Young Silver Birch Research Articles

Tree Biomass and Leaf Area Allometric Relations for Betula pendula Roth Based on Samplings in the Western Carpathians.

Biomass allometric relations are necessary for precise estimations of biomass forest stocks, as well as for the quantification of carbon sequestered by forest cover. Therefore, we attempted to create allometric models of total biomass in young silver birch (Betula pendula Roth) trees and their main components, i.e., leaves, branches, stem under bark, bark, and roots. The models were based on data from 180 sample trees with ages up to 15 years originating from natural regeneration at eight sites in the Western Carpathians (Slovakia). Sample trees represented individuals with stem base diameters (diameter D0) from about 4.0 to 113.0 mm and tree heights between 0.4 to 10.7 m. Each tree component was dried to constant mass and weighed. Moreover, subsamples of leaves (15 pieces of each tree) were scanned, dried, and weighed. Thus, we also obtained data for deriving a model expressing total leaf area at the tree level. The allometric models were in the form of regression relations using diameter D0 or tree height as predictors. The models, for instance, showed that while the total tree biomass of birches with a D0 of 50 mm (and a tree height of 4.06 m) was about 1653 g, the total tree biomass of those with a D0 of 100 mm (tree height 6.79 m) reached as much as 8501 g. Modeled total leaf areas for the trees with the above-mentioned dimensions were 2.37 m2 and 8.54 m2, respectively. The results prove that diameter D0 was a better predictor than tree height for both models of tree component biomass and total leaf area. Furthermore, we found that the contribution of individual tree components to total biomass changed with tree size. Specifically, while shares of leaves and roots decreased, those of all other components, especially stems with bark, increased. The derived allometric relations may be implemented for the calculation of biomass stock in birch-dominant or birch-admixed stands in the Western Carpathians or in other European regions, especially where no species- and region-specific models are available.

Recovery dynamics of ecosystem carbon budgets in a young silver birch stand chronosequence after clear-cut – Estonian case study

ABSTRACT Clear-cutting is an extensively used silvicultural method in the Nordic and Baltic countries, which strongly influences the site’s carbon (C) budget. In the current study, C budgets for a young silver birch stand chronosequence (2–8-year-old) were compiled using the C budgeting method. High variability of annual NEP between stands of similar ages occurred, as the C accumulation ability of young stands was site specific. Heterotrophic respiration (Rh), the main C efflux from the ecosystem, varied between (3.7 and 6.3 t C ha−1 yr−1) across all stands. Modelling of the annual NEP dynamics across the chronosequence revealed the C compensation point at a stand age of 6 years. The estimated cumulative C loss for the period when NEP was negative was almost 5 t C ha−1 and the amount of lost C could have been recaptured already in a 10-year-old stand. The C sink capacity of the studied sites depended mostly on the production of herbaceous plants until the production of the new tree generation became the main driver of ecosystem’s net primary production. Hence, site’s C accumulation capacity largely depends on the density and quality of the new forest regeneration.

Dynamics of fungal community structure in a silver birch (Betula pendula Roth) succession chronosequence on poor-quality post-arable soil

Soil fungal communities are critical components in soil ecosystems, but experimental researches on their responses to the silver birch succession are limited. Arbuscular mycorrhizal (AM) fungi and glomalin-related soil protein (GRSP) – a type of glycoprotein produced by hyphae of AM fungi, are highly correlated with soil physicochemical parameters and are sensitive to changes in the soil environment. This study aimed to analyze the dynamics of a soil fungal community, with particular emphasis on the AM fungi and GRSP contents and their responses to a silver birch succession on abandoned post-arable land. The studies were conducted in central Poland and covered five stands that included arable field (AF) and fallow (FA) land, and 8-year-old/young (YS), 33-year-old/middle (MS), and 40-year-old/old (OS) successions of silver birch. The diversity and compositions of the fungal communities were examined using ITS high-throughput gene sequencing. We found that the dominant soil fungal phylum transitioned from Olpidiomycota through Ascomycota to Basidiomycota with the change from AF to OS. Silver birch development increased the soil fungal diversity and richness compared with that of the AF soil, but these decreased compared with the FA soil. The predominant fungi in the soils under silver birch development belonged to the families Pezizaceae, Russulaceae, and Cortinariceae. The birch succession significantly decreased the abundance of potential pathotrophs and increased the relative abundance of symbiotrophic fungi. The AM fungi abundance varied across the successional stages and was affected by plant cover and N content, and positively correlated with the EE-GRSP and T-GRSP contents. Additionally, the EE-GRSP and T-GRSP contents positively correlated with the TOC, N and SOM content, and Tp, and negatively correlated with Bd. Across the successional stages, the YS was devoid of AM fungi and characterized by the lowest EE-GRSP T-GRSP (1.89 mg g-1), Tp (43.4%), and TOC (7.3 g kg-1) and P (11.7 g kg-1) contents. In summary, the development of young silver birch on generally poor Brunic Arenosols tends to have a negative effect on the soil fungal community and selected soil properties, but these effects ease over time.

The initial overreaction of carbon cycle to elevated atmospheric humidity levels off over time - a FAHM study in a young birch forest

Ecosystem responses to climate change are mainly predicted based on short-term studies. However, the first response can be a temporary overreaction, different from the later response of the more acclimated ecosystem. The current paper is a follow-up study of our previous article, where the effect of elevated atmospheric humidity on forest ecosystem carbon (C) balance was studied in a young silver birch (Betula pendula Roth) forest after two years of humidification. Here, we present the C balance of the same forest measured two years later when humidification treatment had been performed for four years. We revealed that the higher C sequestration capacity of the humidified birch forest ecosystem was an initial overreaction, which levelled off after four years of humidification, when the ecosystem became more acclimated to wetter conditions. Understorey production reacted rapidly and strongly by increasing belowground production more than twofold, but this reaction ceased after four years of humidification treatment. Trees responded to a lesser extent, and the initially decreased aboveground growth was recovered after four years of humidification, when the biomass allocation to tree fine-roots was increased. Our results showed that at early forest age, understorey plant production dominated in the whole ecosystem C sequestration capacity. But in the later stage, the most important C sink was biomass production of birches, and since the tree biomass production no longer differed between the treatments, C sequestration of the whole ecosystem did not differ either. The findings confirm that a preliminary reaction of an ecosystem can be different from the later response, which needs to be taken into account when prognosing the climate change consequences for carbon sequestration.

Young Silver Birch Grows Faster and Allocates Higher Portion of Biomass into Stem Than Norway Spruce, a Case Study from a Post-Disturbance Forest

The aim of the paper was to compare young silver birch (Betula pendula Roth.) and Norway spruce (Picea abies L. Karst) growing at the identical site, from the point of contribution of tree components to their aboveground biomass stock, their wood density, radial increment and aboveground biomass production. Our research activities were performed in the High Tatra Mts., which belong to the Tatra National Park (TANAP), Northern Slovakia. Currently, the substantial part of the TANAP territory is covered by post-disturbance young forests which have been growing there since the large-scale windstorm episode in November 2004. Our study combined non-destructive repeated tree measurements performed at two transects in 2016–2020, with destructive tree sampling of twenty 14-year-old individuals for each species. From the gathered data, we derived models estimating standing stock and annual production of aboveground biomass in individual tree components (foliage, branches, stem bark and stem wood), using diameter at breast height (DBH) as a predictor. The results showed contrasting contributions of tree compartments to aboveground biomass stock between birch and spruce. While spruce trees had four times higher contribution of foliage than birches, the reverse situation (1.5-fold difference) was observed for stem over bark biomass. At the same time, birch trees had a 40% greater diameter increment and a 30% denser stem wood than spruce. As for aboveground biomass production, the contribution of the stem as an economically important component was greater in birch than spruce. The results suggest that, in the young growth stage, birch may be advantageous over spruce in both ecological and production properties. Therefore, we believe that strengthening research activities focused on birch ecology and production issues would bring practical recommendations for better utilization of this tree species in forestry and wood-processing industry sectors

Seemingly Unrelated Mixed-Effects Biomass Models for Young Silver Birch Stands on Post-Agricultural Lands

Secondary succession that occurs on abandoned farmlands is an important source of biomass carbon stocks. Both direct and indirect tree biomass estimation methods are applied on forest lands. Using empirical data from 148 uprooted trees, we developed a seemingly unrelated mixed-effects models system for the young silver birch that grows on post agricultural lands in central Poland. Tree height, biomass of stem, branches, foliage, and roots are used as dependent variables; the diameter at breast height is used as the independent variable. During model elaboration we used restricted cubic spline: 5 knots at the quantiles (0.05, 0.275, 0.5, 0.725, and 0.95) of diameter at breast height provided sufficiently flexible curves for all biomass components. In this study, we demonstrate the use of the model system through cross-model calibration of the biomass component model using tree height measured from 0, 2, 3, and 4 available extreme trees feature in the plot in question. A different number of extreme trees were measured for final model system and our results indicated that for all analyzed components, random-effect predictions are characterized by higher accuracy than fixed-effects predictions.

Mixed-effects generalized height–diameter model for young silver birch stands on post-agricultural lands

The purpose of creating regression equations is often to predict unmeasured features based upon more easily obtainable ones. Species-specific height–diameter (H–D) models of trees are an example of this situation and can be defined as either simple or generalized. Simple H–D models express height as a function of tree diameter at the breast height. They are easily applicable without additional measurement but do not take properly into account the variability in H-D relationship between stands. Meanwhile, generalized models also include stand-level predictors. The H-D data sets are often characterized by a grouped structure. The mixed-effects modeling approach is a mainstream method employed for these types of forestry data. In this study, we created a mixed-effects generalized H–D model for young silver birch stands on post-agricultural lands in central Poland. This model was chosen from among 11 simple nonlinear models based on the goodness of fit and residual behavior. We accounted for two stand-level predictors that did not require additional measurements beyond tree diameter at the breast height: quadratic mean diameter at the breast height and basal area. Fixed- and random-effect predictions were then calculated to illustrate that increases in the number of measured trees improves height predictions. Moreover, the gain in predictive power is the largest if extreme trees (i.e., from the extrema of the diameter range) are used for random-effect prediction.

The effect of thinning on annual net nitrogen mineralization and nitrogen leaching fluxes in silver birch and Scots pine stands

ABSTRACTThinning changes the functioning of the whole forest ecosystem, including carbon and nitrogen (N) cycling. The input of organic matter and N into soil, as well as soil temperature and moisture regimes change, which may have an impact on the intensity of the net nitrogen mineralization (NNM) process. The main aims of this study were to estimate the effect of thinning on annual NNM as well as N leaching intensity in young silver birch and Scots pine stands. Thinning increased annual NNM flux in the silver birch stand, as well as annual net nitrification, while there was no change in the annual net ammonification flux. The effect of thinning on nitrification was more pronounced in the first post-thinning year. The 13-year dynamics of annual NNM in the birch stand revealed a significant decrease, which may be attributed to the effect of previous land use. The annual NNM flux in the Scots pine stand was practically equal in both plots; thinning did not affect N net mineralization intensity. The effect of thinning on the annual NNM flux was site and tree species specific. Thinning did not induce more intensive N leaching. Moreover, in the birch stand thinning even reduced N leaching.

Elevated atmospheric humidity shapes the carbon cycle of a silver birch forest ecosystem: A FAHM study

Processes determining the carbon (C) balance of a forest ecosystem are influenced by a number of climatic and environmental factors. In Northern Europe, a rise in atmospheric humidity and precipitation is predicted. The study aims to ascertain the effect of elevated atmospheric humidity on the components of the C budget and on the C-sequestration capacity of a young birch forest. Biomass production, soil respiration, and other C fluxes were measured in young silver birch (Betula pendula Roth) stands growing on the Free Air Humidity Manipulation (FAHM) experimental site, located in South-East Estonia. The C input fluxes: C sequestration in trees and understory, litter input into soil, and methane oxidation, as well as C output fluxes: soil heterotrophic respiration and C leaching were estimated.Humidified birch stands stored C from the atmosphere, but control stands can be considered as C neutral. Two years of elevated air humidity increased C sequestration in the understory but decreased it in trees. Humidification treatment increased remarkably the C input to the soil. The main reason for such an increase was the higher root litter input into the soil, brought about by the more than two-fold increase of belowground biomass production of the understory in the humidification treatment. Elevated atmospheric humidity increased C sequestration in young silver birch stands, mitigating increasing CO2 concentration in the atmosphere. However, the effect of elevated atmospheric humidity is expected to decrease over time, as plants and soil organisms acclimate, and new communities emerge.

High-pruning of silver birch (Betula pendula Roth): work efficiency as a function of pruning method, pole saw type, slash removal, operator, pruning height and branch characteristics

ABSTRACT The objective of this study was to establish an operational model of work efficiency (net or productive work time per tree) for high-pruning of young silver birch depending on pruning method, pole saw type, operator, pruning height and branch characteristics. The final model included number of branches, cross-sectional area of the thickest branch at the cut, pruning height, pruning method (target or flush pruning) and operator as independent variables. Work time increased with increasing values of each of the three numeric variables. For a given pruning height the number of branches was for all practical purposes more influential than the size of the largest branch. Target pruning was significantly faster than flush pruning, all else being equal. The variation in work efficiency for the five operators in the study spanned a range almost twice as large as that attributed to pruning method. The mean work time for other activities during the pruning operation (supportive work time) was estimated at 17% of the productive work time for pruning.

Pilot study on the effects of elevated air temperature and CO2 on artificially defoliated silver birch saplings

The impacts of elevated temperature and CO2 on young silver birch (Betula pendula Roth) saplings after 0, 25, 50 or 75% artificial defoliation were assessed by measuring plant height and dry mass of aboveground compartments and roots and various morphological and physiological variables. Defoliation either increased or decreased plant growth depending on the severity of damage and the climatic treatment. At 21 °C and 400 mg L−1 CO2, defoliated plants were not able to compensate for the lost foliage, but growth compensation and adaptation to the changed conditions were greater; growth of young defoliated silver birch saplings increased, which led to increased height and a tendency to enhance final aboveground and root biomass and leaf nitrogen and carbon content compared to the nondefoliated controls. Nevertheless, the short-term effect of the different climatic conditions did not result in a significant overgrowth of defoliated plants. A slight increase in temperature and CO2 were the most acceptable conditions for defoliated plants; however, a 4 °C increase with correspondingly higher CO2 was more stressful as shown by less growth in height and biomass allocation to leaves, stems and roots. The findings from the pilot experiment are more applicable to young birch trees, but stress on young trees may be reflected in future tree growth.

Response of artificially defoliated Betula pendula seedlings to additional soil nutrient supply

Abstract: The impact of leaf damage on the growth of young silver birch seedlings with and without additional nutrient supply was investigated by simulating leaf-insect damage and applying different levels (25%, 50% and 75%) of artificial defoliation. Based on field-practical and cost-effective methods, we determined how fertilization practices compensate for foliage loss, and the combined effect on silver birch seedling growth. The mineral fertilizers applied to the 25-75%-defoliated silver birch seedlings reduced the growth in aboveground biomass compared to the fertilized but undamaged seedlings. Our results showed that when the birch seedlings received more nutrients they did not compensate for the loss of foliar mass. However, the seedlings loosing part of their foliar mass and receiving no additional fertilizers did compensate for the foliage loss and their root growth was not weakened, using soil nutrients more effectively. Mineral fertilization up to optimal nutritional balance could be a beneficial tool for increasing growth rate and biomass accumulation in the short-term period. However, our study demonstrated that additional fertilization does not necessarily lead to growth compensation of partly defoliated young birch trees.

Leaf traits and photosynthetic responses of Betula pendula saplings to a range of ground-level ozone concentrations at a range of nitrogen loads

Ground-level ozone (O3) concentrations and atmospheric nitrogen (N) deposition rates have increased strongly since the 1950s. Rising ground-level O3 concentrations and atmospheric N deposition both affect plant physiology and growth, however, impacts have often been studied in isolation rather than in combination. In addition, studies are often limited to a control treatment and one or two elevated levels of ozone and/or nitrogen supply. In the current study, three-year old Betula pendula saplings were exposed to seven different O3 profiles (24h mean O3 concentration of 36–68ppb in 2013, with peaks up to an average of 105ppb) in precision-controlled hemispherical glasshouses (solardomes) and four different N loads (10, 30, 50 or 70kgNha−1y−1) in 2012 and 2013. Here we report on the effects of enhanced O3 concentrations and N load on leaf traits and gas exchange in leaves of varying age and developmental stage in 2013. The response of leaf traits to O3 (but not N) vary with leaf developmental stage. For example, elevated O3 did not affect the chlorophyll content of the youngest fully expanded leaf, but it reduced the chlorophyll content and photosynthetic parameters in aging leaves, relatively more so later than earlier in the growing season. Elevated O3 enhanced the N content of senesced leaves prior to leaf fall, potentially affecting subsequent N cycling in the soil. Enhanced N generally stimulated the chlorophyll content and photosynthetic capacity. Whilst elevated O3 reduced the light-saturated rate of photosynthesis (Asat) in aging leaves, it did not affect stomatal conductance (gs). This suggests that photosynthesis and gs are not closely coupled at elevated O3 under-light saturating conditions. We did not observe any interactions between O3 and N regarding photosynthetic parameters (Vc,max, Jmax, Asat), chlorophyll content, gs, N content in senesced leaves and leaf number. Hence, the sensitivity of these leaf traits to O3 in young silver birch trees is neither reduced nor enhanced by N load.

Biomass conversion and expansion factors for a chronosequence of young naturally regenerated silver birch (Betula pendula Roth) stands growing on post-agricultural sites

Forest stand biomass or carbon storage in the biomass may be estimated by conversion of the trees volume since roughly 50% of tree biomass is carbon. There is a need to find biomass conversion and expansion factors (BCEFs) for young stands, because those established for older ones may not be relevant due to changes in biomass allocation patterns over stand age and development phases. We developed BCEFs for above- and belowground biomass components of young silver birch stands as separate functions of stand age or variables that reflect growth conditions and the biological status of trees, i.e. top height (H100), mean height (Hg), base diameter (D0), quadratic mean diameter at breast height (Dg) or stand volume (V). Data were collected on 120 pure birch stands that regenerated naturally on post-agricultural lands in Poland. We determined BCEFs based on the stem volume and dry biomass of above- and belowground components. We applied segmented linear regression (SLR) to develop equations for BCEF determination for each of the pre-determined age classes using (a) fixed break points (FBP) found with the Ward method and (b) estimated break points (EBP) derived based on the best fit of regression models during piecewise regression estimation. We found that the use of SLR and non-linear regression (NR) approaches produced similar results in terms of quality of fit. However, non-linear parameter estimates are more efficient than linear ones, as NR seems to be more frequently used and easier to process using existing statistical tools, but at the same time the SLR provides biological interpretation of results (i.e. the point where BCEF value stabilizes and beyond which stand features do not influence BCEF). The largest difference between EBP and FBP occurs for stems, and the smallest for roots. For total biomass and all biomass components except stem, BCEFs are very high for the youngest, shortest and thinnest trees and hence stands with low volume. Their values decrease along with age, height, diameter and volume towards the EBPs. For individuals older, taller, thicker and with higher volume than EBP, there is no influence of age, H100, Hg, D0, Dg and V on BCEF values. We confirmed that H100 might be a good biomass predictor for young birch stands, which is important because measuring tree height is not as time consuming as tree diameter measurements, particularly for young and very dense stands, and this parameter can be obtained from remote sensing technology.

Empirical equations for estimating aboveground biomass of <i>Betula pendula</i> growing on former farmland in central Poland

We determined empirical models for estimating total aboveground as well as stem, branches, and foliage dry biomass of young (age up to 16 years) silver birch (Roth.) growing on the post-agricultural lands. Two sets of allometric models for trees with a height below or above 1.3 m (small and large trees respectively) were developed. Simplified models were elaborated based exclusively on appropriate tree diameter (diameter at ground level for small trees, diameter at breast height for large trees), while expanded models also included tree height. Total aboveground biomass was estimated as the sum of biomass of all tree components. To assure additivity of the developed equations, the seemingly unrelated regression approach for the final model fitting was used. Expanded models in both tree groups were characterized by a better fit to the data (Rfor total aboveground biomass for small and large trees equaled 0.8768 and 0.9752, respectively). Diameter at breast height appeared to be a better predictor than diameter at ground level – simplified models had better fit for large trees (R for total aboveground biomass equals 0.9611) than for small ones (R = 0.7516). The developed equations provide biomass predictions consistent with available Latvian, Estonian, Finnish, Swedish, and Norwegian models for silver birch.Betula pendula 2 22

Recovery of the herbaceous layer in the young silver birch and black alder stands that developed spontaneously after a forest fire

AbstractThe studies, which were conducted in southern Poland, focused on the recovery of the herb layer in 17‐year‐old post‐fire silver birch and black alder forests. Although both types of stands, which are of the same age, developed spontaneously, the alder stands occupied damper sites (with thicker A horizons that survived the fire) than those in the birch forests. We surveyed the migration rates of 44 woodland species, primarily ancient woodland indicators, into both forests and the potential differences in these rates depending on their moisture regime and the community type represented by unburned forests, which were treated as the source of the woodland species pool. Additionally, the role of local depressions with high humidity that were covered by post‐fire alder woods in the colonization process, as well as species survivorship and recolonisation, were estimated. Woodland species showed diverse migration paces among the sites; most of them migrated faster on more fertile sites with a higher humidity. Small patches of post‐fire alder woods contributed to the recolonisation process since many woodland species in the herb layer survived the fire due to its high humidity, which inhibited the intensity of the forest fire. The recovery of woodland species in post‐fire woods is the combined effect of regeneration, which relies on autochthonic propagules, and secondary succession, which is based on allochthonic propagules. Local depressions, which provide refuges for fire‐sensitive, dispersal‐limited species, contribute to their survivorship and thus to the successive recovery of herbaceous layers after a fire.

Insect herbivore damage on latitudinally translocated silver birch (Betula pendula) – predicting the effects of climate change

Boreal forests might be challenged by increased herbivory pressure in the future due to global warming, since warming is predicted to increase the abundance of herbivorous insects and to lead to shifts in their distribution towards higher latitudes where they might face more palatable food sources. We studied the effect of the latitudinal translocation of silver birch (Betula pendula Roth) on herbivore damage to 26 micropropagated genotypes originating from six populations ranging from 60 to 67°N in Finland in two growing seasons, 2011 and 2012. The genotypes were planted at three sites located in southern (60°N), central (62°N) and northern (67°N) Finland. The genotypes translocated to lower latitudes from their latitudes of origin were experiencing higher intensity of herbivore damage compared to the genotypes translocated to higher latitudes in 2011, but not in 2012. All genotypes were experiencing herbivore damage by local herbivores of each study site. These results suggest that, as many herbivore species are predicted to shift their ranges towards higher latitudes, they can feed on novel host plant genotypes and may face more palatable food sources than at their present range. This suggests that future climate change will increase herbivore damage to young silver birch. Increased herbivory, in turn, might affect the growth of birch and therefore should be considered when making predictions about the boreal forest composition in the future.

The effect of elevated air humidity on young silver birch and hybrid aspen biomass allocation and accumulation – Acclimation mechanisms and capacity

Climate change is predicted to bring about a rise in precipitation and atmospheric humidity at northern latitudes, which could have a considerable impact on forest ecology and management. This study investigates the effect of elevated relative air humidity (RH) on tree growth and biomass accumulation and allocation in six-year-old seedling-originated silver birch (Betula pendula Roth) and monoclonal hybrid aspen (Populus tremula L.×P. tremuloides Michx.) stands. The study was conducted in the unique Free Air Humidity Manipulation experimental facility in Estonia. Two understory vegetation types (forest and pasture) were used in the experimental plots. As a short-term response during the first manipulation years, a small rise (6–7%) in RH reduced the growth of both tree species. In the fifth humidification year, suppression of growth continued in aspen, but birch acclimated effectively to elevated RH – differences in biomass and stem diameter increments levelled out in humidified (H) and control (C) plots. The H birches ensured biomass accumulation by changing the biomass and morphology of the physiologically most active tree parts: increasing fine-root biomass, as well as specific areas of fine roots (SRA) and leaves (SLA). The effect of elevated RH on most leaf and fine root characteristics of aspens was in a similar direction as that of birches, but weaker, and the plasticity of the functional traits was also lower compared to birches, probably due to the lack of genetic variation in monoclonal aspens. The biomass of young aspens was 22% lower in H plots. The relative aboveground biomass allocation was not affected by elevated RH. The aboveground biomass of humidified birches was higher in plots with forest understory, where root competition was lower compared to the dense root systems of grasses in pasture understory plots. Aspen biomass was not affected by understory vegetation type. We conclude that young silver birches have sufficient phenotypic plasticity to acclimate to elevated RH and the forests retain biomass accumulation. However, the growth acclimation of planted forests of clonal plant material is more complicated and humidity-tolerance should be considered in the selection of new clones for areas where an increase in RH is anticipated.

Biomass dynamics in young silver birch stands on post-agricultural lands in central Poland

The paper analyses the production and allocation of biomass in young, spontaneous silver birch afforestation occurring on post-agricultural lands in the Mazowsze region (central Poland). We investigated 114 sample plots of age varying from 1 to 19 years. During the first 15 years after their establishment on abandoned farm land, the naturally regenerated silver birch stands produced on average approximately 75 tons of dry biomass per hectare. The major (50–70%) part of this biomass was stored in the tree stems and this share increased with age. The fractions of biomass in the foliage and roots decreased over time, while the share of biomass in the branches remained rather constant. The significant age-dependency of the allometric relationships suggested the need to use age-sensitive biomass expansion factors to estimate the biomass from the stem volume.

The effects of elevated atmospheric humidity on soil respiration components in a young silver birch forest

The predicted increase in precipitation at northern latitudes is an important factor affecting the functioning of forest ecosystems, yet the influence of increased atmospheric humidity on the forest ecosystem carbon cycle is still largely unknown. Our objectives were to determine the effect of elevated atmospheric humidity on soil respiration in silver birch (Betula pendula Roth.) plantations in a Free Air Humidity Manipulation experimental facility (FAHM). Soil respiration was monitored monthly from May to October, in 2008 and 2009 in three control and in three misting plots; soil temperature and soil moisture were measured simultaneously. Fine-root and rhizome biomass of the understory was measured by sequential soil cores. Soil microbial biomass and basal respiration were measured using manometric respirometers. After the first two years of manipulation, humidification led to lower soil respiration. Soil temperature was the main factor influencing seasonal dynamics of soil respiration, describing up to 75% of the total variation of soil respiration. Soil moisture had a weak negative effect on soil respiration. Humidification caused a remarkable increase in below-ground biomass and the production of the understory, and a 28% increase in the basal respiration of microbes. However, above-ground biomass and root turnover rate of the understory were almost unchanged. Hence, elevated atmospheric humidity significantly affects carbon cycle of deciduous forest. However, further studies are necessary for a better understanding of soil respiration response to changes in atmospheric humidity, in order to predict carbon balance in changing climate conditions.