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Kinds of Study Sites Selected AbstractsMenstruation does not cause anemia: Endometrial thickness correlates positively with erythrocyte count and hemoglobin concentration in premenopausal womenAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 5 2006Kathryn B.H. Clancy Menstruation has often been cited as a risk factor for iron-deficiency anemia. This study tested whether normal, premenopausal women's luteal endometrial thickness (ET) was associated with their red blood cell count (RBC) and hemoglobin concentrations (Hg), and therefore whether a high ET put women at risk for anemia. Endometrial thickness can be considered a reasonable proxy for menstrual blood loss in normal women. Twenty-six healthy women from the Mogielica Human Ecology Study Site in Poland, aged 20,40 years (29 ± 5.3 years, mean ± SD), were selected. Subjects' ET was measured by transvaginal ultrasound in the luteal phase of the menstrual cycle, and their red blood cell count and hemoglobin concentrations were measured by fasting morning blood samples. Controlling for day of ET measurement, RBC and Hg were positively correlated with ET (r2 = 0.24, P = 0.05; r2 = 0.25, P = 0.04, respectively). We propose that, contrary to popular understanding, a thicker endometrium suggests greater iron reserves, rather than greater risk for anemia, in healthy women. Am. J. Hum. Biol. 18:710,713, 2006. © 2006 Wiley-Liss, Inc. [source] The End of an Era: What Became of the "Managed Care Revolution" in 2001?HEALTH SERVICES RESEARCH, Issue 1p2 2003Cara S. Lesser Objective. To describe how the organization and dynamics of health systems changed between 1999 and 2001, in the context of expectations from the mid-1990s when managed care was in ascendance, and assess the implications for consumers and policymakers. Data Sources/Study Setting. Data are from the Community Tracking Study site visits to 12 communities that were randomly selected to be nationally representative of metropolitan areas with 200,000 people or more. The Community Tracking Study is an ongoing effort that began in 1996 and is fielded every two years. Study Design. Semistructured interviews were conducted with 50,90 stakeholders and observers of the local health care market in each of the 12 communities every two years. Respondents include leaders of local hospitals, health plans, and physician organizations and representatives of major employers, state and local governments, and consumer groups. First round interviews were conducted in 1996,1997 and subsequent rounds of interviews were conducted in 1998,1999 and 2000,2001. A total of 1,690 interviews were conducted between 1996 and 2001. Data Analysis Methods. Interview information was stored and coded in qualitative data analysis software. Data were analyzed to identify patterns and themes within and across study sites and conclusions were verified by triangulating responses from different respondent types, examining outliers, searching for disconfirming evidence, and testing rival explanations. Principal Findings. Since the mid-1990s, managed care has developed differently than expected in local health care markets nationally. Three key developments shaped health care markets between 1999 and 2001: (1) unprecedented, sustained economic growth that resulted in extremely tight labor markets and made employers highly responsive to employee demands for even fewer restrictions on access to care; (2) health plans increasingly moved away from core strategies in the "managed care toolbox"; and (3) providers gained leverage relative to managed care plans and reverted to more traditional strategies of competing for patients based on services and amenities. Conclusions. Changes in local health care markets have contributed to rising costs and created new access problems for consumers. Moreover, the trajectory of change promises to make the goals of cost-control and quality improvement more difficult to achieve in the future. [source] Population dynamics of insects associated with Rumex obtusifolius in different habitatsENTOMOLOGICAL RESEARCH, Issue 2 2006Ohseok KWON Abstract The effect of different habitats on insect communities associated with Rumex obtusifolius was studied in detail. Study sites were selected for their variety of environmental characteristics (vegetation and habitat): shaded woodland, disturbed wasteland and pasture. The results of this study were that insect populations associated with R. obtusifolius responded differently to the different habitats. The observed differences in population dynamics among the insects showed quite clearly their responses to different habitats. There was also a pattern of time partitioning in the exploitation of the host-plant among the insect species observed. Philaenus spumarius at nymphal stage had a peak density on approximately 20 June, Apion frumentarium and Apion spp. (Apion species other than A. frumentarium) had a peak density on approximately 30 June and Aphis rumicis had a peak density on approximately 28 July. This pattern of shift in time for peak population density (time-shift) among the insects sharing a common host-plant may guarantee each insect the opportunity to exploit the plant to a maximum. [source] Structural patterns in coarse gravelriver beds: typology, survey and assessment of the roles of grain size and river regimeGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 1 2002Lea Wittenberg The concept of river-bed stability as indexed by the occurrence of stable bed forms was examined in humid-temperate perennial streams and in Mediterranean ephemeral streams. The study examined the structural patterns of bed forms and their spatial distribution between temperate-humid and Mediterranean streams. Study sites in Northumberland, UK, and Mt. Carmel, Israel, were selected for their morphometric similarity, despite the contrast in climate, vegetation and hydrological regime. Fieldwork was based on a large number of Wolman grain size distributions and structure measurements along cross-sections at seven sites; Differences in mean grain size of bed structures were estimated using the general linear model (GLM) procedure and Duncan's multiple range test. Based on field evidence, river-bed configurations were divided into structural categories, according to the depositional setting of each measured particle on the river bed. Statistical analysis confirmed former qualitative descriptions of small-scale bed forms. The study identified spatial segregation in bed form distribution. In general, 30,40%of the bed material in the surveyed perennial streams was clustered, in contrast to approximately 10%in the ephemeral counterparts. The sorting index revealed higher values for the perennial streams, namely 2.39,3.59 compared with 1.73,2.07 for the ephemeral counterparts. It is suggested that the degree of sediment sorting and the proportion of clusters are strongly related. Sediment sorting, sediment supply and the hydrological regime explain the mechanism of cluster formation. It is assumed that climate shifts or human interference within river basins might affect the regional characteristic flood hydrograph, and consequently alter the sedimentary character of the river bed. In the case where river bed stability is reduced owing to changes in cluster bed form distribution, rivers that normally do not yield a significant amount of sediment might be subject to notable sedimentation problems. [source] Effects of natural disturbance and selective logging on Nothofagus forests in south-central ChileJOURNAL OF BIOGEOGRAPHY, Issue 7 2002William Pollmann Aim Changes in stand structure, floristic composition and tree population dynamics during the last four centuries were described in southern temperate rain forests. The impacts of natural and anthropogenic disturbance since the late 1560s were examined for old-growth and logged forests. Location The study was conducted in montane Nothofagus alpina forests in the Andean Range of south-central Chile. Study sites were located at a range of altitudes between 1000 and 1250 m a.s.l. Methods Temporal variation in species recruitment and annual dendroecological data were used to determine the historical development and disturbance history of three old-growth forests, and three stands after selective logging in the late 1880s to early 1900s. Considering the spatial structure of evergreen vs. deciduous elements, the forests are a mixture of deciduous and evergreen tree species. Results Stem density, maximum stem diameter and basal area differed between the old-growth and logged stands, but species composition did not. At lower altitudes, N. alpina was the dominant canopy species in both old-growth and logged stands, but regeneration of N. alpina was significantly different in these stands. At higher altitudes, N. alpina and N. dombeyi were the dominant canopy species in both old-growth and logged stands, and here regeneration patterns of these Nothofagus species were similar. After selective logging, in mixed forests of shade-intolerant Nothofagus and more shade-tolerant trees (such as Laurelia philippiana) there has been a shift in regeneration from more shade-tolerant resprouting species towards Nothofagus. Major and moderate releases in radial growth, indicative of disturbance, occurred in most of the older trees during the last four centuries, and especially during the last 100 years. Growth rates of N. alpina are higher than those of associated shade-tolerant trees, and apparently increase after disturbances. Main conclusions Results suggest that under disturbance regimes dominated by treefall gaps, and additionally canopy openings by selective logging, maintenance of Nothofagus species appears to be associated with complementary differences in growth rate, sprouting capacity, canopy residence time, and longevity. Such small-scale canopy openings may help explain the relative abundance of N. alpina in montane mixed rain forests in the Andean Range, where the maintenance of Nothofagus species in many stands has been attributed to a high frequency of coarse-scale disturbance. My results serve to emphasize that understanding the species coexistence and forest dynamics in Nothofagus forests may require attention to interspecific differences in life-history characteristics. [source] Evaluation of enamel matrix derivative as an adjunct to non-surgical periodontal therapyJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 8 2003Mauricio A. Gutierrez Abstract Objectives: The aim of this study was to evaluate the adjunctive use of enamel matrix derivative (EMD) on periodontal healing following nonsurgical periodontal therapy (scaling and root planing , SRP). Material and methods: The study was performed as an intraindividual, longitudinal trial of 3 months duration with a double-blinded, split-mouth, controlled, and randomized design. Twenty-two patients with moderate to severe chronic periodontitis were enrolled in the study. In each patient, two sites with pocket depths 5 mm and with radiographic angular bone defects >3 mm were selected. Baseline examination included measurement of probing pocket depth (PPD) and clinical attachment levels (CAL). The presence or absence of plaque and bleeding on probing at selected sites was also recorded. Following initial examination, full-mouth SRP was performed. Study sites were then treated with 24% EDTA for 2 min, followed by thorough irrigation with sterile saline. The sites were then randomized. The experimental site received subgingival application of enamel matrix derivative (Emdogain®, BIORA AB, Malmo, Sweden). The control site received no additional treatment. At 3 months, all sites were re-examined. The response to therapy in experimental and control sites was evaluated, using change in probing depth and CAL as the primary outcome variables. Statistical analysis (paired t -tests) was used to compare response to treatment in control versus experimental sites. Results: Statistically significant changes in PPD and CAL were seen in both treatment groups from baseline to 3 months. The mean PPD reduction was 2.3±0.5 mm for control sites and 2.0±0.3 mm for experimental sites. The mean CAL gain was 1.8±0.4 mm for control sites, and 1.4±0.3 mm for experimental sites. Statistical analysis, however, revealed no significant difference in PPD reduction or CAL gain between experimental and control groups (p>0.4). In addition, no difference was found between treatment groups in bleeding or plaque indices at 3 months. Conclusion: The findings from the present study do not support the use of EMD during routine, nonsurgical debridement of periodontal pockets as measured 3 months post SRP. Zusammenfassung Ziel: Das Ziel dieser Studie war die Evaluation eines adjunktiven Gebrauchs von Schmelzmatrixderivaten (EMD) auf die parodontale Heilung nach nicht chirurgischer parodontaler Therapie (Wurzelreinigung und ,glättung, scaling und root planing , SRP). Material und Methoden: Die Studie wurde als eine intraindividuelle, für 3 Monate longitudinale Studie mit einem doppelt blinden, split-mouth, kontrolliertem und randomisiertem Protokoll durchgeführt. 22 Patienten mit moderater bis schwerer chronischer Parodontitis wurden in die Studie einbezogen. Bei jedem Patient wurden zwei Flächen mit Sondierungstiefen5 mm und mit radiographisch feststellbaren angulären Knochendefekten>3 mm ausgesucht. Die Basisuntersuchung umfasste die Messung der Sondierungstiefen (PPD) und des klinischen Stützgewebeniveaus (CAL). Die An- oder Abwesenheit von Plaque und Provokationsblutung an den ausgesuchten Flächen wurden auch dokumentiert. Nach der anfänglichen Untersuchung wurde eine alle Zähne betreffende SRP durchgeführt. Die Studienflächen wurden dann mit 24% EDTA für zwei Minuten behandelt, gefolgt von einer sorgsamen Spülung mit steriler Kochsalzlösung. Die Flächen wurden dann randomisiert. Die experimentellen Flächen erhielten eine subgingivale Applikation von Schmelzmatrixderivaten (Emdogain®, BIORA AB, Malmö, Schweden). Die Kontrollflächen erhielten keine zusätzliche Behandlung. Zum dritten Monat wurden alle Flächen reexaminiert. Die Antwort auf die Therapie bei den experimentellen und Kontrollflächen wurden evaluiert in Hinsicht der Veränderung der Sondierungstiefe und CAL als die primären Ergebnisvariablen. Statistische Analysen (gepaarter t -Test) wurden für den Vergleich der Behandlung zwischen experimentellen und Kontrollflächen genutzt. Ergebnisse: Statistisch signifikante Veränderungen bei der PPD und dem CAL wurden in beiden Behandlungsgruppen zwischen Basis und 3 Monaten beobachtet. Die mittlere PPD Reduktion betrug 2.3±0.5 mm für die Kontrollflächen und 2.0±0.3 mm für die experimentellen Flächen. Der mittlere CAL Gewinn betrug 1.8±0.4 mm für die Kontrollflächen und 1.4±0.3 mm für die experimentellen Flächen. Die statistischen Analysen erbrachten jedoch keine signifikanten Differenzen für PPD Reduktion und CAL Gewinn zwischen den experimentellen und Kontrollgruppen (p>0.4). Es wurden auch keine Differenzen zwischen den Gruppen hinsichtlich Provokationsblutung und Plaqueindex zum dritten Monat beobachtet. Schlussfolgerung: Die Ergebnisse von der vorliegenden Studie unterstützen nicht die Anwendung von EMD während der routinemäßigen nicht chirurgischen Reinigung der parodontalen Taschen, wie die Messungen drei Monate nach SRP. Résumé Objectif: Le but de cette étude fut d'évaluer l'utilisation des dérivés de la matrice amellaire (EMD) sur la cicatrisation parodontale après un traitement parodontal non chirurgical (détartrage et surfaçage radiculaire). Matériel et méthodes: L'étude fut conçue en essai longitudinal intra-individuel d'une durée de 3 mois randomisée, contrôlée en double aveugle et en bouche croisée. 22 patients atteints de parodontites chroniques modérées ou sévères furent enrôlés. Pour chaque patient, 2 sites avec des profondeurs de poches5 mm et des lésions osseuses angulaires radiographiques>3 mm furent sélectionnés. L'examen initial comportait la mesure des profondeurs de poche au sondage (PPD) et les niveaux cliniques d'attache (CAL). La présence ou l'absence de plaque et de saignement au sondage sur les sites sélectionnés furent aussi enregistrées. Après l'examen initial, un détartrage et un surfaçage complet étaient réalisés. Les sites étudiés étaient alors traités par de l'EDTA à 24% pendant 2 minutes, puis fortement rinçés avec du serum physiologique. Les sites étaient alors répartis aléatoirement. Le site expérimental recevait une application sous gingivale d'EMD (Emdogain®, BIORA AB, Malmo, Sweden). Le site contrôle ne recevait pas de traitement supplémentaire. A 3 mois, les sites étaient réévalués. La réponse au traitement était évaluée par les modifications de profondeur de poches et de niveau d'attache comme variables primaires. L'analyse statistique (Test t apparié) permit de comparer la réponse au traitement. Résultats: Des modifications statistiquement significatives de PPD et de CAL ont été observées dans les deux groupes de traitement. La réduction de PPD moyenne était de 2.3±0.5 mm pour les sites contrôles et de 2.0±0.3 mm pour les sites expérimentaux. Le gain de CAL moyen était respectivement de 1.8±0.4 mm et de 1.4±0.3 mm.L'analyse statistique, cependant, ne révélait pas de différences significatives entre les deux groupes (p>0.4). De plus, aucune différence n'apparaissait entre les groupes pour le saignement et les indices de plaque au troisième mois. Conclusion: Les données de cette étude n'étayent pas l'utilisation routinière d' EMD lors du débridement non chirurgical des poches parodontales lorsqu'on en mesure les résultats 3 mois après détartrage et surfaçage radiculaire. [source] Effects of invasive alien kahili ginger (Hedychium gardnerianum) on native plant species regeneration in a Hawaiian rainforestAPPLIED VEGETATION SCIENCE, Issue 1 2010V. Minden Abstract Questions: Does the invasive alien Hedychium gardnerianum (1) replace native understory species, (2) suppress natural regeneration of native plant species, (3) increase the invasiveness of other non-native plants and (4) are native forests are able to recover after removal of H. gardnerianum. Location: A mature rainforest in Hawai'i Volcanoes National Park on the island of Hawai'i (about 1200 m a.s.l.; precipitation approximately 2770 mm yr,1). Study sites included natural plots without effects of alien plants, ginger plots with a H. gardnerianum -dominated herb layer and cleared plots treated with herbicide to remove alien plants. Methods: Counting mature trees, saplings and seedlings of native and alien plant species. Using non-parametric H -tests to compare impact of H. gardnerianum on the structure of different sites. Results: Results confirmed the hypothesis that H. gardnerianum has negative effects on natural forest dynamics. Lower numbers of native tree seedlings and saplings were found on ginger-dominated plots. Furthermore, H. gardnerianum did not show negative effects on the invasive alien tree species Psidium cattleianum. Conclusions: This study reveals that where dominance of H. gardnerianum persists, regeneration of the forest by native species will be inhibited. Furthermore, these areas might experience invasion by P. cattleianum, resulting in displacement of native canopy species in the future, leading to a change in forest structure and loss of other species dependent on natural rainforest, such as endemic birds. However, if H. gardnerianum is removed the native Hawaiian forest is likely to regenerate and regain its natural structure. [source] Confronting Uncertainty and Missing Values in Environmental Value Transfer as Applied to Species ConservationCONSERVATION BIOLOGY, Issue 5 2010SONIA AKTER conservación de especies; error de transferencia; incertidumbre; transferencia de valor ambiental; valores de no uso Abstract:,The nonuse (or passive) value of nature is important but time-consuming and costly to quantify with direct surveys. In the absence of estimates of these values, there will likely be less investment in conservation actions that generate substantial nonuse benefits, such as conservation of native species. To help overcome decisions about the allocation of conservation dollars that reflect the lack of estimates of nonuse values, these values can be estimated indirectly by environmental value transfer (EVT). EVT uses existing data or information from a study site such that the estimated monetary value of an environmental good is transferred to another location or policy site. A major challenge in the use of EVT is the uncertainty about the sign and size of the error (i.e., the percentage by which transferred value exceeds the actual value) that results from transferring direct estimates of nonuse values from a study to a policy site, the site where the value is transferred. An EVT is most useful if the decision-making framework does not require highly accurate information and when the conservation decision is constrained by time and financial resources. To account for uncertainty in the decision-making process, a decision heuristic that guides the decision process and illustrates the possible decision branches, can be followed. To account for the uncertainty associated with the transfer of values from one site to another, we developed a risk and simulation approach that uses Monte Carlo simulations to evaluate the net benefits of conservation investments and takes into account different possible distributions of transfer error. This method does not reduce transfer error, but it provides a way to account for the effect of transfer error in conservation decision making. Our risk and simulation approach and decision-based framework on when to use EVT offer better-informed decision making in conservation. Resumen:,El valor de no uso (o pasivo) de la naturaleza es importante pero su cuantificación con muestreos pasivos consume tiempo y es costosa. En ausencia de estimaciones de estos valores, es probable que haya menos inversión en acciones de conservación que generen beneficios de no uso sustanciales, tal como la conservación de especies nativas. Para ayudar a superar decisiones respecto a la asignación de dólares para conservación que reflejan la carencia de estimaciones de los valores de no uso, estos valores pueden ser estimados indirectamente por la transferencia de valor ambiental (TVA). La transferencia de valor ambiental utiliza datos existentes o información de un sitio de estudio de tal manera que el valor monetario estimado de un bien ambiental es transferido a otro sitio. Un reto mayor en el uso de TVA es la incertidumbre sobre la señal y el tamaño del error (i.e., el porcentaje en que el valor transferido excede al valor actual) que resulta de la transferencia de estimaciones directas de los valores de no uso de un sitio de estudio a uno político, el sitio adonde el valor es transferido. Una TVA es más útil si el marco de toma de decisiones no requiere información muy precisa y cuando la decisión de conservación está restringida por tiempo y recursos financieros. Para tomar en cuenta la incertidumbre en el proceso de toma de decisiones, se puede seguir una decisión heurística que guie el proceso de decisión e ilustre sobre las posibles ramificaciones de la decisión. Para tomar en cuenta la incertidumbre asociada con la transferencia de valores de un sitio a otro, desarrollamos un método de riesgo y simulación que utiliza simulaciones Monte Carlo para evaluar los beneficios netos de las inversiones de conservación y que considera posibles distribuciones diferentes de la transferencia de error. Este método no reduce el error de transferencia, pero proporciona una manera para considerar el efecto del error de transferencia en la toma de decisiones de conservación. Nuestro método de riesgo y simulación y el marco de referencia basado en decisones sobre cuando utilizar TVA permiten la toma de decisiones en conservación más informadas. [source] Effects of Habitat Fragmentation on Effective Dispersal of Florida Scrub-JaysCONSERVATION BIOLOGY, Issue 4 2010AURÉLIE COULON Aphelocoma c,rulescens; dispersión; flujo génico; fragmentación Abstract:,Studies comparing dispersal in fragmented versus unfragmented landscapes show that habitat fragmentation alters the dispersal behavior of many species. We used two complementary approaches to explore Florida Scrub-Jay (Aphelocoma c,rulescens) dispersal in relation to landscape fragmentation. First, we compared dispersal distances of color-marked individuals in intensively monitored continuous and fragmented landscapes. Second, we estimated effective dispersal relative to the degree of fragmentation (as inferred from two landscape indexes: proportion of study site covered with Florida Scrub-Jay habitat and mean distance to nearest habitat patch within each study site) by comparing genetic isolation-by-distance regressions among 13 study sites having a range of landscape structures. Among color-banded individuals, dispersal distances were greater in fragmented versus continuous landscapes, a result consistent with other studies. Nevertheless, genetic analyses revealed that effective dispersal decreases as the proportion of habitat in the landscape decreases. These results suggest that although individual Florida Scrub-Jays may disperse farther as fragmentation increases, those that do so are less successful as breeders than those that disperse short distances. Our study highlights the importance of combining observational data with genetic inferences when evaluating the complex biological and life-history implications of dispersal. Resumen:,Estudios que comparan la dispersión en paisajes fragmentados versus no fragmentados muestran que la fragmentación del hábitat altera la conducta de dispersión de muchas especies. Utilizamos dos métodos complementarios para explorar la dispersión de Aphelocoma c,rulescens en relación con la fragmentación del paisaje. Primero, comparamos las distancias de dispersión de individuos marcados con color en paisajes continuos y fragmentados monitoreados intensivamente. Segundo, estimamos la dispersión efectiva en relación con el grado de fragmentación (inferida a partir de dos índices del paisaje: proporción del sitio de estudio cubierta con hábitat para A. c,rulescens y la distancia promedio al parche más cercano en cada sitio de estudio) mediante la comparación de regresiones de aislamiento genético por distancia entre 13 sitios de estudio con una gama de estructuras de paisaje. Entre los individuos marcados con color, las distancias de dispersión fueron mayores en los paisajes fragmentados versus los continuos, un resultado consistente con otros estudios. Sin embargo, los análisis genéticos revelaron que la dispersión efectiva decrece a medida que decrece la proporción de hábitat en el paisaje. Estos resultados sugieren que aunque individuos de A. c,rulescens pueden dispersarse más lejos a medida que incrementa la fragmentación, aquellos que lo hacen son reproductores menos exitosos que los que se dispersan a corta distancia. Nuestro estudio resalta la importancia de combinar datos observacionales con inferencias genéticas cuando se evalúan las complejas implicaciones de la dispersión sobre la biología y la historia natural. [source] Patch-Occupancy Modeling as a Method for Monitoring Changes in Forest Floristics: a Case Study in Southeastern AustraliaCONSERVATION BIOLOGY, Issue 3 2009TRENT D. PENMAN fuego prescrito; manejo adaptativo; modelo Bayesiamo; silvicultura; tala Abstract:,The ability to monitor changes in biodiversity is fundamental to demonstrating sustainable management practices of natural resources. Disturbance studies generally focus on responses at the plot scale, whereas landscape-scale responses are directly relevant to the development of sustainable forest management. Modeling changes in occupancy is one way to monitor landscape-scale responses. We used understory vegetation data collected over 16 years from a long-term study site in southeastern Australia. The site was subject to timber harvesting and frequent prescribed burning. We used occupancy models to examine the impacts of these disturbances on the distribution of 50 species of plants during the study. Timber harvesting influenced the distribution of 9 species, but these effects of harvesting were generally lost within 14 years. Repeated prescribed fire affected 22 species, but the heterogeneity of the burns reduced the predicted negative effects. Twenty-two species decreased over time independent of treatment, and only 5 species increased over time. These changes probably represent a natural response to a wildfire that occurred in 1973, 13 years before the study began. Occupancy modeling is a useful and flexible technique for analyzing monitoring data and it may also be suitable for inclusion within an adaptive-management framework for forest management. Resumen:,La habilidad para monitorear cambios en la biodiversidad es fundamental para demostrar el manejo sustentable de los recursos naturales. Los estudios de perturbación generalmente enfocan las respuestas a escala de parcela, mientras que las respuestas a escala de paisaje son directamente relevantes para el desarrollo del manejo sustentable de bosques. El modelado de cambios en la ocupación es una forma de monitorear respuestas a escala de paisaje. Utilizamos datos de la vegetación de sotobosque colectados a los largo de 16 años en un sitio de estudio a largo plazo en el sureste de Australia. El sitio fue sujeto a la cosecha de madera y a quemas prescritas frecuentes. Utilizamos modelos de ocupación para examinar los impactos de estas perturbaciones sobre la distribución de 50 especies de plantas. La cosecha de madera influyó en la distribución de nueve especies, pero los efectos de la cosecha generalmente se perdieron al cabo de 14 años. El fuego prescrito repetido afectó a 22 especies, pero la heterogeneidad de las quemas redujo los efectos negativos pronosticados. Veintidós especies decrecieron en el tiempo independientemente del tratamiento, y solo cinco especies incrementaron en el tiempo. Estos cambios probablemente representan una respuesta natural al incendio no controlado que ocurrió en 1973, 13 años antes de que comenzara el estudio. El modelado de la ocupación es una técnica útil y flexible para analizar datos de monitoreo y también puede ser adecuado para su inclusión en un marco de manejo adaptativo para la gestión de bosques. [source] Shade-Coffee Plantations as Refuges for Tropical Wild Orchids in Central Veracruz, MexicoCONSERVATION BIOLOGY, Issue 3 2005LISLIE SOLIS-MONTERO biología reproductiva; epifitas vasculares; estratificación vertical; estructura poblacional; limitación de polinizador Abstract:,In central Veracruz, Mexico, coffee plantations have replaced large areas of lower montane cloud forest. Shade-coffee plantations with high levels of structural diversity provide refuge for forest-dependent biota (e.g., birds and insects). Orchids typical of natural forest may also be found in the canopy of shade-coffee agroecosystems. It is not known, however, whether these are relicts from the original forest vegetation or if the plantations themselves provide the necessary conditions to support a self-sustained orchid population. We studied the population structure of the epiphytic orchids Jacquiniella teretifolia (Sw.) Britton & Willson, Scaphyglottis livida (Lindl.) Schltr., and Maxillaria densa Lindl. in a shade-coffee plantation (commercial polyculture) in central Veracruz. We also studied the previously undescribed reproductive biology of the latter two species. Our results show that the three orchid species had high population densities (>800 plants/ha). In our study site, 50% to 68% of the orchid plants of the target species were young individuals (less than five shoots). Reproductive structures were present in 80% of individuals larger than 30 shoots in the three species. M. densa is self-incompatible, and the fruit set obtained from cross pollination (42.7%) was higher than that obtained from natural pollination (18.2%), suggesting that this species could be pollinator limited. S. livida is autocompatible, not autogamous, and was not pollinator limited. Our results show that the coffee plantation had abundant orchid populations with log-normal size/age structures. Two of the target species, M. densa and S. livida, depend on pollinators to reproduce. It is clear that pollinators that allow orchids to set a high proportion of fruits persist in shade-coffee plantations. Coffee plantations may not replace the original conditions of a forest, but it is possible that these and other orchid species survive and reproduce in coffee plantations that provide appropriate microclimate conditions for the plants, including pollinators. Resumen:,En el centro de Veracruz, México, las plantaciones de café han reemplazado a extensas áreas de bosque nublado montano. Las plantaciones cafetaleras de sombra con altos niveles de diversidad estructural proporcionan refugio a biota dependiente de bosques (e. g., aves e insectos). En el dosel de agroecosistemas de café de sombra también se pueden encontrar orquídeas típicas de bosques naturales. Sin embargo, no se conoce si son relictos de la vegetación del bosque original o si las plantaciones mismas proporcionan los recursos necesarios para soportar a una población de orquídeas auto sostenida. Estudiamos la estructura de la población de orquídeas epifitas Jacquiniella teretifolia (Sw.) Britton & Willson, Scaphyglottis livida (Lindl.) Schltr y Maxillaria densa Lindl en una plantación de café de sombra (policultivo comercial) en el centro de Veracruz. También estudiamos la biología reproductiva, no descrita previamente, de las últimas dos especies. Nuestros resultados muestran que las tres especies de orquídea tuvieron densidades poblacionales altas (>800 plantas/ha). En nuestro sitio de estudio, entre 50% y 68% de las plantas de las especies estudiadas eran individuos jóvenes (menos de cinco rebrotes). En las tres especies hubo presencia de estructuras reproductivas en 80% de los individuos con más de 30 rebrotes. M. densa es auto incompatible, y el conjunto de frutos obtenido por polinización cruzada (42.7%) fue mayor que el obtenido por polinización natural (18.2%), lo que sugiere que esta especie puede estar limitada por polinizadores. S. livida es autocompatible no autogama, y no fue limitada por polinizadores. Nuestros resultados muestran que la plantación de café tenía poblaciones de orquídeas abundantes con estructuras tamaño/edad log normales. Dos de las especies, M. densa y S. livida, dependen de polinizadores para su reproducción. Es claro que los polinizadores que permiten una alta proporción de frutos a las orquídeas persisten en las plantaciones. Puede que las plantaciones de café no sustituyan las condiciones originales de un bosque, pero es posible que estas, y otras, especies de orquídeas sobrevivan y se reproduzcan en plantaciones de café que proporcionen condiciones microclimáticas adecuadas, incluyendo polinizadores, para las plantas. [source] An Independent Evaluation of Four Quantitative Emergency Department Crowding ScalesACADEMIC EMERGENCY MEDICINE, Issue 11 2006Spencer S. Jones MStat Background Emergency department (ED) overcrowding has become a frequent topic of investigation. Despite a significant body of research, there is no standard definition or measurement of ED crowding. Four quantitative scales for ED crowding have been proposed in the literature: the Real-time Emergency Analysis of Demand Indicators (READI), the Emergency Department Work Index (EDWIN), the National Emergency Department Overcrowding Study (NEDOCS) scale, and the Emergency Department Crowding Scale (EDCS). These four scales have yet to be independently evaluated and compared. Objectives The goals of this study were to formally compare four existing quantitative ED crowding scales by measuring their ability to detect instances of perceived ED crowding and to determine whether any of these scales provide a generalizable solution for measuring ED crowding. Methods Data were collected at two-hour intervals over 135 consecutive sampling instances. Physician and nurse agreement was assessed using weighted , statistics. The crowding scales were compared via correlation statistics and their ability to predict perceived instances of ED crowding. Sensitivity, specificity, and positive predictive values were calculated at site-specific cut points and at the recommended thresholds. Results All four of the crowding scales were significantly correlated, but their predictive abilities varied widely. NEDOCS had the highest area under the receiver operating characteristic curve (AROC) (0.92), while EDCS had the lowest (0.64). The recommended thresholds for the crowding scales were rarely exceeded; therefore, the scales were adjusted to site-specific cut points. At a site-specific cut point of 37.19, NEDOCS had the highest sensitivity (0.81), specificity (0.87), and positive predictive value (0.62). Conclusions At the study site, the suggested thresholds of the published crowding scales did not agree with providers' perceptions of ED crowding. Even after adjusting the scales to site-specific thresholds, a relatively low prevalence of ED crowding resulted in unacceptably low positive predictive values for each scale. These results indicate that these crowding scales lack scalability and do not perform as designed in EDs where crowding is not the norm. However, two of the crowding scales, EDWIN and NEDOCS, and one of the READI subscales, bed ratio, yielded good predictive power (AROC >0.80) of perceived ED crowding, suggesting that they could be used effectively after a period of site-specific calibration at EDs where crowding is a frequent occurrence. [source] Psychological effects of the November 1999 earthquake in Turkey: an epidemiological studyACTA PSYCHIATRICA SCANDINAVICA, Issue 3 2003Objective: This study assessed the traumatic stress symptoms and related factors in two towns affected by two earthquakes, which killed 20 000 people in 1999 in Turkey. Method: A total of 430 people in selected households were seen 18 months after the earthquake. They were given a self-report questionnaire assessing post-traumatic stress (PTSD) and depressive symptoms, demographics and trauma exposure. Results: The rates of PTSD and depression were higher in the site closer to the epicenter. The traumatic stress symptom checklist scores were predicted by fear during earthquake, loss of friends and neighbours, female gender, lower education and living in rented accomodation. Depression was predicted by study site, death of relatives and past psychiatric illness. Conclusion: These results show that severe earthquakes can cause long-lasting morbidity. Our previous findings that showed a differential prediction for depressive and traumatic stress symptoms after earthquakes are also supported. [source] Multi-phase evolution of gnammas (weathering pits) in a Holocene deglacial granite landscape, Minnesota (USA)EARTH SURFACE PROCESSES AND LANDFORMS, Issue 2 2008David Domínguez-Villar Abstract The morphometry of 85 gnammas (weathering pits) from Big Stone County in western Minnesota allows the assessment of the relative ages of the gnamma population. The ratio between maximum and minimum depths is independent of the initial size of the cavity and only depends on the weathering evolution. Therefore, the distribution of depth ratios can be used to assess the gnamma population age and the history of weathering. The asymmetrical distribution of depth ratios measured in Big Stone County forms three distinct populations. When these sets are analyzed independently, the correlation (r2) between maximum and minimum depths is greater than 0·95. Each single population has a normal distribution of depth ratios and the average depth ratios (, -value) for each population are ,1 = 1·60 ± 0·05, ,2 = 2·09 ± 0·04 and ,3 = 2·42 ± 0·08. The initiation of gnamma formation followed the exhumation of the granite in the region. This granite was till and saprolite covered upon retreat of the ice from the Last Glacial Maximum. Nearby outcrops are striated, but the study site remained buried until it was exhumed by paleofloods issuing from a proglacial lake. These Holocene-aged gnammas in western Minnesota were compared with gnammas of other ages from around the world. Our new results are in accordance with the hypothesis that , -values represent the evolution of gnammas with time under temperate- to cold-climate dynamics. Phases of the formation of new gnammas may result from changes in weathering processes related to climate changes. Copyright © 2007 John Wiley & Sons, Ltd. [source] Dating young geomorphic surfaces using age of colonizing Douglas fir in southwestern Washington and northwestern Oregon, USA,EARTH SURFACE PROCESSES AND LANDFORMS, Issue 6 2007Thomas C. Pierson Abstract Dating of dynamic, young (<500 years) geomorphic landforms, particularly volcanofluvial features, requires higher precision than is possible with radiocarbon dating. Minimum ages of recently created landforms have long been obtained from tree-ring ages of the oldest trees growing on new surfaces. But to estimate the year of landform creation requires that two time corrections be added to tree ages obtained from increment cores: (1) the time interval between stabilization of the new landform surface and germination of the sampled trees (germination lag time or GLT); and (2) the interval between seedling germination and growth to sampling height, if the trees are not cored at ground level. The sum of these two time intervals is the colonization time gap (CTG). Such time corrections have been needed for more precise dating of terraces and floodplains in lowland river valleys in the Cascade Range, where significant eruption-induced lateral shifting and vertical aggradation of channels can occur over years to decades, and where timing of such geomorphic changes can be critical to emergency planning. Earliest colonizing Douglas fir (Pseudotsuga menziesii) were sampled for tree-ring dating at eight sites on lowland (<750 m a.s.l.), recently formed surfaces of known age near three Cascade volcanoes , Mount Rainier, Mount St. Helens and Mount Hood , in southwestern Washington and northwestern Oregon. Increment cores or stem sections were taken at breast height and, where possible, at ground level from the largest, oldest-looking trees at each study site. At least ten trees were sampled at each site unless the total of early colonizers was less. Results indicate that a correction of four years should be used for GLT and 10 years for CTG if the single largest (and presumed oldest) Douglas fir growing on a surface of unknown age is sampled. This approach would have a potential error of up to 20 years. Error can be reduced by sampling the five largest Douglas fir instead of the single largest. A GLT correction of 5 years should be added to the mean ring-count age of the five largest trees growing on the surface being dated, if the trees are cored at ground level. This correction would have an approximate error of ±5 years. If the trees are cored at about 1·4 m above the ground surface (breast height), a CTG correction of 11 years should be added to the mean age of the five sampled trees (with an error of about ±7 years). Published in 2006 by John Wiley & Sons, Ltd. [source] Testing of the SIBERIA landscape evolution model using the Tin Camp Creek, Northern Territory, Australia, field catchmentEARTH SURFACE PROCESSES AND LANDFORMS, Issue 2 2002G. R. Hancock Abstract The SIBERIA landscape evolution model was used to simulate the geomorphic development of the Tin Camp Creek natural catchment over geological time. Measured hydrology, erosion and geomorphic data were used to calibrate the SIBERIA model, which was then used to make independent predictions of the landform geomorphology of the study site. The catchment, located in the Northern Territory, Australia is relatively untouched by Europeans so the hydrological and erosion processes that shaped the area can be assumed to be the same today as they have been in the past, subject to the caveats regarding long-term climate fluctuation. A qualitative, or visual comparison between the natural and simulated catchments indicates that SIBERIA can match hillslope length and hillslope profile of the natural catchments. A comparison of geomorphic and hydrological statistics such as the hypsometric curve, width function, cumulative area distribution and area,slope relationship indicates that SIBERIA can model the geomorphology of the selected Tin Camp Creek catchments. Copyright 2002 © Environmental Research Institute of the Supervising Scientist, Commonwealth of Australia. [source] The spatial distribution of badgers, setts and latrines: the risk for intra-specific and badger-livestock disease transmissionECOGRAPHY, Issue 4 2008Monika Böhm The spatial distribution of wildlife hosts and the associated environmental distribution of their excretory products are important factors associated with the risk of disease transmission between wildlife and livestock. At a landscape scale, heterogeneous distribution of a wildlife host will create regional hot spots for disease risk, while at the farm level, distributional patterns of wildlife excretory products as well as habitat use are of primary importance to the assessment of disease risk to livestock. In the UK, badgers have been implicated in the transmission of bovine tuberculosis to cattle. In this study, we focus on the spatial and social organization and habitat use of badgers as well as the distributions of their excretions at latrine and sett sites to assess intra- and inter-species (badger,cattle) disease risk. Across the study site, badger latrines and setts were found in prominent clusters, at distances of up to 250 and 200 m respectively. This was partly due to small-scale clustering of latrines around sett sites, so that disease risk may be higher within the vicinity of setts. The clustered distribution suggests that sites of high risk for TB transmission may be localised within farms. Exclusion of cattle from the few sett and latrine sites within their grazing pasture is therefore likely to provide an effective way of reducing the risk of disease transmission. We also found evidence of social sub-division within badger social groups based on differences in the use of main and outlier setts. This may contribute to localised clusters of infection within the badger population, resulting in heterogeneous patterns of environmental disease risk to the wider host community. A greater understanding of variation in host behaviour and its implications for patterns of disease will allow the development of more targeted and effective management strategies for wildlife disease in group-living hosts. [source] Spatial analysis of an invasion front of Acer platanoides: dynamic inferences from static dataECOGRAPHY, Issue 3 2005Wei Fang It is an open question whether the invading tree species Acer platanoides is invading and displacing native trees within pre-existing forest stands, or merely preferentially occupying new stands of secondary forest growth at the edges of existing forests. Several threads of spatial pattern analyses were used to assess the invasibility of A. platanoides, and to link the invasion to the structure of a plant community in the deciduous forest of the northeastern United States. The analyses were based on maps of a contiguous 100×50 m area along an A. platanoides infestation gradient. The distribution of A. platanoides was highly aggregated and the population importance value increased from 28.1 to 38.5% according to mortality estimated from standing dead trees, while the distribution of native tree species was close to random and importance value of Quercus spp. decreased from 33.4 to 26.9% over time. The size distributions of each tree species across distance indicated that A. platanoides was progressively invading the interior of the forest while the native species (including A. rubrum) were not spreading back towards the A. platanoides monospecific patch. The null hypothesis of no invasibility was rejected based on quantile regressions. There were negative correlations between A. platanoides density and the densities of native species in different functional groups, and negative correlation of A. platanoides density and the species diversity in forest understory. The null hypothesis that A. platanoides invasion did not suppress native trees or understory was rejected based on Dutilleul's modified t-test for correlation, consistent with experimental results in the same study site. The combination of multiple spatial analyses of static data can be used to infer historical dynamical processes that shape a plant community structure. The concept of "envelop effects" was discussed and further developed. [source] Wide-area estimates of saltcedar (Tamarix spp.) evapotranspiration on the lower Colorado River measured by heat balance and remote sensing methods,,ECOHYDROLOGY, Issue 1 2009Pamela L. Nagler Abstract In many places along the lower Colorado River, saltcedar (Tamarix spp) has replaced the native shrubs and trees, including arrowweed, mesquite, cottonwood and willows. Some have advocated that by removing saltcedar, we could save water and create environments more favourable to these native species. To test these assumptions we compared sap flux measurements of water used by native species in contrast to saltcedar, and compared soil salinity, ground water depth and soil moisture across a gradient of 200,1500 m from the river's edge on a floodplain terrace at Cibola National Wildlife Refuge (CNWR). We found that the fraction of land covered (fc) with vegetation in 2005,2007 was similar to that occupied by native vegetation in 1938 using satellite-derived estimates and reprocessed aerial photographs scaled to comparable spatial resolutions (3,4 m). We converted fc to estimates of leaf area index (LAI) through point sampling and destructive analyses (r2 = 0·82). Saltcedar LAI averaged 2·54 with an fc of 0·80, and reached a maximum of 3·7 with an fc of 0·95. The ranges in fc and LAI are similar to those reported for native vegetation elsewhere and from the 1938 photographs over the study site. On-site measurements of water use and soil and aquifer properties confirmed that although saltcedar grows in areas where salinity has increased much better than native shrubs and trees, rates of transpiration are similar. Annual water use over CNWR was about 1·15 m year,1. Copyright © 2008 John Wiley & Sons, Ltd. [source] The cost-effectiveness of consistent and early intervention of harm reduction for injecting drug users in BangladeshADDICTION, Issue 2 2010Lorna Guinness ABSTRACT Aims To assess the cost-effectiveness of the CARE-SHAKTI harm reduction intervention for injecting drug users (IDUs) over a 3-year period, the impact on the cost-effectiveness of stopping after 3 years and how the cost-effectiveness might vary with baseline human immunodeficiency virus (HIV) prevalence. Design Economic cost data were collected from the study site and combined with impact estimates derived from a dynamic mathematical model. Setting Dhaka, Bangladesh, where the HIV prevalence has remained low despite high-risk sexual and injecting behaviours, and growing HIV epidemics in neighbouring countries. Findings The cost per HIV infection prevented over the first 3 years was US$110.4 (33.1,182.3). The incremental cost-effectiveness of continuing the intervention for a further year, relative to stopping at the end of year 3, is US$97 if behaviour returns to pre-intervention patterns. When baseline IDU HIV prevalence is increased to 40%, the number of HIV infections averted is halved for the 3-year period and the cost per HIV infection prevented doubles to US$228. Conclusions The analysis confirms that harm reduction activities are cost-effective. Early intervention is more cost-effective than delaying activities, although this should not preclude later intervention. Starting harm reduction activities when IDU HIV prevalence reaches as high as 40% is still cost-effective. Continuing harm reduction activities once a project has matured is vital to sustaining its impact and cost-effectiveness. [source] Behaviour of male pine sawflies, Neodiprion sertifer, released downwind from pheromone sourcesENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2000Fredrik Östrand Abstract This study investigated the behaviour of male European pine sawflies, Neodiprion sertifer Geoffroy (Hym., Diprionidae), that were released and observed downwind from pheromone traps baited with 100 ,g of the sex pheromone, (2S,3S,7S)-3,7-dimethyl-2-pentadecyl acetate. Releases were done at three distances; either at 5 m from one trap, or at 50 or 200 m from five traps, placed in a line perpendicular to the current wind direction. As control, males were released identically but without any pheromone source present. The behaviour of the males prior to take-off was studied. A total of 1729 males were released, and 80% of them took flight. Males took off significantly faster in the presence of pheromone. Grooming was significantly more frequent in presence of pheromone compared with control. In all pheromone experiments significantly more males displayed grooming, wing fanning and take-off towards the wind compared with the control. Weather data was simultaneously collected at the study site. Wing fanning was negatively correlated with wind speed. Grooming was not influenced by wind speed. Reduced levels of incoming short-wave radiation lowered the take-off frequency significantly. Pheromone-induced behaviour in diprionids seems to be less distinct than in other insects, e.g., Lepidoptera. [source] Accumulation of DDT and mercury in prothonotary warblers (Protonotaria citrea) foraging in a heterogeneously contaminated environmentENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2001Kevin D. Reynolds Abstract Foraging areas of adult prothonotary warblers (Protonotaria citrea) were determined using standard radiotelemetry techniques to determine if soil concentrations of p,p,dichlorodiphenyltrichloroethane (p,p,DDT) and mercury in foraging areas could be used to predict contaminant levels in diets and tissues of nestling warblers. Adult warblers were fitted with transmitters and monitored for approximately 2 d while foraging and feeding 6- to 8-d-old nestlings. Foraging ecology data were integrated with contaminant levels of soil, diets, and tissues into a comprehensive analysis of geographic variation in contaminant exposure and uptake using linear regression. Concentrations of 1,1-dichloro-2,2-bis(p -chlorophenyl)ethylene (DDE) and mercury in nestling tissues varied considerably across the study site. Mean concentration of DDE was greater in eggs than all other tissues, with individual samples ranging from 0.24 to 8.12 ,g/kg. In general, concentrations of DDT in soil were effective in describing the variation of contaminants in adipose samples. Concentrations of mercury in soils accounted for 78% of the variation in kidney samples. This was the best relationship of any of the paired variables. All other relationships showed relatively poor predictive ability. [source] Nest, but Not Egg, Fidelity in a Territorial SalamanderETHOLOGY, Issue 9 2000Megan G. Peterson Egg recognition and subsequent egg brooding are costly forms of parental investment in many species of vertebrates. Life history factors, such as coloniality or risk of brood parasitism, may constrain egg recognition in vertebrates. Female red-backed salamanders (Plethodon cinereus) from my study site are territorial and do not share nest sites with other females. They are terrestrial and neither they nor their eggs are likely to be displaced by environmental factors such as flooding. I experimentally tested, in the laboratory, the hypothesis that female red-backed salamanders can discriminate between their own eggs and the eggs of unfamiliar females. Each female was allowed to move about a test chamber containing two clutches of eggs, one clutch with which it was found in the forest and one that had been found with a distant female. Most females remained with one clutch of eggs, which they brooded during the entire observation period. However, they did not significantly prefer to brood their own eggs over the eggs of another female. In a corollary field experiment, I tested whether brooding females that were displaced 1 m from their nest sites would return to their territories and commence brooding behaviour within 3 d. All 10 displaced females returned to their own nest within this time period and were found brooding their eggs. Because female red-backed salamanders at my study site do not tend to share nest sites with other females and because their eggs remain in stationary nests, selection may not have favoured egg recognition. However, the results suggest that female salamanders indirectly recognize their own eggs by actively recognizing their territorial nest sites. [source] Effects of mute swan grazing on a keystone macrophyteFRESHWATER BIOLOGY, Issue 12 2007MATTHEW T. O'HARE Summary 1. This study describes the early summer foraging behaviour of mute swans (Cygnus olor) on the River Frome, a highly productive chalk stream in southern England in which Ranunculus penicillatus pseudofluitans is the dominant macrophyte. 2. A daily maximum of 41 ± 2.5 swans were present along the 1.1 km study reach during the study period (late May to the end of June). The river was the primary feeding habitat. Feeding activity on the river at dawn and dusk was much lower than during daylight, but we cannot rule out the possibility that swans fed during the hours of darkness. 3. The effects of herbivory on R. pseudofluitans biomass and morphology were quantified. Biomass was lower in grazed areas and swans grazed selectively on leaves in preference to stems. A lower proportion of stems from grazed areas possessed intact stem apices and flowering of the plant was reduced in grazed areas. 4. A model, based on the swans' daily consumption, was used to predict the grazing pressure of swans on R. pseudofluitans. The model accurately predicted the number of bird days supported by the study site, only if grazing was assumed to severely reduce R. pseudofluitans growth. The proportion of the initial R. pseudofluitans biomass consumed by a fixed number of swans was predicted to be greater when the habitat area was smaller, initial R. pseudofluitans biomass was lower and R. pseudofluitans was of lower food value. 5. We concluded that the flux of N and P through the study reach was largely unaffected by swan activity. The quality of R. pseudofluitans mesohabitat (the plant as habitat for invertebrates and fish) was significantly reduced by grazing which also indirectly contributed to reduced roughness (Manning's n) and by inference water depth. Wetted habitat area for fish and invertebrates would also be lowered over the summer period as a consequence of the reduction in water depth. It was estimated that, while grazing, an individual swan may eat the same mass of invertebrates per day as a 300-g trout. 6. There is a need to manage the conflict between mute swans and the keystone macrophyte, R. pseudofluitans, in chalk streams, and the modelling approach used here offers a potentially useful tool for this purpose. [source] Seasonal field metabolic rate and dietary intake in Arabian Babblers (Turdoides squamiceps) inhabiting extreme desertsFUNCTIONAL ECOLOGY, Issue 5 2000A. Anava Abstract 1.,Arabian Babblers (Turdoides squamiceps Cretzsch.; mean adult body mass = 72·5 g) inhabit extreme deserts of Israel. They consume invertebrates and fruits and, at least at our study site, do not drink. It was hypothesized that babblers (1) in general, use relatively less energy and water than other birds of its body mass; and (2) consume a more water-rich diet (mainly fruits) in summer and more energy-rich diet (mainly invertebrates) in winter. Doubly labelled water was used to determine seasonal field metabolic rate (FMR) and water influx rate (WIR) and to estimate dietary selection in free-living Arabian Babblers. 2.,Babblers in winter weighed significantly more than in summer, and males weighed more than females in both seasons. Tritiated water (TOH) space, as a proportion of body mass, was higher in males than in females in summer but no difference between sexes was found in winter. Males in summer had a higher TOH space, proportionally, than males in winter but there was no difference between seasons in females. Mass-specific WIR did not differ between sexes in any season and averaged 0·475 ml g,1 d,1 in winter which was significantly higher than the 0·283 ml g,1 d,1 in summer. 3.,The mean daily energy expenditure of the babblers did not differ either between seasons or between sexes within seasons and averaged 1·61 kJ g,1 d,1 in winter and 1·68 kJ g,1 d,1 in summer. It was calculated that each babbler consumed an average of 5·09 g dry matter invertebrates and 1·83 g dry matter fruits in summer (for a 68·2-g bird; mean adult body mass in summer) and 3·49 g dry matter invertebrates and 6·61 g dry matter fruits in winter (for a 76·9-g bird; mean adult body mass in winter). 4.,When compared with other avian species, FMR and WIR of babblers were lower than bird species in general, but were similar to those of other desert birds. It was calculated that proportional dietary intake, on a dry matter basis, included 0·79 insects and 0·21 fruits in summer and 0·35 insects and 0·65 fruits in winter. Therefore, the babblers consumed a relatively energy-rich diet in summer and water-rich diet in winter which refuted our hypothesis. Most of the metabolizable energy was provided by invertebrates in both seasons; invertebrates provided more water in summer but fruits provided more in winter. [source] RUNOFF PRODUCTION AND EROSION PROCESSES ON A DEHESA IN WESTERN SPAIN,GEOGRAPHICAL REVIEW, Issue 3 2002ANTONIO CEBALLOS ABSTRACT. Runoff generation and soil erosion were investigated at the Guadalperalón experimental watershed (western Spain), within the land-use system known as dehesa, or open, managed evergreen forests. Season and type of surface were found to control runoff and soil-loss rates. Five soil units were selected as representative of surface types found in the study area: hillslope grass, bottom grass, tree cover, sheep trails, and shrub cover. Measurements were made in various conditions with simulated rainfall to gain an idea of the annual variation in runoff and soil loss. Important seasonal differences were noted due to surface cover and moisture content of soil, but erosion rates were determined primarily by runoff. Surfaces covered with grass and shrubs always showed less erosion; surfaces covered with holm oaks showed higher runoff rates, due to the hydrophobic character of the soils. Concentrations of runoff sediment during the simulations confirmed that erosion rates at the study site depended directly on the sediment available on the soil surface. [source] Annual Q10 of soil respiration reflects plant phenological patterns as well as temperature sensitivityGLOBAL CHANGE BIOLOGY, Issue 2 2004J. Curiel yuste Abstract The temperature sensitivity of soil respiration (SR) is often estimated from the seasonal changes in the flux relative to those in soil temperature, and subsequently used in models to interpolate or predict soil fluxes. However, temperature sensitivities derived from seasonal changes in SR (from here on denoted seasonal Q10) may not solely reflect the temperature sensitivity of SR, because seasonal changes in SR can also be affected by other seasonally fluctuating conditions and processes. In this manuscript, we present a case study of how the seasonal Q10 of SR can be decoupled from the temperature sensitivity of SR. In a mixed temperate forest, we measured SR under vegetations with different leaf strategies: pure evergreen, pure deciduous, and mixed. Seasonal Q10 was much higher under deciduous than under evergreen canopies. However, at a shorter time scale, both vegetation types exhibited very similar Q10 values, indicating that the large differences in seasonal Q10 do not represent differences in the temperature sensitivity of the soil metabolism. The seasonal Q10 depends strongly on the amplitude of the seasonal changes in SR (SRs), which, under the particular climatic and edaphic conditions of our forest study site, were significantly larger in deciduous forest. In turn, SRs was positively correlated with the seasonal changes in leaf area index (LAIs), a measure of the deciduousness of the vegetation. Thus, in this temperate maritime forest, seasonal Q10 of SR was strongly influenced by the deciduousness of the vegetation. We conclude that the large differences in seasonal Q10 were not entirely due to different temperature sensitivities, but also to different seasonal patterns of plant activity in the evergreen and deciduous plants of this site. Some coniferous forests may be more seasonal than the one we studied, and the deciduous,evergreen differences observed here may not be broadly applicable, but this case study demonstrates that variation of plant phenological process can significantly contribute to the seasonality of SR, and, hence, calculated Q10 values. Where this occurs, the seasonal Q10 value for SR does not accurately represent temperature sensitivity. Because the strong seasonal correlation between SR and temperature does not necessarily imply a causal relationship, Q10 values derived form annual patterns of SR should be used with caution when predicting future responses of SR to climatic change. [source] A global study of relationships between leaf traits, climate and soil measures of nutrient fertilityGLOBAL ECOLOGY, Issue 2 2009Jenny C. Ordoñez ABSTRACT Aim This first global quantification of the relationship between leaf traits and soil nutrient fertility reflects the trade-off between growth and nutrient conservation. The power of soils versus climate in predicting leaf trait values is assessed in bivariate and multivariate analyses and is compared with the distribution of growth forms (as a discrete classification of vegetation) across gradients of soil fertility and climate. Location All continents except for Antarctica. Methods Data on specific leaf area (SLA), leaf N concentration (LNC), leaf P concentration (LPC) and leaf N:P were collected for 474 species distributed across 99 sites (809 records), together with abiotic information from each study site. Individual and combined effects of soils and climate on leaf traits were quantified using maximum likelihood methods. Differences in occurrence of growth form across soil fertility and climate were determined by one-way ANOVA. Results There was a consistent increase in SLA, LNC and LPC with increasing soil fertility. SLA was related to proxies of N supply, LNC to both soil total N and P and LPC was only related to proxies of P supply. Soil nutrient measures explained more variance in leaf traits among sites than climate in bivariate analysis. Multivariate analysis showed that climate interacted with soil nutrients for SLA and area-based LNC. Mass-based LNC and LPC were determined mostly by soil fertility, but soil P was highly correlated to precipitation. Relationships of leaf traits to soil nutrients were stronger than those of growth form versus soil nutrients. In contrast, climate determined distribution of growth form more strongly than it did leaf traits. Main conclusions We provide the first global quantification of the trade-off between traits associated with growth and resource conservation ,strategies' in relation to soil fertility. Precipitation but not temperature affected this trade-off. Continuous leaf traits might be better predictors of plant responses to nutrient supply than growth form, but growth forms reflect important aspects of plant species distribution with climate. [source] Estimating the spatial distribution of available biomass in grazing forests with a satellite image: A preliminary studyGRASSLAND SCIENCE, Issue 2 2005Michio Tsutsumi Abstract We tested whether available biomass in grazing forests could be estimated by analyzing a satellite image with field data. Our study site was situated in north-eastern Japan and was composed of coniferous forest differing in afforested years, multilayered coniferous forest and deciduous broadleaf forest. The data of available biomass collected in previous studies was used to analyze a Landsat Thematic Mapper (TM) image acquired in summer and we tried to depict a map of the spatial distribution of available biomass in the forest. It was suggested that an analysis should be conducted separately in each of the multilayered coniferous, the other coniferous and broadleaf forests. As a result of regression analysis on the relationship between available biomass and each of several parameters, the first principal component computed with reflectance of the six bands of the Landsat TM was the most appropriate parameter to estimate available biomass. The answer to the question ,Can the spatial distribution of available biomass in a forest be estimated with a satellite image?' is ,Yes, in coniferous forests'. We propose a procedure for depicting a precise map of the distribution of available biomass in a forest with analysis of a satellite image. [source] Gravel-Corrected Kd ValuesGROUND WATER, Issue 6 2000Daniel I. Kaplan Standard measurements of solute sorption to sediments are typically made on the <2 mm sediment fraction. This fraction is used by researchers to standardize the method and to ease experimental protocol so that large labware is not required to accommodate the gravel fraction (>2 mm particles). Since sorption is a phenomenon directly related to surface area, sorption measurements based on the <2 mm fraction would be expected to overestimate actual whole-sediment values for sediments containing gravel. This inaccuracy is a problem for ground water contaminant transport modelers who use laboratory-derived sorption values, typically expressed as a distribution coefficients (Kd), to calculate the retardation factor (Rf), a parameter that accounts for solute-sediment chemical interactions. The objectives of this laboratory study were to quantify the effect of gravel on strontium Kd and Rf values and to develop an empirical method to calculate gravel-corrected Kdgc values for the study site (Hanford Site in Richland, Washington). Three gravel corrections, Kd values, were evaluated: a correction based on the assumption that the gravel simply diluted the Kd<2mm and had no sorption capacity (Kdgc,g=0), a correction based on the assumption that the Kd of the intact sediment (Kdtot was a composite of the Kd<2mm and the Kd>2mm (Kdgc,g = x), and a correction based on surface area (Kdgc,surf). On average, Kd<2mm tended to overestimate Kdtot by 28% to 47%; Kdgc,g = x overestimated Kdtot by only 3% to 5%; and Kdgc,g = 0 and Kdgc,surf underestimated Kdtot by 10% to 39%. Kdgc,g = x provided the best estimate of actual values (Kdtot); however, Kdgc,g = 0 was appreciably easier to acquire. Although other contaminants will likely have different gravel-correction values, these results have important implications regarding the traditional approach to modeling contaminant transport which uses Kd<2mm values. Such calculations may overestimate the tendency of gravel-containing sediments to retard contaminant migration. 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