Siga este link para ver outros tipos de publicações sobre o tema: Banksia nutrition.
Artigos de revistas sobre o tema "Banksia nutrition"
Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos
Veja os 21 melhores artigos de revistas para estudos sobre o assunto "Banksia nutrition".
Ao lado de cada fonte na lista de referências, há um botão "Adicionar à bibliografia". Clique e geraremos automaticamente a citação bibliográfica do trabalho escolhido no estilo de citação de que você precisa: APA, MLA, Harvard, Chicago, Vancouver, etc.
Você também pode baixar o texto completo da publicação científica em formato .pdf e ler o resumo do trabalho online se estiver presente nos metadados.
Veja os artigos de revistas das mais diversas áreas científicas e compile uma bibliografia correta.
1
Grose, M. J. "SUSCEPTIBILITY TO PHYTOPHTHORA AND NUTRITION OF BANKSIA SPECIES". Acta Horticulturae, n.º 185 (junho de 1986): 265–66. http://dx.doi.org/10.17660/actahortic.1986.185.30.
Texto completo da fonte
2
Handreck, KA. "Interactions Between Iron and Phosphorus in the Nutrition of Banksia ericifolia L.f var ericifolia (Proteaceae) in Soil-Less Potting Media". Australian Journal of Botany 39, n.º 4 (1991): 373. http://dx.doi.org/10.1071/bt9910373.
Texto completo da fonteResumo:
Interactive effects of iron and phosphorus on the growth and appearance of Banksia ericifolia L.f. var. ericifolia seedlings were investigated. The seedlings were grown in a pinebark-based soil-less potting medium amended with 0-40 mg L-1 P added as single superphosphate and with Fe supplied either as FeSO4.7H2O (at 0-3 g L-1) or FeEDDHA (at 0-430 mg L-1). Fe deficiency was the dominant visual effect on shoots; its severity increased as P supply increased. Classic symptoms of P toxicity (death of oldest leaves) were produced in plants at the highest levels of P supply and low Fe supply. At each level of added P, Fe tended to lower %P in the shoots, mainly by allowing increased production of dry matter as Fe deficiency was overcome. The highest rate of FeSO4.7H2O addition reduced accumulation of P in the leaves and increased it in the stems. High P additions reduced accumulation of Fe into leaves. At non-toxic additions of P, young leaves had higher concentrations of P than did old leaves, but the reverse applied as P supply became excessive. The leaves of high quality plants contained less than about 0-14% P and more than 30 mg kg-1 Fe. P:Fe ratios for the leaves of such plants were in the range 14-53 (mean 23). Numbers of proteoid root clusters were greatest on plants in media of high Fe supply and low P and declined rapidly as P supply increased above the adequate range. No evidence was found for Fe stress leading to greater development of proteoid roots. Quality scores of at least 85% of maximum were mainly confined to media giving < 3 mg L-1 P in 2 mM DTPA (1:1.5 volume) extracts and amended with at least 1.5 g L-1 FeSO4.7H2O or 215 mg L-1 FeEDDHA. Response in ferrous sulfate treatments was better correlated with extractable P and Fe than with totals added, but there was no difference with FeEDDHA treatments, because additions of FeEDDHA did not decrease extractable P and ferrous sulfate did.
3
Bennett, L. T., e P. M. Attiwill. "The Nutritional Status of Healthy and Declining Stands of Banksia integrifolia on the Yanakie Isthmus, Victoria". Australian Journal of Botany 45, n.º 1 (1997): 15. http://dx.doi.org/10.1071/bt96025.
Texto completo da fonteResumo:
Banksia integrifolia L.f. has been in decline on calcareous sands of the Yanakie Isthmus, southern Victoria, since early 1980. Early studies indicated that the decline is associated with a particular soil condition possibly a nutritional imbalance involving Fe. However, in foliage samples collected from the three main soil types of the Isthmus, declining trees had similar concentrations of Fe but lower concentrations of Ca than healthy trees. Comparisons were made of seasonal variation in concentrations of macro- and micro-nutrients in foliage and litterfall from healthy trees (to minimise secondary changes associated with decline) within healthy and declining sites on the same soil type. On average, litterfall and the nutrient content of litterfall was greatest within the canopy area of B. integrifolia of the healthy stand. Banksias of the healthy stand also had greater concentrations of N, P, K and Na in fully-expanded leaves, resorbed greater proportions of phloem-mobile nutrients from senescent leaves and accumulated more Ca in senescent leaves. However, there was no evidence of nutritional imbalance in healthy trees within declining stands. It is argued that the lower foliar Ca in declining trees on three soil types and lower nutritional status of healthy trees within declining stands were due to lower productivity and lower water use and were therefore a result or an indication of decline rather than a cause.
4
van Tets, I. G. "Can Flower-Feeding Marsupials Meet Their Nitrogen Requirements on Pollen in The Field?" Australian Mammalogy 20, n.º 3 (1998): 383. http://dx.doi.org/10.1071/am98383.
Texto completo da fonteResumo:
Two arboreal marsupials, the eastern pygmy possum (Cercartetus nanus) and the sugar glider (Petaurus breviceps) have exceptionally low maintenance nitrogen requirements on pollen diets. This study compares their nitrogen requirements with the density of Banksia pollen that is available in the Barren Grounds Nature Reserve, New South Wales, a site where both species are known to forage on Banksia inflorescences. The pollen density was sufficiently high that both species were capable of meeting their maintenance nitrogen requirements on pollen whenever Banksia spp. were in flower. C. nanus required a smaller proportion of its home range than P. breviceps to do so and pollen was likely to be of much greater nutritional significance to both species in winter than in summer. This corresponds closely with the results of field studies comparing the diets of these mammals at different times of the year. Pollen is an important source of nitrogen for flower-feeding marsupials but its importance will vary between species depending on the marsupial's requirements, its body size and on the quantity of pollen that is available.
5
Bhadra, Mithu, Pabitra Paul, Tanima Das e Ashish Mukhopadhyay. "Physical growth pattern and nutritional status among adolescent Bhumij boys of Khatra Block, Bankura District, West Bengal, India". INTERNATIONAL JOURNAL OF EXPERIMENTAL RESEARCH AND REVIEW 16 (30 de agosto de 2018): 1–6. http://dx.doi.org/10.52756/ijerr.2018.v16.001.
Texto completo da fonteResumo:
A cross-sectional study of 238 adolescent Bhumij boys aged 11-16 years of Khatra block, Bankura district of West Bengal, India was undertaken to study their physical growth and nutritional status. The subjects were classified into six age groups: 11-11.9 (n=35), 12-12.9 (n=41), 13-13.9 (n=39), 14-14.9 (n=45), 15-15.9 (n=40), 16-16.9 (n=38). Physical growth status (estimated by height and weight) was compared with national standard. Nutritional status (undernutrition) was determined by the age and sex specific BMI cutoffs (less than fifth percentile values) based on the National Health and Nutrition Examination Survey (NHANES I). Results shows that studied Bhumij boys were slightly shorter than the national standard at each age and heavier at late adolescence. The overall rate of undernutrition was 53.36%. The rates of undernutrition varied between 47.37% among 16 year olds to 57.50% at age 15 years. There was a gradual increasing trend of undernutrition from 11 to 15 years. Thereafter, there was a slight declining trend in the rates of undernutrition at age 16 (47.37%) years. In general, this study provided facts that the adolescent Bhumij boys had alarming rates of undernutrition. These rates of undernutrition were; in general, agree with the earlier Indian studies but higher than those found among adolescents in several developing countries.
6
Xu, Feng, Maryamsadat Vaziriyeganeh e Janusz J. Zwiazek. "Effects of pH and Mineral Nutrition on Growth and Physiological Responses of Trembling Aspen (Populus tremuloides), Jack Pine (Pinus banksiana), and White Spruce (Picea glauca) Seedlings in Sand Culture". Plants 9, n.º 6 (27 de maio de 2020): 682. http://dx.doi.org/10.3390/plants9060682.
Texto completo da fonteResumo:
Responses of trembling aspen (Populus tremuloides), jack pine (Pinus banksiana), and white spruce (Picea glauca) seedlings to root zone pH ranging from 5 to 9 were studied in sand culture in the presence of two mineral nutrition levels. After eight weeks of treatments, effects of pH on plant dry weights varied between the plant species and were relatively minor in white spruce. Higher nutrient supply significantly increased dry weights only in trembling aspen subjected to pH 5 treatment. There was little effect of pH and nutrition level on net photosynthesis and transpiration rates in white spruce and jack pine, but net photosynthesis markedly declined in aspen at high pH. Chlorophyll concentrations in young foliage decreased the most in trembling aspen and jack pine. The effects of high pH treatments on the concentrations of Mg, P, Ca, Mn, Zn, and Fe in young foliage varied between the plant species with no significant decreases of Fe and Zn recorded in trembling aspen and white spruce, respectively. This was in contrast to earlier reports from the studies carried out in hydroponic culture. The sand culture system that we developed could be a more suitable alternative to hydroponics to study plant responses to pH in the root zone. Plant responses to high pH appear to involve complex events with a likely contribution of nutritional effects and altered water transport processes.
7
Thiffault, Evelyne, Nicolas Bélanger, David Paré e Alison D. Munson. "How do forest harvesting methods compare with wildfire? A case study of soil chemistry and tree nutrition in the boreal forest". Canadian Journal of Forest Research 37, n.º 9 (setembro de 2007): 1658–68. http://dx.doi.org/10.1139/x07-031.
Texto completo da fonteResumo:
An important tenet of the natural disturbance paradigm as a basis for sustainable forest management is that impacts of interventions fall within the range of natural variation observed for the disturbance in question. We evaluated differences in soil nutrients, soil acid–base status, and tree nutrition between two harvesting methods (whole-tree (WTH) and stem-only (SOH)) and wildfire, 15–20 years after disturbance, to assess whether these harvesting methods have biogeochemical impacts that are within the natural range of variation caused by wildfires in boreal coniferous stands of Haute-Mauricie (Quebec). Both SOH and WTH created conditions of forest floor effective cation-exchange capacity, exchangeable Ca and K concentrations, base saturation, Ca:Al molar ratio, and organic C concentrations that were lower than the range of values for wildfires. We hypothesize that the immediate deposition of soluble base cations and the incorporation of recalcitrant organic matter that characterize wildfires generate biogeochemical conditions that are not emulated by either harvesting method. The improved soil nutritional environment after wildfire compared with SOH and WTH was reflected in jack pine ( Pinus banksiana Lamb.) foliar nutrient composition but not in black spruce ( Picea mariana (Mill.) BSP) foliage. The results raise uncertainties about the long-term base nutrient availability of the harvested sites on Boreal Shield soils.
8
Thorpe, H. C., e V. R. Timmer. "Early growth and nutrient dynamics of planted Pinus banksiana seedlings after slash-pile burning on a boreal forest site". Canadian Journal of Soil Science 85, n.º 1 (1 de fevereiro de 2005): 173–80. http://dx.doi.org/10.4141/s04-011.
Texto completo da fonteResumo:
Containerized jack pine (Pinus banksiana Lamb.) seedlings were planted in 10 paired slash-pile-burn and control plots established on a recent clearcut in north eastern Ontario to assess early impacts of intensive fire on soils and plant growth and nutrition. Root zone soil and seedlings were sampled one growing season after planting. The control seedlings exhibited modest growth without gain in N content, indicating reliance on internal nutrient reserves for growth on this low-fertility site. Slash-pile burning reduced seedling mortality, and markedly increased height, rootcollar diameter, and biomass growth, as well as uptake of N, P, K, Ca and Mg. The response was attributed to greatly improved soil fertility following fire, characterized by increased pH, extractable NO3- and NH4+ , available P, and exchangeable K, Ca and Mg. Significant correlations between corresponding soil tests and seedling nutrient composition indicated that laboratory extractions effectively reflected nutrient availability to plants. The highest correlations were associated with N. Vector diagnosis identified N as the most limiting nutrient constraining growth on the burns, even though base cation increases (mainly from ash) were relatively larger than extractable N in the soil. These early responses in soils and plants to intensive fire may have long-term effects on plantation development. Key words: Slash pile, prescribed fire, soil fertility, seedling nutrition
9
., Shilpita Bhandari, Mihir Ghosh . e Kaushik Bose . "SOCIO-DEMOGRAPHIC CHARACTERISTICS AND PREVALENCE OF UNDER NUTRITION AMONG ADULT SABARS OF BANKURA DISTRICT, WEST BENGAL, INDIA". International Journal of Advancement in Life Sciences Research 2, n.º 1 (31 de janeiro de 2019): 1–10. http://dx.doi.org/10.31632/ijalsr.2019v02i01.001.
Texto completo da fonte
10
Fleming, Patricia A., e Tracey L. Moore. "Do experimental methods affect estimates of pollen digestion by birds?" Australian Journal of Zoology 59, n.º 6 (2011): 407. http://dx.doi.org/10.1071/zo12016.
Texto completo da fonteResumo:
Pollen protoplasts may supply important nutritional resources for birds; however, they are locked up within the mechanically strong and biochemically complex pollen wall. Previous studies of pollen digestion in birds have yielded highly variable and often contradictory results. We tested whether these differences could reflect the vastly different methodologies that have been used. We used a standard method to investigate digestion of Banksia grandis (Proteaceae) pollen in New Holland honeyeaters (Phylidonyris novaehollandiae). Four types of B. grandis pollen were examined: fresh, frozen for a week, stored in conditions to stimulate pregermination for 24 h, or collected by honeybees. Our data indicate that although pollen treatment may influence digestibility of the pollen grains, these differences do not reach statistical significance because they are dwarfed by a high degree of variability between birds fed the same diet as well as variability in gut transit time (generally more pollen grains were digested over longer transit times). Similar patterns were observed for red wattlebirds (Anthochaera carunculata) fed bee-collected pollen. We believe that feeding behaviour or gut transit time may explain the marked differences between previous studies of pollen digestion by nectarivores, particularly the conflicting results for New Holland honeyeaters.
11
Mukhopadhyay, DiptaKanti, Satabdi Mitra, AdityaPrasad Sarkar e Indrajit Saha. "Are household food security, nutrient adequacy, and childhood nutrition clustered together? A cross-sectional study in Bankura, West Bengal". Indian Journal of Public Health 63, n.º 3 (2019): 203. http://dx.doi.org/10.4103/ijph.ijph_357_18.
Texto completo da fonte
12
Patsa*, Malay Kumar, Dibya Pal, Srimanta Sen, Mousumi Ganguly, Nirmalya Kumar Sinha, Dulal Chandra Das, Sumendev Chakrabortty e Monalisa Das. "Relationship of menstrual disorders with nutritional status of college girls from Bankura District, West Bengal, India." International Journal of Bioassays 5, n.º 04 (31 de março de 2016): 4515. http://dx.doi.org/10.21746/ijbio.2016.04.0012.
Texto completo da fonteResumo:
Menstrual disorders are the most common complaints of the women. This often leads to anxiety, depression and other such psychological problems. The present study was conducted to find out the association of nutritional status with menstrual pattern and menstrual disorders of college girls. This study was employed on ninety-seven female college students (18- 22 years) of Bankura district. A pre-tested, semi-structured questionnaire was used to collect socioeconomic data and information regarding menstrual pattern and disorders. Anthropometric parameters including body mass index (BMI), body fat percentage (PBF), body adiposity index (BAI) was determined and mid-thigh circumference (MTC) was measured of each girls. From this study it was found that the Age at menarche (AAM) of college girls was 12.76±1.32 which was inversely related to the socioeconomic status and some anthropometric parameters like BMI, PBF, BAI, MTC etc. Monthly per capita income (MPCI) was an important determinant of weight (F=4.374; P=0.015), BMI (F=3.414; P=0.037), PBF (F=3.600; P=0.031) among the college girls. Pearson Product Moment Correlation showed that AAM, maternal education, number of sibling, number of family members, MPCI was associated with some anthropometric parameters viz. BMI, MTC, PBF, BAI. Linear Regression analysis showed that among the five factors (viz. AAM, maternal education, number of sibling, number of family members, MPCI) the maternal education and MPCI was the main determining factor for BMI. The prevalence of PMS, dysmenorrhoea and leucorrhoea was 67.01%, 73.20% and 85.57% in this study population. It can be concluded that AAM was inversely related to the anthropometric parameters (BMI, PBF, BAI, MTC) and more than two third of the college students was suffering from different menstrual disorders. U-shaped relationship between BMI and dysmenorrhea clearly focused the influence of body fat on dysmenorrhoea.
13
Brandt, J. P., Y. Hiratsuka e D. J. Pluth. "Adhesives for seed placement during artificial inoculation of Pinus banksiana seedlings with the dwarf mistletoe Arceuthobium americanum". Canadian Journal of Botany 81, n.º 10 (1 de outubro de 2003): 1039–43. http://dx.doi.org/10.1139/b03-098.
Texto completo da fonteResumo:
Lodgepole pine dwarf mistletoe (Arceuthobium americanum Nutt. ex Engelm.) is a serious pest of jack pine (Pinus banksiana Lamb.). Research investigating factors such as host resistance, influence of host nutrition on infection rates, and effect of temperature and humidity on the life cycle of the pathogen is limited by our ability to consistently infect the host through artificial means. A greenhouse experiment utilizing a completely randomized design with four replicates was conducted to test the effectiveness of three chemical compounds and the natural viscin of the dwarf mistletoe seed to act as adhesives during artificial inoculation of jack pine seedlings. Synthetic adhesives used were anhydrous lanolin (LAN), hydroxypropylcellulose (HPC), and polyvinyl acetate (PVA). The percentage of infected seedlings was significantly higher with HPC compared with that of PVA, LAN, and the seed's viscin. HPC, as the superior adhesive, and the techniques described should allow consistent production of seedlings infected with dwarf mistletoe for research, regardless of the dwarf mistletoe species involved. Problems encountered during the testing of the adhesives are discussed in relation to the nature of the adhesives and their application.Key words: anhydrous lanolin, hydroxypropylcellulose, polyvinyl acetate, viscin.
14
Shit, Subhadeep, Pranita Taraphdar, DiptaK Mukhopadhyay, Apurba Sinhababu e AkhilB Biswas. "Assessment of nutritional status by composite index for anthropometric failure: A study among slum children in Bankura, West Bengal". Indian Journal of Public Health 56, n.º 4 (2012): 305. http://dx.doi.org/10.4103/0019-557x.106421.
Texto completo da fonte
15
Kumar Patsa, Malay. "Relationship Between Nutritional Status and Academic Performance of Primary School Children in Rural Bankura Region of West Bengal, India". Bioscience Biotechnology Research Communications 14, n.º 2 (15 de junho de 2021): 686–91. http://dx.doi.org/10.21786/bbrc/14.2.37.
Texto completo da fonte
16
Gupta, Avisek, Tanjib Hassan Mullick, Gourab Biswas e Sohanjan Chakraborty. "A study on feeding practice and its effect on growth and morbidity of infants in the first 6 months of life in slums of Bankura Municipality". Asian Journal of Medical Sciences 13, n.º 11 (1 de novembro de 2022): 219–27. http://dx.doi.org/10.3126/ajms.v13i11.44973.
Texto completo da fonteResumo:
Background: Infant feeding practice in first 6 months of life is a major determinant of growth, nutritional status, and morbidity. Aims and Objectives: This study conducted to assess the infant feeding practice in first 6 months of life and to determine its effect on growth, nutritional status, and morbidity of study participants. Materials and Methods: A population-based longitudinal study was conducted among 49 infants in slums of Bankura Municipality within 1 week of their birth and they were followed up to the age of 6 months. Results: Proportions of male and female infants were almost equal. Proportions of exclusively breastfed infants at 0, 3, and 6 months were 87.8%, 79.6%, and 46.9%,respectively. Mean weight and length gain at 6 months were significantly higher in infants with increased duration of exclusive breastfeeding (P=0.008 and 0.042, respectively). Mean cumulative infant feeding score (at 6 months) was higher among normal babies (115.6±0.7.3) than the underweight babies (110.0±3.7). Mean cumulative morbidity score at 6 months was lower in infants who were exclusively breastfed for 6 months (7.2±2.5) than those who were exclusively breastfed for <6 months (7.8±2.6). Mean weight gain (at 6 months) was significantly increased with higher maternal education (P=0.030). Linear regression showed that weight gain and length gain had significantly positive linear relation with cumulative infant feeding score at 6 months, whereas cumulative morbidity score had negative but not significant correlation with weight gain and significantly negative linear relation with length gain. Conclusion: This study identified that various components of infant feeding practice in study participants were suboptimal. It was also observed from this study that feeding practice was important determinant for growth, nutritional status, and morbidity.
17
Browning, Mark H. R., e Thomas C. Hutchinson. "The effects of aluminum and calcium on the growth and nutrition of selected ectomycorrhizal fungi of jack pine". Canadian Journal of Botany 69, n.º 8 (1 de agosto de 1991): 1691–99. http://dx.doi.org/10.1139/b91-214.
Texto completo da fonteResumo:
The influence of Al and Ca on the growth, in axenic culture, of three ectomycorrhizal fungi associated with jack pine (Pinus banksiana Lamb.) was examined. Isolates of Hebeloma crustuliniforme (St. Amans) Quél., Rhizopogon rubescens (Tul.) Tulasne, and Suillus tomentosus (Kauff.) Singer, Snell & Dick were obtained from basidiocarps collected in jack pine stands of different ages. Basidiocarps and the soil surrounding them were analyzed for Al and Ca, as well as other elements. Each fungal species was grown for 4 weeks in nutrient solutions containing 37, 185, 370, or 740 μM Al combined in a factorial design with 25, 125, 250, or 500 μM Ca and maintained at pH 3.8. Growth of all three fungal species was reduced at 370 μM Al. Significant interaction was found between fungal species and Al treatment for all six elements measured in mycelial tissue. Stepwise increments in external Al concentration resulted in reduced mycelial concentrations of Ca, Mg, and K, and increased mycelial concentrations of Al, P, and Fe in H. crustuliniforme. High external Al levels resulted in reduced mycelial concentrations of all elements measured except Al and P in R. rubescens. In contrast, for S. tomentosus the same external Al levels increased the mycelial concentrations of all elements except Ca. The response of the three ectomycorrhizal fungi to Ca also differed. Growth of H. crustuliniforme was stimulated by stepwise increments in external Ca concentrations from 25 to 500 μM. Increments in calcium had no effect on the growth of R. rubescens. High external levels of Ca acted synergistically with high external Al concentrations to reduce growth by S. tomentosus. Unlike the other two species, the response of S. tomentosus to Al and Ca could not have been predicted from the soil and basidiocarp analyses. Alterations in Ca to Al ratios of soils may influence the succession of ectomycorrhizal fungi on conifer root systems. Key words: ectomycorrhizae, jack pine, aluminum, calcium, basidiocarps.
18
Thiffault, Nelson, e François Hébert. "Mechanical site preparation and nurse plant facilitation for the restoration of subarctic forest ecosystems". Canadian Journal of Forest Research 47, n.º 7 (julho de 2017): 926–34. http://dx.doi.org/10.1139/cjfr-2016-0448.
Texto completo da fonteResumo:
Sustainable forest management implies successful regeneration following disturbances. Tree regeneration in subarctic ecosystems can, however, be constrained by limitations to seedling establishment related to cold soils, slow decomposition rates, and competition by ericaceous species. We established a field trial at the northern limit of commercial forests in Québec, Canada, to evaluate to what extent mechanical site preparation (MSP) and planting of a nurse N2-fixing species could promote conifer establishment on a site burned in 2007. The experiment comprised four treatments applied in 2010: standard MSP (disc trenching), standard MSP plus planting of Alnus crispa, intensive MSP, with larger furrows than standard MSP, and a control. Main plots were divided and planted in 2011 with Picea mariana (Mill.) Britton, Stearns & Poggenb. or Pinus banksiana Lamb. We monitored seedling survival, growth, nutrition, and microsite over a 3-year period. Results revealed interactions between treatments and planted species. Mechanical site preparation resulted in higher conifer growth relative to the control conditions, and planting Alnus resulted in growth gains similar to those obtained from intensive MSP. We measured competitive interactions between Alnus and the conifers that might eventually cancel out the initial benefits derived from facilitation by planting the nurse species. Longer term monitoring of interspecific interactions is needed to unravel the mechanisms responsible for the facilitative effect and identify the best management practices.
19
Urli, Morgane, Nelson Thiffault, Daniel Houle, Sylvie Gauthier e Yves Bergeron. "Role of green alder in boreal conifer growth: competitor or facilitator?" FACETS 5, n.º 1 (1 de janeiro de 2020): 166–81. http://dx.doi.org/10.1139/facets-2019-0064.
Texto completo da fonteResumo:
Sustainable forest management implies successful regeneration after disturbances. Low N availability and competition can, however, limit tree establishment in boreal ecosystems. To develop silviculture strategies that maintain productivity in such context, we established a field trial in northern Québec, Canada. We evaluated if a companion N2-fixing species ( Alnus alnobetula) promotes or hinders Picea mariana and Pinus banksiana establishment over six growing seasons. We tested if Alnus has a facilitation effect through nutritional processes and a competition effect through light interception. Foliar stable nitrogen isotope ratio ( δ15N = 15N/14N, ‰) results confirmed that Alnus obtains a substantial part of its N through biological fixation and represents an N source in this system. Although we did not observe increased foliar N concentrations in either conifer species in the presence of Alnus, Pinus growth was nonetheless higher in presence of Alnus, whereas no difference was observed for Picea. In the plots where Alnus cohabited with the conifers, the former had a negative impact on seedling growth, suggesting a significant competition for light. Overall, the net effect of Alnus was positive for Pinus and neutral for Picea. Our results have significant implications for silviculture in N-limited systems, especially in the context of climate change that imposes increased levels of stress on regeneration.
20
Richard, Pierre J. H. "Le couvert végétal du Québec-Labrador il y a 6000 ans BP : essai". Géographie physique et Quaternaire 49, n.º 1 (30 de novembro de 2007): 117–40. http://dx.doi.org/10.7202/033033ar.
Texto completo da fonteResumo:
RÉSUMÉ Une carte du couvert végétal du Québec-Labrador est proposée pour l'époque des 6000 ans BP, à partir des données paléopalynologiques et paléobotaniques. Une Toundra arbustive dense s'interposait entre les mers de Tyrrell ou d'Iberville et les glaces résiduelles qui occupaient alors plus de 100 000 km2 en Ungava (Nunavik) et jusque dans la région de Schefferville. Étroite au sud des glaciers, cette Toundra s'étalait à l'est des glaces sur plus de 400 km jusqu'à la mer du Labrador, au nord du 54° de latitude. La limite des arbres s'établissait donc alors à peu près au centre de l'actuelle zone de Taïga (Forêt boréale ouverte), mais la limite nord de la Forêt fermée correspondait déjà à peu près à la position moderne. Comme la Toundra, la Taïga de l'époque était arbustive, plus dense et plus diversifiée qu'actuellement, sans doute en raison d'un climat favorable, mais aussi d'une plus grande richesse des sols en éléments nutritifs. Les domaines forestiers méridionaux des Pessières, des Sapinières et des Érablières atteignaient dans l'ensemble les limites modernes de leur aire de peuplement, mais l'abondance de certaines essences compagnes différait le plus souvent de l'actuelle. Ces différences sont attribuables 1) à une migration tardive de certaines essences, telles le pin gris (Pinus banksiana) dans les Pessières occidentales ou le hêtre à grande feuilles (Fagus grandifolia) dans les Érablières, 2) à une incidence généralement plus faible des feux naturels, 3) à un entourbement moindre des stations hydriques, et 4) à un climat dans l'ensemble plus clément. L'analyse régionale permet d'identifier des gradients et des champs phytogéographiques plus nuancés éventuellement influencés par le climat, notamment en zones montagnardes et subalpines.
21
Pretty, J. L., e M. Dobson. "Leaf transport and retention in a high gradient stream". Hydrology and Earth System Sciences 8, n.º 3 (30 de junho de 2004): 560–66. http://dx.doi.org/10.5194/hess-8-560-2004.
Texto completo da fonteResumo:
Abstract. To a large extent, the invertebrate fauna in wooded streams rely upon detritus inputs from the surrounding vegetation as their main food source. Conifer plantations may alter the timing and nutritional quality of leaf inputs into streams, but detritus retention may also be reduced. While it has often been assumed that conifer needles are retained less than broadleaved species, this has never been tested experimentally. This study describes the results of a leaf release experiment carried out in a small headwater stream, comparing the retention of pine needles and oak leaves (wet and dry) over a range of discharges. In addition, retention was compared before and after placing logs in the stream to examine the effect of woody debris on retention efficiency. Retention efficiency was significantly different among the three leaf types tested with wet oak leaves being most retentive, followed by dry oak leaves with dry pine needles being least retentive. Retention efficiency declined significantly with increasing discharge for all three leaf types. The addition of logs increased the retention of dry oak leaves and pine needles, but not wet oak leaves. The predominant features (stones, logs, eddies and bankside vegetation) that accounted for retention varied with discharge and the leaf type used. The results indicate that while conifer needles may be inherently less retentive than broadleaves, the presence of woody debris within the stream channel increases their retention. However, this small-scale study would need to be expanded to investigate the retention dynamics of conifer needles in plantation streams. Nevertheless, management strategies that allow the formation of woody debris accumulations in plantation streams could be valuable in enhancing detritus retention and consequently could benefit invertebrate communities. Keywords: pine needles, retention efficiency, woody debris, discharge