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•We combined a State-Space model with a Stand Density Management Diagram (SDMD).•Stand specificities are captured by local-model parameters in distinct dynamic SDMDs.•Tree-size ...distributions are estimated from mean and cumulative stand variables.•Dynamic Structural SDMD is applicable for state prediction and growth projection.•Management alternatives can be optimized for any particular stand using its DSSDMD.
A forest stand model that is able to account for individual stand characteristics and uses this information for state prediction, growth and yield projection and for management decisions at individual-stand level can be expected to possess the best properties and be of the highest utility. The aim of our study was to combine the advantages of the graphically presented whole-stand models called Stand Density Management Diagrams (SDMDs) with those of the state-space models to develop an improved, stand-specific density management model and to examine its performance with data from even-aged natural stands and plantations.
A dynamic, structural Stand Density Management Diagram (DSSDMD) consisting of a whole-stand model and distribution sub-models was developed. The whole-stand model is composed of a state vector and transition functions and is presented diagrammatically by four sets of isolines on a density-total volume/biomass chart. The state, developmental scenarios and thinning schedules of any stand are simulated on its individual DSSDMD and are characterized by three principal local model parameters, two of which are stand-specific and the third is common to a range of stands of the species under the same environmental conditions.
Dynamic Structural Stand Density Management Diagrams (DSSDMDs) were constructed for plantations of two pine species (Pinus radiata D. Don and P. sylvestris L.) and for natural even-aged stands of Quercus robur L. and Betula pubescens Ehrh. The goodness-of-fit tests revealed that, in most cases, regression equations explained more than 95% of the variation in the modelled variable and yielded a Root Mean Square Error <15% and bias <2% from the mean experimental variable values. When used for predicting or projecting total stand volume or biomass, the models performed acceptably well, in terms of the critical error estimate, within the observed range of ages and projection intervals. Management alternatives, according to specified objective, can be optimized for any particular stand using its DSSDMD, and the model can be incorporated into a simulator to ensure its most efficient usage.
Greenhouse gas (GHG) fluxes from peatland soils are relatively well studied, whereas tree stem fluxes have received far less attention. Simultaneous year-long measurements of soil and tree stem GHG ...fluxes in northern peatland forests are scarce, as previous studies have primarily focused on the growing season. We determined the seasonal dynamics of tree stem and soil CH4, N2O and CO2 fluxes in a hemiboreal drained peatland forest. Gas samples for flux calculations were manually collected from chambers at different heights on Downy Birch (Betula pubescens) and Norway Spruce (Picea abies) trees (November 2020–December 2021) and analysed using gas chromatography. Environmental parameters were measured simultaneously with fluxes and xylem sap flow was recorded during the growing season. Birch stems played a greater role in the annual GHG dynamics than spruce stems. Birch stems were net annual CH4, N2O and CO2 sources, while spruce stems constituted a CH4 and CO2 source but a N2O sink. Soil was a net CO2 and N2O source, but a sink of CH4. Temporal dynamics of stem CH4 and N2O fluxes were driven by isolated emissions' peaks that contributed significantly to net annual fluxes. Stem CO2 efflux followed a seasonal trend coinciding with tree growth phenology. Stem CH4 dynamics were significantly affected by the changes between wetter and drier periods, while N2O was more influenced by short-term changes in soil hydrologic conditions. We showed that CH4 emitted from tree stems during the wetter period can offset nearly half of the soil sink capacity. We presented for the first time the relationship between tree stem GHG fluxes and sap flow in a peatland forest. The net CH4 flux was likely an aggregate of soil-derived and stem-produced CH4. A dominating soil source was more evident for stem N2O fluxes.
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•Birch stems more important in annual peatland forest GHG dynamics than spruce stems•Temporal stem CH4 and N2O flux dynamics driven by isolated emissions' peaks•Sustained higher or lower water table depth determines net stem and soil CH4 flux•Rapid changes in soil hydrologic conditions, e.g. freeze-thaw, drive N2O emissions•Stem CH4 emissions can offset nearly half of the soil sink during the wetter period
Introgressive hybridisation between arctic dwarf birch (Betula nana) and European downy birch (B. pubescens) is relatively common in natural woodlands in Iceland. As dwarf birch is a diploid species ...and downy tree birch a tetraploid species, their hybrids are triploid. In the introgression process, triploid hybrids, which are partially fertile, can backcross with the parental species, producing progenies comprising introgressed diploid, triploid and tetraploid plants. Triploid plants produce both normal triporate pollen (with three pores) and abnormal, aborted pollen, due to dysfunctional meiosis. The type of pollen abnormality that can be detected and quantified is non‐triporate pollen (with four or more pores in the pollen wall). We therefore used the presence of non‐triporate pollen as a marker to trace birch hybridisation in the past. In the current study we examined fossil pollen in samples from Holocene sediments from three locations: Grímsnes (SW), Eyjafjördur (N) and Thistilsfjördur (NE Iceland). All three peat monoliths had the starting age of 10.3 cal. ka BP. Ages were calibrated based on known tephra layers and by radiocarbon dating. The size of Betula pollen grains was measured, and the species proportions calculated from size. Non‐triporate grains were detected in samples from all three locations and throughout the Holocene, but with different frequencies. The peaks of intense hybridisation followed birch woodland expansion in two major periods of the Holocene, both coinciding with a warming of climate. The first period occurred in the Early Holocene, around 9.5–7 cal. ka BP, when the climate warmed rapidly after deglaciation. The second period occurred around 5–3.5 cal. ka BP, well within the mid‐Holocene Northern Hemisphere warming. A new wave of birch hybridisation appears to have started in the last few decades as the climate has warmed. Birch woodlands are likely to become more widespread. Introgressed shrub birch is likely to be more competitive over dwarf birch.
LAY DESCRIPTION
We microscopically examined birch (Betula) pollen in samples from peat sediments extracted from three geographically diverse locations in Iceland and throughout the Holocene epoch, which began 10,000 years ago. By measuring the size of individual pollen grains, we were able to differentiate pollen of the shrub‐like downy birch (B. pubescens) from its closely related dwarf birch species (B. nana). The results revealed an establishment and a rapid expansion of birch woodland predominated by B. pubescens soon after the retreat of the Icelandic Pleistocene icesheet. We also found abnormal looking pollen grains in the samples, essentially those having more than the usual three pores on the pollen wall, so‐called non‐triporate pollen. This type of pollen abnormality is common among pollen produced by triploid birch hybrids, the progeny of hybridisation between diploid dwarf birch and tetraploid downy birch. Non‐triporate grains were detected in samples from all three locations and throughout the Holocene, but with different frequencies. The results showed peaks of intense hybridisation following woodland expansion in the initial period of the Holocene, from about 9000 years ago, and again in the warming period of the mid‐Holocene Thermal Maximum, the period between 5000 and 3000 years ago. Triploid hybrids that were produced during the intense period of hybridisation could backcrossed with the dwarf birch or the downy birch, allowing gene flow by introgression between the two species, presumably making birch more adaptive to environmental changes. Thus, climate warming in the current era is expected to promote this introgressive hybridisation resulting in significant change of landscape of the birch woodland in Iceland.
Summary
The replacement of native birch with Norway spruce has been initiated in Norway to increase long‐term carbon storage in forests. However, there is limited knowledge on the impacts that ...aboveground changes will have on the belowground microbiota.
We examined which effects a tree species shift from birch to spruce stands has on belowground microbial communities, soil fungal biomass and relationships with vegetation biomass and soil organic carbon (SOC).
Replacement of birch with spruce negatively influenced soil bacterial and fungal richness and strongly altered microbial community composition in the forest floor layer, most strikingly for fungi. Tree species‐mediated variation in soil properties was a major factor explaining variation in bacterial communities. For fungi, both soil chemistry and understorey vegetation were important community structuring factors, particularly for ectomycorrhizal fungi. The relative abundance of ectomycorrhizal fungi and the ectomycorrhizal : saprotrophic fungal ratio were higher in spruce compared to birch stands, particularly in the deeper mineral soil layers, and vice versa for saprotrophs.
The positive relationship between ergosterol (fungal biomass) and SOC stock in the forest floor layer suggests higher carbon sequestration potential in spruce forest soil, alternatively, that the larger carbon stock leads to an increase in soil fungal biomass.
Silver birch (Betula pendula Roth) and downy birch (Betula pubescens Ehrh.) are the two most common broadleaf species in Sweden, together making up approximately 12% of the standing timber volume. ...The two birch species are usually not distinguished in practice, although they tend to differ in terms of volume production, timber quality, and site preferences. To map the proportion of the two birch species in Sweden's young forests, we used survey data from 123 stands 6-7 years after clearfelling, and data from Sweden's meteorological and hydrological institute. We also examined Sweden's young forests in terms of area, volume, and stem density between 1983 and 2021, using national forest inventory data. Proportions of the two birch species varied significantly across Sweden, and the average temperature sum over the first five years after clearfelling explained 72% of the variation. There was no significant change in area of forest classified as young forest in Sweden, over the last four decades, although there was a significant increase in volume and stem density in Sweden's young forests, with birch making up most of the increase in stem numbers.
Large-scale replacements of native birch with spruce have been carried out in Western Norway for economic reasons. This tree species shift potentially affects biotic components such as the eucaryome, ...consisting of microscopic animals (Metazoa), protists and fungi, which are key players in the functioning of forest ecosystem. The impact on the belowground eukaryome and its interactions with vegetation and soil properties is not well assessed. We examined the impact of replacing native birch with Norway spruce plantations on the eukaryome of the boreal forest floor in Western Norway using 18S rDNA metabarcoding. The tree species shift from birch to spruce had significant impacts on the eukaryome at both taxonomic (Metazoa) and functional categories (phagotrophs, phototrophs, parasites and osmotrophs). The distinct differences in eukaryome communities were related to changes in understorey vegetation biomass and soil chemistry following the tree species shift. This had a negative effect on eukaryome richness, particularly affecting phagotrophs and parasites, while the opposite was observed for osmotroph richness. Our results indicated that the spruce plantations altered the eukaryome communities and their food-web patterns compared to what was found in the native birch forest soil. This information should be taken into consideration in forest management planning.
The values of the fractional distribution of aboveground (AGB) and belowground biomass (BGB), root/shoot ratios (R/S) and stemwood density were estimated for silver (Betula pendula) and downy birch ...(Betula pubescens) along site index and age gradients for Estonia. Biomass models were used, in which the diameter at breast height (D1.3, measured above root collar), tree height, age and site index served as independent variables. The models for AGB and BGB were elaborated based on the data of 117 and 30 model trees, respectively. Strong allometric relationships were revealed between D1.3 and total AGB (with foliage), stem mass and BGB. For trees with D1.3 < 15 cm, individual models predicted similar biomass patterns for both species, for larger trees, species-specific models are suggested. The relative share of stem mass in AGB was 80–90% for all site index and age classes, being significantly higher for silver birch. The average relative share of stembark, branches, leaves and the R/S, were significantly higher for downy birch. Mean oven-dry mass stemwood density for silver and downy birch was 0.573 g cm−3, there was no statistically significant difference between the species. The mean R/S ratio was 0.29 and 0.43 for silver and downy birch, respectively.
Abstract
Phenological research is engaged in monitoring the influence of climate change on the natural environment. The International Phenological Gardens (IPG) network provides a valuable dataset of ...standardized tree phenology records dating back to the mid-20th century. To make best use of this actively growing record, it is important to investigate how network data can be applied to predict the timing of phenological events in natural populations. This study compared clonally propagated IPG downy birch (Betula pubescens Ehrh.) and hazel (Corylus avellana L.) specimens of central European provenance to nearby wild populations at the western-most margin of the IPG network, in the south-west of Ireland. In addition to monitoring by trained scientists, observations by citizen scientists were included. The order of the timing of phenological events among sites was consistent across 2 years, confirming reproducibility of the results. IPG trees had the earliest B. pubescens leaf unfolding and C. avellana flowering dates of the sites studied. In addition, leaf unfolding occurred later in the wild populations than expected from the temperature responses of the B. pubescens and C. avellana IPG clones. Natural variation in phenology also exceeded the historical change observed at the IPG site, suggesting a potential genetic basis for climate adaptation. Trunk circumference, reflecting the age-dependent increase in tree size, was found to influence C. avellana phenology, with earlier timing of phenological events in larger trees. This finding highlights tree size as an important consideration in the management of phenological gardens and tree phenology research in general.
Graphical Abstract
Graphical Abstract
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.
The greenhouse-gas (GHG) balance of CH4 and N2O emissions and CO2 respiration in peatlands plays a key role in climate change. A GHG balance is mostly calculated from point measurements. In this ...study we propose and test a geophysical method of low frequency domain electromagnetic method (FDEM) as a proxy for forest-floor CO2 respiration and CH4 emissions in two 50 × 100 m drained peatlands in Estonia: a Downy birch and a Scots pine stand from April to September 2015. The FDEM measurement campaign in September 2015 yielded a detailed map of topsoil electrical conductivity. We explain the predictive power of FDEM on GHG emissions through relationships with dry bulk density of soil. Although we over- or underestimated some fluxes owing to soil heterogeneity, we composed reasonably credible GHG emission maps. The initial results seem promising and we recommend further application of FDEM methods.
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•We tested the FDEM as proxy for CO2 and CH4 emissions in drained peatlands.•FDEM correlates with CO2 production and CH4 fluxes.•Upscaling point CH4 fluxes into an annual sequence of detailed maps.•FDEM is a promising tool for mapping GHG emissions.
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