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.     

产地和萌发温度对胡枝子种子萌发的影响

以3个不同产地的胡枝子种子为材料,研究产地和萌发温度条件对种子萌发的影响,结果表明:产地对胡枝子种子的发芽指数无明显影响,但对种子发芽率和平均发芽时间均有极显著影响;其中黑龙江帽儿山产地种子的发芽率最高,发芽时间也最长;内蒙古扎兰屯产地种子发芽率和发芽时间居中;吉林蛟河产地种子发芽率最低,发芽时间却最短.萌发温度条件对胡枝子种子的发芽率、发芽指数和发芽时间均有极显著影响.15℃条件下种子的发芽率最高,20℃条件下种子的发芽指数最高,25℃条件下种子的平均发芽时间最短,30℃条件下种子各项发芽指标最差.产地与萌发温度的交互作用对种子发芽率和发芽指数影响不显著,但对种子发芽时间有极显著影响.     

Effects of moist chilling and solid matrix priming on germination of loblolly pine (Pinus taeda L.) seeds

Loblolly pine (Pinus taeda L.) seeds from sources with a mild climate under maritime influence (North Carolina) required shorter moist chilling to achieve maximum germination vigor than seeds from sources with a harsher continental climate (Oklahoma). Solid matrix priming (SMP) for 6 d achieved as much as 60 d of moist chilling to improve rapidity, synchrony and completeness of germination for three of the four families studied. SMP after moist chilling increased the rapidity, synchrony and completeness of germination. The benefit of SMP was greatest for non-stratified seeds and the benefit decreased with length of moist chilling. In general, delaying planting for one week after SMP had minor effects on germination when seeds were kept in the SMP matrix at 4°C. Delayed planting after SMP can increase germination rapidity and synchrony of seeds that have received long moist chilling and reduce the benefit of SMP in non-moist-chilled seeds.     

Current growth differences of Norway spruce (Picea abies), Scots pine (Pinus sylvestris) and birch (Betula pendula and Betula pubescens) in different regions in Sweden

Abstract

The choice of species in forestry is important, and a real issue as large areas of wind-damaged forest land in southern Sweden need to be regenerated. To compare the growth potential between the most common tree species in Sweden, ratios between site quality derived from site index values determined with site properties were used. A regression function to determine site index for birch from site properties was used to complement the known relationships between site properties and site index for spruce and pine. In large regions of Sweden the distribution of site quality classes was calculated to compare the special characteristics and demands of the three species. On average, the growth difference for pine compared to spruce was about 60% in southern Sweden and 95% in northern Sweden. Corresponding figures between birch and spruce were 40% and 60%. Birch was expected to produce around 60% of pine in northern Sweden and about 70% in southern Sweden. However, it must be stressed that the comparison is based on survey data encompassing mainly naturally regenerated birch, whereas spruce and pine are mainly planted.     

温度和光照对多花黄精种子萌发的影响

为了解多花黄精种子的萌发特性,探索其种子萌发的最适宜条件,以年珠林场收集的多花黄精种子为研究材料,开展其种子形态测定以及温度和光照对其种子萌发特性影响的研究。结果表明：温度对多花黄精种子发芽率、发芽势、发芽指数和平均发芽时间的影响达到显著水平;在10℃～35℃范围内,随着温度的升高,种子的发芽率、发芽势和发芽指数均呈现先增加后减小的趋势,而平均发芽时间则呈现先减小后增加的趋势;当温度为25℃时,种子发芽率、发芽势和发芽指数最高,分别为93.4%、70.1%和48.5,平均发芽时间最低为11.4 d。光照对多花黄精种子发芽率、发芽势、发芽指数和平均发芽时间的影响不显著。试验结果为多花黄精栽培育苗提供技术支持和理论支撑。     

Effect of seed coverings and seed pretreatments on the germination response of <Emphasis Type="Italic">Alnus glutinosa</Emphasis> and <Emphasis Type="Italic">Betula pubescens</Emphasis> seeds

The germination of common alder (Alnus glutinosa (L.) Gaertn.) and downey birch (Betula pubescens Ehrh.) seeds is often poor in bare-root nurseries. The effect of a variety of seed coverings and a few seed pretreatments on seedling emergence was examined in this study in an attempt to address this problem. Seeds of each species were sown in trays containing nursery soil, covered with grit, gravel, sand, combinations of these coverings, a hydromulch or a sealed plastic cloche and then incubated for 6 weeks at 17–20°C. The grit combined with sand or gravel, the hydromulch and the cloche increased seedling emergence when compared with the standard grit. In another experiment, seeds of each species were fully imbibed (FI) (>50% moisture content, MC), as per standard practice, or adjusted to target MC (TMC) (30–35% MC) levels, and then chilled to release dormancy. Some seeds of each MC treatment were primed at 20°C for 2 days following chilling, after which all seeds were evaluated in laboratory tests and a nursery trial. Germination potential of the FI seeds declined in the lab tests by the second test date, which was reflected in low seedling emergence in the nursery in birch. The primed FI seeds of alder germinated most rapidly in the nursery, but other effects were not significant. Seedling emergence was better in the nursery in response to the TMC than the FI pretreatment in birch.

Effects of seed moisture content,stratification and sowing date on the germination of Corylus avellana seeds

For Corylus avellana, pericarp permeability,seed desiccation tolerance, and the effect of warm and cold moist stratification combinations on germination and of outdoor sowing date on dormancy breaking and seedling emergence were investigated. Seeds with(intact fruit nut)and without the pericarp were subjected to an imbibition test, and water uptake was measured. After nuts had been stored for 5 months at 3–5℃, seeds and desiccated seeds were cold-stratified at 3–5 ℃(for 0, 1, 2 or 3 months),then tested for germination. Nuts were warm-stratified at 20–25℃(for 0, 1 or 2 months), then cold-stratified(for 0,1, 2 or 3 months) and tested for seed germination. The nuts were sown outdoors on three dates in the same year of their collection: 15 September(immediately after collection), 2 November, and 17 December, and emerged seedlings were counted the following spring. The pericarp was not a barrier to water uptake by the seed;however, the seeds imbibed water faster and had more mass when the pericarp was removed. Seeds tolerated desiccation;germinationpercentage was not reduced when seed moisture content was reduced to 8.71%. Germination of seeds without the pericarp(regardless of the moisture content) was the highest when the seeds were cold-stratified for 2 months.When seeds with the pericarp were tested for germination,2 months of warm stratification before a 2-month cold stratification maximized seed germination. For outdoor sowing of nuts, sowing date affected percentage of seedling emergence the following spring;early autumn sowing(immediately after collection) resulted in the best emergence.     

赤霉素浸种与低温层积对桂花种子发芽的影响

对桂花种子进行了层积前赤霉素浸种与低温层积相结合的催芽试验。结果表明，桂花种子具有休眠特性，低温层积能够增进桂花种子萌发。层积前用赤霉素浸泡促进桂花种子萌发的作用明显，试验以3000mg／L赤霉素浸泡2天和2000mg／L赤霉素浸泡2天或4天最好，极显著或显著地高于其它处理组合。赤霉素浸泡必须与低温层积相结合，其作用效果才能发挥，试验中以层积60天最好。清水浸泡促进萌发的效果不明显。     

Effects of seed water content and storage temperature on the germination parameters of white spruce, black spruce and lodgepole pine seed

The effect of seed water content (WC) (2–3, 5–6 and 22–25%, on a fresh weight basis), storage temperature (+4, −20, −80 and −196°C) and storage duration (6, 12, 24, 48 and 60 months) on the germination of white spruce (Picea glauca (Moench) Voss), black spruce (Picea mariana (Mill.) B.S.P.) and lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) seed was investigated. Germination of white spruce control (untreated) seeds and seeds adjusted to 2–3% and 5–6% WC declined after 48 months of storage at −80 and −196°C, with a further decline at 60 months at −20, −80, −196°C. Germination remained high when control white spruce seeds and seeds with 2–3, 5–6% WC were stored at +4°C, over all storage durations. Generally, black spruce and lodgepole pine exhibited high germination at all storage temperatures at 2–3% and 5–6% WC as well as the control (untreated) seed, for up to 60 months in storage. Germination declined for all three species when seed was conditioned to 22–25% WC. This loss in germination was partially recovered in white spruce seed stored at +4, −20 and −80°C after storage durations of 24, 12 and 48 months, respectively, and in black spruce seeds stored at −20 and −196°C after storage durations of 24 months. Mean germination time (MGT) was relatively constant for all species, under all conditions, except for seed conditioned to 22–25% WC, where MGT increased for white spruce seed stored 48 months at −80 and −196°C, and for black spruce seed stored 24 months at +4 and −80°C and 60 months at −196°C. These results show that the optimal storage temperatures are 4°C for white spruce, and 4, −20, −80, and −196°C for black spruce and lodgepole pine, and 2–6% water content is optimal for all 3 species at these temperatures.     

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.     

Seasonal changes in contents of root starch and soluble carbohydrates in 4–6‐year old Betula pubescens and Popuius tremula

Roots of 4–6‐year old European aspen and pubescent birch were collected monthly during 1983–87 and 1983–88, and analysed to determine their starch, fructose and glucose concentration. Carbohydrate concentrations in aspen roots fluctuated with low levels in May‐June. Seasonal variation was not as consistent in birch roots as in aspen roots. The drop during May‐June occur as consistently in birch. Total carbohydrate concentrations in roots of birch collected from six latitudes (56–67°N) in Sweden showed similar patterns of variation. There were no significant difference between starch concentrations among roots of different diameters (2–11 mm), nor did concentrations differ between sites at different distances (5–25 cm) from the main stem. It was difficult to visually differentiate between low and medium starch levels. Some practical implications of the results are discussed     

Seed germination and seedling establishment of Neotropical dry forest species in response to temperature and light conditions

A study was conducted to examine the germination requirements of Cedrela odorata, Guaiacum sanctum and Calycophyllum candidissimum seeds, and the effect of light intensity on survival and growth of C. Odorata and G. Sanctum seedlings planted on open, partially-open and beneath the canopy of a dry forest in Nicaragua. The results show that germination of C. Candidissimum seeds was significantly higher in light than darkness at constant temperatures ranging from 20–35oC. Both C. Odorata and G. Sanctum seeds germinated in light and darkness to a varying extent, and the optimal germination temperature was around 20-25oC. Alternating temperature regimes did not improve germination. Survival of G. Sanctum seedlings was 70% beneath the canopy and 80% in the open, and its relative growth rate in collar diameter was 1.88 mm/month in the open and 1.42 mm/month in the understory. Survival was generally poor for C. Odorata, particularly in the understory. We concluded that light is an absolute requirement for the germination of C. Candidissimum seeds while germination of C. Odorata and G. Sanctum seeds are more sensitive to temperature. Owing to its high survival rate on open site, G. Sanctum could serve as a candidate species for reforestation of degraded sites.     

Prediction of individual tree growth in managed stands of mixed Picea abies (L) Karst,and Betula pendula Roth & Betula pubescens Ehrh.

The individual tree growth in stands of mixed Norway spruce (Picea abies (L.) Karst.) and birch (Betula pendula Roth & Betula pubescens Ehrh.) is estimated using basal area and height growth functions for each species separately. The individual tree growth models are distant dependent and the number, size and proximity of neighbours are expressed as size‐ratio competition indices. The competition indices were calculated using a basal area factor gauge to define competitors. The tree growth functions are based on data from nine mixed stands of Norway spruce and birch. The recursive multivariate regression approach is used. The growth functions have standard deviation about the function/standard deviation about the mean (sf/sm) values between 31 and 61% and the evaluations made with root mean square error (rmse) give estimates which vary between 8 and 45 % of the observed mean value. These values are comparable with the precision reported in other studies. In the present investigation the distant dependent indices are important independent variables. It seems suitable to describe the change in growth conditions from retarded to released growth by means of size ratio competition indices. For birch, a positive effect on growth is obtained the more the total competition consists of Norway spruce. For Norway spruce a negative effect on growth is obtained the more the total competition consists of Norway spruce. The lower competitors have a positive effect on the growth of the spruce trees. The interpretation should be that it is better to have a small competitor than a larger one, not that small competitors as such have a positive effect on growth of Norway spruce.     

池杉“种子包”日光变温催芽育苗试验

采用无毒透明塑料薄膜“种子包”拌砂日光变温催芽育苗,可节省种子50％以上,发芽进程缩短一个多月,密度均匀,苗木整齐,粗壮,1年生苗高、粗生长量分别是对照苗的125.9％和127.4％。     

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.     

The influence of heterogeneous habitats on the germination ofAcanthopanax senticosus seeds and the dynamics of its seed pool

Differences in germination ofA. Senticosus, an important shrub under the Korean Pine broad-leavd forest and its secondary forest in heterogeneous habitats and the dynamics of its seed pool have been studied by observations in location. The results showed that transformation rates from seeds to seedlings were in the following order: 16.8% in Larch plantations, 4.1% in Mongolian oak forests, 2.7% in Birch forests, 1.8% in Korean Pine plantations, and 0.5% in hard wood forests. The life-span of seeds was determined to be four years in the simulating seed pool under Larch plantations. The percentage of the seedling output was, 14.5% in the 2nd year, 10.1% in the 3rd year, and 1.8% in the 4th year. Other types of the seed output were those: decayed 33.1%, senescent, 22.3%, predated by mice 14.1%, which was variable due to the variation in the number of mouse, and only 1.17% were eaten by insects and ofher soil animals. The project was supported by National Science Foud of China     

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.     

Variability in height growth,survival and nursery carryover effect of Betula papyrifera provenances

Eleven paper birch (Betula papyrifera Marsh.) provenances from a single geographic region in northern Idaho and four geographic regions in British Columbia (BC) were studied to determine whether morphometric variability was due to species' genetics, growing environment, or their interaction. Seedlings were grown at three nurseries in BC and Idaho and planted in a randomised single-tree interlocking block design at Skimikin (50°47′) and Red Rock (53°45′) common gardens in BC. Geographic variation in birch height growth was regulated by genetics and a complex interaction with environmental factors. Growth does not follow latitudinal, longitudinal or elevational clines although provenances at the southern garden showed better height growth compared to the northern garden. Greater percentages of seedling mortality were observed at the northern garden compared to provenances planted at the southern garden. Birch height growth was significantly influenced by nursery displacement effects up to four years after establishment. The safe range of southward seed-transfer distance may be as much as 5°, and beyond this limit a detrimental effect likely occurs. Collectively, these results suggest that a provenance best suited to one environment might not be the best for another environment. However, these findings will be useful in understanding the genecology of paper birch when establishing operational seed-transfer guidelines in BC.     

Effect of different seed treatments on dormancy breaking and germination in three species in arid and semi-arid lands

Seeds of many woody plant species have one of several types of dormancy. They do not germinate unless specific environmental signals are in place or events occur. This study was conducted to evaluate the effects of scarification treatments on seed dormancy and germination of Acacia nilotica (L.) Willd. ex Del., Prosopis juliflora (Sw.) DC. and Dodonaea viscosa (L.) Jacq. The following treatments were applied: T1, untreated seed (control); T2, sulphuric acid (97%) for 45 min; T3, boiling water for 5 min. The seeds were cultured on a Murashige and Skoog (MS) medium after sterilization. The responses of seeds to treatments were compared with each other and with the control treatment. Germination was observed daily for a 30-day period. Results indicated positive responses to treatments, while impermeable seed coats may be responsible for low germination rates in intact seeds as seen experimentally in the untreated control. The highest germination was obtained for P. juliflora and D. viscosa acid-scarified seeds (80.8%-90.8%) and for scarified seeds of A. nilotica (50.2%) boiled in water. The germination indices, i.e., final germination percentage (FG), mean daily germination (MDG) and germination rate (GR), were significantly affected by treatments and species (p<0.01).     

Seasonal changes in bud dormancy in relation to bud morphology, water and starch content, and abscisic acid concentration in adult trees of Betula pubescens

Annual cycles of change in bud morphology, bud burst ability, abscisic acid (ABA) concentration, and starch and water content were studied in mid-crown terminal buds of short shoots and underground basal buds of Betula pubescens Ehrh. In particular, we investigated the roles of ABA and bud water content in the regulation of bud growth. Basal buds differed morphologically from terminal buds of short shoots in that their leaf initials did not develop into embryonic foliage leaves and their total size did not increase significantly during summer. Bud burst ability, measured by forcing detached short shoots and stumps under controlled conditions, was maintained in the basal buds throughout the year, whereas the terminal buds of short shoots remained dormant until October, thereafter their bud burst ability increased gradually and reached a maximum in March-April. The ABA concentration of the basal buds was relatively constant throughout the sampling period (1-3 micro g g(DW) (-1)), whereas that of the terminal buds of short shoots, which was much higher (5-10 micro g g(DW) (-1)), showed a distinct seasonal cycle with a maximum from August to November. Bud ABA concentration decreased during the first 10 days of forcing, especially in basal buds. In both bud types, the amount of starch increased toward the autumn, declined in November, and was negligible in the terminal buds of short shoots between January and March, but in April, the amount was high again in both bud types. Water content varied characteristically in both bud types, although more distinctly in the terminal buds of short shoots, with an increase in spring before bud burst and a decrease during the summer until September. The significant morphological and physiological differences between the mid-crown terminal buds of short shoots and the underground basal buds may partly explain the characteristic growth habit of the basal buds and their development into coppice shoots after cutting the tree. The results also indicate a role for ABA in maintaining dormancy of the terminal buds of short shoots and emphasize the relationship between tissue water status and ABA concentration.