on a north-facing slope and its vegetation is rather diverse. In the lower parts, the most common plant communities are those of Quercus dalechampii Ten. mixed in some places with Carpinus betulus L., Fagus sylvatica L., Pinus nigra Arn. and Pinus sylvestris L. At higher altitudes, plant communities of F. sylvatica dominate, followed by those of Pinus sylvestris with some Abies alba Mill. and Picea abies (L.) Karst. The mire is formed in a depression on an area of 6 ha, surrounded by an almost pure forest of Pinus sylvestris with an admixture of Picea abies, A. alba, F. sylvatica, Betula pendula Roth., Sorbus aucuparia L., Q. dalechampii and an undergrowth of Juniperus communis L., Vaccinium myrtillus L. and V. vitis-idaea L. The mire vegetation is represented by sparse moss cover (Sphagnum spp.) and includes various species of Carex, Juncus, Potentilla, Ranunculus, Galium. The basin is fed by rainfall and water from melting snow. During the last two decades most of the mire surface on the hummocks has been overgrown by pine trees (Huttunen et al., 1992; Bozilova et al., 2011). The climate in the area is montane with a mean annual temperature of 5–10 ◦S and a mean annual precipitation of 600–800 mm with a maximum in May–June. The basic soil types are brown forest (60%), humic-carbonate and cinnamomic-forest.

This study evaluates the potential of various hardwood combinations in plywood production in response to increasing wood demand and a changing roundwood supply in Central Europe. Six different combinations of nine-layer plywood were produced using 2 mm rotary-cut veneers from lime (Tilia spp.), Norway maple (Acer platanoides), European hornbeam (Carpinus betulus), Sycamore maple (Acer pseudoplatanus), mountain ash (Sorbus aucuparia), and European beech (Fagus sylvatica) with phenol–formaldehyde adhesive, and they were compared to silver birch (Betula pendula) plywood as a reference. The raw densities of the test panels varied between 0.85 and 1.04 times the reference density (795 kg m−3). Flexural strengths (the modulus of rupture, MOR) ranged from 68 N mm−2 to 104 N mm−2 for a parallel fibre orientation and 44 N mm−2 to 61 N mm−2 for a perpendicular fibre orientation of the top layers. The modulus of elasticity (MOE) ranged from 7160 N mm−2 to 11,737 N mm−2 for the parallel fibre orientation and from 4366 N mm−2 to 5575 N mm−2 for the perpendicular orientation. The tensile shear strength varied between 0.91 and 1.69 times the reference (1.49 N mm−2). The thickness swelling after 24 h was higher in all variants than the reference (6.4%), with factors between 1.39 and 1.64. A significant effect was observed when layers with a lower density were arranged on the outside and those with a higher density in the core, resulting in a more uniform density distribution across the cross-section after hot pressing. This created a levelling effect on mechanical and physical properties, especially the modulus of rupture (MOR) and the modulus of elasticity (MOE). Overall, the evaluated hardwood combinations demonstrated comparable properties to the birch reference and industrially produced birch plywood.

Creation and study of the potential of bioresource collections (BC) of living organisms, including woody plants, is one of the priority areas of the state policy of the Russian Federation. The Voronezh Region is unique for studying the genus Betula, since two species of this genus naturally grow here: diploid - silver birch and tetraploid - downy birch. These and introduced species, complex hybrids, as well as their reciprocal hybrids are the basis of BC F1 and F2; provide selection for somatic and adaptive heterosis. The seed progeny (families) of F2 growing in conditions of leached chernozem were tested - C-4, C-20, C-27, C-31 and C-51 (silver birch); B-3, B-11, B-12, B-20 (downy birch); hybrids C-2 x b. The article presents data on the growth of birch hybrids from different subsections: Albae (Betula mandshurica Nakai, B. papyrifera Marsh., B. pendula Roth and B. pubescens Ehrh.) and Costatae (Betula lenta L.). The age of the test crops is 32 years. The possibility of obtaining intersectional birch hybrids and the prospects of crossing for obtaining genotypes with a large habitus, in which the paternal component exceeds the maternal one in terms of ploidy level, are shown.

Abstract. Urban trees have the capability to enhance ecological city resilience. By providing vital ecosystem services mitigation of urban heat island effects, management of stormwater, or support of biodiversity can be improved. Climate change, however, poses challenges to urban trees in general, and in particular for Bavarian cities. This study uses the climate envelope approach to assess the future climatic suitability of native and non-native tree species in 21 Bavarian cities (Germany). Using climate projections from the CHELSA dataset under the SSP5-RCP8.5 scenario, we evaluate temperature and precipitation thresholds for 12 tree species over three periods (2011–2040, 2041–2070, and 2071–2100). The results were compared with the land cover share of the respective cities. The results show distinct variations in climatic suitability across cities and time periods. Several species remain climatically suitable over time, especially Black locust, London plane, and European hornbeam. However, tree species, like European beech, Norway maple, and Silver birch, experience a marked decline. These findings underscore the urgent need for a paradigm shift in urban green space management. Although the study employs climate envelope methodologies that have inherent limitations, it provides a proof-of-concept for integrating climate projections with urban data such as tree inventories and land use patterns. Overall, the research contributes to our understanding of urban tree adaptation strategies and highlights the importance of prioritizing heat-tolerant species to preserve urban biodiversity and ecosystem services.

Accurate information regarding forest tree species composition is useful for a wide range of applications, both for forest management and scientific research. Remote sensing is an efficient tool for collecting spatially explicit information on forest attributes. With the launch of the Sentinel-2 mission, new opportunities have arisen for mapping tree species owing to its spatial, spectral, and temporal resolution. The short revisit cycle (five days) is crucial in vegetation mapping because of the reflectance changes caused by phenological phases. In our study, we evaluated the utility of the Sentinel-2 time series for mapping tree species in the complex, mixed forests of the Polish Carpathian Mountains. We mapped the following nine tree species: common beech, silver birch, common hornbeam, silver fir, sycamore maple, European larch, grey alder, Scots pine, and Norway spruce. We used the Sentinel-2 time series from 2018, with 18 images included in the study. Different combinations of Sentinel-2 imagery were selected based on mean decrease accuracy (MDA) and mean decrease Gini (MDG) measures, in addition to temporal phonological pattern analysis. Tree species discrimination was performed using the Random Forest classification algorithm. Our results showed that the use of the Sentinel-2 time series instead of single date imagery significantly improved forest tree species mapping, by approximately 5–10% of overall accuracy. In particular, combining images from spring and autumn resulted in better species discrimination.

The article presents the data of experiments on determination of development stability (using leaf blades as an example) in trees obtained by self-pollination and open pollination of families from maternal trees of downy birch B-11 and B-14 (of seed origin). A one-way ANOVA analysis of variance was performed for the leaf blade length trait for two species – downy birch and silver birch, differing in reproduction systems, allogamous and autogamous forms. As a result, it was shown that the leaf blade length in highly self-fertile forms of downy birch significantly differs with different methods of pollination of maternal trees – self-pollination and open pollination. The maternal trees of these species were selected in the Voronezh State Nature Biosphere Reserve named after V.M. Peskov (VGPBZ), where test cultures F1 were created by hybridization and self-pollination (sq. 298). The data on the violation of bilateral development of birch leaf blades, which is typical for ecologically unfavorable habitats of trees, were obtained, although the experimental plants are in ecologically clean conditions of the VGPBZ. In the first case, for all downy birch trees (regardless of the pollination method), control scores were obtained that exceeded the standard indicator given in the regulatory documents for assessing the state of the environment, the excesses amounted to 2.4 (B-14 sp) to 5.6 (B-11 op) times. Phenotypic instability of vegetative organs in the polyploid birch species compared to the diploid one was confirmed, which can affect the productivity of birch plantations. Keywords: developmental stability, leaf blade, silver birch, downy birch, allogamy, autogamy, phenotype, ANOVA analysis

Bronze birch borer (Agrilus anxius Gory) is the key pest of birches (Betula spp.) in North America, several of which have been recommended for ornamental landscapes based on anecdotal reports of borer resistance that had not been confirmed experimentally. In a 20-yr common garden experiment initiated in 1979 in Ohio, North American birch species, including paper birch (Betula papyrifera Marshall), 'Whitespire' gray birch (Betula populifolia Marshall), and river birch (Betula nigra L.), were much more resistant to bronze birch borer than species indigenous to Europe and Asia, including European white birch (Betula pendula Roth), downy birch (Betula pubescens Ehrh.), monarch birch (Betula maximowicziana Regel), and Szechuan white birch (Betula szechuanica Jansson). Within 8 yr of planting, every European white, downy, and Szechuan birch had been colonized and killed, although 100% of monarch birch had been colonized and 88% of these plants were killed after nine years. Conversely, 97% of river birch, 76% of paper birch, and 73% Whitespire gray birch were alive 20 yr after planting, and river birch showed no evidence of colonization. This pattern is consistent with biogeographic theory of plant defense: North American birch species that share a coevolutionary history with bronze birch borer were much more resistant than naïve hosts endemic to Europe and Asia, possibly by virtue of evolution of targeted defenses. This information suggests that if bronze birch borer were introduced to Europe or Asia, it could threaten its hosts there on a continental scale. This study also exposed limitations of anecdotal observation as evidence of host plant resistance.

The results of a study of birch test cultures obtained by different methods of ex situ pollination and introduced into culture in vitro are presented. To identify the phenotypic, cultural and cytological characteristics of two birch species naturally growing in the Central Black Earth Region - silver birch (diploid) and downy birch (tetraploid), test cultures of seed origin F1 and F2 were specially created. The article presents data on phenotypic (growth in height in the juvenile and reproductive periods of ontogeny), genetic selection (seed propagation system) variability and some characteristics of the introduction of F1 seed progeny of breeding forms of local birch species into in vitro culture. To predict the growth characteristics of seed progeny of breeding forms of local birch species obtained by different methods of pollination - self-pollination and open pollination at different stages of ontogeny (at the age of 2 and 10 years), a statistical processing of the feature of growth in height of families was carried out using the rank Spearman's correlation coefficient ρ. Species specificity was shown in response to different pollination methods, morphogenic activity of self-fertile and self-sterile forms of these birch species on a nutrient medium ½ MC + 6-benzylaminopurine 1 mg/l, primary shoot formation of explants and regenerative capacity in these species, the nature of morphogenesis (formation of the main escape). For the polyploid species (downy birch), a higher level of self-fertility was established, as well as a more intensive growth of shoots in height than for drooping birch; primary explants in the former had a different character of morphogenesis (there was a joint initiation of the main shoot with adventitious ones) than in silver birch (formation of the main shoot), which indicates a greater adaptive potential for polyploid species and their greater opportunities for inclusion in genetic breeding experiments and obtaining valuable breeding forms.

The growing importance of forest plantations increases the demand for phytopathogen resistant forest trees. This study describes an effective method for early detection and identification of the main fungal phytopathogens in planting material of silver birch (Betula pendula) and downy birch (B. pubescens), based on the estimation of the size of the internal transcribed spacers (ITS1 and ITS2) in the 18S-5.8S-28S rDNA gene cluster, which are species-specific for most micromycetes. The electrophoretic assay of the ITS1 and ITS2 loci has allowed us to identify predominant phytopathogenic fungal species in downy and silver birch in planta. This new molecular genetic method can be used to screen birch and other forest trees for different fungal pathogens to evaluate disease resistance. This information can be useful in breeding new genotypes of forest trees, including transgenic clones with modified wood composition.

The Amazon rainforest has a large area occupied by rivers and wetlands, responsible for the majority of biogenic methane (CH4) emission in the region. Biogenic emissions of CH4, which is a potent greenhouse gas, are a key source of uncertainty for the global budget. Atmospheric transport models can be useful to assess the spatial distribution of CH4 concentrations and the influence of land use and climate change. It is important to use computational models with updated emission data to obtain more accurate results in atmospheric gas transport simulations. Here we present an analysis performed with the Weather Research and Forecasting model coupled with the Greenhouse Gases module (WRF-GHG), using updated maps of wetland and fast carbon pool to calculate biogenic emissions of CH4 in the Amazon region. Three wetland maps (wetmaps) and two fast carbon pool (CPOOL) maps were used in the simulations. The resulting methane concentrations were compared to in situ observations at the ATTO tower (Amazon Tall Tower Observatory). The simulations were performed from 1st to 13th January 2023 (considering the first seven days as spin up), in a single domain with 6 km resolution and grid of 212 x 121 centered at ATTO. Boundary conditions were provided by ERA5 and CAMS. The simulation using the default emission model along with the minimum inundation wetmap and the updated CPOOL map showed results closer to observational data (bias of 15 ppb) than the other simulations (bias in the range 20-320 ppb). Using the default maps resulted in an overestimation of 4.1% in CH4 concentrations at ATTO. The modeled CH4 concentrations time series showed a pronounced diurnal variability, likely driven by boundary layer dynamics and advection. On the other hand, observations showed rather constant concentrations, suggesting that background regional emissions dominate the CH4 signal at ATTO. Considering a model grid cell over a section of the Amazon River near the ATTO site (150 km southeast), simulated emissions ranged between 42 (minimum inundation and updated CPOOL map) and 623 (maximum inundation and default CPOOL map) mg CH4 m^-2 day^-1, while WetCHARTs emission inventories are in the range 153-276 mg CH4 m^-2 day^-1 and the literature reports averages of 18-21 mg CH4 m^-2 day^-1 for the Amazon River, based on field measurements. Overall, the results show a high sensibility of the WRF-GHG model towards the choice of wetland and CPOOL maps in Amazonia. Also, the correct representation of CH4 background concentrations is key to improve the simulations of near surface concentrations in areas less impacted by local wetland emissions, like ATTO.

Interest in silver birch ( Betula pendula Roth) and downy birch ( Betula pubescens Ehrh.) has greatly increased in recent years partly as a result of pressures to restore and expand native woodlands but also due to renewed interest in birch as a tree capable of producing quality timber. Despite the many advantages of birch as a commercial timber tree—ease of establishment, fast growth on good sites, high value timber and a short rotation, it has a poor reputation in Britain largely as a result of the poor form of the existing, mainly unmanaged resource. The following points need to be considered if stands of quality birch trees are to be produced in an economical timescale. (1) Sites: silver birch needs good sites that are relatively well drained with light mineral soils. Downy birch does well on moist to wet sites. (2) Regeneration: natural regeneration through a shelterwood is the preferred system of regenerating birch as some overhead protection is beneficial to germination success. About 20–40 seed trees should be left per hectare. Good ground preparation and control of grazing are essential. The vast majority of seedlings are recruited in the first year of the regeneration cycle therefore planting should be considered if the initial regeneration success is poor. Direct seeding is also a successful method of regeneration. Birch readily regenerates naturally into suitably prepared open areas next to existing birch woods but these should not be too big, e.g. gaps or strips 20–60 m wide have been suggested in the literature. (3) Maintenance: density of regeneration needs to be reduced to about 2500–3000 stems ha −1 by the time the trees are about 3–6 m tall. Birch seedlings must always be taller than the competing vegetation. (4) Thinning: thinning should begin when the mean height of the stand is about 8–10 m. At this point at least half the number of trees should be removed with the emphasis on retaining dominants and co-dominants of good form. The aim is to maintain about half the height of the tree as living crown to sustain a high rate of growth. Additional thinnings will be required at intervals of 5 to 7 years and final thinning should leave around 300–500 stems ha −1 . (5) Rotation: a rotation of 40–50 years is possible on good sites and perhaps 50–55 years on less favourable sites.