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Site Characteristics (site + characteristic)
Kinds of Site Characteristics Selected AbstractsRacial Wage Differences among Young Male Job Changers: The Relative Contribution of Migration, Occupation Change, Site Characteristics, and Human CapitalGROWTH AND CHANGE, Issue 1 2006AMY M. WOLAVER ABSTRACT We demonstrated racial differences in the relationship between migration, location, and predicted wages for young male workers who have changed employers. An Oaxaca decomposition allowed a measuring of the contributions of migration, occupation change, site features, and human capital to the racial wage gap. Migration decreases black,white wage differences, and wage compensation for site attributes favors white householders. Constraints on occupation choice and migration dampen the ability of blacks to improve wages. Because most job changes occur in the first ten years of a career, these results on young workers give important general insights into the origins and persistence of racial wage gaps. [source] Meteorological factors affecting the diversity of airborne algae in an urban atmosphereECOGRAPHY, Issue 5 2006Naveen K. Sharma Aeroalgal sampling of Varanasi City, India, was done using a Tilak Rotorod sampler and exposing agarised Bold basal medium Petri plates during March 2003 to February 2005. Amongst the 34 airborne algal genera recorded, cyanobacteria dominated the aero-algal flora, followed by green algae and diatoms. The generic diversity of airborne algae as well as the constituting groups exhibited seasonal variation. The most favored period for the appearance of cyanobacteria in the air was summer, while winter favored green algae. Presence of diatoms was almost uniform throughout the year. The presence of algal particles in the air depended upon the abundance and dynamics of algal source and their release and dispersal in the atmosphere. Best model selection with Akaike information criteria indicated temperature, relative humidity, rainfall, wind velocity as the most important climatic factors determining algal diversity. These factors exert their effect both directly by influencing entrainment and dispersal of algae from the source, and indirectly by regulating the dynamics of the possible algal source (soil, water, plant body, wall and roof of the building) by supporting or inhibiting the algal growth. In a closed environment and at low altitude sampling site characteristic is also an important factor. Open area near to the countryside had maximal aero-algal diversity. [source] Effects of plant diversity, plant productivity and habitat parameters on arthropod abundance in montane European grasslandsECOGRAPHY, Issue 4 2005Jörg Perner Arthropod abundance has been hypothesized to be correlated with plant diversity but the results of previous studies have been equivocal. In contrast, plant productivity, vegetation structure, abiotic site conditions, and the physical disturbance of habitats, are factors that interact with plant diversity, and that have been shown to influence arthropod abundance. We studied the combined effect of plant species diversity, productivity and site characteristics on arthropod abundance in 71 managed grasslands in central Germany using multivariate statistics. For each site we determined plant species cover, plant community biomass (productivity), macro- and micronutrients in the soil, and characterized the location of sites with respect to orographic parameters as well as the current and historic management regimes. Arthropods were sampled using a suction sampler and classified a priori into functional groups (FGs). We found that arthropod abundance was not correlated with plant species richness, effective diversity or Camargo's evenness, even when influences of environmental variables were taken into account. In contrast, plant community composition was highly correlated with arthropod abundances. Plant community productivity influenced arthropod abundance but explained only a small proportion of the variance. The abundances of the different arthropod FGs were influenced differentially by agricultural management, soil characteristics, vegetation structure and by interactions between different FGs of arthropods. Herbivores, carnivores and detritivores reacted differently to variation in environmental variables in a manner consistent with their feeding mode. Our results show that in natural grassland systems arthropod abundance is not a simple function of plant species richness, and they emphasize the important role of plant community composition for the abundance patterns of the arthropod assemblages. [source] Analysis of nest occupancy and nest reproduction in two sympatric raptors: common buzzard Buteo buteo and goshawk Accipiter gentilisECOGRAPHY, Issue 5 2002Oliver Krüger Nest site selection can have important fitness consequences in birds. I analysed the habitat characteristics of 392 nests of two sympatric raptor species (common buzzard Buteo buteo and goshawk Accipiter gentilis) in Germany and their relation to nest occupation rate and nest reproductive success. For common buzzard, multivariate models explained only small proportions of the variance in nest occupation rate and nest reproductive success (13,19%). Important variables related to nest occupation rate were human disturbances, intra- and interspecific neighbour density, the amount of forested area and nest tree crown cover. Variables related to nest site reproductive success also included human disturbance, intra- and interspecific neighbour density and nest tree crown cover as well as nest distance to the nearest forest edge. In contrast, models for the goshawk explained a much higher proportion of the variation in nest occupation rate and nest reproductive success (41,43%). Important variables related to nest occupation rate were the remoteness of the nest site and direct human disturbance. Variables related to nest site reproductive success were remoteness of the nest site and good hunting habitat. Goshawks seem to be more sensitive to human disturbance than buzzards. A multiple discriminant analysis showed that nest site characteristics substantially overlapped between the species and there is a good evidence that competition for optimal nest sites occurs. Thus, buzzards might be constrained by the dominant goshawk in their nest site selection. [source] Fate of Pesticides in the Environment and its BioremediationENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 6 2005M. Gavrilescu Abstract The present paper is an overview of the presence and fate of pesticides as persistent organic pollutants in the environment as well as of the potential for their detoxification, also combined with chemical and physical treatment. It contains information gathered from a range of currently available sources. The fate of pesticides in the environment is analyzed considering the processes that determine their persistence and mobility, grouped into transport, transfer and transformation processes. Few pesticide characteristics such as persistence, mobility and biodegradability are emphasized. The fate of a pesticide and the potential for its persistence and mobility from the site of application are considered to be affected by the chemical and physical properties of the pesticide, site characteristics such as soil and groundwater individuality, climate and local weather conditions, biological population, and the handling practices of the pesticide user. Bioremediation, as one of the most environmentally-sound and cost-effective methods for the decontamination and detoxification of a pesticide-contaminated environment is discussed especially considering the factors affecting the biodegradability of pesticides such as biological factors and the characteristics of the chemical compounds. In situ and ex situ bioremediation as possible types of bioremediation activities are weighted up. Also, the paper includes some considerations for developing strategies regarding the choice of bioremediation technology, as well as advantages and disadvantages of the bioremediation of environmental components polluted with pesticides. [source] Contribution of native and non-native species to fish communities in French reservoirsFISHERIES MANAGEMENT & ECOLOGY, Issue 3-4 2004P. Irz Abstract Previous studies showed that only 20% of the variability in fish community structure in French reservoirs could be explained by site characteristics. In addition, no relationship was found between the relative abundance of species and stocking effort. Therefore, deliberate or uncontrolled introductions are likely to be the source of a great part of the observed communities. The objective of this study was to assess the importance of species introductions in French reservoirs. Fifty-one reservoirs were sampled to obtain species presence/absence data. Local native (LNaR) and non-native (LNNR) species richness were negatively correlated. LNaR was strongly correlated to the lake surface area, depth and catchment area, whereas LNNR was independent of environmental variables. Furthermore, LNaR was positively correlated to regional native richness. Conversely, local total richness was independent of regional total richness, but was related to the reservoirs' environmental characteristics. It was hypothesised that the native fish communities in French reservoirs are unsaturated and species introductions lead to saturated communities. [source] Probability models for pine twisting rust (Melampsora pinitorqua) damage in Scots pine (Pinus sylvestris) stands in FinlandFOREST PATHOLOGY, Issue 1 2005U. Mattila Summary Factors affecting the probability that pine twisting rust (Melampsora pinitorqua) damage occur in a Scots pine (Pinus sylvestris) stand were analysed using the 7th Finnish National Forest Inventory data (NFI7) from southern Finland in 1977,1983. The inventory was based on systematic sampling. The NFI7 data was measured in clusters, each of which consisted of 21 sample plots. In addition to the stand and site characteristics measured for forest management planning purposes, the data included records of damage by pine twisting rust and occurrence of aspens (Populus tremula, the other host plant of the pathogen) in the stands. Two multilevel logit models were developed for predicting the overall probability of pine twisting rust damage and the probability of severe pine twisting rust damage. Site and stand characteristics were used as explanatory variables in the models. Residual variance in the models was studied on the inventory crew, cluster and year levels. The occurrence of aspens and site fertility were the most important factors increasing the probability that pine twisting rust damage will occur in a stand. The damage probability also decreased with increasing effective temperature sum calculated for the location. The overall damage probability was equally high on peatlands and on mineral soil if there were aspens in the stand. If, however, there were no aspens in the stand, the probability of damage was higher on mineral soils than on peatlands. In addition, the overall probability was lower in naturally regenerated stands than in planted or sown stands, and it decreased with increasing mean age of pines. In both models, the residual variance was significant on the both the inventory crew and the cluster levels. Résumé Les facteurs de probabilité d'occurrence d'un dégât de rouille courbeuse (Melampsora pinitorqua) dans un peuplement de Pin sylvestre (Pinus sylvestris) ont été analysés en utilisant les données du 7 Inventaire Forestier National de Finlande (NF17) pour la Finlande du Sud et la période 1977,1983. L'inventaire est basé sur un échantillonnage systématique. Les données de NF17 sont mesurées dans des groupes constitués de 21 placettes. En plus des caractéristiques de la station et du peuplement mesurées à des fins de gestion forestière, les données comprennent des notations de dégâts par la rouille courbeuse et de présence des trembles (hôte alternant de 1'agent pathogène) dans les peuplements. Des modèles logit multiniveaux ont été développés pour prédire la probabilité globale de dégât de rouille courbeuse et la probabilité de dégât sévère. Les caractéristiques de la station et du peuplement ont été utilisées comme variables explicatives dans les modèles. La variance résiduelle des modèles a étéétudiée au niveau de 1'observateur, du groupe de placettes et de 1'année. La présence de trembles et la fertilité de la station sont les facteurs les plus importants d'augmentation de la probabilité de dégât de rouille dans un peuplement. D'autre part, la probabilité de dégât décroît avec la somme des températures effectives calculée pour le site. La probabilité globale de dégât est aussi élevée sur sols de tourbières que sur sols minéraux dans le cas où des trembles sont présents dans le peuplement. En 1'absence de trembles dans le peuplement, la probabilité de dégât est plus importante sur sols minéraux qu'en tourbières. Enfin, la probabilité de dégât est plus faible dans les peuplements régénérés naturellement que dans les peuplements semés ou plantés, et elle décroít avec 1'âge moyen des pins. Pour les deux modèles, la variance résiduelle est significative au niveau observateur et groupe de parcelles. Zusammenfassung Faktoren, die die Wahrscheinlichkeit einer Schädigung durch den Kieferndrehrost (Melampsora pinitorqua) in Beständen von Pinus sylvestris beeinflussen, wurden anhand der Daten der 7. Finnischen Nationalen Forstinventur (NF17) aus den Jahren 1977,1983 in Südfinnland untersucht. Die Datenerhebung basierte auf einer systematischen Probenahme. Die NF17 Daten wurden in Clustern erhoben, jedes Cluster bestand aus 21 Probeflächen. Neben den Bestandes- und Standortsmerkmalen, die für die forstliche Planung erhoben wurden, wurden Angaben zum Befall (schwach, stark) mit Kieferndrehrost und zum Vorkommen von Zitter-Pappel (Populus tremula, alternativer Wirt des Pathogens) berücksichtigt. Es wurden zwei Multi Logit - Modelle entwickelt zur Vorhersage der Gesamtwahrscheinlichkeit einer Kieferndrehrost-Schädigung sowie der Wahrscheinlichkeit einer schweren Schädigung durch den Pilz. Die Standorts- und Bestandesmerkmale wurden als erklärende Variablen verwendet. In den Modellen wurde die Restvarianz bezüglich Inventur-Erhebungsgruppe, Cluster und Jahr geprüft. Das Vorkommen von Zitter-Pappel und die Bodenfertilität waren die wichtigsten Faktoren für eine zunehmende Wahrscheinlichkeit einer Kieferndrehrost-Schädigung auf Bestandesebene. Die Schadenswahrscheinlichkeit verringerte sich mit zunehmender Temperatursumme, die für den Standort berechnet wurde. Die Gesamtschadenswahrscheinlichkeit war auf Torf- und Mineralböden gleich hoch, sofern Zitter-Pappeln im Bestand vorkamen. Ohne Zitter-Pappeln war die Schadenswahrscheinlichkeit auf Mineralböden höher. Zudem war die Gesamtschadenswahrscheinlichkeit in natürlich regenerierten Beständen niedriger als in gepflanzten oder gesäten Beständen, und sie nahm mit zunehmendem Durchschnittsalter der Kiefern ab. In beiden Modellen war die Restvarianz auf der Ebene der Inventur-Erhebungsgruppe und der Probecluster signifikant. [source] Model predicting dynamics of biomass, structure and digestibility of herbage in managed permanent pastures.GRASS & FORAGE SCIENCE, Issue 2 2006Abstract To investigate seasonal and annual interactions between management and grassland dynamics, a simple mechanistic model of the dynamics of production, structure and digestibility in permanent pastures was constructed. The model is designed to respond to various defoliation regimes, perform multiple-year simulations and produce simple outputs that are easy to use as inputs for a model of ruminant livestock production. Grassland communities are described using a set of average functional traits of their constituent grass groups. The sward is subdivided into four structural compartments: green leaves and sheath, dead leaves and sheath, green stems and flowers, and dead stems and flowers. Each compartment is characterized by its biomass, age and digestibility. Only above-ground growth is modelled, using a light-utilization efficiency approach modulated by a seasonal pattern of storage and mobilization of reserves. Ageing of plant parts is driven by cumulative thermal time from 1 January and by biomass flows. Age affects senescence, abscission and digestibility of green compartments and, therefore, the quality of green leaves and stems can increase or decrease over time in relation to net growth and defoliation dynamics. The functional traits having the greatest impact on model outputs are seasonal effects, period of reproductive growth and effects of temperature on photosynthetic efficiency. The functional traits of the grass groups were parameterized for temperate pastures of the Auvergne region in France. The other model inputs are few: proportion of functional groups, basic weather data (incident photosynthetically active radiation, mean daily temperature, precipitation and potential evapotranspiration) and site characteristics (nitrogen nutrition index, soil water-holding capacity). In the context of a whole-farm simulator, the model can be applied at a field scale. [source] Model predicting dynamics of biomass, structure and digestibility of herbage in managed permanent pastures.GRASS & FORAGE SCIENCE, Issue 2 2006Abstract A mechanistic model, simulating the dynamics of production, structure and digestibility of managed permanent pastures, was developed. Its evaluation consisted of (i) studying model response to a range of grassland communities, cutting frequencies and site characteristics, and (ii) testing the model against experimental data, focusing on biomass accumulation and digestibility during three different cutting cycles, herbage production under a frequent cutting regime, and sward dynamics during the winter. The model realistically predicted the dynamics of biomass, structure and digestibility of herbage for various communities of permanent pastures, in different sites and under different management conditions for upland areas of the Auvergne region in France. The predicted responses to environmental conditions and cutting regimes were close to field observations and experimental results. Although the model successfully predicted the dynamics of average herbage production, it lacked precision in predicting the low biomass production observed in relation to the weather conditions found in a few specific years. The model was able to predict the dynamics of the sward during winter and is, therefore, fit for producing multiple-year simulations. To improve the prediction of variability of biomass production and to predict the medium- to long-term dynamics of permanent pastures, the model could be refined by adding seasonal and multiple-year variation in nitrogen availability and in the proportion of grass functional groups in the grassland community. [source] Stochastic Cost Optimization of Multistrategy DNAPL Site RemediationGROUND WATER MONITORING & REMEDIATION, Issue 3 2010Jack Parker This paper investigates numerical optimization of dense nonaqueous phase liquid (DNAPL) site remediation design considering effects of prediction and measurement uncertainty. Results are presented for a hypothetical problem involving remediation using thermal source reduction (TSR) and bioremediation with electron donor (ED) injection. Pump-and-treat is utilized as a backup measure if compliance criteria are not met. Remediation system design variables are optimized to minimize expected net present value (ENPV) cost. Adaptive criteria are assumed for real-time control of TSR and ED duration. Source zone dissolved concentration data enabled more reliable and lower cost operation of TSR than soil concentration data, but using both soil and dissolved data improved results sufficiently to more than offset the additional cost. Decisions to terminate remediation and monitoring or to initiate pump-and-treat are complicated by measurement noise. Simultaneous optimization of monitoring frequency, averaging period, and lookback periods to confirm decisions, in addition to remediation design variables, reduced ENPV cost. Results indicate that remediation design under conditions of uncertainty is affected by subtle interactions and tradeoffs between design variables, compliance rules, site characteristics, and uncertainty in model predictions and monitoring data. Optimized designs yielded cost savings of up to approximately 50% compared with a nonoptimized design based on common engineering practices. Significant improvements in accuracy and reductions in cost were achieved by recalibrating the model to data collected during remediation and re-optimizing design variables. Repeating this process periodically is advisable to minimize total costs and maximize reliability. [source] Quantifying diffuse pathways for overland flow between the roads and streams of the mountain ash forests of central Victoria AustraliaHYDROLOGICAL PROCESSES, Issue 9 2006Patrick N. J. Lane Abstract Limiting connectivity between road runoff sources and stream networks is crucial for preservation of water quality in forested environments. Where flow is non-eroding, the length of hillslope available to accommodate volumes of discharged water is the key to restricting connectivity. Hairsine et al. (2002, Hydrological Processes16: 2311,2327) proposed a probabilistic model of diffuse overland flow that predicted the hillslope lengths required to infiltrate road discharge, based on the concept of volume to breakthrough (Vbt). This paper extends this analysis to a different forest environment with the aim of testing the portability of the Hairsine et al. (2002) model. The volume of flow required to travel overland to a distance of 5 and 10 m (Vbt5 and Vbt10) from drainage outlets was measured in deep, highly conductive mountain soils in the Upper Tyers catchment, Victoria, Australia. Rainfall, hydraulic conductivity and soil depths contrasted markedly with those in the Hairsine et al. (2002) study, and represent an extreme in Australian forests. Statistical analyses revealed the population of Vbt5 to be indistinguishable from that observed by Hairsine et al. (2002), indicating the model is valid for a range of forest soils. There was no significant correlation of sediment plume length with site characteristics such as slope, width of flow, or existence of incised pathways. It is suggested there are universal properties of pathways draining tracks and roads, with bioturbation acting to restore available pore spaces filled by antecedent plumes. Drain discharge design criteria may be developed for local conditions using the Hairsine et al. (2002) model, providing a robust tool for protection of water quality in the siting of new forest roads, and maintenance of exiting roads and tracks. Copyright © 2006 John Wiley & Sons, Ltd. [source] The effect of truck traffic and road water content on sediment delivery from unpaved forest roadsHYDROLOGICAL PROCESSES, Issue 8 2006Gary J. Sheridan Abstract A study investigated the effect of truck-traffic intensity and road water-content on the quality of runoff water from unsealed forest roads. Three sections of a gravel-surfaced forest road were instrumented and exposed to low and high levels of truck traffic during wet winter conditions and dry summer conditions between July 2001 and December 2002. Rainfall, runoff, road moisture, and traffic were measured continuously, and suspended and bedload sediments were integrated measurements over 2-week site-service intervals. The median suspended sediment concentration from the three road segments under low truck-traffic conditions (less than nine return truck passes prior to a storm) was 269 mg l,1, increasing 2·7-fold to a median of 725 mg l,1 under high truck-traffic conditions (greater than or equal to nine return truck passes prior to a storm). These concentrations, and increases due to traffic, are substantially less than most previously reported values. When these data are expressed as modified universal soil loss equation (MUSLE) erodibility values K, accounting for differences in rainfall energy, site characteristics and runoff, high traffic resulted in a road surface that was four times more erodible than the same road under low traffic conditions. Using multiple regression, traffic explained 36% of the variation in MUSLE erodibility, whereas road water content was not significant in the model. There was little difference in the erodibility of the road when trafficked in low water-content compared with high water-content conditions (MUSLE K values of 0·0084 versus 0·0080 respectively). This study shows that, for a good quality well-maintained gravel forest road, the level of truck traffic affects the sediment concentration of water discharging from the road, whereas the water content of the road at the time of that traffic does not (note that traffic is not allowed during runoff events in Victoria). These conclusions are conditional upon the road being adequately maintained so that trafficking does not compromise the lateral drainage of the road profile. Copyright © 2005 John Wiley & Sons, Ltd. [source] When the prairie varies: the importance of site characteristics for strategising insect conservationINSECT CONSERVATION AND DIVERSITY, Issue 4 2009CHRIS LOONEY Abstract., 1.,The bunchgrass prairies of the Palouse region in eastern Washington state and adjacent Idaho have been mostly converted to agriculture in the past century. Prairie habitat currently exists only on small remnants scattered across the landscape. 2.,The invertebrate fauna of these habitat remnants is poorly known, both in terms of species diversity and community composition. 3.,Baited pitfall traps were used to sample carrion-attracted beetles during June and July of 2003 from high-quality prairie remnants of varying size and soil characteristics. 4.,Twenty-three beetle species in five families were found. Species richness and Shannon-Wiener diversity were not significantly correlated with habitat area or perimeter,area ratio. 5.,Beetle abundance and community structure were strongly correlated with soil characteristics. Deeper, loessal soils had greater overall beetle abundance than shallower, rocky soils, although some species were more frequently captured in shallower, rocky soil sites. 6.,Conservation plans emphasising only remnant size and condition do not sufficiently capture variability in insect communities across Palouse prairie remnants. [source] An efficient multivariate approach for estimating preference when individual observations are dependentJOURNAL OF ANIMAL ECOLOGY, Issue 5 2008Steinar Engen Summary 1We discuss aspects of resource selection based on observing a given vector of resource variables for different individuals at discrete time steps. A new technique for estimating preference of habitat characteristics, applicable when there are multiple individual observations, is proposed. 2We first show how to estimate preference on the population and individual level when only a single site- or resource component is observed. A variance component model based on normal scores in used to estimate mean preference for the population as well as the heterogeneity among individuals defined by the intra-class correlation. 3Next, a general technique is proposed for time series of observations of a vector with several components, correcting for the effect of correlations between these. The preference of each single component is analyzed under the assumption of arbitrarily complex selection of the other components. This approach is based on the theory for conditional distributions in the multi-normal model. 4The method is demonstrated using a data set of radio-tagged dispersing juvenile goshawks and their site characteristics, and can be used as a general tool in resource or habitat selection analysis. [source] The geographical range structure of the holly leaf-miner.JOURNAL OF ANIMAL ECOLOGY, Issue 5 2004Summary 1Spatial variation and covariation in host-plant quality, herbivore abundance and herbivore mortality were examined across the natural geographical range in Europe of holly Ilex aquifolium and the host-specific holly leaf-miner Phytomyza ilicis. 2Although measures of host-plant quality showed substantial between-site variation, no simple spatial pattern in any of the measures (only phosphorus content and leaf mass showed correlations with latitude, longitude or altitude) was detected, and few correlations with tree or local site characteristics. 3In contrast, measures of the abundance of the leaf-miner exhibited marked spatial patterns, resulting in a lack of simple covariance between leaf-miner abundance and host-plant quality. 4Different apparent mortalities of the leaf-miner exhibited varied spatial patterns in their intensity, but no evidence of range-wide density dependence, again resulting in few patterns of covariance between intensity of mortality and measures of host-plant quality. 5The population dynamics of the holly leaf-miner across its geographical range are complex. At any site, the mortality that a population experiences is the sum of largely independent yet spatially structured components, against a background of varying host-plant quality. Despite lacking any marked spatial structure, host-plant quality may have important local effects. These are difficult to detect regionally, and thus may principally contribute noise to regional patterns of levels of oviposition, abundance and mortality. [source] The influence of parental behavior on vulnerability to nest predation in tropical thrushes of an Andean cloud forestJOURNAL OF AVIAN BIOLOGY, Issue 6 2009Konrad Halupka The Skutch hypothesis predicts that parental activity around the nest may attract the attention of predators and thus, in the tropics where predation pressure may be high, selection favors reduced parental activity. This hypothesis has been questioned by studies demonstrating that parents can decrease the risk of nest predation through nest defense. The link between parental activity and predation risk may be further confounded by nest site characteristics. We examined the effects of parental behavior and nest site on clutch survival in two sympatric tropical thrushes (Myadestes ralloides and Turdus leucops). We compared survival rates of clutches in three treatments: 1) natural nests at the incubation stage, 2) unattended nests (un-manipulated nests of the same species, with clutches unattended by parents), and 3) exposed clutches (eggs exposed in unconcealed positions, unprotected by the nest). Parental activity had a positive effect on clutch survival, which was revealed by significantly higher survival rate of clutches in attended nests compared to unattended nests. The effect of nest site was less clear: clutches in unattended natural nests survived better than clutches in exposed sites selected by humans, but results were insignificant. We propose that parent birds can exclude a group of opportunistic predators, that are able to destroy unattended clutches. Nest site characteristics may be less important in determining clutch survival in the tropics, where predator guilds are more diverse, making completely safe sites difficult to find. Our results challenge Skutch's hypothesis and point to the need for more data from tropical latitudes. [source] Vegetation and disturbance history of a rare dwarf pitch pine community in western New England, USAJOURNAL OF BIOGEOGRAPHY, Issue 10-11 2002Glenn Motzkin Abstract Aim, This study documents the vegetation history and age-structure of a rare, ridgetop dwarf pine,oak community and compares the dynamics of this unusual vegetation with similar dwarf pine communities found elsewhere in the north-eastern United States (US). Location, The study area is located on the summit of Mt Everett in the Taconic Mountains of south-western Berkshire County, Massachusetts, USA (42°06,N 73°26,W). Methods, Vegetation composition, tree age-structure, physical site characteristics, and evidence of fire and other disturbances were determined for twelve 15 × 15 m plots in dwarf pine,oak vegetation and two plots in oak forests on the summit. Age-structure analyses, tree-ring patterns, and historical records of human and natural disturbance were used to investigate the long-term history and dynamics of the summit vegetation. Results, The summit of Mt Everett has been dominated by dwarf pines (1,3 m tall) and ericaceous shrubs similar to the modern vegetation throughout the historical period; there is no evidence that tall-stature forests occurred on the site at any point in the past few centuries. The summit supports uneven-aged stands; pitch pine (Pinus rigida) recruitment began in the 1830s and occurred in every decade since the 1860s. Average pitch pine age is seventy-eight with a range of 12,170 years. Red oak (Quercus rubra) and red maple (Acer rubrum) increased in importance in the twentieth century, with most stems establishing from 1940 to 1980. Pitch pine radial growth rates averaged <0.5 mm year,1 while red oak and red maple averaged 1.0 and 0.8 mm year,1, respectively. In some areas, hardwoods have overtopped pitch pines, apparently resulting in pitch pine mortality. Whereas most dwarf pitch pine communities occur on sites that burn frequently and have a high degree of cone serotiny, we found no evidence of recent fires or cone serotiny. Small amounts of macroscopic charcoal that we documented may have resulted from fires in the pre-European or early historical periods. Conclusions, Harsh edaphic conditions and chronic low-level disturbances on the summit, including frequent winter storms, have apparently contributed to the establishment, long-term persistence, and slow radial growth of dwarf pitch pines on Mt Everett. The ability of dwarf pines to persist on a site in the absence of frequent fire is highly unusual among North-eastern barrens and has not been well-incorporated into previous conceptual ecological models of these communities. Our results suggest that even among North-eastern barrens, the summit of Mt Everett is characterized by highly unusual vegetation and dynamics. The site has long been recognized as regionally significant and should be afforded the strictest conservation protection. With no evident history of human disturbance or recent fire, there is no apparent need for immediate active management of the site. [source] Nest site characteristics and nesting success of the five-spotted wrasse Symphodus roissali in the north-western Mediterranean SeaJOURNAL OF FISH BIOLOGY, Issue 1 2006N. Raventos The effects of site characteristics on the distribution of nests and nesting success were examined in the five-spotted wrasse Symphodus roissali in the north-western Mediterranean Sea. Nesting males selected nest sites mainly on flat substrata and close to a margin in the rocky littoral strip; however, substratum slope and degree of shelter from wave action were the determinants for a greater success. [source] A Nested Logit Approach to Household MobilityJOURNAL OF REGIONAL SCIENCE, Issue 1 2001Thomas A. Knapp This study analyzes personal and site characteristics in a model of intraMSA and interMSA mobility. Households are assumed to choose a single type of move, intraMSA or interMSA, while simultaneously choosing a central city or suburban destination. We demonstrate that a nested logit model is appropriate on both theoretical and empirical grounds. The sample consists of intrametropolitan and intermetropolitan movers drawn from the 1990 U.S. Census PUMS. Personal characteristics drawn from the PUMS are matched to numerous site characteristics (climatic measures, other amenities, state and local fiscal characteristics, and other urban quality measures) drawn from a variety of sources. Nested logit direct and cross elasticities are presented for a number of site attributes. [source] Predicting Root Density in Streambanks,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 2 2008Candice Piercy Abstract:, Roots of riparian vegetation increase streambank erosion resistance and structural stability; therefore, knowledge of root density and distribution in streambanks is useful for stream management and restoration. The objective of this study was to compare streambank root distributions for herbaceous and woody vegetation and to develop empirical models to predict root density. Root length density, root volume ratio, soil physical and chemical properties, and above-ground vegetation densities were measured at 25 sites on six streams in southwestern Virginia. The Mann-Whitney test was used to determine differences in root density along stream segments dominated by either woody or herbaceous vegetation. Multiple linear regression was used to develop relationships between root density and site characteristics. Study results showed that roots were evenly distributed across the bank face with the majority of roots having diameters less than 2 mm. Soil bulk density and above-ground vegetation were key factors influencing root density. While significant relationships were developed to predict root density, the predictive capabilities of the equations was low. Because of the highly variable nature of soil and vegetation properties, it is recommended at this time that soil erodibility and root density be measured in the field for design and modeling purposes, rather than estimated based on empirical relationships. [source] Management history and climate as key factors driving natterjack toad population trends in BritainANIMAL CONSERVATION, Issue 5 2010A. L. McGrath Abstract Along with other amphibian populations in Europe and elsewhere, natterjack toad Bufo calamita populations in Britain have declined since at least 1960. Conservation management since the 1970s has aimed to halt the decline and maintain viable populations at key sites throughout the species' recent historical range. Here, we assess population trends from 1985 to 2006 at 20 British B. calamita sites and evaluate the role of active management in maintaining good conservation status. We investigated the effects of 25 climatic, site-characteristic and conservation management variables on population trends using general linear models. In single-variable analyses, rainfall variables showed negative relationships with population trends. Among the site characteristics, being located at the very edge of the species' range (northern Irish Sea coast) and occurrence of common toad (B. bufo) were negatively related to B. calamita population trends. Management history (populations established via translocation as opposed to native populations) had a significant positive effect; as had sites that received greater translocation releases, undergone Species Recovery Programme management, and where common toad was absent. In multiple-variable analyses, the combined effects of management history and average pre-breeding season rainfall accounted for inter-site variation in population trends. The rainfall effects in single- and multiple-variable analyses were strongly influenced by three sites with very high rainfall whilst no clear effect was apparent for the remaining sites. This study highlights the role of climatic factors in population decline, and the importance of conservation management in stabilizing population trends. Climate change over the next 50,100 years is predicted to have limited impacts on most B. calamita populations in Britain, but strongly positive impacts on the most threatened populations located at the very edge of species' range that will benefit from reduced precipitation. A need for active conservation management will remain for the foreseeable future. [source] Tree regeneration before and after restoration treatments in managed boreal Picea abies standsAPPLIED VEGETATION SCIENCE, Issue 2 2009M. De Chantal Abstract Questions: What are the short-term effects of restoration treatments, including fire and/or partial cutting with dead wood creation, on seedling density and distribution among microsites, and do they differ between upland and paludified biotopes? Location: Mature managed Picea abies -dominated stands in southern Finland. Methods: The restoration treatments consisted of four levels of cutting, with and without fire: uncut, low-CWD (partial cutting leaving 50 m3 ha,1 of standing retention trees and 5 m3 ha,1 of down retention trees, DRT), intermediate-CWD (as previous but with 30 m3 ha,1 of DRT), and high-CWD (as previous but with 60 m3 ha,1 of DRT). Results: The cutting treatment alone did not affect seedling density. Fire had an immediate effect, both by itself in upland biotopes (decreasing effect on P. abies density) and in combination with cutting in paludified biotopes (increasing effect on Betula spp. density). The density of other deciduous species (Sorbus aucuparia, Populus tremula, and Salix spp.) was not affected. Before treatments, seedlings grew predominantly on level ground and mounds. After treatments, more Betula, but fewer P. abies and other deciduous species, grew on these microsites. More Betula and other deciduous species grew next to CWD and under a fallen crown; more P. abies grew under a fallen crown in unburned stands. Conclusion: The post-treatment tree seedling density and distribution among microsites can be affected by restoration treatments. However, knowledge of local site characteristics and their interaction with different restoration treatments is needed to achieve the goals set for restoration at the stand and landscape levels. [source] Distances to Emergency Department and to Primary Care Provider's Office Affect Emergency Department Use in ChildrenACADEMIC EMERGENCY MEDICINE, Issue 5 2009Annameika Ludwick MD Abstract Objectives:, Patients of all ages use emergency departments (EDs) for primary care. Several studies have evaluated patient and system characteristics that influence pediatric ED use. However, the issue of proximity as a predictor of ED use has not been well studied. The authors sought to determine whether ED use by pediatric Medicaid enrollees was associated with the distance to their primary care providers (PCPs), distance to the nearest ED, and distance to the nearest children's hospital. Methods:, This historical cohort study included 26,038 children age 18 and under, assigned to 332 primary care practices affiliated with a Medicaid health maintenance organization (HMO). Predictor variables were distance from the child's home to his or her PCP site, distance from home to the nearest ED, and distance from home to the nearest children's hospital. The outcome variable was each child's ED use. A negative binomial model was used to determine the association between distance variables and ED use, adjusted for age, sex, and race, plus medical and primary care site characteristics previously found to influence ED use. Distance variables were divided into quartiles to test for nonlinear associations. Results:, On average, children made 0.31 ED visits/person/year. In the multivariable model, children living greater than 1.19 miles from the nearest ED had 11% lower ED use than those living within 0.5 miles of the nearest ED (risk ratio [RR] = 0.89, 95% CI = 0.81 to 0.99). Children living between 1.54 and 3.13 miles from their PCPs had 13% greater ED use (RR = 1.13, 95% CI = 1.03 to 1.24) than those who lived within 0.7 miles of their PCP. Conclusions:, Geographical variables play a significant role in ED utilization in children, confirming the importance of system-level determinants of ED use and creating the opportunity for interventions to reduce geographical barriers to primary care. [source] Growth and yield of winter wheat (Triticum aestivum L.) and corn (Zea mays L.) near a high voltage transmission lineBIOELECTROMAGNETICS, Issue 2 2003G. Soja Abstract The objective of this study was to determine the effects of an electromagnetic field from a high voltage transmission line on the yield of agricultural crops cultivated underneath and near the transmission line. For 5 years, experiments with winter wheat and corn were carried out near the 380 kV transmission line Dürnrohr (Austria),Slavetice (Czech Republic). Different field strengths were tested by planting the crops at different distances from the transmission line. The plants were grown in experimental plots (1.77 m2), aligned to equal electric field strengths, and were cultivated according to standard agricultural practice. The soil for all plots was homogenized layer-specifically to a depth of 0.5 m to guarantee uniform soil conditions in the plant root environment. The soil was sampled annually for determinations of carbon content and the behavior of microbial biomass. During development of the vegetation, samples were collected at regular intervals for growth rate analyses. At physiological maturity, the plots (n,=,8) were harvested for grain and straw yield determinations. The average electric and magnetic field strengths at four distances from the transmission line (nominal distances: 40, 14, 8, and 2 m) were between 0.2 and 4.0 kV/m and between 0.4 and 4.5 µT, respectively. No effect of the field exposures on soil microbial biomass could be detected. The wheat grain yields were 7% higher (average of 5 years) in the plots with the lowest field exposure than in the plots nearer to the transmission line (P,<,.10). The responses of the plants were more pronounced in years with drought episodes during grain filling than in humid years. No significant yield differences were found for corn yields. The extent of the yield variations attributed to the distance from the transmission line was small compared to the observed annual variations in climatic or soil specific site characteristics. Bioelectromagnetics 24:91,102, 2003. © 2003 Wiley-Liss, Inc. [source] New Perspectives in Comparative Ecology of Neotropical Rain Forests: Reflections on the Past, Present, and FutureBIOTROPICA, Issue 1 2004Jennifer S. Powers ABSTRACT In an effort to understand variations in ecological patterns among lowland tropical rain forests, Alwyn Gentry and colleagues synthesized data sets from four of the premier Neotropical field stations,La Selva (Costa Rica), Barro Colorado Island (Panama), Cocha Cashu (Peru), and the Biological Dynamics of Forest Fragmentation Project (Brazil). To promote the kind of geographically comparative tropical ecology advocated in the 1990 Gentry book, the Organization for Tropical Studies and the Smithsonian Tropical Research Institute organized a course in 2001 that visited each of these field stations. Papers from some of the studies resulting from this course are highlighted in this special section. These studies are notable for the consistent methods applied across forests, and they underscore the acute need and bright future for comparative tropical ecology. Key site characteristics for each of the field stations are summarized here. RESUMEN En un esfuerzo de entender las variaciones en patrones ecológicos entre selvas tropicales de bajura, Alwyn Gentry y colegas sintetizaron bases de datos en las cuatro principales estaciones biológicos del Neotrópico: La Selva (Costa Rica), Barro Colorado Island (Panamá), Cocha Cashu (Perú), y el Proyecto de Dinámica Biológica de Fragmentación de Bosque (Brasil). Con el fin de promover el estudio ecologico tropical comparativa a nivel geográfico recomendada por Gentry en 1990 la Organización para Estudios Tropicales y el Smithsonian Tropical Research Institution organizaron un curso en el año 2001, el cual visitó cada una de éstas estaciones. Los artículos científicos de algunos de los estudios producto de este curso se presentan en esta sección especial. Estos estudios son notables debido a la consistencia en los metodología aplicada a través de los cuatro sitios. Asimismo, estos estudios denotan la necesidad y el potencial de Uevar a cabo mas investigación a nivel de ecología tropical comparativa. Caracteristicas importantes para cada una de las estaciones de campo son resumidos en esta sección. [source] Availability and Quality of Computed Tomography and Magnetic Resonance Imaging Equipment in U.S. Emergency DepartmentsACADEMIC EMERGENCY MEDICINE, Issue 8 2008Adit A. Ginde MD Abstract Objectives:, The objective was to determine the availability and quality of computed tomography (CT) and magnetic resonance imaging (MRI) equipment in U.S. emergency departments (EDs). The authors hypothesized that smaller, rural EDs have less availability and lower-quality equipment. Methods:, This was a random selection of 262 (5%) U.S. EDs from the 2005 National Emergency Department Inventories (NEDI)-USA (http://www.emnet-usa.org/). The authors telephoned radiology technicians about the presence of CT and MRI equipment, availability for ED imaging, and number of slices for the available CT scanners. The analysis was stratified by site characteristics. Results:, The authors collected data from 260 institutions (99% response). In this random sample of EDs, the median annual patient visit volume was 19,872 (interquartile range = 6,788 to 35,757), 28% (95% confidence interval [CI] = 22% to 33%) were rural, and 27% (95% CI = 21% to 32%) participated in the Critical Access Hospital program. CT scanners were present in 249 (96%) institutions, and of these, 235 (94%) had 24/7 access for ED patients. CT scanner resolution varied: 28% had 1,4 slice, 33% had 5,16 slice, and 39% had a more than 16 slice. On-site MRI was available for 171 (66%) institutions, and mobile MRI for 53 (20%). Smaller, rural, and critical access hospitals had lower CT and MRI availability and less access to higher-resolution CT scanners. Conclusions:, Although access to CT imaging was high (>90%), CT resolution and access to MRI were variable. Based on observed differences, the availability and quality of imaging equipment may vary by ED size and location. [source] Effects of Three Characteristic Amino Acid Residues of Pharaonis Phoborhodopsin on the Absorption Maximum ,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2000Kazumi Shimono ABSTRACT Phoborhodopsin (pR or sensory rhodopsin II, sRII) or pharaonis phoborhodopsin (ppR or pharaonis sensory rhodopsin II, psRII) has a unique absorption maximum (,max) compared with three other archaeal rhodopsins: ,max of pR or ppR at ca 500 nm and others at 560,590 nm. Alignment of amino acid sequences revealed three sites characteristic of the shorter wavelength,absorbing pigments. The amino acids of these three sites are conserved completely among archaeal rhodopsins having longer ,max, and are different from those of pR or ppR. We replaced these amino acids of ppR with amino acids corresponding to those of bacteriorhodopsin, Val-108 to Met, Gly-130 to Ser and Thr-204 to Ala. The ,max of V108M mutant was 502 nm with a slight redshift. G130S and T204A mutants had ,max of 503 and 508 nm, respectively. Thus, each site contributes only a small effect to the color tuning. We then constructed three double mutants and one triple mutant. The opsin-shifts of these mutants suggest that Val-108 and Thr-204 or Gly-130 are synergistic, and that Gly-130 and Thr-204 work additively. Even in the triple mutant, the ,max was 515 nm, an opsin-shift only ca 30% of the shift value from 500 to 560 nm. This means that there is another yet unidentified factor responsible for the color tuning. [source] | |||||||||||||||||||