Growth responses and related biochemical and ultrastructural changes of the photosynthetic apparatus in birch (Betula pendula) saplings exposed to low concentrations of ozone

Saplings of ozone-sensitive and ozone-tolerant birch (Betula pendula Roth.), clones B and C, respectively, were exposed to ozone concentrations that were 1.7-fold higher than ambient for one growing season under open-field conditions. Ambient air was used as the control treatment. In the ozone-sensitive clone B, there was an initial stimulation of leaf area growth in response to the ozone treatment, but further ozone exposure caused reductions in leaf and stem biomass growth, Rubisco and chlorophyll a contents, net photosynthesis, water use efficiency and chloroplast size. It also caused an alteration in chloroplast shape and injury to thylakoid membranes. In the ozone-tolerant clone C, ozone fumigation did not affect growth rate, and there were no consistent changes in chlorophyll content, photosynthesis or water use efficiency. There were also fewer ultrastructural abnormalities in the chloroplasts of clone C than of clone B. Based on the observed biochemical, physiological and structural changes in chloroplasts of clone B in response to low concentrations of ozone, we conclude that the increasing concentration of tropospheric ozone represents a risk to natural birch populations.     

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.     

Physiological and morphological responses of olive plants to ozone exposure during a growing season

We studied physiological (gas exchange and stomatal aperture) and morphological (individual leaf area and stomatal density) responses in leaves of five-year-old olive plants (Olea europaea L. cvs. Frantoio and Moraiolo) exposed to filtered air containing < 3 ppb O(3) or 100 ppb O(3) for 5 h day(-1) for 120 days in fumigation chambers. After 100 days of treatment, leaf drop and development of necrotic spots were observed in O(3)-fumigated plants of Moraiolo but not of Frantoio. Significant reductions in photosynthetic activity (57%) and stomatal conductance (69%) were detected in O(3)-fumigated plants of Frantoio compared with control plants. In O(3)-fumigated plants of Moraiolo, the decrease in photosynthetic activity (17%) was not statistically significant, but a significant reduction in stomatal conductance (40%) was observed. In both cultivars, leaves that developed after exposure to O(3) showed decreased stomatal aperture (63.6 and 54.8% with respect to the Frantoio and Moraiolo controls, respectively) and one-sided leaf area, and increased stomatal density compared with control leaves. Actual transpiring stomatal surface decreased substantially in both Frantoio (59.8%) and Moraiolo (56.3%) in response to O(3) treatment. Relative transpiring stomatal surface (RTSS) in Frantoio decreased from 0.54 (control) to 0.27% (O(3) treated) of total leaf surface. The corresponding values for Moraiolo were 0.79 and 0.42%. However, because the RTSS of Moraiolo leaves in the O(3) treatment was 0.42 versus 0.27% in Frantoio, the potential uptake of O(3) was higher for Moraiolo plants than for Frantoio plants. The large O(3)-induced reduction in transpiring stomatal surface in both cultivars could have significant effects on olive productivity in the Mediterranean area, where high O(3) concentrations persist for long periods during the year.     

Long-term photosynthetic acclimation to increased atmospheric CO(2) concentration in young birch (Betula pendula) trees

To study the long-term response of photosynthesis to elevated atmospheric CO(2) concentration in silver birch (Betula pendula Roth.), 18 trees were grown in the field in open-top chambers supplied with 350 or 700 &mgr;mol mol(-1) CO(2) for four consecutive growing seasons. Maximum photosynthetic rates, stomatal conductance and CO(2) response curves were measured over the fourth growing season with a portable photosynthesis system. The photosynthesis model developed by Farquhar et al. (1980) was fitted to the CO(2) response curves. Chlorophyll, soluble proteins, total nonstructural carbohydrates, nitrogen and Rubisco activity were determined monthly. Elevated CO(2) concentration stimulated photosynthesis by 33% on average over the fourth growing season. However, comparison of maximum photosynthetic rates at the same CO(2) concentration (350 or 700 &mgr;mol mol(-1)) revealed that the photosynthetic capacity of trees grown in an elevated CO(2) concentration was reduced. Analysis of the response curves showed that acclimation to elevated CO(2) concentration involved decreases in carboxylation efficiency and RuBP regeneration capacity. No clear evidence for a redistribution of nitrogen within the leaf was observed. Down-regulation of photosynthesis increased as the growing season progressed and appeared to be related to the source-sink balance of the trees. Analysis of the main leaf components revealed that the reduction in photosynthetic capacity was accompanied by an accumulation of starch in leaves (100%), which was probably responsible for the reduction in Rubisco activity (27%) and to a lesser extent for reductions in other photosynthetic components: chlorophyll (10%), soluble protein (9%), and N concentrations (12%) expressed on an area basis. Despite a 21% reduction in stomatal conductance in response to the elevated CO(2) treatment, stomatal limitation was significantly less in the elevated, than in the ambient, CO(2) treatment. Thus, after four growing seasons exposed to an elevated CO(2) concentration in the field, the trees maintained increased photosynthetic rates, although their photosynthetic capacity was reduced compared with trees grown in ambient CO(2).     

Isolation of genes up-regulated by copper in a copper-tolerant birch (Betula pendula) clone

Suppression subtractive hybridization (SSH) was used to isolate genes differentially expressed following exposure to copper (Cu) in a naturally selected Cu-tolerant birch (Betula pendula Roth.) clone originating from a disused lead/zinc smelter. Of the 352 cDNA fragments initially isolated, 108 were up-regulated by Cu, of which 55 showed over twofold induction by macroarray analysis. Searches against protein databases (Blastx) and sequence analysis provided the tentative identity of 21 genes. Three fragments lacked homology to any sequences in the databases. Most of the identified genes are involved in cellular transport, regulation or cell rescue and defense. Several genes have not previously been reported to be up-regulated by Cu, e.g., plasma intrinsic protein 2, glutamine synthetase and multi-drug resistance-associated protein (MRP4). The expression of MRP4, a vacuolar sorting receptor-like protein and an unidentified gene was studied in more detail by quantitative real-time PCR. These genes showed stronger up-regulation by Cu in the roots and shoots of the Cu-tolerant birch clone compared with a less tolerant clone. Clear clonal differences in gene expression were observed, e.g., for the regulator of chromosome condensation family protein, DnaJ protein homolog, vacuolar sorting receptor-like protein and MRP4. These findings contribute to our understanding of Cu tolerance in birch, a pioneer plant in metal-contaminated soils.     

Nitrogen and phosphorus leaching and uptake by container birch seedlings (Betula pendula Roth) grown in three different fertilizations

Leaching of nitrogen (N) and phosphorus (P) through container peatmedium and N and P uptake by seedlings were determined in commercial productionof birch grown with three different types of fertilization. Half of the amountof nutrients was premixed into the peat medium and the other half was appliedasliquid (=fertigated) in the treatment (PF) commonly used in Finland. In twoother treatments all nutrients, either totally (P-VN) or partly (P-N) inslow-release form, were premixed into the peat. Independently of the treatment,the largest proportion (60 to 80%) of total N leached during May and June.During two growing seasons, the amounts of N leached from PF treatments (9 to36kg ha^–1) were as large as the amounts of Nleachedfrom P-VN and P-N treatments (24 to 46 kg ha^–1).Due to fertigations between container trays, however, the total N load perhectare was greatest in the PF treatments. In the soil water 0.5meter beneaththe container area, the N concentration varied from 10 to 60 mgl^–1. The morphological and chemical properties of theseedlings did not differ greatly between treatments.     

Variations in phenology and growth of European white birch (Betula pendula) clones

Phenology can have a profound effect on growth and climatic adaptability of northern tree species. Although the large interannual variations in dates of bud burst and growth termination have been widely discussed, little is known about the genotypic and spatial variations in phenology and how these sources of variation are related to temporal variation. We measured bud burst of eight white birch (Betula pendula Roth) clones in two field experiments daily over 6 years, and determined the termination of growth for the same clones over 2 years. We also measured yearly height growth. We found considerable genetic variation in phenological characteristics among the birch clones. There was large interannual variation in the date of bud burst and especially in the termination of growth, indicating that, in addition to genetic effects, environmental factors have a strong influence on both bud burst and growth termination. Height growth was correlated with timing of growth termination, length of growth period and bud burst, but the relationships were weak and varied among years. We accurately predicted the date of bud burst from the temperature accumulation after January 1, and base temperatures between +2 and -1 degrees C. There was large clonal variation in the duration of bud burst. Interannual variation in bud burst may have important consequences for insect herbivory of birches.     

Seasonal and within-stem variations of neutral lipids in silver birch (Betula pendula) wood

Neutral lipids were analyzed in stem wood of a 7-year-old clone and in five 35-70-year-old mature trees of silver birch (Betula pendula Roth). In young trees and in mature wood of old trees, the free fatty acid fraction comprised less than 5% of the concentration of triacylglycerols (TG). The concentration of free linoleic acid was lowest in March when the young trees were dormant and highest during midsummer and September. In mature trees, the TG concentration increased toward the pith, indicating that living parenchyma cells close to the pith have a large TG storage capacity. The TG concentration (mean 0.51 +/- 0.02% of wood dry mass) remained constant throughout the year in young trees, whereas the concentration of beta-sitosterol, the dominant free sterol (mean 82.5 +/- 0.4% of total free sterols), decreased during spring and early summer when the temperature gradually increased, and increased during autumn when the trees became dormant. In young trees, we detected a seasonal interconversion between the free and esterified forms of beta-sitosterol and campesterol, and within the steryl ester fraction between squalene and betulaprenol-7. The concentration of esterified sterols/isoprenoids was exceptionally high, especially in the inner regions of mature stem wood (mean 0.6 +/- 0.03% of wood dry mass). No heartwood formation was detected.     

Photosynthesis and canopy characteristics in genetically defined families of silver birch (Betula pendula)

Net photosynthetic rates (A) of leaves in upper and lower crown layers (A(upper) and A(lower)), leaf area index (LAI), mean tilt angle (MTA), several leaf characteristics, and volume growth were observed in fast- and slow-growing families of a 14-year-old full-sib and half-sib family progeny test of Betula pendula Roth. Each measure of net photosynthetic rate was calculated after correcting measured net photosynthesis for the effects of environmental variables. The differences in A(upper) and LAI among families were significant. The proportions of the total variance assigned to family for A(upper), A(lower) and LAI were 33.64, 28.93 and 54.99%, respectively. The mean A(upper) and LAI of the fast-growing families were significantly higher than those of the slow-growing families, whereas the mean A(lower) of the fast-growing families was significantly lower than that of the slow-growing families. There were also significant differences among families in leaf size, leaf shape, and the ratios leaf fresh weight/area and leaf dry weight/area. Between 27.55 and 54.55% of the total variance in these characteristics could be assigned to the family effect. Volume growth was positively correlated with A(upper) and LAI, but it was most strongly correlated with A(upper) x LAI.     

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.     

Early developmental responses of mountain birch (Betula pubescens subsp. czerepanovii) seedlings to different concentrations of phosphorus

Phenolic compounds, identified by high performance liquid chromatography (HPLC), and growth were investigated in the first true leaves, cotyledons, stems and roots of 2.5-week-old seedlings of mountain birch (Betula pubescens subsp. czerepanovii (Orlova) H?metahti) grown with 1.5, 15 and 50 ppm phosphorus (P). Phenolic compounds in seeds and unfertilized 6-day-old seedlings were also studied. Seeds contained few phenolics, but had an abundance of condensed tannins. There were fewer HPLC phenolic compounds in 6-day-old seedlings than in 2.5-week-old seedlings. In 2.5-week-old seedlings, growth of the first true leaves, but not of other plant parts, was affected by P regime. In the first true leaves and stems, the concentration of condensed tannins was significantly affected by P, being higher at 1.5 ppm than at higher concentrations. The concentration of total HPLC phenolics was significantly affected by P only in stems.     

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.     

Ethylenediurea (EDU) effects on hybrid larch saplings exposed to ambient or elevated ozone over three growing seasons

Ground-level ozone (O3) pollution is a persis-tent environmental issue that can lead to adverse effects on trees and wood production,thus indicating a need for forestry interventions to mediate O3 effects.We treated hybrid larch (Larix gmelinii var.japonica × L.kaempferi)saplings grown in nutrient-poor soils with 0 or 400 mg L-1 water solutions of the antiozonant ethylenediurea(EDU0,EDU400) and exposed them to ambient O3 (AOZ;08:00-18:00 ≈ 30 nmol mol-1) or elevated O3 (EOZ;08:00-18:00≈ 60 nmol mo1-1) over three growing sea-sons.We found that EDU400 protected saplings against most effects of EOZ,which included extensive visible foliar injury,premature senescence,decreased photosyn-thetic pigment contents and altered balance between pig-ments,suppressed gas exchange and biomass production,and impaired leaf litter decay.While EOZ had limited effects on plant growth (suppressed stem diameter),it decreased the total number of buds per plant,an effect that was not observed in the first growing season.These results indicate that responses to EOZ might have implications to plant competitiveness,in the long term,as a result of decreased potential for vegetative growth.However,when buds were standardized per unit of branches biomass,EOZ significantly increased the number of buds per unit of biomass,suggest-ing a potentially increased investment to bud development,in an effort to enhance growth potential and competitiveness in the next growing season.EDU400 minimized most of these effects of EOZ,significantly enhancing plant health under O3-induced stress.The effect of EDU was attributed mainly to a biochemical mode of action.Therefore,hybrid larch,which is superior to its parents,can be significantly improved by EDU under long-term elevated O3 exposure,providing a perspective for enhancing afforestation practices.     

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.     

Monolignol oxidation by xylem peroxidase isoforms of Norway spruce (Picea abies) and silver birch (Betula pendula)

We partially purified peroxidase isoform fractions from xylem extracts of a gymnosperm, Norway spruce (Picea abies (L.) Karst.), and an angiosperm, silver birch (Betula pendula Roth.), to determine the participation of xylem-localized peroxidases in polymerization of different types of lignin in vivo. Several peroxidase fractions varying in isoelectric point values from acidic to basic were tested for their ability to catalyze the oxidation of the monolignols coniferyl alcohol, sinapyl alcohol and p-coumaryl alcohol in vitro. All of the xylem peroxidases extracted from Norway spruce and most of those from silver birch showed the highest rate of oxidation with coniferyl alcohol in the presence of hydrogen peroxide. The exception was an acidic peroxidase fraction (pI 3.60-3.65) from silver birch that exhibited higher oxidation activity for sinapyl alcohol than for coniferyl alcohol. For the xylem enzyme fractions extracted from silver birch, the ability to oxidize the artificial phenolic substrate syringaldazine coincided with high specific activity for sinapyl alcohol. Therefore, we conclude that the acidic, neutral and basic xylem peroxidases of Norway spruce all function in the synthesis of guaiacyl-type lignin, whereas in silver birch the acidic peroxidases preferentially oxidize sinapyl subunits. The latter provides a mechanism for synthesis of guaiacyl-syringyl lignin typical of tracheid cell walls in angiosperm trees.     

Effects of copper and cadmium on uptake and leakage of K(+) in birch (Betula pendula) roots

Uptake and leakage experiments were performed to study the effects of copper and cadmium on K(+) fluxes in birch (Betula pendula Roth) roots. Labeled rubidium ((86)Rb(+)) was used as a tracer for K(+). Plants were pretreated with Cu or Cd (0, 2, 5 or 25 microM) for 0-300 min and then transferred to radiolabeled nutrient solution (150 microM K(+)) with or without 2,4-dinitrophenol (DNP) to separate the effects of heavy metal on active and passive K(+) influxes. Passive K(+) influx was decreased by pretreatment with Cu but was only slightly affected by pretreatment with Cd. Pretreatment with 2 microM Cu increased active K(+) influx, whereas pretreatment with 25 microM Cu decreased active K(+) influx and intermediate Cu concentrations (5 microM) did not affect active K(+) influx. The pretreatment effects of Cu on active and passive K(+) influxes increased with increasing pretreatment time. During the first hour, pretreatment with Cd decreased active K(+) influx with increasing pretreatment time, whereafter recovery began. To measure K(+) efflux, birch plants were loaded with (86)Rb(+) for 7 days before being exposed to Cu or Cd (0, 1, 3, 5 or 10 microM) in unlabeled nutrient solutions for 24 h. Net efflux of K(+) was measured as (86)Rb(+)-activity in the nutrient solutions 24 h after a heavy metal had been introduced. Efflux of K(+) increased with increasing Cu or Cd concentration in the unlabeled nutrient solution.The data indicate that Cu and Cd affected K(+) influx differently and that recovery mechanism(s), which were induced shortly after heavy metal introduction, counteracted the heavy-metal induced inhibition of active K(+) influx. Efflux of K(+) from plant roots over a 24-h period indicated that Cu and Cd had similar effects on K(+) efflux. There was no evidence of a recovery mechanism counteracting the heavy-metal-induced inhibition of K(+) efflux.     

The effects of heavy thinning on stem quality and timber properties of silver birch (Betula pendula Roth)

A study was carried out into the effects of heavy thinning onstem quality and timber properties of silver birch (Betula pendulaRoth). Comparisons were made with lightly thinned and unthinnedbirch stands. Birch stands from the UK were also compared withsimilarly managed stands from Germany and Denmark. In general,trees from lightly thinned and unthinned stands had similarcharacteristics. Heavy thinning enhanced diameter incrementthrough greater ring width in comparison with the other treatments.The timber properties of basic density, grain angle and shrinkagecoefficients in the radial, tangential and longitudinal directions,however, were largely unaffected. More and bigger branches andgreater stem taper were found on trees from heavily thinnedstands, but these stems still met the current Finnish veneerbirch quality and dimension standards. Comparisons between birchstands, managed by heavy and light thinning, from the UK andGermany and Denmark revealed no meaningful differences in timberproperties. The results suggest that veneer dimension and qualitylogs could be produced in the UK in rotations as short as 40years on good sites if heavy thinning is adopted.     

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.     

Methods for combining phenological time series: application to bud burst in birch (Betula pendula) in Central Finland for the period 1896-1955

We compared four methods for combining separate fragmentary phenological time series into a single long reliable series. The systematic linear effect of differences in observers, genotypes, geography and climate at the observation points produces disturbing variation in the observations and bias in the means of some time points. The three methods based on the adjustment of individual series eliminated the disturbing variation and bias. The methods were compared based on phenological observations of bud burst in birch (Betula pendula Roth). The method based on a linear mixed model of analysis of variance and the maximum likelihood estimation was considered preferable to the other methods.