Interactive effects of elevated ozone and temperature on carbon allocation of silver birch (Betula pendula) genotypes in an open-air field exposure

In the present experiment, the single and combined effects of elevated temperature and ozone (O(3)) on four silver birch genotypes (gt12, gt14, gt15 and gt25) were studied in an open-air field exposure design. Above- and below-ground biomass accumulation, stem growth and soil respiration were measured in 2008. In addition, a (13)C-labelling experiment was conducted with gt15 trees. After the second exposure season, elevated temperature increased silver birch above- and below-ground growth and soil respiration rates. However, some of these variables showed that the temperature effect was modified by tree genotype and prevailing O(3) level. For instance, in gt14 soil respiration was increased in elevated temperature alone (T) and in elevated O(3) and elevated temperature in combination (O(3) + T) treatments, but in other genotypes O(3) either partly (gt12) or totally nullified (gt25) temperature effects on soil respiration, or acted synergistically with temperature (gt15). Before leaf abscission, all genotypes had the largest leaf biomass in T and O(3) + T treatments, whereas at the end of the season temperature effects on leaf biomass depended on the prevailing O(3) level. Temperature increase thus delayed and O(3) accelerated leaf senescence, and in combination treatment O(3) reduced the temperature effect. Photosynthetic : non-photosynthetic tissue ratios (P : nP ratios) showed that elevated temperature increased foliage biomass relative to woody mass, particularly in gt14 and gt12, whereas O(3) and O(3) + T decreased it most clearly in gt25. O(3)-caused stem growth reductions were clearest in the fastest-growing gt14 and gt25, whereas mycorrhizal root growth and sporocarp production increased under O(3) in all genotypes. A labelling experiment showed that temperature increased tree total biomass and hence (13)C fixation in the foliage and roots and also label return was highest under elevated temperature. Ozone seemed to change tree (13)C allocation, as it decreased foliar (13)C excess amount, simultaneously increasing (13)C excess obtained from the soil. The present results suggest that warming has potential to increase silver birch growth and hence carbon (C) accumulation in tree biomass, but the final magnitude of this C sink strength is partly counteracted by temperature-induced increase in soil respiration rates and simultaneous O(3) stress. Silver birch populations' response to climate change will also largely depend on their genotype composition.     

Effects of elevated concentrations of ozone and carbon dioxide on the electrical impedance of leaves of silver birch (Betula pendula) clones

Effects of elevated concentrations of tropospheric ozone ([O3]) and carbon dioxide ([CO2]) on leaves of two silver birch (Betula pendula Roth) clones were monitored for three growing seasons (1998, 1999, 2000) by means of electrical impedance spectroscopy (EIS). The field trial with open-top chambers (OTCs) was conducted on two clones (Clone 4 and Clone 80) with five treatments and four independent replicates. Treatments were: (1) outside control, (2) chamber control, (3) 2x ambient [O3], (4) 2x ambient [CO2] and (5) 2x ambient [CO2] + 2x ambient [O3]. Fumigations started in 1999 and continued in 2000. Measurements were made in 1998 before the fumigations and thereafter EIS was carried out four times in each season. The impedance spectra of about 10 leaves from each tree at each time were measured at 42 frequencies between 80 and 1 MHz. Leaf spectra were modeled by a distributed circuit element model (DCE) (one DCE in series with a resistor), which yields the extracellular and intracellular resistances, the relaxation time and the distribution coefficient of the relaxation time. The EIS properties of the leaves changed significantly during the growing season when new leaves were expanding. The clones differed in their EIS properties. Clone 4 had a significantly higher extracellular resistance and distribution coefficient than Clone 80. The clones responded similarly to the fumigation treatments. Differences between treatments emerged especially during the second fumigation season in 2000. Elevated [O3] reduced both the relaxation time and the extracellular resistance, indicating cell membrane damage. Elevated [CO2] increased the intracellular resistance, indicating changes in symplastic composition. The biological interpretation of the EIS parameters in birch leaves is discussed.     

欧洲垂桦引种繁育技术试验

为了丰富东北寒冷地区树种资源,1985年从加拿大引进欧洲垂桦在哈尔滨地区进行栽培及繁殖技术试验,结果表明:欧洲垂桦在哈尔滨地区表现出抗逆性强、易繁殖等特性,在引种地正常开花结果,说明欧洲垂桦在哈尔滨地区引种是成功的。     

垂枝桦组织培养技术研究

对垂枝桦芽茎段组织培养技术的外植体启动培养、丛生芽增殖以及试管苗生根等方面开展研究。结果表明:在1/2MS+6-BA1.00 mg.L-1+NAA0.05 mg.L-1+蔗糖30 g.L-1的培养基上,外植体诱导率最高;在1/2MS+6-BA0.20 mg.L-1+NAA1.50 mg.L-1+蔗糖30 g.L-1的培养基上,外植体增殖系数最高,可达5～8倍;在1/2MS+NAA0.50 mg.L-1+蔗糖20 g.L-1的培养基中,继代苗的生根率可达100.0%。     

Dependence of dormancy release on temperature in different origins of Pinus sylvestris and Betula pendula seedlings

The chilling requirement of rest completion and the high temperature requirement of growth initiation were determined in three origins of silver birch (Betula pendula Roth.) seedlings and five origins of Scots pine (Pinus sylvestris L.) seedlings. In both the pine and birch the chilling requirement was highest in maritime Scottish origins and lowest in the most continental Finnish and Russian origins. The requirement for southern mountainous Spanish and Bulgarian pine origins was in between. In terms of the high temperature requirement, there were no clear differences between origins. These results suggest that owing to their high chilling requirement, which prevents the beginning of growth and the loss of frost hardiness during the frost‐exposed season, origins from a maritime climate could be the most tolerant under climatic warming.     

三倍体欧洲山杨组培技术的研究

通过对三倍体欧洲山杨组培技术的研究试验，采用增殖与生根同步进行的方法进行快繁，其年增殖次数可达8次，平均每次增殖培数为4．4倍，可以达到工厂化生产的指标要求。培养出的组培苗质量好，移栽成活率高，而且可以降低苗木的成本。     

Biochemical acclimation patterns of Betula pendula and Pinus sylvestris seedlings to elevated carbon dioxide concentrations

Acclimation of photosynthesis to increasing atmospheric carbon dioxide concentration ([CO2]; 350 to 2,000 micromol mol-1) was followed in silver birch (Betula pendula Roth.) and Scots pine (Pinus sylvestris L.) seedlings for two years. Chlorophyll fluorescence and concentrations of Rubisco, chlorophyll, total soluble protein and nitrogen were monitored together with steady-state gas exchange at three CO2 concentrations (ambient [CO2] (345 +/- 20 micromol mol-1), the growth [CO2] and 1950 +/- 55 micromol mol-1). Rubisco and chlorophyll concentrations decreased in birch and Scots pine with increasing growth [CO2]. A nonlinear response was recorded for Rubisco and chlorophyll concentrations in birch, which was correlated with a significant decrease in specific leaf area. Nitrogen concentration decreased in birch leaves, but was unchanged in Scots pine needles. The species differed substantially in their steady-state CO2 exchange response to increasing growth [CO2]. The principal effect in birch was a significant nonlinear decrease in the steady-state gas exchange rate at the ambient [CO2], whereas in Scots pine the main effect was a significant increase in the steady-state gas exchange rate at the growth [CO2].     

欧洲白桦无性系苗期光合特性的比较

对2种栽培条件下欧洲白桦优良无性系1/86、2/86和本地白桦的净光合速率、蒸腾速率及相关生理指标进行了测定.结果表明:在净光合速率方面,田间栽培和盆栽方式下的本地白桦明显高于1/86、2/86,而 1/86、2/86之间则没有明显差异;田间栽培下的3种白桦相应高于盆栽条件下的净光合速率.在蒸腾速率方面,田间栽培条件下的3个白桦品种之间没有明显差异;盆栽条件下的本地白桦显著高于1/86、2/86, 而1/86、2/86之间则没有差异;田间栽培下的1/86、2/86明显高于盆栽的蒸腾速率,而本地白桦在2种栽培方式下没有差异.     

疣枝桦播种育苗技术

疣枝桦（Betula pendula Roth．），又名垂枝桦，系新疆阿尔泰山及天山特有物种，属落叶阔叶乔木。其树皮白色，树体高大，冠幅圆满，枝叶繁茂，翠绿葱郁。其树叶在入秋经霜打之后，金黄灿亮；在落叶之后，其白色树干也自成一片风景，是良好的植树造林及城市庭院绿化树种，最适宜种植成片林。由于其种子颗粒小、种皮坚硬、发芽时间长，且苗期生长慢，管理要求细致。因此，疣枝桦播种育苗需要掌握以下技术。     

欧洲白桦早期生长性状变异分析

欧洲白桦(2 a生)13个家系间的苗高性状变异较小,变异范围在22.78%～37.14%之间;家系间地径生长变异较大,而家系内地径生长变异较小,变异范围为20.15%～50.32%.方差分析结果表明:家系问2 a生苗高与地径生长均达差异显著水平.通过2 a连续测定,综合考虑苗高及地径2个性状,初步认为6号、9号、1号、10号及13号等5个家系生长表现良好,且家系内苗木高生长及地径生长变异较小,生长稳定.     

Differential responses of silver birch (Betula pendula) ecotypes to short-day photoperiod and low temperature

We investigated interrelations of dormancy and freezing tolerance and the role of endogenous abscisic acid (ABA) in the development of silver birch (Betula pendula Roth) ecotypes in controlled environments. Short-day treatment induced growth cessation, bud set and dormancy development, as well as initiation of cold acclimation and an increase in freezing tolerance. Subsequent low temperature and short days (12-h photoperiod) resulted in a significant increase in freezing tolerance, whereas bud dormancy was gradually released. The concentration of ABA increased in response to short days and then remained high, but ABA concentrations fluctuated irregularly when the dormant plants were subsequently exposed to low temperature during short days. Although there was a parallel development of freezing tolerance and bud dormancy in response to short days, subsequent exposure to low temperature had opposite effects on these processes, enhancing freezing tolerance and releasing dormancy. Compared with the southern ecotype, the northern ecotype was more responsive to short days and low temperature, exhibiting earlier initiation of cold acclimation, growth cessation and an increase in ABA concentrations in short days, and higher freezing tolerance, faster dormancy release and greater alteration in ABA concentrations when subsequently exposed to low temperature during short days. The rates and extent of the increases in ABA concentration may be related to increases in freezing tolerance and dormancy development during short days, whereas the extent of the fluctuations in ABA concentration may play an important role in enhancing freezing tolerance and releasing dormancy during a subsequent exposure to low temperature during short days.     

Effect of Temperature on the Induction of Bud Dormancy in Ecotypes of Betula pubescens and Betula pendula

The purpose of this study was to determine the influence of temperature applied during short day-induced budset on induction of dormancy in six ecotypes of Betula pubescens Ehrh. and two ecotypes of Betula pendula Roth. Seedlings were grown in a phytotron at constant temperatures of 9–21°C under a 12 h photoperiod (SD) during dormancy induction. Induction of dormancy was monitored by following bud flushing and shoot growth after transfer to long photoperiod conditions (24 h) at 18°C. Chilling requirement was studied in seedlings exposed to 10 weeks of SD. In both species induction of bud dormancy developed most rapidly at 15–18°C, and both 9–12°C and 21°C delayed the induction of dormancy. Raising the temperature (from 9 to 21°C) applied during induction of dormancy significantly increased the chilling requirement. These responses were noted for all ecotypes tested, but in general the northern ecotypes entered dormancy more quickly than the southern ones. No such trend was recorded for chilling requirement, although a B. pubescens ecotype from Iceland and another from the coast of northern Norway appeared to require a longer chilling treatment than the other ecotypes. In conclusion, induction and depth of bud dormancy in birch are significantly affected by temperature conditions and these effects may explain some of the annual variation in dormancy and chilling requirement observed in nature.     

种子处理方式对欧洲垂枝桦发芽率及苗木生长的影响

以引进的俄罗斯欧洲垂枝桦种子为材料,研究了冷藏、沙藏和雪藏3种种子处理对欧洲垂枝桦场圃发芽率及苗木生长的影响。结果表明:不同种子处理的场圃发芽率、苗高、地径、地上生物量、地下生物量和全株生物量存在显著差异,种子雪藏处理的场圃发芽率、苗高、地径、地上生物量、地下生物量和全株生物量等指标均优于其他处理,其场圃发芽率、生长量和生物量最高。     

欧洲垂枝桦不同种源种子形态及萌发特性研究

以引进俄罗斯欧洲垂枝桦不同种源种子为材料,对不同种源种子形态及其萌发特性进行研究的结果表明:不同种源种子吸水量没有显著差异,而在种长、种宽、种厚、翅长、翅宽、千粒重、含水率、生活力、发芽率、发芽势和发芽指数存在显著差异;新西伯利亚种源种子最大、质量最重、发育最好、有生活力种子高达82.75%;采用混雪冷藏处理种子萌发能力最强,新西伯利亚种源种子发芽率、发芽势、发芽指数分别达到67.63%、55.41%、27.19;而对照种源采用低温冷藏处理种子萌发效果最差,其发芽率、发芽势、发芽指数分别为38.51%、32.42%、11.89。     

Micropropagation of a mature colchicine-polyploid and irradiation-mutant of Betula pendula Roth

Tetraploid plantlets were regenerated from cultured apical and axillary buds of a 23-year-old colchicine-polyploid and irradiation-mutant Betula pendula Roth tree. Bud explants were grown on modified Murashige and Skoog medium supplemented with 2.0 mg l(-1) benzylaminopurine (BAP) and 0.01 mg l(-1) 1-naphthaleneacetic acid (NAA). The medium allowed both induction of adventitious buds and development of shoots. The cut ends of new shoots produced new buds and shoots during a 4-week culture period. The micropropagated shoots were rooted on modified Murashige and Skoog medium containing 0.1 mg l(-1) NAA as the sole growth regulator. Plantlets were transferred to a peat/soil mixture (1:1) in the greenhouse, acclimated and then transplanted to a cold frame. The regenerated plantlets had a tetraploid chromosome set (4n = 56) and an altered leaf morphology typical of colchicine-polyploid birches. The leaves were hypertrophied and asymmetrical, with curly leaf margins. The mutant nature of the parent tree was also evident in the light-green color of the leaves of the plantlets.     

Genetic stability analysis of introduced Betula pendula,Betula kirghisorum,and Betula pubescens families in saline-alkali soil of northeastern China

Approximately, 20% of arable land worldwide, as well as nearly half of irrigated land, is subjected to salt stress. Osmotic stress and ion toxicity due to saline soils cause low crop yields. In this study, we introduced 18 families of salt-tolerant birch (Betula pendula Roth., Betula kirghisorum Sav.-Ryczg., and Betula pubescens Ehrh) into five high-salinity locations in northeastern China and evaluated their survival abilities. We also analyzed variation and stability of genotype–environment interactions of the different families under an additive main effect and multiplicative interaction model. Survival rate analysis indicated that the introduced families were well adapted to the high-salinity environments, whereas native families died. Variation analysis revealed significant differences between location × family interaction mean values for height and basic stem diameter (BSD), suggesting that most genotypes responded differently to different sites. The heritability of tree height and BSD at different sites varied from 0.416 to 0.940, with the coefficient of phenotypic variation ranging from 9.88% to 35.53%. Stability analysis indicated that some families had high tree heights but were sensitive to environmental conditions, whereas others were resistant but had average tree heights. These results suggest that families should be bred in various habitats to assess growth under favorable and unfavorable environments.     

Genotypic variation in drought response of silver birch (Betula pendula): leaf water status and carbon gain

To assess genotypic variation in drought response of silver birch (Betula pendula Roth), we studied the plasticity of 16 physiological traits in response to a 12-14-week summer drought imposed on four clones in two consecutive years. In a common garden experiment, 1-year-old clonal trees from regions with low (550 mm year(-1)) to high rainfall (1270 mm year(-1)) were grown in 45-l pots, and leaf gas exchange parameters, leaf water potentials, leaf osmotic potentials and leaf carbon isotope signatures were repeatedly measured. There were no clonal differences in leaf water potential, but stomatal conductance (gs), net photosynthesis at ambient carbon dioxide concentration, photosynthetic water-use efficiency, leaf carbon isotope composition (delta13C) and leaf osmotic potentials at saturation (Pi0) and at incipient plasmolysis (Pip) were markedly influenced by genotype, especially gs and osmotic adjustment. Genotypes of low-rainfall origin displayed larger osmotic adjustment than genotypes of high-rainfall origin, although their Pi0 and Pip values were similar or higher with ample water supply. Genotypes of low-rainfall origin had higher gs than genotypes of high-rainfall origin under both ample and limited water supply, indicating a higher water consumption that might increase competitiveness in drought-prone habitats. Although most parameters tested were significantly influenced by genotype and treatment, the genotype x treatment interactions were not significant. The genotypes differed in plasticity of the tested parameters and in their apparent adaptation to drought; however, among genotypes, physiological plasticity and drought adaptation were not related to each other. Reduction of gs was the first and most plastic response to drought in all genotypes, and allowed the maintenance of high predawn leaf water potentials during the drought. None of the clones exhibited non-stomatal limitation of photosynthesis. Leaf gs, photosynthetic capacity, magnitude of osmotic adjustment and delta13C were all markedly lower in 2000 than in 1999, indicating root limitation in the containers in the second year.     

Growth,stem quality and nutritional status of Betula pendula and Betula pubescens in pure stands and mixtures

The growth, technical quality and nutritional status of pure and mixed silver birch (Betula pendula Roth) and downy birch (Betula pubescens Ehrh.) plantations were studied 21 and 22 years after planting on afforested organic soil arable land and on upland forest soil. In mixtures, 50% of both birch species was planted. Silver birch trees grew better, but had higher mortality than downy birch trees on both sites. Mortality of both species was highest, and the difference in their growth smallest, on organic soil. In pure stands on organic soil, downy birch dominant height, diameter and mean volume were 96%, 92% and 82% of those of silver birch and on mineral soil 87%, 84% and 60%, correspondingly. On mineral soil, silver birch had a higher mean annual increment (MAI) (5.8 m³ ha^?1a^?1) than downy birch (3.9 m³ ha^?1a^?1), but on organic soil the MAI of both species was similar (3.3–3.4 m³ ha^?1 a^?1). Planting birches in mixture did not affect the growth of the trees on organic soil. On mineral soil, the mean diameter and mean volume of silver birch trees were higher in mixed than in pure plantations. The technical stem quality of both tree species was low. On mineral soils, pure silver birch is more productive than mixture, but on peat soil the higher growth of silver birch could contribute to increased productivity and downy birch would ensure sufficient survival for future timber production.     

Effects of dormancy and environmental factors on timing of bud burst in Betula pendula

We tested three theories predicting the timing of bud burst in mature birch (Betula pendula Roth) trees utilizing a 60-year phenological time series together with meteorological temperature observations. Predictions of the timing of bud burst based on light conditions in addition to temperature were more accurate than predictions based on dormancy development and temperature (prediction standard error of 2.4 days versus 4.3 days). The signal from light conditions, represented by fixed calendar date, determined the start of bud ontogenesis rather than dormancy release. We suggest that models developed to predict the timing of bud burst be utilized in the analysis of plant responses to climate change and of climate change itself.