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Clear Relationships (clear + relationships)
Selected AbstractsEuropean classes for the reaction to fire performance of wood-based panelsFIRE AND MATERIALS, Issue 6 2010Birgit A.-L. Östman Abstract The classification system for the reaction to fire performance of building products in Europe has been applied to wood-based panels as being ,products with known and stable fire performance'. The European classification system includes two sub-systems, one main system for all construction products except floorings and the other for flooring products. Panel properties such as density, thickness, joints and types of end-use application including different substrates have been studied thoroughly and are included in the classification. Most wood-based panels fall in classes D-s2, d0 or Dfl -s1 (for floorings). Testing has been performed according to EN 13823 SBI-Single Burning Item test, EN ISO 9239-1 Radiant panel test, and EN ISO 11925-2 Small flame test. Clear relationships between the main Euroclass fire performance parameters and product parameters (such as density and thickness) have been demonstrated. Tables with reaction to fire classification of different wood-based panels and end-use applications have been developed in two steps, approved by the European Commission and published in their Official Journal. The table is also included in the harmonized product standard and may be used for CE-marking. Copyright © 2010 John Wiley & Sons, Ltd. [source] Can taxonomic distinctness assess anthropogenic impacts in inland waters?FRESHWATER BIOLOGY, Issue 9 2006A case study from a Mediterranean river basin Summary 1. It is increasingly recognised that adequate measures of biodiversity should include information on the ,relatedness' of species within ecological assemblages, or the phylogenetic levels at which diversity is expressed. Taxonomic distinctness measures provide a series of indices to achieve this, which are independent of sample size. Taxonomic distinctness has been employed widely in marine systems, where it has been suggested that this index can provide a reliable measure of anthropogenic impact. 2. We tested the behaviour of three related taxonomic distinctiveness indices (Average Taxonomic Distinctness, ,+; Variation in Taxonomic Distinctness, ,+; and Total Taxonomic Distinctness, s,+) in relation to putative levels of anthropogenic impact in inland waters and their potential utility in environmental monitoring, using an extensive data set for aquatic beetles from the south-east of the Iberian Peninsula. 3. Taxonomic distinctness measures were not able to identify human disturbance effects and there were no clear relationships between these new biodiversity measures and the disturbance level recorded at individual localities. Furthermore, the taxonomic distinctness measures used were apparently less sensitive to the effects of anthropogenic impact than other diversity metrics, such as species richness and rarity. 4. We conclude that taxonomic distinctness indices may not always perform as well as other metrics in the assessment of environmental quality. In addition, taxonomic distinctness measure should be interpreted with caution, as their performance and ability to detect anthropogenic disturbance may depend on the phylogenetic structure of sampled taxa within a region, and their evolutionary and ecological history. [source] Accounting for residual effects of previously applied nitrogen fertilizer on intensively managed grasslandsGRASS & FORAGE SCIENCE, Issue 1 2010T. V. Vellinga Abstract Only 0·20,0·70 of the fertilizer-nitrogen (N) applied to grassland is taken up in herbage in the harvest directly following application. Residual effects at subsequent harvests can be large but are poorly quantified, and rarely taken into account in current management practices. An increased understanding of N-use efficiency per harvest can improve operational management. This study systematically assessed the residual effects of previously applied N fertilizer on N uptake, dry matter (DM) yield and soil mineral-N (SMN) during the whole of the growing season. It is based on field experiments conducted on peat and mineral soils in 1991,1994. Statistical models were derived for SMN, N uptake and DM yield as a function of previously and freshly applied N fertilizer. There were clear residual effects of previously applied N in later cuts. They were relatively greater at higher levels of N fertilizer. On peat soils, 0·15,0·25 of the N applied was recovered as SMN. On mineral soils the proportion was maximally 0·08. There was a clear relationship between SMN and N uptake in the subsequent cut on mineral soils but not on peat soils. The value of SMN as a tool to adjust fertilizer-N application rates was hence found to be limited. There were clear relationships between the amount of previously applied N and the N uptake in subsequent cuts, on both soil types and over the whole of the growing season. It was concluded that the total amount of previously applied N is a useful indicator for adjusting N-fertilizer application rates. [source] Effect of autumn and winter meteorological variables on spring aphid populations in the Po valley, Northern ItalyJOURNAL OF APPLIED ENTOMOLOGY, Issue 8 2001D. Rongai Prediction of aphid populations is crucial to the successful application of control strategies. In previous studies clear relationships between aphid catches and meteorological variables were highlighted. The primary objective of this study was to quantify the effects of autumn and winter meteorological variables on the aphid species populations the following spring. The data on all the species caught at two Italian sites (Ozzano Emilia and Budrio) up to 31 May from 1992 to 1999 were used for this study. Different models were found according to the aphid biological cycle (i.e. holocycle, anholocycle, holo-anholocycle). A fourth group of minor species, designated as ,others', was properly modelled as holo-anholocycle species. A satisfactory fit was observed when holocycle species were plotted against minimum temperature and precipitation in October, anholocycle species against minimum temperature and precipitation in December,January, holo-anholocycle species and ,others' against wind speed and number of frosty days in November, and minimum temperature and precipitation in December,January. Model response was more consistent at Budrio (open flat site) than at Ozzano Emilia (flat site delimited by a hill). A coherent pattern was found with an overall comparison of the estimates against observations. The possibility offered by these empirical models for forecasting spring aphid populations of all species at a given site is clearly of interest. This first study encouraged further investigation aimed at validating models before applying them in practice. [source] Carbohydrate storage enhances seedling shade and stress tolerance in a neotropical forestJOURNAL OF ECOLOGY, Issue 2 2007JONATHAN A. MYERS Summary 1To survive in forest understoreys, seedlings must depend on carbohydrate reserves when they experience negative carbon balance imposed by occasional light reduction and tissue loss to herbivores and diseases. We present the first experimental evidence in support of this hypothesis, using seven woody neotropical species. 2We transplanted seedlings that had recently expanded their first photosynthetic cotyledon or leaf to the forest understorey (1% of full sun) and quantified initial biomass and total non-structural carbohydrate (TNC) in stems, roots and storage cotyledons. We then randomly assigned seedlings to control and two stress treatments: light reduction (0.08% of full sun for 8 weeks) and complete defoliation. 3First-year survival of control seedlings, a comparative measure of shade tolerance, differed widely among species. The two stress treatments reduced survival and relative growth rates (RGR) of all species. Shade-tolerant species were little impacted by the stress treatments, whereas the two least shade-tolerant species experienced 100% mortality. 4In all treatments, 8-week and first-year survival was positively correlated with initial TNC pool size in stems and roots. By contrast, survival was generally not correlated with initial TNC concentration in any organ, TNC pools in cotyledons, seed mass or seedling biomass. 5TNC in stems and roots, but not in cotyledons, decreased in response to light reduction and defoliation over 8 weeks. Leaf area recovery of defoliated seedlings was positively correlated with initial TNC pools in stems and roots. 6First-year survival in each treatment was negatively correlated with 0,8 week RGR of control seedlings, suggesting higher stress tolerance of species with inherently slow growth rates in shade. RGR of control seedlings from 0 to 8 weeks was negatively correlated with initial TNC pools, but not concentrations, in stems and roots. After 8 weeks, RGR was positive for all species, without clear relationships with survival or TNC. 7We conclude that carbohydrate storage in stems and roots enhances long-term survival in shade by enabling seedlings to cope with periods of biotic and abiotic stress. Carbohydrate storage is a key functional trait that can explain species differences in growth and survival that lead to species coexistence through niche assembly processes and life-history trade-offs. [source] Reproductive migration of brown trout in a small Norwegian river studied by telemetryJOURNAL OF FISH BIOLOGY, Issue 1 2004A. Rustadbakken The movement of 34 large (39,73 cm standard length) brown trout Salmo trutta was monitored using radio telemetry for up to 74 days in Brumunda, a small Norwegian river (mean annual discharge 3·3 m3 s,1) flowing into the large Lake Mjøsa. The maximum range of movement in the river was 20 km. No clear relationships existed between individual movement and water discharge, temperature and barometric pressure. Brown trout migrated at all levels of water discharge. At low discharge (<2 m3 s,1) movements were nocturnal. A weir 5·3 km from the outlet restricted ascending brown trout at low (c. 6° C), but not at high (c. 8° C) water temperatures. Spawning occurred in September to October and tagged individuals spent 2,51 days at the spawning sites. Mean migration speed from tagging to when the fish reached the spawning area, and from when they left the spawning areas and reached the lake was 1·0 and 2·3 km day,1, respectively. All tagged brown trout that survived spawning returned to the lake after spawning. [source] Native harvester ants threatened with widespread displacement exert localized effects on serpentine grassland plant community compositionOIKOS, Issue 2 2005Halton A. Peters Seed-harvesting ants can influence the abundance and distribution of plant species through both the selective harvesting of seeds and the construction of nutrient-rich nest mounds, but the relative contributions of these two mechanisms have not been addressed by previous studies. Furthermore, the impact of ant seed harvesting in California serpentine grasslands remains unresolved because of divergent results from several previous experiments. This study investigates the influence of harvester ants on serpentine grassland plant species composition by examining two potential signatures of seed harvesting ants on plant community composition: species composition on versus off ant nest mounds, and species abundance as a function of distance from nest mounds. Of the 28 plant species identified in this study, 22 exhibited spatial patterns consistent with effects of seed harvesting, nest construction, or both. Although most species showed significant gradients in abundance with distance from a nest, there were no clear relationships between plant species distributions and previously reported harvester ant seed foraging patterns. Harvester ant nest mounds supported plant communities that were distinct from the surrounding serpentine grassland, with notably higher densities of legumes and invasive annual grasses. Comparison of our results with those of previous studies indicates that the patterns we observed are generally consistent over time, but affect more species and a larger fraction of the grassland than previously reported. Unaffected areas of the grassland seem likely to serve as important refuges for some plant species. [source] Relationship between antimicrobial proteins and airway inflammation and infection in cystic fibrosisPEDIATRIC PULMONOLOGY, Issue 4 2009Scott D. Sagel MD Abstract Antimicrobial proteins are important in lung defense and are potential therapeutic agents in chronic airways infection such as seen in cystic fibrosis (CF). In preparation for future clinical studies, we sought (1) to determine levels of three antimicrobial proteins [lactoferrin, lysozyme, and secretory leukoprotease inhibitor (SLPI)] in the CF airway and (2) to examine the relationships between these antimicrobial proteins and airway inflammation and infection. We examined bronchoalveolar lavage fluid (BALF) from 45 individuals with CF and 23 disease control individuals. Airway inflammation was measured through BALF neutrophil counts and neutrophil elastase activity. Infection was assessed through quantitative counts of CF-related bacterial pathogens. BALF lysozyme activity and lactoferrin levels were elevated in individuals with CF compared to controls whereas SLPI levels were not different between the groups. Among the CF subjects, lysozyme activity and lactoferrin increased with age while SLPI decreased with age. Lysozyme activity and lactoferrin concentrations correlated positively with neutrophil counts but not with bacterial colony counts. SLPI levels were inversely related to both neutrophil counts and bacterial colony counts. This study provides information concerning the levels of antimicrobial proteins present in the CF airway that are relevant to future clinical trials of these compounds and demonstrates clear relationships between antimicrobial protein-specific levels and airway inflammation and infection. Pediatr Pulmonol. 2009; 44:402,409. © 2009 Wiley-Liss, Inc. [source] How does photorespiration modulate leaf amino acid contents?PLANT CELL & ENVIRONMENT, Issue 7 2002A dual approach through modelling, metabolite analysis Abstract The aim of this work was to establish the quantitative impact of photorespiration on leaf amino acid contents. Attached leaves of wheat and potato were incubated for 30,40 min under defined conditions in which net CO2 uptake (A) was manipulated by irradiance, ambient CO2 or ambient O2. The incubated portion of the leaf was sampled by a rapid-quench method and photorespiratory flux (vo) was modelled from the measured rate of net CO2 uptake. In both wheat and potato, the ratio between glycine and serine showed a strong positive correlation with vo. Aspartate and alanine correlated negatively with vo but glutamate and glutamine showed less clear relationships. In potato, glutamate and glutamine did not correlate clearly with either A or vo. In wheat, glutamine showed a general increase with A but no relationship with vo, whereas 2-oxoglutarate contents correlated positively with vo and negatively with A. As a result, glutamine : glutamate and glutamine : 2-oxoglutarate increased with net CO2 uptake in wheat, observations that are attributed primarily to imperfect and variable coupling between the supply of NH3 in primary nitrogen assimilation and the associated delivery of 2-oxoglutarate to the chloroplast. A simple theoretical analysis is used to illustrate the potentially marked impact of primary nitrogen assimilation on leaf glutamine, even against a background of high rates of photorespiratory ammonia recycling. [source] Dynamics of species-rich upland hay meadows over 15 years and their relation with agricultural management practicesAPPLIED VEGETATION SCIENCE, Issue 3 2007C.N.R. Critchley Stace (1997) Abstract Questions: Has the species-rich vegetation of upland hay meadows been maintained under low intensity management imposed by an agri-environment scheme? Is the target plant community re-establishing where it has been modified previously by intensive agricultural practices? What combinations of management practices and soil properties are associated with changes towards or away from the target community? Location: The Pennines, northern England, UK. Methods: A survey of 116 hay meadows in 1987 was repeated in 2002 by recording plant species in permanent quadrats. Changes in community variables (species richness, Ellenberg values, upland hay meadow community coefficients) were analysed in species-rich, modified species-rich and degraded grassland types. Redundancy Analysis and Generalised Linear Models were used to show the relationship between management practices and soil properties and change in species composition and community variables. Results: Few sites contained the species-rich grassland type, and here forb richness declined. In the modified species-rich type, total and grass species richness increased but Ellenberg N-values also increased. Total and grass species richness increased in the degraded type and the community coefficient increased. Management was weakly related to change in species composition but showed clear relationships with the community variables. Re-establishment of the target species-rich community was more likely with late cutting, in the absence of cattle or prolonged spring grazing, and at lower soil nutrient status. Conclusion: The species-rich community was not maintained but some reversion occurred in degraded grassland. Inorganic fertiliser application and intensive spring grazing should be avoided and cutting delayed until late July. [source] Hurricane Impacts on a Mangrove Forest in the Dominican Republic: Damage Patterns and Early Recovery,BIOTROPICA, Issue 3 2001Ruth E. Sherman ABSTRACT On 22 September 1998, Hurricane Georges passed over the Dominican Republic causing extensive damage to a 4700 ha mangrove forest that has been the site of a detailed study of vegetation and ecosystem dynamics since 1994. We resurveyed the vegetation in permanent plots at 7 and 18 months after the hurricane to document structural damage of the forest and evaluate early recovery patterns. The intensity of damage was patchy across the landscape. Mortality (>5 cm DBH) ranged from 14 to 100 percent (by density) among the 23 different plots and averaged 47.7 percent across all plots. Reductions in total basal area ranged from 9 to 100 percent, averaging 42.4 percent. Mortality increased by 9 percent between surveys at 7 and 18 months post-hurricane. Interspecific differences in susceptibility to wind damage appeared to be a primary factor contributing to spatial patterns in mortality. Laguncularia racemosa experienced much less mortality (26%) than either Rhizophora mangle (50%) or Avicennia germinans (64%), and plot-level mortality was strongly associated with differences in species composition. There were no clear relationships between canopy height and tree damage at this site. Over 80 percent of the of the surviving R. mangle trees exhibited less than 50 percent crown damage, whereas ca 60 percent of the L. racemosa survivors suffered almost complete (75,100%) crown loss. By 18 months after the hurricane, the percentage of L. racemosa trees in the 75 to 100 percent damage class was reduced to 20 percent; in contrast, the health of many R. mangle individuals appeared to be declining, as the percentage of trees in the 50 to 100 percent damage class increased from 16 to 36 percent. Understory light levels, as measured by the gap light index, increased from an average value of 3 percent in the pre-hurricane forest to 51 percent at 7 months after the hurricane and decreased slightly to 47 percent at 18 months. Few saplings (>1 m tall and <5 cm DBH) survived the hurricane; 72 percent of the tagged individuals in transect-based plots and 66 percent of saplings in pre-hurricane canopy gaps were killed. Seedling and sapling populations of all three species appear to be recovering rapidly although their densities still are lower than in the pre-hurricane forest. It is too early to predict the trajectory of forest recovery, and continued monitoring of the spatial and temporal patterns of forest development is needed to improve our understanding of the role that large-scale disturbance events play on the dynamics of mangrove forest ecosystems. RESUMES El 22 de septiembre de 1998, el huracán Georges pasó sobre la República Dominicana causando daños extensos a 47 km2 de manglar que ha sido objeto un estudio detallado de vegetacion y dinámica de la communidad desde 1994. Se tomarón muestras de la vegetación en parcelas permanentes 7 y 18 meses después de paso del huracán para documentar los daños estructurales del bosque y evaluar los modelos de recuperacion temprana que siguieron posteriormente. La intensidad del daño fue irregular a través del paisaje. La mortalidad (>5 cm de dap) fue de 14 a 100 por ciento (para la densidad) en las 23 parcelas con un promedio de 47.7 por ciento. La reducción en área basal total fue de 9 a 100 por ciento con un promedio de 42.4 por ciento. La mortalidad aumentó 9 por ciento a los 7 y 18 meses después del huracán. Las diferencias interspecificas en la susceptibilidad a los daños causados por el viento fueron un factor contribuyente importante en los patrones espacios de mortalidad. Laguncularia racemosa sufrió menor mortalidad (26%) que Rhizophora mangle (50%) o Avicennia germinans (64%), la mortalidad en las parcelas estuvo asociada fuertemente con la diferencia en composición de especies. No hubo ningún patron definido entre la altura del dosel y el daño del árbol. Más del 80 por ciento de los árboles sobrevivientes de R. mangle exhibieron daoñres menores de 50 por ciento en sus copas, mientras que ca 60 por ciento de los L. racemosa sobrevivientes sufrió una perdida casi total (75-100%). Dieciocho meses despues del huracan, el porcentaje de arboles de L. racemosa con daños del 75-100 por ciento se redujó a 20 por ciento; en contraste, la salud de muchos individuos de R. mangle disminuyó conforme el porcentaje de árboles con daños del 50-100 por ciento aumentó de 16 a 36 por ciento. Los niveles de penetración de luz en el sotobosque, medidos como el indice de iluminacion en los claros, aumentó de un promedio de 3 por ciento antes del huracán. a 51 por ciento 7 meses después del huracán, y disminuyo ligeramente a 47 por [source] | |||||||||||||