| interspecific variation in resistance of asian, european, and north american birches (betula spp.) to bronze birch borer (coleoptera: buprestidae). | bronze birch borer (agrilus anxius gory) is the key pest of birches (betula spp.) in north america, several of which have been recommended for ornamental landscapes based on anecdotal reports of borer resistance that had not been confirmed experimentally. in a 20-yr common garden experiment initiated in 1979 in ohio, north american birch species, including paper birch (betula papyrifera marshall), 'whitespire' gray birch (betula populifolia marshall), and river birch (betula nigra l.), were muc ... | 2011 | 22251643 |
| 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 |
| selective behaviour of honeybees in acquiring european propolis plant precursors. | honey bees harvest resins from various plant species and use them in the hive as propolis. while there have been a number of studies concerning the chemical composition of this antimicrobial product, little is known about selective behavior and bee preference when different potential plant sources of resin are available. the main objective of this paper was to investigate some aspects of behavioral patterns of honeybees in the context of resin acquisition. samples of propolis originating from te ... | 2016 | 27294416 |
| the contribution of trees to ecosystem methane emissions in a temperate forested wetland. | wetland-adapted trees are known to transport soil-produced methane (ch4 ), an important greenhouse gas to the atmosphere, yet seasonal variations and controls on the magnitude of tree-mediated ch4 emissions remain unknown for mature forests. we examined the spatial and temporal variability in stem ch4 emissions in situ and their controls in two wetland-adapted tree species (alnus glutinosa and betula pubescens) located in a temperate forested wetland. soil and herbaceous plant-mediated ch4 emiss ... | 2015 | 25665153 |
| studies on the role of abscisic acid in the initiation of bud dormancy in alnus glutinosa and betula pubescens. | the effects of leaf-applied (+-)-abscisic acid on the growth and dormancy of betula pubescens ehrh. and alnus glutinosa gaertn. growing under long days provide no evidence that leaf-applied abscisic acid induces or promotes the formation of resting buds in these species. radiotracer studies show that a small percentage of the radioactivity applied as [2-(14)c]abscisic acid to the leaves accumulates in the apical region of the shoot. of the radioactivity that was recovered from this region after ... | 1975 | 24435437 |
| defining an adequate sample of earlywood vessels for retrospective injury detection in diffuse-porous species. | vessels of broad-leaved trees have been analyzed to study how trees deal with various environmental factors. cambial injury, in particular, has been reported to induce the formation of narrower conduits. yet, little or no effort has been devoted to the elaboration of vessel sampling strategies for retrospective injury detection based on vessel lumen size reduction. to fill this methodological gap, four wounded individuals each of grey alder (alnus incana (l.) moench) and downy birch (betula pube ... | 2012 | 22761707 |
| photosynthesis, nutrient accumulation and growth of two betula species exposed to waterlogging in late dormancy and in the early growing season. | increased risk of soil waterlogging in winter and spring at northern latitudes will potentially affect forest production in the future. we studied gas exchange, chlorophyll content index, chlorophyll fluorescence, nutrient concentration and biomass accumulation in 1-year-old silver (betula pendula roth) and pubescent birch (betula pubescens ehrh.) seedlings. we hypothesized that b. pubescens has different physiological mechanisms that make it tolerate waterlogging better than b. pendula. the tre ... | 2017 | 28338895 |
| multispecies genetic structure and hybridization in the betula genus across eurasia. | boreal and cool temperate forests are the major land cover of northern eurasia, and information about continental-scale genetic structure and past demographic history of forest species is important from an evolutionary perspective and has conservation implications. however, although many population genetic studies of forest tree species have been conducted in europe or eastern asia, continental-scale genetic structure and past demographic history remain poorly known. here, we focus on the birch ... | 2017 | 27763698 |
| waterlogging in late dormancy and the early growth phase affected root and leaf morphology in betula pendula and betula pubescens seedlings. | the warmer winters of the future will increase snow-melt frequency and rainfall, thereby increasing the risk of soil waterlogging and its effects on trees in winter and spring at northern latitudes. we studied the morphology of roots and leaves of 1-year-old silver birch (betula pendula roth) and pubescent birch (betula pubescens ehrh.) seedlings exposed to waterlogging during dormancy or at the beginning of the growing season in a growth-chamber experiment. the experiment included 4-week dorman ... | 2016 | 26420790 |
| sap-feeding insects on forest trees along latitudinal gradients in northern europe: a climate-driven patterns. | knowledge of the latitudinal patterns in biotic interactions, and especially in herbivory, is crucial for understanding the mechanisms that govern ecosystem functioning and for predicting their responses to climate change. we used sap-feeding insects as a model group to test the hypotheses that the strength of plant-herbivore interactions in boreal forests decreases with latitude and that this latitudinal pattern is driven primarily by midsummer temperatures. we used a replicated sampling design ... | 2015 | 25044643 |
| mitochondrial toxin betulinic acid induces in vitro eryptosis in human red blood cells through membrane permeabilization. | betulinic acid (ba), a compound isolated from the bark of white birch (betula pubescens), was reported to induce apoptosis in many types of cancer through mitochondrial dysfunction with low side effects in normal cells. because of these features, ba is regarded as a potential anti-cancer agent. however, the effect of ba on the induction of cell death in human erythrocytes remains unknown. given that ba is a mitochondrial toxin and mitochondria are the central cell death regulator, we hypothesize ... | 2014 | 24241250 |
| effects of species-specific leaf characteristics and reduced water availability on fine particle capture efficiency of trees. | trees can improve air quality by capturing particles in their foliage. we determined the particle capture efficiencies of coniferous pinus sylvestris and three broadleaved species: betula pendula, betula pubescens and tilia vulgaris in a wind tunnel using nacl particles. the importance of leaf surface structure, physiology and moderate soil drought on the particle capture efficiencies of the trees were determined. the results confirm earlier findings of more efficient particle capture by conifer ... | 2013 | 23735814 |
| rapid wound-induced resistance in white birch (betula pubescens) foliage to the geometrid epirrita autumnata: a comparison of trees and moths within and outside the outbreak range of the moth. | two strains of a geometrid defoliator, epirrita autumnata, were used in bioassays to test existence and relative efficacy of rapid, wound-induced foliage resistance in two provenances of the white birch. one birch and one moth strain originated in the outbreak range of the moth and another outside it. both birch provenances responded to manual leaf damage by changes in foliage quality which significantly retarded growth of the insects, reducing their pupal weights and protracting larval periods. ... | 1985 | 28310669 |
| do understory or overstory traits drive tree encroachment on a drained raised bog? | one of the most important threats to peatland ecosystems is drainage, resulting in encroachment of woody species. the main aim of this study was to check which features -ndash- overstory or understory vegetation -ndash- are more important for shaping the seedling bank of pioneer trees colonizing peatlands (pinus sylvestris and betula pubescens). we hypothesized that tree stand parameters will be more important predictors of natural regeneration density than understory vegetation parameters, and ... | 2017 | 28376255 |
| influence of nitrogen availability on growth of two transgenic birch species carrying the pine gs1a gene. | an alternative way to increase plant productivity through the use of nitrogen fertilizers is to improve the efficiency of nitrogen utilization via genetic engineering. the effects of overexpression of pine glutamine synthetase (gs) gene and nitrogen availability on growth and leaf pigment levels of two betula species were studied. untransformed and transgenic plants of downy birch (b. pubescens) and silver birch (b. pendula) were grown under open-air conditions at three nitrogen regimes (0, 1, o ... | 2017 | 28067821 |
| phenological research of climate changes in the north part of lithuania by the phenological garden of šiauliai university. | šiauliai university botanical garden is a member of the international phenological garden network since 2005. it is the only one botanical garden in the east europe that participated in the programme. in 2015, 18 species were observed. for research, data of 14 plants was used. the aim of this study is to estimate the responsiveness of the species of plants of the phenological garden to annual and monthly precipitation and temperature of the air. the main variables in this investigation were grow ... | 2017 | 27604576 |
| ecosystem nitrogen fixation throughout the snow-free period in subarctic tundra: effects of willow and birch litter addition and warming. | nitrogen (n) fixation in moss-associated cyanobacteria is one of the main sources of available n for n-limited ecosystems such as subarctic tundra. yet, n2 fixation in mosses is strongly influenced by soil moisture and temperature. thus, temporal scaling up of low-frequency in situ measurements to several weeks, months or even the entire growing season without taking into account changes in abiotic conditions cannot capture the variation in moss-associated n2 fixation. we therefore aimed to esti ... | 2017 | 27391280 |
| shelters of leaf-tying herbivores decompose faster than leaves damaged by free-living insects: implications for nutrient turnover in polluted habitats. | leaf-eating insects can influence decomposition processes by modifying quality of leaf litter, and this impact can be especially pronounced in habitats where leaf-eating insects reach high densities, for example in heavily polluted areas. we hypothesized that the decomposition rate is faster for shelters of leaf-tying larvae than for leaves damaged by free-living insects, in particular due to the accumulation of larval frass within shelters. we exposed litter bags containing samples of three dif ... | 2016 | 27288287 |
| unidirectional diploid-tetraploid introgression among british birch trees with shifting ranges shown by restriction site-associated markers. | hybridization may lead to introgression of genes among species. introgression may be bidirectional or unidirectional, depending on factors such as the demography of the hybridizing species, or the nature of reproductive barriers between them. previous microsatellite studies suggested bidirectional introgression between diploid betula nana (dwarf birch) and tetraploid b. pubescens (downy birch) and also between b. pubescens and diploid b. pendula (silver birch) in britain. here, we analyse introg ... | 2016 | 27065091 |
| nutrient fluxes from insect herbivory increase during ecosystem retrogression in boreal forest. | ecological theory, developed largely from ungulates and grassland systems, predicts that herbivory accelerates nutrient cycling more in productive than unproductive systems. this prediction may be important for understanding patterns of ecosystem change over time and space, but its applicability to other ecosystems and types of herbivore remain uncertain. we estimated fluxes of nitrogen (n) and phosphorus (p) from herbivory of a common tree species (betula pubescens) by a common species of herbi ... | 2016 | 27008782 |
| seventeen-year trends in spring and autumn phenophases of betula pubescens in a boreal environment. | trends in the timing of spring and autumn phenophases of betula pubescens were investigated in the southern, middle, and northern boreal zones in finland. the field observations were carried out at 21 sites in the finnish national phenological network in 1997-2013. the effective temperature sum of the thermal growth period, i.e. the sum of the positive differences between diurnal mean temperatures and 5 °c (ets1), increased annually on average by 6-7 degree day units. timing of bud burst remaine ... | 2016 | 26686678 |
| transfer of elements relevant to nuclear fuel cycle from soil to boreal plants and animals in experimental meso- and microcosms. | uranium (u), cobalt (co), molybdenum (mo), nickel (ni), lead (pb), thorium (th) and zinc (zn) occur naturally in soil but their radioactive isotopes can also be released into the environment during the nuclear fuel cycle. the transfer of these elements was studied in three different trophic levels in experimental mesocosms containing downy birch (betula pubescens), narrow buckler fern (dryopteris carthusiana) and scandinavian small-reed (calamagrostis purpurea ssp. phragmitoides) as producers, s ... | 2016 | 26363398 |
| how reproducible are the measurements of leaf fluctuating asymmetry? | fluctuating asymmetry (fa) represents small, non-directional deviations from perfect symmetry in morphological characters. fa is generally assumed to increase in response to stress; therefore, fa is frequently used in ecological studies as an index of environmental or genetic stress experienced by an organism. the values of fa are usually small, and therefore the reliable detection of fa requires precise measurements. the reproducibility of fluctuating asymmetry (fa) was explored by comparing th ... | 2015 | 26157612 |
| comparative analyses of plastid and aflp data suggest different colonization history and asymmetric hybridization between betula pubescens and b. nana. | birches (betula spp.) hybridize readily, confounding genetic signatures of refugial isolation and postglacial migration. we aimed to distinguish hybridization from range-shift processes in the two widespread and cold-adapted species b. nana and b. pubescens, previously shown to share a similarly east-west-structured variation in plastid dna (pdna). we sampled the two species throughout their ranges and included reference samples of five other betula species and putative hybrids. we analysed 901 ... | 2015 | 26113148 |
| sámi reindeer herders' perspective on herbivory of subarctic mountain birch forests by geometrid moths and reindeer: a case study from northernmost finland. | geometrid moths and semi-domesticated reindeer are both herbivores which feed on birch leaves in the subarctic mountain birch forests in northern fennoscandia. the caterpillars of autumnal and winter moths have episodic outbreaks, which can occasionally lead to extensive defoliation of birch forests. earlier studies have shown that reindeer have a negative effect on the regeneration of defoliated birches by grazing and browsing their seedlings and sprouts. | 2015 | 25825690 |
| decomposition of birch leaves in heavily polluted industrial barrens: relative importance of leaf quality and site of exposure. | the decrease in litter decomposition rate in polluted habitats is well documented, but the factors that explain the observed variation in the magnitude of this pollution effect on litter decomposition remain poorly understood. we explored effects of environmental conditions and leaf quality on decomposition rate of mountain birch (betula pubescens ssp. czerepanovii) leaves in a heavily polluted industrial barren near the nickel-copper smelter at monchegorsk. litter bags filled with leaves collec ... | 2015 | 25663340 |
| carbon sequestration is related to mycorrhizal fungal community shifts during long-term succession in boreal forests. | boreal forest soils store a major proportion of the global terrestrial carbon (c) and below-ground inputs contribute as much as above-ground plant litter to the total c stored in the soil. a better understanding of the dynamics and drivers of root-associated fungal communities is essential to predict long-term soil c storage and climate feedbacks in northern ecosystems. we used 454-pyrosequencing to identify fungal communities across fine-scaled soil profiles in a 5000 yr fire-driven boreal fore ... | 2015 | 25494880 |
| rapid carbon turnover beneath shrub and tree vegetation is associated with low soil carbon stocks at a subarctic treeline. | climate warming at high northern latitudes has caused substantial increases in plant productivity of tundra vegetation and an expansion of the range of deciduous shrub species. however significant the increase in carbon (c) contained within above-ground shrub biomass, it is modest in comparison with the amount of c stored in the soil in tundra ecosystems. here, we use a 'space-for-time' approach to test the hypothesis that a shift from lower-productivity tundra heath to higher-productivity decid ... | 2015 | 25367088 |
| essential and non-essential elements in natural vegetation in southern norway: contribution from different sources. | concentrations of essential and non-essential elements in five widespread species of natural boreal vegetation were studied with respect to seasonal variation and contribution from different sources. the plant species included in the study were betula pubescens, sorbus aucuparia, vaccinium myrtillus, vaccinium uliginosum, calluna vulgaris and deschampsia flexuosa. concentrations of elements essential to plants remained essentially constant or decreased slightly throughout the growing season. con ... | 2015 | 25268568 |
| effect of heat treatment of wood on the morphology, surface roughness and penetration of simulated and human blood. | wood has been used as a model material for the development of novel fiber-reinforced composite bone substitute biomaterials. in previous studies heat treatment of wood was perceived to significantly increase the osteoconductivity of implanted wood material. | 2014 | 24840198 |
| molecular footprints of the holocene retreat of dwarf birch in britain. | past reproductive interactions among incompletely isolated species may leave behind a trail of introgressed alleles, shedding light on historical range movements. betula pubescens is a widespread native tetraploid tree species in britain, occupying habitats intermediate to those of its native diploid relatives, b. pendula and b. nana. genotyping 1134 trees from the three species at 12 microsatellite loci, we found evidence of introgression from both diploid species into b. pubescens, despite the ... | 2014 | 24762172 |
| treeline advances along the urals mountain range - driven by improved winter conditions? | high-altitude treelines are temperature-limited vegetation boundaries, but little quantitative evidence exists about the impact of climate change on treelines in untouched areas of russia. here, we estimated how forest-tundra ecotones have changed during the last century along the ural mountains. in the south, north, sub-polar, and polar urals, we compared 450 historical and recent photographs and determined the ages of 11,100 trees along 16 altitudinal gradients. in these four regions, boundari ... | 2014 | 24756980 |
| spatial heterogeneity in the timing of birch budburst in response to future climate warming in ireland. | in order to predict the impact of future climate warming on trees it is important to quantify the effect climate has on their development. our understanding of the phenological response to environmental drivers has given rise to various mathematical models of the annual growth cycle of plants. these models simulate the timing of phenophases by quantifying the relationship between development and its triggers, typically temperature. in addition, other environmental variables have an important rol ... | 2014 | 24037345 |
| gas chromatographic and mass spectrometric characterization of trimethylsilyl derivatives of some terpene alcohol phenylpropenoids. | this paper reports mass spectra and linear temperature programmed retention indices (i(t)) for 31 esters of mono- and sesquiterpene alcohols with hydroxycinnamic acids. in this study, 14 phenylpropenoids were synthesized by esterification of terpenols with p-coumaric, ferulic, caffeic and sinapinic acids. other phenylpropenoids were semi-quantitatively isolated by column chromatography from exudates covering the buds of two birch species (betula pubescens and b. litwinowii). main diagnostic ions ... | 2013 | 23749131 |
| simulated browsing affects leaf shedding phenology and litter quality of oak and birch saplings. | herbivore effects on leaf litter can have a strong impact on ecosystem nutrient cycling. although such effects are well described for insect herbivory, research on the impacts of browsing by mammalian herbivores on leaf litter dynamics and nutrient cycling has been more limited, particularly at the level of the individual plant. clipping treatments (66% shoot removal twice, plus unclipped) were applied to analyse the effect of browsing on the phenology (start date and pattern of leaf shedding) a ... | 2013 | 23574752 |
| effect of different steam explosion conditions on methane potential and enzymatic saccharification of birch. | birch (betula pubescens) was steam exploded at 13 different conditions with temperatures ranging from 170 to 230 °c and residence times ranging from 5 to 15 min. increasing severity in the pretreatment led to degradation of xylan and formation of pseudo-lignin. the effect of the pretreatments was evaluated by running enzymatic saccharification and anaerobic digestion followed by analysis of sugar and methane yields, respectively. enzymatically released glucose increased with pretreatment severit ... | 2013 | 23131658 |
| genetic and environmental factors behind foliar chemistry of the mature mountain birch. | previous studies of mountain birch (betula pubescens spp. czerepanovii) repeatedly have found differences between individual trees in herbivory-related traits, but rarely have yielded estimates of the additive genetic variation of these traits or of their relationship to habitat. we used thirty-year-old birch half-sibs in a northern common garden to estimate the effect of genetics and local microhabitat on resistance-related traits. genetic estimates of foliar chemistry have been studied only ra ... | 2012 | 22684775 |
| nonvolatile chemical cues affect host-plant ranking by gravid polygonia c-album females. | in a multiple-choice test, the preference of egg-laying polygonia c-album (comma butterfly) females was studied for oviposition on plants bearing surrogate leaves treated with crude methanol extracts obtained from leaves of seven host-plant species: humulus lupulus, urtica dioica, ulmus glabra, salix caprea, ribes nigrum, corylus avellana, and betula pubescens. the ranking order of surrogate leaves treated with host-plant extracts corresponded well to that reported on natural foliage, except r. ... | 2012 | 22486046 |
| the minimum temperature for budburst in betula depends on the state of dormancy. | vegis has put forward the theory that the range of growth-promoting temperatures changes during the induction and the release of dormancy. we have tested the response of buds of betula pubescens ehrh. and b. pendula roth. on temperature during the induction and release of dormancy. betula seedlings were exposed to dormancy-inducing high-temperature and short-day conditions and subsequently to dormancy-releasing chilling conditions in darkness. to monitor the dormancy status of the seedlings, sub ... | 2012 | 22391009 |
| performance of moth larvae on birch in relation to altitude, climate, host quality and parasitoids. | we studied topographical and year-to-year variation in the performance (pupal weights, survival) and larval parasitism of epirrita autumnata larvae feeding on mountain birch in northernmost finland in 1993-1996. we found differences in both food plant quality and parasitism between sites ranging from 80 m to 320 m above sea level. variation in food plant quality had particularly marked effects on larval survival. the advanced phenology of the birches in relation to the start of the larval period ... | 1999 | 28308059 |
| multiplicity of biochemical factors determining quality of growing birch leaves. | due to rapidly changing physical and biochemical characteristics of growing leaves, correlations between traits of foliage biochemistry and the performance indices of flush feeding herbivores may vary considerably following relatively minor changes in experimental conditions. we examined the effects of the seasonal and inter-tree variation of a comprehensive array of biochemical compounds on the success of an early season geometrid, epirrita autumnata, feeding on maturing foliage of mountain bir ... | 1999 | 28308041 |
| growth response of altitudinal ecotypes of mountain birch to temperature and fertilisation. | high- and low-altitude ecotypes of mountain birch (betula pubescens ssp. czerepanovii) showed clear differences in their responses to various experimental conditions, including two temperature regimes and four fertilisation rates. there was, however, no simple way to characterise the elevational ecotypes in terms of relative growth rate, nitrogen (n) productivity, or root n uptake rate. the leaf n concentration was generally higher in the high-altitude seedlings than in the low-altitude seedling ... | 1999 | 28308155 |
| birch family and environmental conditions affect endophytic fungi in leaves. | we investigated whether variation in foliar endophyte frequency among mountain birch trees from different maternal families was due in part to genetic differences among trees. the effect of different environmental conditions on the susceptibility of these mountain birch families to foliar endophytes was tested. the 3-year study was conducted in two tree gardens (altitudinal difference 180 m) with ten families of mountain birch. the frequency of the commonest endophytic fungus in mountain birch l ... | 1999 | 28307689 |
| delayed induced changes in the biochemical composition of host plant leaves during an insect outbreak. | in birch, betula pubescens, herbivore-induced delayed induced resistance (dir) of defoliated trees may cause a strong reduction in the potential fecundity of a geometrid folivore epirrita autumnata. in this study, we examined the biochemical basis of dir in birch leaves during a natural outbreak of e. autumnata. a set of experimental trees was defoliated at four sites by wild larvae in the peak year of the outbreak, whereas control trees were protected from defoliation by spraying with an insect ... | 1998 | 28308525 |
| wood ants and a geometrid defoliator of birch: predation outweighs beneficial effects through the host plant. | soil amelioration by a wood-ant species and its consequences for the larval performance of autumnal moths feeding on mountain birch were studied at various distances from the nest mound. soil nitrate and ammonium nitrogen did not show any clear relationship with distance. however, trees growing in the mound had over 20% more foliar nitrogen than more distant trees. when moth larvae were experimentally protected from predation, their survival rate and final weight tended to decrease with increasi ... | 1998 | 28308030 |
| variation of total phenolic content and individual low-molecular-weight phenolics in foliage of mountain birch trees (betula pubescens ssp.tortuosa). | we studied seasonal and between-tree variation in the composition and content of total and individual low-molecular-weight phenolics (lmwp) in leaves of mountain birch trees (betula pubescens ssp.tortuosa). the major phenolic compounds were chlorogenic acid, quercetin-3-o-β-d-glucuronopyranoside, myricetin-3-o-(5-acetyl)-l-rhamnopyranoside, and 1-o-galloyl-β-d-(2-o-acetyl)-glucopyranose. the content of total phenolics, as well as the sum of individual lmwp, varied only slightly among trees while ... | 1996 | 24227214 |
| variation among and within mountain birch trees in foliage phenols, carbohydrates, and amino acids, and in growth ofepirrita autumnata larvae. | leaf quality of the mountain birch (betula pubescens ssp.tortuosa) for herbivores was studied at several hierarchical levels: among trees, among ramets within trees, among branches within ramets, and among short shoots within branches. the experimental units at each level were chosen randomly. the indices of leaf quality were the growth rate of the larvae of a geometrid,epirrita autumnata, and certain biochemical traits of the leaves (total phenolics and individual phenolic compounds, total carb ... | 1995 | 24233674 |
| inhibition of growth, and effects on nutrient uptake of arctic graminoids by leaf extracts - allelopathy or resource competition between plants and microbes? | previous research has shown that plant extracts, e.g. from boreal dwarf shrubs and trees, can cause reduced growth of neighbouring plants: an effect known as allelopathy. to examine whether arctic and subarctic plants could also be affected by leaching of phytochemicals, we added extracts from the commonly occurring arctic dwarf shrubs cassiope tetragona and empetrum hermaphroditum, and from mountain birch, betula pubescens ssp. tortuosa to three graminoid species, carex bigelowii, festuca vivip ... | 1995 | 28306988 |
| host plant utilization in the comma butterfly: sources of variation and evolutionary implications. | a major challenge in the study of insect-host plant interactions is to understand how the different aspects of offspring performance interact to produce a preference hierarchy in the ovipositing females. in this paper we investigate host plant preference of the polyphagous butterfly polygonia c-album (lepidoptera: nymphalidae) and compare it with several aspects of the life history of its offspring (growth rate, development time, adult size, survival and female fecundity). females and offspring ... | 1994 | 28313958 |
| relationship of aluminium and calcium to net co2 exchange among diverse scots pine provenances under pollution stress in poland. | light-saturated net photosynthesis (asat), dark respiration (rd), and foliar nutrient content of eight european scots pine (pinus sylvestris l.) provenances were measured at experimental sites in western poland. two-year-old seedlings were planted in 1984 at two sites with similar soils in areas of contrasting air pollution. one site was near a point source of so2 and other pollutants, and another 12 km to the southeast in an area free of acute air pollution was treated as a control. the eight p ... | 1994 | 28313592 |
| simulated acid rain affects birch leaf endophyte populations. | endophytes were frequently isolated from mountain birch (betula pubescens var. tortuosa (ledeb.) nyman) leaves at a subarctic site where natural air pollution is low. we tested whether simulated acid rain had any influence on the occurrence of endophytes. dry controls with only ambient rain and irrigated controls treated with spring water of ph 6 were compared with acid treatments at ph 3 and ph 4, prepared by adding both sulphuric and nitric acids. treatments began in 1985 and leaf samples were ... | 1993 | 24190092 |
| sources of variation in rapidly inducible responses to leaf damage in the mountain birch-insect herbivore system. | studies on rapidly inducible resistance in trees against insect herbivores show substantial variation in the strength of responses. here we report the results of a study which examined causes of this variation. we bioassayed the quality of leaves of two developmental phases (young vs. mature) of the mountain birch betula pubescens ssp. tortuosa by measuring the growth of two instars of epirrita autumnata larvae. we used only short shoot leaves from trees of a natural stand, uniform in size and a ... | 1992 | 28313538 |
| consequences of herbivory in the mountain birch (betula pubescens ssp tortuosa): importance of the functional organization of the tree. | three types of experiments indicate that the functional organization of the mountain birch may influence the ways in which the tree responds to simulated or natural herbivory. the first experiment showed that herbivory to both short and long shoot leaves affects plant development but, because growth largely proceeds by resources of the previous year, is manifested only in the year following the damage. the second experiment showed that even partial damage to a single long shoot leaf caused the a ... | 1990 | 28312670 |
| induced resistance in mountain birch: defence against leaf-chewing insect guild and herbivore competition. | the effect of leaf damage simulating the feeding of early season insect herbivore species, e.g. epirrita autumnata, to mountain birch, betula pubescens ssp. tortuosa, on the performance of insect larvae was studied with eleven leaf-chewing sawfly species. i found variation in the results that was due to short- and long-term inducible responses and to the phenology of herbivore species. in general, early and mid-season species were more strongly affected by induced reactions than late-season spec ... | 1989 | 28312543 |
| foliage phenols and nitrogen in relation to growth, insect damage, and ability to recover after defoliation, in the mountain birch betula pubescens ssp tortuosa. | we studied growth of the mountain birch, and the role of foliage phenols, nitrogen, and variance in the timing of bud burst, as potential defensive characters, in finnish lapland in 1975-1979. annual and local variation both in phenol and nitrogen concentration of foliage were significant. individual trees retained their position in the foliage and nitrogen distribution of the population in successive years, as well as in the order of leaf flush in spring. growth of twigs, mature leaf size, and ... | 1985 | 28310668 |
| wound-induced changes in the palatability of betula pubescens and b. pendula. | leaves of betula were damaged artificially in april, june and august 1982. palatability of damaged and adjacent undamaged leaves was assessed against controls in bioassays using the polyphagous lepidoptera spodoptera littoralis and orgyia antiqua. assessments were carried out at intervals from six hours to five months following each damage date. palatability (relative proportions of leaves consumed) was significantly lower than controls in damaged and adjacent leaves after six hours and remained ... | 1984 | 28311065 |
| the influence of ants on the survival of mountain birches during an oporinia autumnata (lep., geometridae) outbreak. | the present study reports the influence of ants on the survival of mountain birch (betula pubescens ssp. tortuosa) during an oporinia autumnata (lep., geometridae) outbreak. undamaged "green islands" with a radius of 15-20 m were observed around formica aquilonia mounds in a defoliated area in finnish lapland. the herbivore densities and grazing pressure were shown to be low within this radius. the foraging strategy of ants and their influence on birch growth are discussed. | 1980 | 28309626 |
| some physiological responses to d,l abscisin (dormin). | the responses to synthetic d,l abscisin have been studied in a variety of tests. when fed in aqueous solution continuously to leaves of seedlings growing under long day conditions, d,l abscisin caused the cessation of extension growth and the formation of typical resting-buds in betula pubescens, acer pseudoplatanus and ribes nigrum. abscisin also inhibited the growth of non-dormant buds of potato when applied to the whole tubers, but was much less effective when applied to isolated tuber plugs. ... | 1967 | 24554370 |
| apical dominance and the effect of gravity on nutrient distribution. | the effect of orientation with resepct to gravity on the accumulation of phosphorus-32 into lateral and leader apices has been investigated in seedling trees of betula pubescens. in upright, well-branched seedlings, showing only weak apical dominance, basally injected (32)p is distributed more or less equally among the lateral and leader apices. re-orientation treatments which result in the assumption of strong dominance by a lateral apex also result in a marked accumulation of (32)p into that a ... | 1966 | 24557931 |