Maximum yield and the C-D effects in natural white birch stands

The competition-density effect for natural Japanese white bitch (Betula platyphylla var.japonica) stands, located in the northern part of Hokkaido Island, was examined for various growth stages to establish mean tree weight-density relationships over a considerable extent of stand growth of white birch. Aboveground yields of investigated stands ranged from 16.0 to 161.7 t·ha⁻¹, and it was recognized that maximum aboveground yield of this species was about 160 t·ha⁻¹. ConstantsA andB of the reciprocal equation of the C-D effect, 1/w=AN+B (w, mean tree weight; N, tree density), were related to mean height classes of birch stands. ConstantB was related to the entire mean height classes as the allometric relationship. On the other hand, constantA had an allometric relationship to mean height classes under 16 m, but became fixed over the 16 m class. White birch stands can come up to the maximum yield approximately at the stage of the 16 m class. The asymptotic tendency seemed to be appropriate for constantA-mean height class relationship. The maximum yield of white birch stands was predicted by the asymptotic value ofA. The trend of mean tree weight-density relationships with stand growth also changed with constantA. It was considered that maximum yield was an important characteristic for practical applications of the C-D effect to agriculture and forestry.     

Correlation of greenhouse bioassay with field response to fertilizer by paper birch

Summary Bulk soil samples were collected from the top 15 cm of untreated areas adjacent to field fertilizer trials at 2 locations. Amounts of N, P, K, and lime equivalent to the field treatments were mixed with the soil in 15-cm diameter pots. Paper birch (Betula papyrifera March.) trees were grown from seed for a greenhouse bioassay. Height and dry weight of the bioassay seedlings were significantly correlated with 3-year volume growth of 10-year-old paper birch seedlings in the field. Correlation coefficients were 0.88 for height growth and 0.91 for dry weight growth on one site, and 0.72 and 0.63 on the other. With further refinements and observations on a larger number of sites, this bioassay technique should be a valuable tool for estimating potential response to fertilizer by young paper birch in the field, and for ranking the relative productivity of different soils.     

Rooting strategy of naturally regenerated beech in Silver birch and Scots pine woodlands

This study investigated the belowground development and strategy of late-successional European beech (Fagus sylvatica L.) in ageing natural Scots pine (Pinus sylvestris L.) and Silver birch (Betula pendula Roth.) woodlands in a French volcanic mid-elevation area. For this purpose root biomass, root profile and fine-root architecture of competitor trees were examined in 53 mixed pine–beech and 42 birch–beech woodlands along a stand maturation gradient, using the root auger technique (0–75-cm). The total beech fine-root biomass highly correlated with aerial dimensions such as stem height and girth, whereas it moderately correlated with its age, thus indicating the effects of competition. Basic stand biometric data such as stand density and basal area had no significant effect on beech root biomass. Conversely, competition indices taking into account the vertical dimensions of competitor trees were efficient, probably due to redundancy with beech height. At similar age and height, beeches under birch had a greater belowground development than beeches under pine. Each species exhibited specific rooting pattern and plasticity of fine-root architecture along the gradients of stand maturation and competition. Beech had a heart-shaped rooting habit in both mixings, which strongly increased along stand maturation. Its fine-root system adopted a foraging strategy to respond to increasing stand competition. The Scots pine fine-root system was plate-like and showed a low morphological plasticity, thus presumably a conservative strategy. Silver birch exhibited a high biomass and a foraging capacity in the topsoil but a loose root system in the subsoil. The coexistence of pine and beech roots in the upper soil presumably leads to a high belowground competition. Beech root system becomes predominant throughout the soil profile and it adopts an efficient foraging strategy, but at the expense of its belowground development. Conversely, the niche partitioning strategy between beech and birch may explain why beech develops strongly belowground in spite of the fact that birch has a dense rooting and a competitive fine-root architecture. As a consequence, beech mid-term regeneration and development may be facilitated under birch as compared with pine.     

Boron uptake by ectomycorrhizas of silver birch

Boron (B) is an essential micronutrient for plants but it is thought not to be essential for fungi. We studied whether the extraradical mycelia of Paxillus involutus in symbiosis with silver birch (Betula pendula) take up B and transport it to the host plant. We grew mycorrhizal plants in flat microcosms with a partitioning wall, below which there was only extraradical mycelium. A boric acid solution enriched in ¹⁰B was applied to these mycelia. Increased ¹⁰B/¹¹B isotope ratios were subsequently measured in birch leaves, stems, and roots plus mycorrhizas in the upper compartment. Boron was therefore taken up by the mycorrhizal mycelia and transported to the host plant in this species combination.     

Changes in the chemical content of birch (<Emphasis Type="Italic">Betula pendula </Emphasis>Roth) leaves in the air polluted Krusne hory mountains

Analyses of birch leaves (Betula pendula Roth) sampled from trees in the air polluted Krusne hory mountains and Decin sandstone highlands were performed in 1995 and 1998. The results revealed a connection between reduction of air pollutants and overall decrease in sulphur and nitrogen content of the leaves. Simultaneously, in many stands an increase in calcium content and a decrease in contents of phosphorus, magnesium and potassium occurred. The content of microelements and non-nutrient elements did not change.     

Morphological plasticity of regeneration subject to different levels of canopy cover in mixed-species, multiaged forests of the Romanian Carpathians

Morphological plasticity was studied for advanced regeneration trees in different light environments of the mountainous, mixed-species forests in the Carpathian Mountains of Romania. The primary species in these mixtures were very shade tolerant silver fir (Abies alba Mill.) and European beech (Fagus sylvatica L.), and midtolerant Norway spruce (Picea abies (L.) Karst). Seedlings/saplings of these species were selected for measurements in different stands from two different geographical locations. Various morphological traits (specific leaf area, live crown ratio, crown width to length ratio, terminal to lateral ratio, number of internodal shoots, number of shoots in terminal whorl, stem symmetry, stem orientation, stem forking) for each regenerating tree were measured during summers of 2001 and 2002. Percentage of above canopy light and stand basal area measures were used to assess the available growing space for each seedling/sapling. Regression relationships were developed for the different morphological indicators as a function of these two variables. All species adapted their morphology along the gradient in light and basal area. Spruce seemed to be less adapted to low light conditions than both fir and beech. However, no significant differences in terms of shade tolerance were detected using the above indicators. In really dense stand conditions (less than 20% above canopy light and stand basal area above 36 m² ha⁻¹), probability for stem forking in beech increased. In open, all three species adapted their morphology for vigorous growth. Under such conditions, spruce was better adapted than fir.     

Carbon, nitrogen and phosphorus in volcanic soils following afforestation with native birch (Betula pubescens) and introduced larch (Larix sibirica) in Iceland

Afforestation has become an important tool for soil protection and land reclamation in Iceland. Nevertheless, the harsh climate and degraded soils are growth-limiting for trees, and little is know about changes in soil nutrients in maturing forests planted on the volcanic soils. In the present chronosequence study, changes in C, N and total P in soil (0–10 and 10–20 cm depth) and C and N in foliar tissue were investigated in stands of native Downy birch (Betula pubescens Enrh.) and the in Iceland introduced Siberian larch (Larix sibirica Ledeb.). The forest stands were between 14 and 97 years old and were established on heath land that had been treeless for centuries. Soils were Andosols derived from basaltic material and rhyolitic volcanic ash. A significant effect of tree species was only found for the N content in foliar tissue. Foliar N concentrations were significantly higher and foliar C/N ratios significantly lower in larch needles than in birch leaves. There was no effect of stand age. Changes in soil C and the soil nutrient status with time after afforestation were little significant. Soil C concentrations in 0–10 cm depth in forest stands older than 30 years were significantly higher than in heath land and forest stands younger than 30 years. This was attributed to a slow accumulation of organic matter. Soil N concentrations and soil P_tot were not affected by stand age. Nutrient pools in the two soil layers were calculated for an average weight of soil material (400 Mg soil ha⁻¹ in 0–10 cm depth and 600 Mg soil ha⁻¹ in 10–20 cm depth, respectively). Soil nutrient pools did not change significantly with time. Soil C pools were in average 23.6 Mg ha⁻¹ in the upper soil layer and 16.9 Mg ha⁻¹ in the lower soil layer. The highest annual increase in soil C under forest compared to heath land was 0.23 Mg C ha⁻¹ year⁻¹ in 0–10 cm depth calculated for the 53-year-old larch stand. Soil N pools were in average 1.0 Mg N ha⁻¹ in both soil layers and did not decrease with time despite a low N deposition and the uptake and accumulation of N in biomass of the growing trees. Soil P_tot pools were in average 220 and 320 kg P ha⁻¹ in the upper and lower soil layer, respectively. It was assumed that mycorrhizal fungi present in the stands had an influence on the availability of N and P to the trees. Responsible Editor: Hans Lambers.     

长白山白桦山杨次生林细根形态特征和解剖结构对氮沉降的响应

根系作为植物与土壤物质交换和养分循环的桥梁,长期以来一直是生态学研究的热点。于2017年7月植物生长季,对长白山模拟11年氮(N)沉降控制试验样地的白桦(Betula platyphylla)山杨(Populus davidiana)天然次生林进行了根系采样,并利用根序法研究了根系形态特征和解剖结构对不同梯度N添加处理的响应,旨在探求两物种根系之间潜在生态联系。本试验共设置了三个N添加梯度,分别为对照(CK,0 g N m~(-2 )a~(-1))、低N处理(T_L,2.5 g N m~(-2 )a~(-1))和高N处理(T_H,5.0 g N m~(-2 )a~(-1))。研究结果如下:1)T_L显著抑制白桦和山杨前三级细根皮层厚度的生长。白桦通过增加皮层细胞直径(一级根增加了72.77%,二级根增加了53.22%,三级根增加了39.96%)但减少皮层层数来降低皮层厚度,而山杨主要通过皮层细胞直径的减少(一级根下降了40.80%,二级根下降了28.17%)来降低其皮层厚度。2)T_H显著抑制山杨前三级细根生长。主要通过增加皮层厚度(一级根增加了68.78%,二级根增加了50.81%,三级根增加了88.53%)以及降低导管横截面积来抑制吸收养分,从而达到影响生长的目的。3)白桦T_H相比于T_L细根直径呈抑制生长状态。其主要通过抑制中柱直径(一级根下降了17.61%,二级根下降了16.89%,三级根下降了20.62%)的生长来实现。以上结果表明,在同一立地条件下,白桦和山杨的细根对不同浓度N沉降的响应方式不同。     

Optimization of sucrose and inorganic nitrogen concentrations for somatic embryogenesis of birch (Betula pendula Roth.) callus cultures: A statistical approach

The effects of different concentrations of sucrose and inorganic nitrogen on somatic embryogenesis of birch (Betula pendula Roth.) callus cultures were studied using Box-Wilson statistical experimental design. The experimental results were processed by regression analysis, and mathermatical models describing the effects of the selected variables were derived. On the basis of the modeling, maximum embryo production can be achieved with 35 mM total inorganic nitrogen and 20.8 g 1^-1 sucrose in the medium.     

The Role of Sucrose in Regulation of Trunk Tissue Development in Betula pendula Roth

Comparative ultrastructural analysis of the conducting and non-conducting phloem cells in the common straight-grained silver birch (Betula pendula var. pendula) and the Karelian birch (B. pendula var. carelica) with abnormal patterned wood was carried out, leading to the conclusion that there is an elevated sucrose content in the conducting phloem of the Karelian birch. A connection between sucrose levels and formation of abnormalities in the development of conducting tissues in the Karelian birch trunk was surmised. Experiments in which exogenous sucrose was applied to the silver birch trunk tissues have demonstrated the effects of different sucrose concentrations (0 g L⁻¹, 10 g L⁻¹, 25 g L⁻¹, 50 g L⁻¹, 100 g L⁻¹) on the formation of xylem and phloem structural elements, and they yielded the types of tissue development that correspond to the abnormal tissue development in the Karelian birch trunk.     

Demography of Betula pubescens ssp. tortuosa sown in contrasting habitats close to the birch tree-limit in Central Sweden

Seeds of mountain birch (Betula pubescens Ehrh. ssp. tortuosa (Ledeb.) Nyman) were sown on permanent plots in three contrasting habitats close to the birch tree-limit in Central Sweden. The habitats differed mainly in regard to the length of the growth period, as determined by the pattern of local snow-accumulation. Germination success, seedling demography (1981–1983) and related aspects of the early stages were studied. Germination was found to start shortly after snowmelt in the year after ripening, in all three habitats. The conclusion is that germination is not the crucial phase of the life-cycle. In the habitat with the longest growth period, and where spontaneous birch stands are present, mortality mainly occurred in summer, evidently caused by soil drought. With shortening of the growth period, however, mortality during the winter became increasingly important. Survival was clearly correlated with the length of the growth period and the autumn height of seedlings. Factors which affect ecesis determine the altitude of the tree-limit and the long-term stability of the mountain birch forest ecosystem.     

An Analysis of Vegetation Restoration on Opencast Oil Shale Mines in Estonia

We compared four types of 30‐year‐old forest stands growing on spoil of opencast oil shale mines in Estonia. The stand types were: (1) natural stands formed by spontaneous succession, and plantations of (2) Pinus sylvestris (Scots pine), (3) Betula pendula (silver birch), and (4) Alnus glutinosa (European black alder). In all stands we measured properties of the tree layer (species richness, stand density, and volume of growing stock), understory (density and species richness of shrubs and tree saplings), and ground vegetation (aboveground biomass, species richness, and species diversity). The tree layer was most diverse though sparse in the natural stands. Understory species richness per 100‐m² plot was highest in the natural stand, but total stand richness was equal in the natural and alder stands, which were higher than the birch and pine stands. The understory sapling density was lower than 50 saplings/100 m² in the plantations, while it varied between 50 and 180 saplings/100 m² in the natural stands. Growing stock volume was the least in natural stands and greatest in birch stands. The aboveground biomass of ground vegetation was highest in alder stands and lowest in the pine stands. We can conclude that spontaneous succession promotes establishment of diverse vegetation. In plantations the establishment of diverse ground vegetation depends on planted tree species.     

Spatial variation in sapwood area to leaf area ratio and specific leaf area within a crown of silver birch

Spatial variation in sapwood area to leaf area ratio (Huber value, HV) and specific leaf area (SLA) was examined in branches of closed-canopy trees of silver birch (Betula pendula Roth). HV increased basipetally within a crown and decreased with increasing branch order, but exhibited no significant radial trend along a primary branch. HV was primarily determined by branch position in a crown and branch diameter at the sampling point, being independent of the size of the tree and branch. Greater HV in the lower-crown branches is considered a means to mitigate differences in hydraulic transport capacity between the branches located in different canopy layers. Beside branch position and sampling location on a branch, SLA depended significantly on several other variables characterising tree and branch size. SLA increased basipetally within a crown and along a primary branch, but exhibited no significant trend with branch orders. Because height caused leaf area (A_L) to diminish more rapidly than leaf dry weight, A_L primarily determined the vertical variation in SLA.     

<Emphasis Type="Italic">Melaleuca quinquenervia</Emphasis> dominated forests in Florida: analyses of natural-enemy impacts on stand dynamics

Melaleuca quinquenervia (melaleuca) is a native of Australia but has become an invasive plant in Florida, USA. We conducted a long-term demographic study of melaleuca in three sections (central, transitional, and peripheral) of monoculture stands located in Florida, and quantified absolute density, diameter at breast height and basal area of trees by section at three sites. Additionally, we monitored the impacts of natural enemy (insects and fungi) on melaleuca populations which became apparent after 2001. Both absolute density and basal area, from before (1997–2001) and after noticeable natural-enemy impact (2002–2005), were compared. Prior to the natural-enemy impact, absolute density of melaleuca trees declined primarily due to self-thinning and associated losses of small trees, but diameter at breast height increased, as did the basal area. Later during the period when natural enemies prevailed, absolute density declined at a significantly greater rate across all sections but was highest at the periphery. The decrease in mean absolute density and basal area/ha of melaleuca during the natural-enemy impacted period coincided with the increased incidence of the populations of plant-feeding insects and fungi. The mean diameter at breast height continued to increase in all sections of the stands throughout the study period. An increasing trend in basal area prior to natural-enemy impact was reversed after increase in natural-enemy abundance and noticeable impact in all three sections of the stands. These findings lend support to a growing body of literature that implicates natural enemies as increasingly important density-independent regulators of M. quinquenervia populations. The U.S. Government's right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged     

Prevention of flower development in birch and other plants using a BpFULL1::BARNASE construct

The prevention of flower formation is important for avoiding the spread of transgenes from genetically modified plants into wild populations. Moreover, the resources not expended for the generation of flowers and fruits might be allocated to increased vegetative growth. We have been developing methods for preventing flower formation in silver birch (Betula pendula), a tree species of considerable economical importance in the boreal region. Here we study the suitability of the promoter of BpFRUITFULL-LIKE1 (BpFULL1, formerly BpMADS5) for tissue-specific ablation of inflorescences in Arabidopsis, tobacco and birch. With all these species, the development of inflorescences was successfully prevented. The results show that the BpFULL1::BARNASE construct has potential biotechnological applications in different plant species.This revised version was published online in March 2005 because the name of the second author (M. Hassinen) was missing.     

Carbon transfer associated with assimilation of organic nitrogen sources by silver birch (Betula pendula Roth.)

Summary Qualitative and quantitative aspects of heterotrophic carbon assimilation by mycorrhizal plants of birch (Betula pendula) were examined. Plants were grown aseptically from seed in the mycorrhizal condition with the fungus Hebeloma crustuliniforme and in the non-mycorrhizal condition, with protein as their sole exogenous nitrogen source. Yields and nitrogen contents were determined in some of the plants, while the roots of others were supplied with ¹⁴C-labelled protein and their shoots exposed for up to 72 h to different irradiance regimes. Only mycorrhizal plants utilised the organic nitrogen. Uptake of carbon associated with this utilisation and its translocation to the leaves was demonstrated directly by means of autoradiography. Amounts of activity transferred to shoots were greatest in low irradiance regimes. Calculation of net carbon gain from the heterotrophic source, based upon the assumption that breakdown products of protein are assimilated as amino-acids, indicates that over a 55-day growth period up to 9% of plant C may be derived from protein. The physiological and ecological significance of these findings are discussed.     

The chemical composition of throughfall beneath oak, birch and pine canopies in Northwest Germany

The chemical composition of rainwater is altered upon its passage through tree canopies. In order to investigate how rainwater chemistry is affected by canopy-dependent processes in characteristic forest types of Northwest German sandy lowland regions – oak–birch-forests, Betula pubescens Ehrh. swamp forests, and stands of Pinus sylvestris L. – comparative studies on the chemical composition of throughfall were carried out at seven forest sites, situated in close proximity within a nature reserve. Additionally, rainwater was sampled at three heathland sites for analysis of open-field precipitation and at three sites along an oak–birch-forest edge. Throughfall concentrations of most of the parameters analysed were significantly higher than open-field concentrations, especially with regard to electric conductivity, NH₄-N, K⁺, and KMnO₄-index. Ion concentrations in throughfall were the lowest in a 10-year-old stand of Betula pendula Roth. and Pinus sylvestris and in a Betula pubescens swamp forest and were highest beneath a stand of Pinus sylvestris. Except for Na⁺, Cl⁻, and NO₃⁻, ion concentrations in both throughfall and open-field precipitation increased during the growing season (May–October). In throughfall, Ca²⁺, Mg²⁺, K⁺, and Mn²⁺ were strongly correlated. Enrichment ratios between throughfall and open-field deposition varied among sites and elements and were the highest for K^‰+, Mg^2‰+, and Mn^2‰+. Estimates of canopy leaching indicated high leaching rates of K^‰+ and Mn^2‰+ and moderate leaching of Mg^2‰+. The contribution of foliar leaching to throughfall deposition was higher at the deciduous than at the coniferous stands.     

Growth performance of hybrid families by crossing selfed lines of Betula pendula Roth

Hybrid breeding is an effective approach in many agricultural crops. In allogamous tree species severe inbreeding depression and long reproductive cycles generally prohibit its use. However, three generations of selfing in silver birch (Betula pendula Roth) were obtained by forcing trees to flowering under greenhouse conditions. Hybrids were produced by crossing first-, second and third-generation selfed lines. The effects of different levels of parental inbreeding on the growth performance of hybrid families were observed in a 9-year-old field progeny test. Also, provenance crosses were carried out between selfed lines from different parts of Finland and several other European countries. Observations of growth performance of the provenance hybrids were made in the same trial. The results indicated that the mean stem volumes were significantly different between classes of parental in breeding coefficients (F_P) (P<0.0001), and were positively correlated with F_P (r=0.9106, P<0.05). Within-family variation of the hybrid families decreased with an increase of F_P. The performance of the provenance crosses between parents at a relatively close distance did not depart significantly from the standard controls. However, when the cross distance was extended far to the south, hybrids grew faster, indicating either higher heterozygosity or an extended growth period.     

Effects of CO2-mediated changes in paper birch and white pine chemistry on gypsy moth performance

We examined the effects of CO₂-mediated changes in the foliar chemistry of paper birch (Betula papyrifera) and white pine (Pinus strobus) on performance of the gypsy moth (Lymantria dispar). Trees were grown under ambient or enriched CO₂ conditions, and foliage was subjected to plant chemical assays and insect bioassays. Enriched CO₂ atmospheres reduced foliar nitrogen levels and increased condensed tannin levels in birch but not in pine. Foliar carbohydrate concentrations were not markedly altered by CO₂ environment. Gypsy moth performance was significantly affected by CO₂ level, species, and the CO₂ x species interaction. Under elevated CO₂ conditions, growth was reduced for larvae fed birch, while development was prolonged for larvae fed pine. Although gypsy moths performed better overall on birch than pine, birch-fed larvae were influenced more by CO₂-mediated changes in host quality.     

Tree regeneration patterns on Mount Usu, northern Japan, since the 1977–78 eruptions

Although the summit of Mount Usu was deforested by the 1977–78 eruptions, vegetative regeneration on the caldera rim was rapid due to the erosion of thick volcanic deposits by snow and rain. To obtain the mechanisms underlying regeneration patterns after the eruptions, we monitored the growth of permanently-marked stems from 1983 to 1990. Regeneration was from resprouting-branches buried in the volcanic deposits on the caldera rim, while on the crater basin, where thick volcanic deposits accumulated, regeneration was from seedlings. The seedling regeneration lagged approximately 3 years behind vegetative regeneration. Stem densities averaged 14,000 ha^-1 in the vegetatively-regenerated community on the caldera rim, and 28,000 ha^-1 in the seedling regeneration on the crater basin. Populus maximowiczii accounted for ca. 75% of total stems on the caldera rim, while P. maximowiczii accounted for ca. 30% on the crater basin where Salix integra and Betula platyphylla var. japonica were also common. In both stands, immigration and mortality rates were very low. The growth of vegetatively regenerated stems expressed as stem height and diameter was significantly faster than that of stems grown from seedlings. Herbivory damage on the terminal shoots of tall stems was restricted on the caldera rim and was restricted for B. platyphylla var. japonica on the crater basin, perhaps due to fast growth supporting herbivore avoidance or low palatability. Height growth was restricted when neighbors established in close proximity, especially in the seedling-regenerated forest. The results suggest that vegetative regeneration is rapid due to three mechanisms: 1) faster plant growth; 2) herbivore avoidance; and 3) decreased interference by neighboring.