| the enrichment of (18)o in leaf water under natural conditions. | the enrichment of (18)o in the water of transpiring leaves under natural conditions is described. in the first series two, later three species at the same location and at the same time are compared (birch betula pubescens l., oak quercus robur ehrh., larch larix decidua mill., and spruce picea abies karst). all four show parallel enrichment properties. in addition two beeches (fagus silvatica l.) were observed, one at jülich, the other at the solling hills. they show similar (18)o/(16)o ratio fl ... | 1978 | 756054 |
| antimicrobial effects of finnish plant extracts containing flavonoids and other phenolic compounds. | plant phenolics, especially dietary flavonoids, are currently of growing interest owing to their supposed functional properties in promoting human health. antimicrobial screening of 13 phenolic substances and 29 extracts prepared from finnish plant materials against selected microbes was conducted in this study. the tests were carried out using diffusion methods with four to nine microbial species (aspergillus niger, bacillus subtilis, candida albicans, escherichia coli, micrococcus luteus, pseu ... | 2000 | 10857921 |
| comparison of the element composition in several plant species and their substrate from a 1500000-km2 area in northern europe. | leaves of 9 different plant species (terrestrial moss represented by: hylocomium splendens and pleurozium schreberi; and 7 species of vascular plants: blueberry, vaccinium myrtillus; cowberry, vaccinium titis-idaea; crowberry, empetrum nigrum; birch, betula pubescens; willow, salix spp.; pine, pinus sylvestris and spruce, picea abies) have been collected from up to 9 catchments (size 14-50 km2) spread over a 1500000 km2 area in northern europe. soil samples were taken of the o-horizon and of the ... | 2001 | 11669279 |
| influence of extreme pollution on the inorganic chemical composition of some plants. | leaves of nine different plant species (terrestrial moss: hylocomium splendens and pleurozium schreberi, blueberry: vaccinium myrtillus, cowberry: vaccinium vitis-idaea, crowberry: empetrum nigrum, birch: betula pubescens, willow: salix spp., pine: pinus sylvestris, and spruce: picea abies) have been collected from up to nine catchments (size 14-50 km2) spread over a 1,500,000 km2 area in northern europe. additional soil samples were taken from the o-horizon and the c-horizon at each plant sampl ... | 2001 | 11706797 |
| patterns in content of phenolic compounds in leaves of mountain birches along a strong pollution gradient. | the contents of individual low-molecular weight phenolic compounds (lmwps) in mountain birch, betula pubescens ssp. czerepanovii, leaves collected during 1996-1998 in six plots 7-65 km south of the nickel-copper smelter at monchegorsk, kola peninsula, nw russia, were reported. a high-performance liquid chromatography-electrospray ionisation-mass spectrometry (hplc-esi-ms) was used for the rapid identification of low-molecular weight phenolics. quantification was performed by the analytical high- ... | 2001 | 11592418 |
| [isolation of a myricetin-3-digalactoside from betula verrucosa and betula pubescens]. | | 1957 | 13459352 |
| olfactory responses of ips duplicatus from inner mongolia, china to nonhost leaf and bark volatiles. | leaf and bark volatiles from nonhost angiosperm trees were tested on ips duplicatus by gas chromatographic-electroantennographic detection (gc-ead) and by pheromone-baited traps in sweden and inner mongolia, china, respectively. gc-ead analysis of the headspace volatiles from fresh bark chips of betula pubescens revealed trans-conophthorin, two green leaf volatiles (glvs): 1-hexanol and (z)-3-hexen-1-ol, and two c8 alcohols: 3-octanol and 1-octen-3-ol, that consistently elicited antennal respons ... | 2001 | 11471951 |
| extensive sharing of chloroplast haplotypes among european birches indicates hybridization among betula pendula, b. pubescens and b. nana. | extensive sharing of chloroplast haplotypes among the silver birch, betula pendula roth., the downy birch, b. pubescens ehrh., and the dwarf birch, b. nana l., was discovered using polymerase chain reaction-restriction fragment length polymporphism markers. the geographical component of the genetic variation was stronger than the species component: the species were not significantly different while 11% of the variation could be attributed to differentiation between the two main regions studied, ... | 2004 | 14653797 |
| the shoot apical meristem restores its symplasmic organization during chilling-induced release from dormancy. | the shoot apex of overwintering perennials ceases its morphogenetic activity at the end of the growing season and transforms into a bud which is dormant and freezing-tolerant. in birch (betula pubescens) these events are triggered by short photoperiod, and involve the production of 1,3-beta-d-glucan containing sphincters on the plasmodesmata. as a result, all symplasmic pathways shut down. here we show that breakage of bud dormancy by chilling involves restoration of the symplasmic organization ... | 2001 | 11439114 |
| seasonal variation in the content of hydrolysable tannins in leaves of betula pubescens. | the contents of 13 hydrolysable tannins in the leaves of white birch (betula pubescens l.) trees were analysed at twelve stages throughout the growing season. all individual galloylglucoses, from 1-o-galloyl-beta-d-glucopyranose to 1,2,3,4,6-penta-o-galloyl-beta-d-glucopyranose, accumulated in young leaves, while ellagitannins showed significantly variable seasonal trends. the major ellagitannin during the whole growing season was pedunculagin while 2,3-(s)-hhdp-glucopyranose. the end product of ... | 2001 | 11336256 |
| clonal differences in copper and zinc tolerance of birch in metal-supplemented soils. | metal tolerance of a range of birch clones (betula pendula and betula pubescens) originating from metal-contaminated sites in england, wales, belgium and finland were tested in soils supplemented with several concentrations of copper (cu) or zinc (zn) (500, 2000, 5000 mg kg-1 dry wt. soil of cuso(4).5h2o or znso(4).7h2o) for 4 months and with sub-toxic metal supplements (500 mg cuso4, 2000 mg znso4) for 6 months. when grown at high concentrations of metals, severe toxicity symptoms (growth inhib ... | 2001 | 11202657 |
| phenolic and phenolic-related factors as determinants of suitability of mountain birch leaves to an herbivorous insect. | we investigated the role of phenolic and phenolic-related traits of the leaves of mountain birch (betula pubescens ssp. czerepanovii) as determinants of their suitability for the growth of larvae of the geometrid epirrita autumnata. as parameters of leaf suitability, we determined the contents of total phenolics, gallotannins, soluble and cell-wall-bound proanthocyanidins (pas and pab, respectively), lignin, protein precipitation capacity of tannins (ppc), and leaf toughness. in addition, we exa ... | 2001 | 11152944 |
| characterisation of hydrolysable tannins from leaves of betula pubescens by high-performance liquid chromatography-mass spectrometry. | a high-performance liquid chromatography-electrospray ionisation mass spectrometry (hplc-esi-ms) method, assisted by diode array detection, for the characterisation of individual hydrolysable tannins in birch leaves was developed. with the method, it was found that birch (betula pubescens) leaves contained an exceptionally complex mixture of hydrolysable tannins; 14 gallotannins and 20 ellagitannins were identified. the developed hplc-esi-ms method allows the qualitative and quantitative determi ... | 1999 | 10669296 |
| effects of resource availability on carbon allocation and developmental instability in cloned birch seedlings. | abundant nitrogen improves seedling growth and establishment. vigorous growth brings about changes in rates and patterns of plant development and changes in the relationship between primary and secondary metabolism, which may make seedlings more susceptible to herbivores and pathogens than are slow-growing seedlings. we studied how nitrogen fertilization and manual defoliation of source leaves affect growth, carbon allocation, and developmental instability in cloned seedlings of white birch (bet ... | 2000 | 10648201 |
| dehydrins in cold-acclimated apices of birch (betula pubescens ehrh. ): production, localization and potential role in rescuing enzyme function during dehydration | dehydrins accumulate in various plant tissues during dehydration. their physiological role is not well understood, but it is commonly assumed that they assist cells in tolerating dehydration. since in perennials the ability of the shoot apex to withstand dehydration is pivotal for survival through winter, we investigated if and how dehydrins may be involved. a first step in assessing such a role is the identification of their subcellular location. we therefore mapped the location of dehydrin hom ... | 1999 | 10550618 |
| air-pollutant dispersal patterns and vegetation damage in the vicinity of three aluminium smelters in norway. | dispersal patterns for fluoride and damage to vegetation was studied near three aluminium smelters in norway. leaf samples from three broad-leaved species (betula pubescens ehrh., salix caprea l. and sorbus aucuparia l.) were collected and leaf injury and the plants overall vitality were evaluated systematically in areas with different distance and direction from the emission sources. both dispersal patterns and the distribution of damages were mainly determined by the predominant wind direction ... | 1999 | 10535145 |
| root versus canopy uptake of heavy metals by birch in an industrially polluted area: contrasting behaviour of nickel and copper. | we investigated root versus canopy uptake of nickel and copper by mountain birch, betula pubescens subsp. czerepanovi, close to a nickel-copper smelter on the kola peninsula, northwest russia. to distinguish between aerial contamination of leaf surfaces by dust particles and root-derived contamination of leaves by soluble metals, we transplanted seedlings from a control site to clean and metal-contaminated soils and exposed these seedlings both in clean and polluted sites. patterns of leaf surfa ... | 2000 | 15092987 |
| variation in ozone sensitivity among clones of betula pendula and betula pubescens. | forty clones of betula pendula and 6 clones of betula pubescens, originating from southern and central finland, were ranked in order of ozone sensitivity according to visible injuries, growth and leaf senescense under low ozone exposure. the plants were fumigated in natural climatic conditions using an open-air exposure system during two growing seasons. control plants were grown under ambient air, and the elevated-ozone exposures were 1.6x the ambient in 1994 and 1.7x the ambient in 1995. the d ... | 1997 | 15093472 |
| host-driven population dynamics in an herbivorous insect. | understanding the nature and relative importance of endogenous (density-dependent) and exogenous (density-independent) effects on population dynamics remains a central problem in ecology. evaluation of these forces has been constrained by the lack of long time series of population densities and largely limited to populations chosen for their unique dynamics (e.g., outbreak insects). especially in herbivore populations, the relative contributions of bottom-up and top-down effects (resources and n ... | 1999 | 10485895 |
| genetic and environmental factors affecting the allergenicity of birch (betula pubescens ssp. czerepanovii [orl.] hämet-ahti) pollen. | environmental variation, such as an increase of mean temperature due to the greenhouse effect, as well as the genetic factors may affect the allergenicity of pollen and thus, the prevalence of allergies. the connection between these factors and the allergen content of pollen is poorly understood. | 1998 | 9824411 |
| comparative studies of allergenic extracts prepared from freshly collected, dried, or dried and defatted pollen. | fresh pollen samples of parietaria judaica, betula pubescens, dactylis glomerata and olea europaea were collected and aliquot portions of these pollens were stored after drying in hot air, while other portions were dried and then defatted with diethylether. the different pollen materials were extracted with aqueous media to obtain the non-dialyzable allergenic protein constituents. review of the production data, together with comparative analyses of the uv-absorption spectra and of ige binding p ... | 1995 | 7582159 |
| measurement of xylanase activity with insoluble xylan substrate. | insoluble xylan was prepared from ground birch (betula pubescens) pulp by alkali extraction and precipitation with ethanol. the only sugar detected after acid hydrolysis of the preparation was xylose. the insoluble xylan was used as substrate in a nephelometric assay to determine the xylanase (ec 3.2.1.8, 1,4-beta-d-xylan xylanohydrolase and ec 3.2.1.37, 1,4-beta-d-xylan xylohydrolase) activities of aspergillus and trichoderma enzymes. the nephelometric method is reliable in evaluating xylanase ... | 1985 | 3922355 |
| performance of the cyclic autumnal moth, epirrita autumnata, in relation to birch mast seeding. | the mast depression hypothesis has been put forward to explain the 9- to 10-year population cycle of the autumnal moth (epirrita autumnata; lepidoptera: geometridae) in northern fennoscandia. we analysed long-term data from finnish lapland in order to evaluate the critical assumption of the mast depression hypothesis: that better individual performance of herbivores, followed by high annual growth rate of populations, occurs in the year following mast seeding of the host, the mountain birch ( be ... | 2003 | 12721824 |
| resource allocation in different parts of juvenile mountain birch plants: effect of nitrogen supply on seedling phenolics and growth. | the composition and concentrations of phenolic compounds were studied in the first true leaves, cotyledons, stems and roots of 2.5-week-old seedlings of mountain birch (betula pubescens ssp. czerepanovii). the differences in secondary compounds among these plant parts were both qualitative and quantitative. in all parts, condensed tannins accounted for more than 50% of the phenolics. in the first true leaves and cotyledons, chlorogenic acid was the most abundant of the hplc phenolics. the main c ... | 2003 | 12702020 |
| putting the insect into the birch-insect interaction. | leaf maturation in mountain birch (betula pubescens ssp. czerepanovii) is characterized by rapid shifts in the types of dominant phenolics: from carbon-economic flavonoids aglycons in flushing leaves, via hydrolysable tannins and flavonoid glycosides, to carbon-rich proanthocyanidins (condensed tannins) in mature foliage. this shift accords with the suggested trade-offs between carbon allocation to plant defense and growth, but may also relate to the simultaneous decline in nutritive leaf traits ... | 2003 | 12684856 |
| spatial responses of two herbivore groups to a geometrid larva on mountain birch. | direct or plant-mediated interactions between herbivores may modify their spatial distribution among and within plants. in this study, we examined the effect of a leaf-chewing geometrid, the autumnal moth (epirrita autumnata), on two different herbivore groups, leaf rolling deporaus betulae weevils and eriocrania spp. leafminers, both feeding on mountain birch (betula pubescens ssp. czerepanovii). the exact locations of herbivores within tree canopies were mapped during three successive summers. ... | 2003 | 12647161 |
| xylem ray parenchyma cells in boreal hardwood species respond to subfreezing temperatures by deep supercooling that is accompanied by incomplete desiccation. | it has been accepted that xylem ray parenchyma cells (xrpcs) in hardwood species respond to subfreezing temperatures either by deep supercooling or by extracellular freezing. present study by cryo-scanning electron microscopy examined the freezing responses of xrpcs in five boreal hardwoods: salix sachalinensis fr. schmit, populus sieboldii miq., betula platyphylla sukat. var japonica hara, betula pubescens ehrh., and red osier dogwood (cornus sericea), in which xrpcs have been reported to respo ... | 2003 | 12586897 |
| host-associated allozyme variation in tree cambium miners, phytobia spp. (diptera: agromyzidae). | the larvae of the agromyzid flies that belong to the genus phytobia lioy feed by mining in the differentiating xylem just below the cambium of growing forest trees. the genus, which is apparently one of the most primitive groups in the agromyzidae, comprises over 50 currently recognized species. most of the species are mono- or oligophagous, and the host plants belong to numerous genera in about 60 families. thus, phytobia is an attractive candidate for studies on the evolution of insect-plant r ... | 2002 | 12399999 |
| environmental conditions and host genotype direct genetic diversity of venturia ditricha, a fungal endophyte of birch trees. | we investigated whether genetic variation of a common foliar endophyte of birch trees, venturia ditricha, is affected by environmental conditions or host genotype. fungal samples were collected from 10 half-sibling families of mountain birch (betula pubescens ssp. czerepanovii) grown in two environmental conditions with different daily average temperatures: a forested river valley and an adjacent open tundra (altitudinal difference 180 m). genetic analysis of v. ditricha isolates was done using ... | 2002 | 12353749 |
| wound-induced oxidative responses in mountain birch leaves. | the aim of the study was to examine oxidative responses in subarctic mountain birch, betula pubescens subsp. czerepanovii, induced by herbivory and manual wounding. | 2006 | 16254021 |
| nitrate reductase activity in some subarctic species and uv influence in the foliage of betula pendula roth. seedlings. | nitrate reductase (nr) activity was studied in the foliage of five subarctic species: mature trees of european white birch (betula pubescens erch. s.s.), scots pine (pinus sylvestris l.), norway spruce (picea abies l. karst), ericaceous shrub bilberry (vaccinium myrtillus l.), naturally growing in a forest, and seed-grown silver birch (betula pendula roth.) seedlings in an ultraviolet (uv) exclusion field experiment at the pallas-ounastunturi national park in finnish lapland (68 degrees n). mean ... | 2002 | 11846159 |
| morphological, cytogenetic, and molecular evidence for introgressive hybridization in birch. | extensive morphological variation of tetraploid birch (betula pubescens) in iceland is believed to be due to gene flow from diploid dwarf birch (b. nana) by means of introgressive hybridization. a combined morphological and cytogenetic approach was used to investigate this phenomenon in two geographically separated populations of natural birch woodland in iceland. the results not only confirmed introgressive hybridization in birch, but also revealed bidirectional gene flow between the two specie ... | 2001 | 11773247 |
| phenological modifications in plants by various edaphic factors. | various mechanical, chemical and physical soil analyses were carried out, in addition to weather observations, for 3 years at several sites along an oceanic-continental gradient in a fjord district in western norway. all the environmental factors observed were correlated with the spring and a few late-season phenophases of many native and cultivated woody plants and some herbs by simple, linear correlations and by stepwise multiple and partial analyses. different techniques were used to try and ... | 2001 | 11769320 |
| 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) hämetahti) 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 ... | 2003 | 14597429 |
| photoperiod and temperature differentially regulate the expression of two dehydrin genes during overwintering of birch (betula pubescens ehrh.). | the overwintering of trees in northern areas depends on processes regulated by photoperiod and temperature. to identify the physiological and genetic factors involved in this environmental control, three latitudinal ecotypes of pubescent birch (betula pubescens ehrh.) growing in a common garden experiment were used. each ecotype responded to the shortening of the photoperiod according to its specific critical daylength, resulting in the induction of freezing tolerance and dehydration of buds fir ... | 2004 | 14739271 |
| budburst phenology of white birch in industrially polluted areas. | effects of environmental contamination on plant seasonal development have only rarely been properly documented. monitoring of leaf growth in mountain birch, betula pubescens subsp. czerepanovii, around a nickel-copper smelter at monchegorsk hinted advanced budburst phenology in most polluted sites. however, under laboratory conditions budburst of birch twigs cut in late winter from trees naturally growing around three point polluters (nickel-copper smelter at monchegorsk, aluminium factory at ka ... | 2007 | 17175079 |
| influence of environment, fertilizer and genotype on shoot morphology and subsequent rooting of birch cuttings. | differences in rooting ability of birch (betula pubescens j.f. ehrh.) cuttings were observed as a result of differences in genotype and physiology of the stock plants. the uniformity in response among cuttings from micropropagated plants compared with cuttings from seed plants confirmed the advantage of using micropropagated plants to study environmental effects. shoot morphology of the seed stock plants was influenced by both photoperiod and thermoperiod. a day/night temperature of 15/25 degree ... | 1995 | 14966006 |
| root produced dhzr-, zr- and ipa-like cytokinins in xylem sap in relation to coppice shoot initiation and growth in cloned trees of betula pubescens. | six-year-old cloned betula pubescens ehrh. trees, grown outdoors at 65 degrees 01' n, were cut on six dates during the growing season to study coppice shoot development in relation to root-produced cytokinin-like compounds. bleeding sap was collected over timed intervals for two days after cutting, and endogenous cytokinin-like compounds were measured by elisa assay in hplc-purified fractions of xylem sap. initiation and development of coppice shoots on the clonally propagated plants were compar ... | 1994 | 14967625 |
| 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 s ... | 1994 | 14967673 |
| effects of sample drying and storage, and choice of extraction solvent and analysis method on the yield of birch leaf hydrolyzable tannins. | in this study, i investigated the effects of different methods of sample drying and storage, and the choice of extraction solvent and analysis method on the concentrations of 14 individual hydrolyzable tannins (hts), and insoluble ellagitannins in birch (betula pubescens) leaves. freeze- and vacuum-drying of birch leaves were found to provide more reliable results than air- or oven-drying. storage of leaves at -20 degrees c for 3 months before freeze-drying did not cause major changes in tannin ... | 2003 | 12918916 |
| effect of carbon dioxide concentration on biomass production and partitioning in betula pubescens ehrh. seedlings at different ozone and temperature regimes. | seedlings of betula pubescens were grown at two co(2) concentrations, in combination with either two o(3) concentrations or two air temperatures, during 34-35 days at 24 h day(-1) photoperiod in growth chambers placed in a greenhouse. increasing the co(2) concentration from 350 to 560 micromol mol(-1) at 17 degrees c air temperature increased the dry weight of the main leaves, main stem, branches and root. the mean relative growth rate (rgr) was increased 10% by co(2) enrichment, while increasin ... | 1995 | 15091583 |
| effects of sulphur dioxide and nitrogen dioxide, singly and in mixture, on the macroscopic growth of three birch clones. | an investigation of some aspects of the effects of low concentrations of the gases, sulphur dioxide and nitrogen dioxide, singly and in mixture, was made on the growth of three birch clones, two of betula pendula roth. (silver birch) and one of betula pubescens ehr. (downy birch). comparative measurements of the growth form and dry mass increment were made over one year in glasshouses supplied with charcoal-filtered ambient air, and so(2) and no(2), singly or in mixture, at mean concentrations o ... | 1987 | 15092731 |
| density patterns of gall mites (acarina:eriophyidae) in a polluted area. | trends in the densities of six species of gall mites on european aspen (populus tremula) and on two birch species (betula pubescens and b. pendula) were compared in an air pollution gradient from the harjavalta copper-nickel smelter, sw finland. the densities of gall mites on both birch species decreased towards the smelter and were negatively correlated with the levels of copper and nickel in the birch leaves. in contrast, the densities of aspen mites correlated neither with distance from the p ... | 1996 | 15093531 |
| rapid evolution towards heavy metal resistance by mountain birch around two subarctic copper-nickel smelters. | adaptations to pollution among long-lived trees have rarely been documented, possibly because of their long reproductive cycles and the evolutionarily short timescales of anthropogenic pollution. here, i present the results of a greenhouse experiment that suggest rapid evolutionary adaptation of mountain birch [betula pubescens subsp. czerepanovii (orlova) hämet-ahti] to heavy metal (hm) stress around two copper-nickel smelters in nw russia. the adaptation incurs a cost with reduced performance ... | 2008 | 18194230 |
| rapid herbivore-induced changes in mountain birch phenolics and nutritive compounds and their effects on performance of the major defoliator, epirrita autumnata. | insect damage changes plant physiology and chemistry, and such changes may influence the performance of herbivores. we introduced larvae of the autumnal moth (epirrita autumnata borkh.) on individual branches of its main host plant. mountain birch (betula pubescens ssp. czerepanovii (orlova) hämet-ahti) to examine rapid-induced plant responses, which may affect subsequent larval development. we measured systemic responses to herbivory by analyzing chemistry, photosynthesis, and leaf growth, as w ... | 2004 | 15112726 |
| mycorrhizal colonisation of mountain birch (betula pubescens ssp. czerepanovii) along three environmental gradients: does life in harsh environments alter plant-fungal relationships? | environmental stress affects ectomycorrhizal communities (ecm), but it is not known how general the detected ecm responses are. we investigated ecm fungi on roots of mountain birch, betula pubescens subsp. czerepanovii (orlova) hämet-ahti, along three environmental gradients, two natural (altitude, seashore) and one human-induced (pollution), within the kola peninsula, nw russia. chlorophyll fluorescence of birch leaves indicated no environmental stress even in the conditions that were presumed ... | 2009 | 18327653 |
| reduction in size and fecundity of the autumnal moth, epirrita autumnata, in the increase phase of a population cycle. | increasing fecundity with increasing density has been observed for many cyclic herbivore populations, including some forest lepidoptera. we monitored population density, body size and reproductive capacity of the cyclic lepidopteran, the autumnal moth (epirrita autumnata, geometridae), from the early increase phase to the devastating outbreak density in northernmost norway. larval density of the species increased exponentially from 1998 to 2002 and remained at the outbreak level also in 2003. wi ... | 2004 | 15338264 |
| stature of sub-arctic birch in relation to growth rate, lifespan and tree form. | sub-arctic mountain birch betula pubescens var. pumila communities in the north atlantic region are of variable stature, ranging from prostrate scrubs to forests with trees up to 12 m high. four hypotheses were tested, relating growth and population characteristics of sub-arctic birch woodland and scrub to tree stature; i.e. the variable stature of birch woods is due to differences in (1) the mean growth rate; (2) the age-related patterns of growth rate; (3) the life expectancy of stems; or (4) ... | 2004 | 15374837 |
| defensive effect of surface flavonoid aglycones of betula pubescens leaves against first instar epirrita autumnata larvae. | the surface of birch leaves contains glandular trichomes that secrete exudates containing flavonoid aglycones. we investigated the biological activities of white birch (betula pubescens) leaf surface exudates against larvae of the autumnal moth, epirrita autumnata, a common insect pest of birch. we found that tree-specific mortality (up to 100%) of first instar larvae correlated strongly with the tree-specific contents of surface flavonoid aglycones (r(s) = 0.905) in emerging leaves. we also fou ... | 2004 | 15672669 |
| climatic warming increases isoprene emission from a subarctic heath. | emissions of isoprene, a reactive hydrocarbon, from subarctic vegetation are not well documented. however, the arctic is likely to experience the most pronounced effects of climatic warming, which may increase temperature-dependent isoprene emission. here, we assessed isoprene emission from a subarctic heath subjected to a 3-4 degrees c increase in air temperature and mountain birch (betula pubescens ssp. czerepanovii) litter addition for 7-8 yr, simulating climatic warming and the subsequent ex ... | 2008 | 18680543 |
| sources of variation in concentrations of nickel and copper in mountain birch foliage near a nickel-copper smelter at monchegorsk, north-western russia: results of long-term monitoring. | concentrations of nickel and copper, two principal metal pollutants of the 'severonikel' smelter at monchegorsk, nw russia, were measured in unwashed leaves of mountain birch, betula pubescens subsp. czerepanovii, collected in eight study sites along the pollution gradient during 1991-2003. in spite of significant decline in metal emissions, concentrations of foliar metals in most of the study sites did not decrease, indicating that soil contamination remains extremely high. multiyear mean value ... | 2005 | 15701396 |
| pollution resistance of mountain birch, betula pubescens subsp. czerepanovii, near the copper-nickel smelter: natural selection or phenotypic acclimation? | mountain birch, betula pubescens subsp. czerepanovii (orlova) hamet-ahti, is one of the very few woody plants surviving in the heavily polluted industrial barrens of the kola peninsula, north-western russia. the present study was designed to find out whether long-lasting pollution impact caused selection of resistant birch genotypes, and to investigate possible trade-offs between pollution resistance and performance by exploring growth of birch seedlings in the different environments. in the rec ... | 2004 | 15722090 |
| phenology and abundance in relation to climatic variation in a sub-arctic insect herbivore-mountain birch system. | the two forest-defoliating geometrid moth species operophtera brumata and epirrita autumnata are known to exhibit different altitudinal distribution patterns in northern birch forests. one possible explanation for this is that altitudinal climatic variation differentially affects the performance of two species through mismatching larval and host plant phenology. we explored this hypothesis by investigating the relationship between larval phenology and leaf phenology of betula pubescens, which is ... | 2005 | 16003503 |
| do competition and herbivory alter the internal nitrogen dynamics of birch saplings? | deciduous trees recycle nitrogen within their tissues. the aim of this study was to test the hypothesis that reductions in plant growth, caused by competition and herbivory, reduce the sink strength for n during autumn nutrient withdrawal, and reduce the storage capacity and hence the amount of n remobilized in the following spring. we used (15)n-labelled fertilizer to quantify n uptake, leaf n withdrawal and remobilization. betula pubescens saplings were grown with either molinia caerulea or ca ... | 2005 | 16219080 |
| newly hatched neonate larvae can glycosylate: the fate of betula pubescens bud flavonoids in first instar epirrita autumnata. | betula pubescens bud flavonoid aglycones reportedly have negative effects on the performance of first instar epirrita autumnata and, thus, may defend birch leaves from larval defoliation. we hypothesized that the detrimental effects of these lipophilic flavonoids on larvae are due to their high levels in birch buds and/or the inability of naïve neonates to glycosylate them, which we have shown to occur in fifth instars. to test the latter hypothesis, we investigated the biochemical transformatio ... | 2006 | 16572299 |
| growing seasons of nordic mountain birch in northernmost europe as indicated by long-term field studies and analyses of satellite images. | the phenophases first greening (bud burst) and yellowing of nordic mountain birch (betula pubescens ssp.tortuosa, also called b. p. ssp. czerepanovii) were observed at three sites on the kola peninsula in northernmost europe during the period 1964-2003, and at two sites in the trans-boundary pasvik-enare region during 1994-2003. the field observations were compared with satellite images based on the gimms-ndvi dataset covering 1982-2002 at the start and end of the growing season. a trend for a d ... | 2006 | 16832653 |
| sexual reproduction advances autumn leaf colours in mountain birch (betula pubescens ssp. czerepanovii). | autumnal change in leaf colour of deciduous trees is one of the most fascinating displays in nature. current theories suggest that autumn leaf colours are adaptations to environmental stress. here i report that the number of ripening female catkins altered timing of yellow autumn leaf colours in mountain birch. the tree's autumnal colour change was brought forward if the tree matured plenty of female catkins. since yellow colour pigments in leaves are unmasked as leaf nitrogen is re-translocated ... | 2006 | 16911002 |
| solar ultraviolet radiation alters alder and birch litter chemistry that in turn affects decomposers and soil respiration. | solar ultraviolet (uv)-a and uv-b radiation were excluded from branches of grey alder (alnus incana) and white birch (betula pubescens) trees in a field experiment. leaf litter collected from these trees was used in microcosm experiments under laboratory conditions. the aim was to evaluate the effects of the different uv treatments on litter chemical quality (phenolic compounds, c, n and lignin) and the subsequent effects of these changes on soil fauna and decomposition processes. we measured th ... | 2009 | 19597848 |
| [triterpenes of betula pendula roth and betula pubescens ehrh. comparative study of the bark]. | | 1966 | 5220364 |
| connection of gnomonia intermedia to discula betulina and its relationship to other taxa in gnomoniaceae. | discula betulina is a foliar pathogen on birch (betula) and gnomonia intermedia is found on overwintered birch leaves. perithecia of g. intermedia developed in vitro on colonies of d. betulina isolated from birch tissues in late summer, and single ascospores of g. intermedia consistently developed into colonies similar to d. betulina, producing typical d. betulina conidia. isolates of d. betulina could be grouped into two mating types, which produced fertile perithecia of g. intermedia when mate ... | 2007 | 17164084 |
| recent invasion of the mountain birch betula pubescens ssp. tortuosa above the treeline due to climate change: genetic and ecological study in northern sweden. | mountain birch, betula pubescens ssp. tortuosa, forms the treeline in northern sweden. a recent shift in the range of the species associated with an elevation of the treeline is commonly attributed to climate warming. using microsatellite markers, we explored the genetic structure of populations along an altitudinal gradient close to the treeline. low genetic differentiation was found between populations, whereas high genetic diversity was maintained within populations. high level of gene flow c ... | 2007 | 17210030 |
| element contents in leaves of four plant species (birch, mountain ash, fern and spruce) along anthropogenic and geogenic concentration gradients. | forty samples each of leaves of birch (betula pubescens ehrh.), european mountain ash (sorbus aucuparia (l.)) and bracken fern (pteridium aquilinum (l.) kuhn) as well as spruce needles (picea abies (l.) karsten) were collected along a 120 km south-north transect running through norway's largest city, oslo. concentrations of 25 chemical elements (ag, au, b, ba, ca, cd, co, cr, cu, fe, hg, k, la, mg, mn, mo, na, ni, p, pb, s, sb, sr, ti, and zn) as well as loss on ignition for the 4 sample materia ... | 2007 | 17379275 |
| seasonal fluctuations in leaf phenolic composition under uv manipulations reflect contrasting strategies of alder and birch trees. | seasonal variation in leaf phenolic composition may be important for acclimation of plants to seasonal changes in their biotic and abiotic environment. for a realistic assessment of how plants respond to solar uv-b (280-315 nm) and uv-a (315-400 nm) radiation, seasonal variation in both environment and plant responses needs to be taken into account. this also has implications for studies concerning stratospheric ozone depletion and resulting increased uv-b radiation, as other environmental varia ... | 2010 | 20626643 |
| foliar phenolics are differently associated with epirrita autumnata growth and immunocompetence. | the quality of available food may affect insect herbivores directly (via growth and survivorship) and/or indirectly (by modifying insect vulnerability to parasitoids and pathogens). we examined the relationship between different phenolic compounds, belonging to various phenolic groups, in betula pubescens spp. czerepanovii (mountain birch) foliage and the larval performance of the geometrid epirrita autumnata (autumnal moth). direct effects on insect performance were described by pupal weight, d ... | 2007 | 17415626 |
| morphological variation among betula nana (diploid), b. pubescens (tetraploid) and their triploid hybrids in iceland. | introgressive hybridization between two co-existing betula species in iceland, diploid dwarf birch b. nana and tetraploid downy birch b. pubescens, has been well documented. the two species are highly variable morphologically, making taxonomic delineation difficult despite stable ploidy levels. here an analysis is made of morphological variation within each ploidy group with an aim to establishing a reliable means to distinguish the species. | 2007 | 17495985 |
| remediation of heavy metal-contaminated forest soil using recycled organic matter and native woody plants. | the main aim of this study was to determine how the application of a mulch cover (a mixture of household biocompost and woodchips) onto heavy metal-polluted forest soil affects (i) long-term survival and growth of planted dwarf shrubs and tree seedlings and (ii) natural revegetation. native woody plants (pinus sylvestris, betula pubescens, empetrum nigrum, and arctostaphylos uva-ursi) were planted in mulch pockets on mulch-covered and uncovered plots in summer 1996 in a highly polluted scots pin ... | 2007 | 17596623 |
| [an orientational examination of the effects of extracts from mixtures of herbal drugs on selected renal functions]. | the paper aimed to determine the effects of mixtures of selected medicinal plants on some physiological renal functions, i.e. excretion of urine and electrolytes and changes in the quantity of prostaglandins e2 (pge2) and kallikrein-kinins in rat blood plasma after water and salt load. the following medicinal plants were selected for the examination: downy birch (betula pubescens ehrh.), everlasting flower (helichrysum arenarium l. moench.), hawthorn (crataegus oxyacantha l.), woodland strawberr ... | 2007 | 17619305 |
| fragmented environment affects birch leaf endophytes. | the effect of environmental fragmentation on the species distribution and frequency of horizontally transmitted endophytic fungi in betula pubescens and betula pendula leaves was studied in an archipelago in southwestern finland. the study system consisted of 14 islands, ranging in size and distance to the mainland, and five mainland sites. endophytic fungi were grown out from surface-sterilized leaves. the frequency of endophytic fungi mainly depended on the size of the island, explaining 32-35 ... | 2007 | 17635229 |
| trends in phenology of betula pubescens across the boreal zone in finland. | timing of plant phenophases is a useful biological indicator which shows how nature responds to the variation in climate. thus, long phenological observation series help to estimate the impact of changing climate on forest plants. we investigated whether phenological patterns of downy birch betula pubescens respond to warming climate and whether the intensity of the responses varies among phytogeographical zones. we studied data collected by the finnish national phenological network from 30 obse ... | 2008 | 17957389 |
| fecundity of the autumnal moth depends on pooled geometrid abundance without a time lag: implications for cyclic population dynamics. | 1. the abundance and fecundity-related body size variation of the cyclic autumnal moth epirrita autumnata were monitored from the early increase phase and throughout the outbreak to the end of the density decline in northernmost norway during 1999-2006. another geometrid, the winter moth operophtera brumata, did not increase in density until the autumnal moth had its post-peak in 2004, and was at its own peak concurrent with the steeply declining autumnal moth abundance in 2005-06. 2. the body s ... | 2008 | 18284477 |
| defoliation increases carbon limitation in ectomycorrhizal symbiosis of betula pubescens. | boreal forest trees are highly dependent on root-colonizing mycorrhizal fungi. since the maintenance of mycorrhizal symbiosis implies a significant carbon cost for the host plant, the loss of photosynthetic leaf area due to herbivory is expected to reduce the host investment in mycorrhizae. we tested this hypothesis in a common garden experiment by exposing ectomycorrhizal white birch (betula pubescens ehrh.) seedlings to simulated insect defoliation of 50 or 100% intensity during either the pre ... | 2004 | 15148601 |
| autumn coloration as a signal of tree condition. | hamilton and brown suggested that bright autumn coloration in trees is an energetically expensive and therefore honest (handicap) signal of defensive commitment against insects. if this is so, one should expect that the intensity of the proposed signal should depend strongly on tree health. however, to the best of our knowledge, the link between vigour and autumn colour has never been tested. we explored the relationship between autumn coloration and tree condition (i.e. leaf fluctuating asymmet ... | 2004 | 15252978 |
| reproduction of mountain birch along a strong pollution gradient near monchegorsk, northwestern russia. | we explored effects of severe pollution on sexual reproduction of mountain birch, betula pubescens subsp. czerepanovii, by counting catkins on sample branches and weighing both somatic and generative structures of both short and long shoots from birches growing at 21 sites around large nickel-copper smelter at monchegorsk, northwestern russia. proportion of reproducing trees, production of catkins, shoot and catkin weight, as well as the relative difference in weight of somatic structures of gen ... | 2004 | 15325460 |
| from plants to birds: higher avian predation rates in trees responding to insect herbivory. | background: an understanding of the evolution of potential signals from plants to the predators of their herbivores may provide exciting examples of co-evolution among multiple trophic levels. understanding the mechanism behind the attraction of predators to plants is crucial to conclusions about co-evolution. for example, insectivorous birds are attracted to herbivore-damaged trees without seeing the herbivores or the defoliated parts, but it is not known whether birds use cues from herbivore-d ... | 2008 | 18665271 |
| effect of birch (betula spp.) and associated rhizoidal bacteria on the degradation of soil polyaromatic hydrocarbons, pah-induced changes in birch proteome and bacterial community. | two birch clones originating from metal-contaminated sites were exposed for 3 months to soils (sand-peat ratio 1:1 or 4:1) spiked with a mixture of polyaromatic hydrocarbons (pahs; anthracene, fluoranthene, phenanthrene, pyrene). pah degradation differed between the two birch clones and also by the soil type. the statistically most significant elimination (p < or = 0.01), i.e. 88% of total pahs, was observed in the more sandy soil planted with birch, the clearest positive effect being found with ... | 2009 | 18675498 |
| concentrations of foliar quercetin in natural populations of white birch (betula pubescens) increase with latitude. | we investigated latitudinal and regional variations in the composition and concentrations of foliar flavonoids and condensed tannins in wild populations of white birch (betula pubescens ehrh) in a large climatic transect in finland. concentrations of quercetin derivatives were correlated positively with latitude. by contrast, the concentrations of apigenin and naringenin derivatives were correlated negatively with latitude. these compound-specific latitudinal gradients compensated each other, re ... | 2008 | 18946705 |
| stomatal resistance, photosynthesis and water relations in mountain birch in the subarctic. | the role of water in regulating stomatal aperture and carbon assimilation of mountain birch (betula pubescens ehrh. ssp. tortuosa (ledeb.) nyman) was studied in the swedish subarctic. stomata exhibited a clear response to changes in humidity and water potential. high evaporative demand caused stomatal closure at midday. the diurnal curve of net photosynthesis, measured on a warm day in early july, had two peaks, and photosynthetic rate was reduced by 25-30% at midday. | 1986 | 14975847 |
| metabolic modifications of birch leaf phenolics by an herbivorous insect: detoxification of flavonoid aglycones via glycosylation. | the metabolic modifications of birch (betula pubescens ehrh.) leaf phenolics in the digestive tract of its major defoliator, larvae of the autumnal moth epirrita autumnata, were studied. the main phenolic acids of birch, i.e. chlorogenic and p-coumaroylquinic acids, were isomerised in the alkaline digestive tract. moreover, only 16 to 92% of the ingested amounts of chlorogenic acid were found in the faeces of individual larvae; the missing portion is possibly being used in the formation of react ... | 2004 | 18998416 |
| larval parasitism of the autumnal moth reduces feeding intensity on the mountain birch. | plants respond to grazing by herbivorous insects by emitting a range of volatile organic compounds, which attract parasitoids to their insect hosts. however, a positive outcome for the host plant is a necessary precondition for making the attraction beneficial or even adaptive. parasitoids benefit plants by killing herbivorous insects, thus reducing future herbivore pressure, but also by curtailing the feeding intensity of the still living, parasitised host. in this study, the effect of parasiti ... | 2009 | 19066967 |
| mountain birch under multiple stressors--heavy metal-resistant populations co-resistant to biotic stress but maladapted to abiotic stress. | stress adaptations often include a trade-off of weakened performance in nonlocal conditions, resulting in divergent selection, and potentially, genetic differentiation and evolutionary adaptation. results of a two-phase (greenhouse and field) common garden experiment demonstrated adaptation of mountain birch (betula pubescens subsp. czerepanovii) populations from industrially polluted areas of the kola peninsula, north-western russia, to heavy metals (hm), whereas no adaptations to wind or droug ... | 2009 | 19226419 |
| the effect of heat treatment of wood on osteoconductivity. | wood is a natural porous fibre composite, which has some structural similarities to bone. recently, it has been used as a modelling material in developing synthetic fibre-reinforced composite to be used as load-bearing non-metallic artificial bone material. in this study, the behaviour of wood implanted into bone was studied in vivo in the femur bone of the rabbit. wood was pre-treated by heat, which altered its chemical composition and structure, as well as the biomechanical properties. in the ... | 2009 | 19231305 |
| effects of a warmer climate on seed germination in the subarctic. | in a future warmer subarctic climate, the soil temperatures experienced by dispersed seeds are likely to increase during summer but may decrease during winter due to expected changes in snow depth, duration and quality. because little is known about the dormancy-breaking and germination requirements of subarctic species, how warming may influence the timing and level of germination in these species was examined. | 2009 | 19443459 |
| effect of ecosystem retrogression on stable nitrogen and carbon isotopes of plants, soils and consumer organisms in boreal forest islands. | in the prolonged absence of catastrophic disturbance, ecosystem retrogression occurs, and this involves increased nutrient limitation, and reduced aboveground and belowground ecosystem processes rates. little is known about how the nitrogen and carbon stable isotope ratios (delta(15)n and delta(13)c) of plants, soils and consumer organisms respond to retrogression in boreal forests. we investigated a 5000 year chronosequence of forested islands in the boreal zone of northern sweden, for which th ... | 2009 | 19462406 |
| the rhizosphere and pah amendment mediate impacts on functional and structural bacterial diversity in sandy peat soil. | to reveal the degradation capacity of bacteria in pah polluted soil and rhizosphere we combined bacterial extradiol ring-cleavage dioxygenase and 16s rrna analysis in betula pubescens rhizoremediation. characterisation of the functional bacterial community by rflp revealed novel environmental dioxygenases, and their putative hosts were studied by 16s rrna amplification. plant rhizosphere and pah amendment effects were detected by the rflp/t-rflp analysis. functional species richness increased in ... | 2010 | 20022155 |
| forage quantity, quality and depletion as scale-dependent mechanisms driving habitat selection of a large browsing herbivore. | 1. mechanisms that affect the spatial distribution of animals are typically scale-dependent and may involve forage distribution. forage quality and quantity are often inversely correlated and a much discussed trade-off is whether or not to select for high-quality forage at the expense of forage abundance. this discussion has rarely involved scale-dependence or been applied to northern browsing herbivores. at small spatial scales, browsers are assumed to select for the best quality forage. but, a ... | 2010 | 20443990 |
| root aeration in wetland trees by pressurized gas transport. | tracer gas studies and oxygen uptake measurements have shown that pressurized gas transport improves oxygen supply to roots in the wetland tree species taxodium distichum l. rich. (taxodiaceae), betula pubescens j.f. ehrh. (betulaceae), and populus tremula l. (salicaceae), but not in acer pseudoplatanus l. and ilex aquifolium l., which are found in drier habitats. in the deciduous tree species betula pubescens and populus tremula, pressurized gas transport was most evident during the resting per ... | 1992 | 14969985 |
| effects of elevated ultraviolet-b radiation on a plant-herbivore interaction. | enhanced ultraviolet-b (uv-b) radiation may have multiple effects on both plants and animals and affect plant-herbivore interactions directly and indirectly by inducing changes in host plant quality. in this study, we examined combined effects of uv-b and herbivory on the defence of the mountain birch (betula pubescens ssp. czerepanovii) and also the effects of enhanced uv-b radiation on a geometrid with an outbreak cycle: the autumnal moth (epirrita autumnata). we established an experiment mimi ... | 2010 | 20473770 |
| the ecological significance of phenology in four different tree species: effects of light and temperature on bud burst. | the process of adaptation is the result of stabilising selection caused by two opposite forces: protection against an unfavourable season (survival adaptation), and effective use of growing resources (capacity adaptation). as plant species have evolved different life strategies based on different trade offs between survival and capacity adaptations, different phenological responses are also expected among species. the aim of this study was to compare budburst responses of two opportunistic speci ... | 2010 | 21113629 |
| experimental evidence for herbivore limitation of the treeline. | the treeline ecotone divides forest from open alpine or arctic vegetation states. treelines are generally perceived to be temperature limited. the role of herbivores in limiting the treeline is more controversial, as experimental evidence from relevant large scales is lacking. here we quantify the impact of different experimentally controlled herbivore densities on the recruitment and survival of birch betula pubescens tortuosa along an altitudinal gradient in the mountains of southern norway. a ... | 2010 | 21141202 |
| ectomycorrhizal roots select distinctive bacterial and ascomycete communities in swedish subarctic forests. | ectomycorrhizal (ecm) roots represent important niches for interactions with bacteria and ascomycete fungi, since they have a large surface area and receive a direct supply of plant assimilates from their tree hosts. we tested the hypothesis that the roots colonized by specific ecm fungi harbour distinct bacteria/ascomycete communities. roots were collected from two different locations in a subarctic shrub forest dominated by betula pubescens. bacterial and ascomycete communities were analysed b ... | 2010 | 21176055 |
| ethanol extract from birch bark (betula pubescens) suppresses human dendritic cell mediated th1 responses and directs it towards a th17 regulatory response in vitro. | extracts and fractions from birch bark have been used to treat various diseases, such as skin disorders and rheumatism, and for analgesic effects. results from studies in vitro and in vivo have shown that birch bark extracts can have immunoregulatory effects. these effects have mainly been attributed to the various triterpenes found in birch bark. the effects of birch bark from betula pubescens on immune responses have not been reported. ethanol extract was prepared from dry birch bark (dbbee) a ... | 2011 | 21237202 |
| browsing affects intra-ring carbon allocation in species with contrasting wood anatomy. | current knowledge on tree carbon (c) allocation to wood is particularly scarce in plants subjected to disturbance factors, such as browsing, which affects forest regeneration worldwide and has an impact on the c balance of trees. furthermore, quantifying the degree to which tree rings are formed from freshly assimilated vs. stored carbohydrates is highly relevant for our understanding of tree c allocation. we used (13)c labelling to quantify seasonal allocation of stored c to wood formation in t ... | 2011 | 21388994 |
| [comparative evaluation of 238u and 226ra absorption by herbaceous and woody species under man-made pollution]. | the results of studies on uranium and radium distribution in soil and vegetation at the territory contaminated by wastes of radium plant in 1930-1950 are presented. specific activities of 226ra and 238u in soil varied as 0.01-200 and 0.004-7.58 bq/g per ash respectively. the radionuclides are mainly concentrated in the upper layer of soil profile. in the vegetation concentrations of 226ra and 238u varied as 0.64-132 0.001-0.02 bq/g per ash respectively. among the woody species studied, betula pu ... | 2010 | 21434390 |
| potential macro-detritivore range expansion into the subarctic stimulates litter decomposition: a new positive feedback mechanism to climate change? | as a result of low decomposition rates, high-latitude ecosystems store large amounts of carbon. litter decomposition in these ecosystems is constrained by harsh abiotic conditions, but also by the absence of macro-detritivores. we have studied the potential effects of their climate change-driven northward range expansion on the decomposition of two contrasting subarctic litter types. litter of alnus incana and betula pubescens was incubated in microcosms together with monocultures and all possib ... | 2011 | 21735203 |
| Assessment of biological and environmental phenology at a landscape level from 30 years of fixed-date repeat photography in northern Sweden. | A 30-year series (1978-2007) of photographic records were analysed to determine changes in lake ice cover, local (low elevation) and montane (high elevation) snow cover and phenological stages of mountain birch (Betula pubescens ssp. czerepanovii) at the Abisko Scientific Research Station, Sweden. In most cases, the photographic-derived data showed no significant difference in phenophase score from manually observed field records from the same period, demonstrating the accuracy and potential of ... | 2011 | 21954723 |
| comparative measurements of transpiration and canopy conductance in two mixed deciduous woodlands differing in structure and species composition. | transpiration of two heterogeneous broad-leaved woodlands in southern england was monitored by the sap flux technique throughout the 2006 growing season. grimsbury wood, which had a leaf area index (lai) of 3.9, was dominated by oak (quercus robur l.) and birch (betula pubescens l.) and had a continuous hazel (corylus avellana l.) understory. wytham woods, which had an lai of 3.6, was dominated by ash (fraxinus excelsior l.) and sycamore (acer pseudoplatanus l.) and had only a sparse understory. ... | 2008 | 18381276 |
| species-specific effect of uv-b radiation on the temporal pattern of leaf growth. | recent molecular and physiological studies have demonstrated that ultraviolet-b radiation (uv-b) can affect some of the processes involved in leaf growth, but the phases of leaf growth affected have not been clearly delimited. we used functional growth analysis to assess the effects of uv-b radiation on the time course of leaf growth in seedlings of two birch species (betula pendula and betula pubescens). our aim was to identify the phase(s) of leaf development affected by uv-b radiation. in a g ... | 2012 | 22224454 |
| changes in crown architecture as a strategy of mountain birch for survival in habitats disturbed by pollution. | although trees in polluted areas often exhibit modified growth habits, the immediate causes of changes in crown architecture and their consequences for persistence of plant populations in disturbed habitats are not well understood. we compared individuals of mountain birch, betula pubescens ssp. czerepanovii, growing in severely disturbed habitats (industrial barrens) surrounding a nickel-copper smelter in north-western russia, with birches growing in unpolluted habitats. they were found to have ... | 2012 | 23274240 |
| ecological role of reindeer summer browsing in the mountain birch (betula pubescens ssp. czerepanovii) forests: effects on plant defense, litter decomposition, and soil nutrient cycling. | mammalian herbivores commonly alter the concentrations of secondary compounds in plants and, by this mechanism, have indirect effects on litter decomposition and soil carbon and nutrient cycling. in northernmost fennoscandia, the subarctic mountain birch (betula pubescens ssp. czerepanovii) forests are important pasture for the semidomestic reindeer (rangifer tarandus). in the summer ranges, mountain birches are intensively browsed, whereas in the winter ranges, reindeer feed on ground lichens, ... | 2007 | 17123112 |
| doubled volatile organic compound emissions from subarctic tundra under simulated climate warming. | *biogenic volatile organic compound (bvoc) emissions from arctic ecosystems are important in view of their role in global atmospheric chemistry and unknown feedbacks to global warming. these cold ecosystems are hotspots of climate warming, which will be more severe here than averaged over the globe. we assess the effects of climatic warming on non-methane bvoc emissions from a subarctic heath. *we performed ecosystem-based chamber measurements and gas chromatography-mass spectrometry (gc-ms) ana ... | 2010 | 20456056 |