Site-specific Component Research Articles

Holocene vegetation reconstruction in the forest–steppe of Mongolia based on leaf waxes and macro-charcoals in soils

Abstract. Vegetation and climate reconstruction in the forest–steppe of Mongolia is still challenging regarding the pattern of forest and grassland distribution during the Holocene. Different sediments containing paleosols and humic layers provide geomorphological archives for landscape development in Mongolia. n-Alkane and macro-charcoal ratios represent specific indicators to distinguish the share between grasses and trees. In a preliminary study, we investigated the applicability of these two paleo-proxies from soils for vegetation reconstruction comparing different relief positions and site conditions in the northern Khangai Mountains of Mongolia. n-Alkanes that are deposited from leaf waxes in the soil have the potential to indicate vegetation composition on a local scale. Depending on site-specific environmental conditions, n-alkanes are subjected to different degrees of microbiological decomposition, which is more intensive in soils of dry steppe than of forests. Mongolian forests are often underlain by permafrost that may reduce microbiological activity. In steppe soils, the decomposition of n-alkanes increases the quantity of mid-chain n-alkanes that adulterate the biomarker proxy signal to indicate more forest share. Macro-charcoals in soils have a site-specific component, but additional eolian input of macro-charcoals from long-distance transport can provide a distinct proportion in sediments. Thus, eolian influx of wood-derived macro-charcoal can dominate the proxy signal at sites where trees were few or had never existed. Radiometric dating of several paleosols and humic layers has shown that both proxies coincide as evidence for high grassland-to-forest ratios during the Early Holocene. By contrast, the proxy signals diverge for the Late Holocene. For this period, n-alkanes generally indicate more grassland, whereas macro-charcoals show increased wood-derived proportions. We imply that this difference is caused by increased forest fires and simultaneously spreading steppe area. A main portion of leaf waxes and charcoal particles in soils directly derive from the covering and nearby vegetation, whereas large lakes and glacier may receive these biomarkers from a larger catchment area. Thus, we conclude that soil archives provide proxies on a more local and site-specific scale than other archives do. Although the temporal resolution of soil archives is lower than for the other ones, biomarker proxies for paleosols and humic layer can be related to periods of distinct geomorphological processes. Further investigations comparing the multi-proxy data of different geomorphological archives are necessary to improve the paleo-ecological reconstruction for landscape development in Mongolia.

The search for hard-rock kappa (κ) in NGA-East: A semi-automated method for large, challenging datasets in stable continental regions

This article describes the work undertaken within the Next Generation Attenuation (NGA)-East project with the aim of estimating κ0 (the site-specific component of the high-frequency decay parameter, κ) for rock sites in Central and Eastern North America (CENA), using the project’s shallow crustal dataset. We introduce a methodology to address the numerous challenges in CENA: a large dataset in a low-seismicity stable continental region, with poor magnitude and distance coverage, undesirable recording sensor characteristics (low sampling rates leading to poor high-frequency resolution), high uncertainty in the regional stress drop, and lack of site-specific velocity characterization. We use two band-limited κ estimation approaches, the acceleration and displacement spectrum (AS and DS), applied above and below the source corner frequency ( fc), respectively. For band-limited approaches, the key requirement is an estimate of fc, which—apart from the event magnitude readily available in the flatfile—also heavily depends on the highly uncertain stress drop. By considering lower and upper bounds on regional stress drop, we propose a new method to quickly and automatically screen such very large datasets to identify all possible recordings for which band-limited κ approaches can be used. Combining them produces better-quantify estimates of κ and its epistemic uncertainties for this challenging dataset. The mean κ0 values combining the two methods are 13 ± 23 ms for horizontal ground motion.

Estimation of the High-Frequency Attenuation Parameter Kappa for the Zagreb (Croatia) Seismic Stations

The city of Zagreb (Croatian capital) is situated in the contact area of three major regional tectonic units: the SE Alps, NW Dinarides, and Tisza Unit in the southwestern margin of the Pannonian Basin. The Zagreb seismic zone encompasses the Medvednica Mountains and the city of Zagreb with its surrounding areas, which was struck by the strongest instrumentally recorded earthquake (M5.5) on 22 March 2020. The objective of this contribution is the estimation of the high-frequency attenuation spectral parameter kappa (κ) and its local site-specific component for the Zagreb (Croatia) seismic stations to which we were particularly encouraged after the scale of the damage after the Zagreb 2020 earthquake. We tested linear dependence of κ with epicentral distance using traditional linear least square regression, linear regression for data with errors, and constrained model at close distances to estimate near-site attenuation (κ0). Regression-estimated site kappa values at zero-distance are within the range of the uncertainty (±1 standard deviation) with constrained κ0 value as well within the range of existing global κ0 and VS30 (shear wave velocity in the top 30 m) values. Spatial distribution of κ within the Zagreb seismic zone shows that κ is not isotropic and high-frequency attenuation anisotropy is probably affected by local and regional geological variability, regional active faults and a complex tectonic structure in each direction.

Influence of the Site-Specific Component of Kappa on the Magnitude-Dependency of Within-Event Aleatory Variabilities in Ground-Motion Models

AbstractThe aleatory-variability component (standard deviation) of a ground motion has a large influence on results of a probabilistic seismic hazard assessment. kappa, a measure of high-frequency attenuation, has site- and record-specific effects that have been suggested as reasons for observing heteroscedastic aleatory variability within earthquake ground motions. Specifically, kappa has been proposed as a reason why ground motions from small earthquakes are more variable than those from large earthquakes, which is modeled by magnitude-dependent within-event standard deviations in ground-motion prediction equations (GMPEs). In this study, we use ground motions simulated using the stochastic method to examine the influence of the site-specific component of kappa on aleatory variability of earthquake ground motions and examine the hypothesis that this could be a cause of the observed heteroscedasticity in this variability. We consider simulations with both fixed and continuous stress drop distributions and the site-specific component of kappa to demonstrate that variation in the stress drop parameter contributes minimally to magnitude-dependency, unlike the site-specific component of kappa, which causes significant magnitude-dependency. Variation in the site-specific component of kappa is, therefore, proposed to be at least partially responsible for the magnitude-dependency captured in the aleatory-variability components of some recent GMPEs. It is found, however, that the expected impact of the site-specific component of kappa on aleatory variability is much greater than modeled in these GMPEs, which suggests that there could be a mitigating effect that is not captured within the simulations (e.g., correlated inputs to the simulations).

Within-Station Variability in Kappa: Evidence of Directionality Effects

ABSTRACT One of the most commonly used parameters to describe seismic attenuation is the high-frequency spectral decay parameter Kappa (κr), yet the physics behind it remain little understood. A better understanding of potential factors that lead to large scatter in estimated values of κr constitutes a critical need for ground-motion modeling and seismic hazard assessment at large. Most research efforts to date have focused on studying the site-to-site and model-to-model variability of κ, but the uncertainties in individual κr estimations associated with different events at a selected site (which we refer to as the within-station variability of κr) remain uncharacterized. As a direct corollary, obtaining robust estimates of the site-specific component κ0, and their corresponding interpretation become a challenge. To understand the sources of the variability observed in κr (and κ0) at a single site, we select 10 Japanese Kiban–Kyoshin network (KiK-net) downhole arrays and investigate the systematic contributions from ground-motion directionality. We observe that κr estimated from a single horizontal component is orientation dependent. In addition, the influence of ground-motion directionality is a function of local site conditions. We propose an orientation-independent κr-value, which is not affected either by ground-motion directionality or by the events’ azimuths. In addition, we find that focal depth of events used in κr calculations affects the estimation of the regional attenuation component κR, which, in turn, influences the within-station variability in the κ0 model.

Long-term microphytoplankton variability patterns using multivariate analyses: ecological and management implications.

Microphytoplankton data along the southern Tunisian coasts have been monitored weekly since 1995. This study used the data collected during the period 2000-2007 to determine the temporal variability patterns and to characterize the geographical structures of microphytoplankton populations. The methodological approach consisted in isolating the temporal variability common to all sampled sites and in analyzing the "residual" site-specific component. Multivariate ordination methods were used to determine the seasonal and interannual variability. The temporal pattern shared by all sites was highlighted and the seasonal cycle of the most frequent phytoplankton communities contrasted the diatoms winter-spring species to the dinoflagellates summer-fall species. Multitable comparison allowed the identification of three areas exhibiting similar phytoplankton population variability. The results, despite the coastal location of sampling sites, indicated that hydrodynamic and geomorphologic properties of the different areas as well as anthropogenic activities play a key role in the structure of the phytoplankton communities.

Microscopic Aquatic Predators Strongly Affect Infection Dynamics of a Globally Emerged Pathogen

Research on emerging infectious wildlife diseases has placed particular emphasis on host-derived barriers to infection and disease. This focus neglects important extrinsic determinants of the host/pathogen dynamic, where all barriers to infection should be considered when ascertaining the determinants of infectivity and pathogenicity of wildlife pathogens. Those pathogens with free-living stages, such as fungi causing catastrophic wildlife declines on a global scale, must confront lengthy exposure to environmental barriers before contact with an uninfected host. Hostile environmental conditions therefore have the ability to decrease the density of infectious particles, reducing the force of infection and ameliorating the impact as well as the probability of establishing an infection. Here we show that, in nature, the risk of infection and infectious burden of amphibians infected by the chytrid fungus Batrachochytrium dendrobatidis (Bd) have a significant, site-specific component, and that these correlate with the microfauna present at a site. Experimental infections show that aquatic microfauna can rapidly lower the abundance and density of infectious stages by consuming Bd zoospores, resulting in a significantly reduced probability of infection in anuran tadpoles. Our findings offer new perspectives for explaining the divergent impacts of Bd infection in amphibian assemblages and contribute to our understanding of ecosystem resilience to colonization by novel pathogens.

PS2-42: Developing High-Quality Laboratory Results for the Virtual Data Warehouse: The Importance of Single-site Quality Assessment

2 Kaiser Permanente Northwest Background/Aims: Assessment of data incorporated into the Virtual Data Warehouse (VDW) is crucially important when building a new content area such as laboratory results. At KPCO, we identified two main challenges while constructing tables of laboratory results for the VDW. The first was ensuring that we constructed clinically meaningful laboratory test types. The second was confirming that we identified and classified the correct set of records from source data repositories. The aim of our work was therefore to ensure that these two challenges were successfully met Methods: Initial priority tests were broadly categorized as chemistry, hematology, microbiology, or challenge tests. Many laboratory results could be characterized into a single test type. Other laboratory results required one or more of the following characteristics to differentiate subtypes: assay method; test subtypes such as isoenzymes; result type; fasting status; specimen site; and challenge dose and time since dose. Laboratory results were extracted from two data repositories. The first database includes records from 1999-2004. The second database stores records since 2005 with partial backfill of records from 2004 and earlier. Variable names and values did not follow a common naming convention between the two data sources. Extraction and classification rules were based on Logical Observation Identifiers Names and Codes (LOINCs), test names, result units, and Current Procedural Terminology (CPT) codes. Results: We identified numerous issues while developing the VDW laboratory content area: incomplete clinical information; distinct laboratory types with similar names; missing, incorrect, obsolete, or site-specific component codes; incorrect sample collection times; changes in source data streams; clinical practices that differ from guidelines; and little background knowledge of laboratory tests among those processing the data. Each challenge and the approach to addressing each issue will be illustrated with an example. Conclusions: A systematic approach to collection and processing of laboratory results can yield high-quality, clinically useful data. Key elements of this systematic approach include a logical and flexible taxonomy of laboratory types and careful consideration of identifier codes and supplemental information to categorize laboratory results. Developers

Do biological expansion factors adequately estimate stand-scale aboveground component biomass for Norway spruce?

We developed site specific component (stem, branch, and foliage) biomass functions for two sites in Sweden (64° and 57° North latitude) where four treatments (control, irrigated, fertilized, irrigated plus fertilized) were applied in the existing Norway spruce stands ( Picea abies L. Karst.) for 17 years. We tested for site effects in the component biomass equations and compared site specific biomass estimates to those generated using published functions ( Lehtonen et al., 2004; Wirth et al., 2004). Site effects were significant for all components and indicated it would be unlikely to generate equations that well estimate biomass across the Norway spruce range as implicitly indicated in our efforts to generate species biomass expansion factors. We rejected our hypothesis that the published functions would well estimate component biomass for control plots. The published functions did not compare well with site specific component biomass estimates for the other treatments; both published functions well estimated stem mass up to stem mass of 25 Mg ha −1, beyond which stem mass was overestimated, and both functions over and under estimated foliage and branch mass. Nor did the published functions compare well with each other, with stem, foliage and branch mass estimate differences of 12, 55, −8% and 11, 77, and 59% for the southern and northern sites, respectively, when averaged over all treatments and years. Adding limiting resources through fertilization increased stem, foliage and branch mass 57, 11, 18% and 120, 37, and 69% at the southern and northern sites, respectively, which would increase carbon sequestration and available stemwood and bioenergy materials. We recommend that more effort is spent in process-based modeling to better predict mass at a given site and ultimately provide better estimates of carbon sequestration and bioenergy material production changes.

Statistical Analysis of Reference Evapotranspiration on the Tibetan Plateau

Net radiation is an important and site-specific component to determine reference evapotranspiration ( ET0 ) . The empirical Angstrom coefficients for radiation estimation in the FAO56 Penman–Monteith (PM) equation were calibrated using observed daily solar radiation and actual sunshine duration on the Tibetan Plateau. The calibrated Angstom coefficients included annual coefficients for nine meteorological stations separately and aggregation of nine stations. The calibrated annual coefficients for each station separately were applied to estimate net radiation and further employed to estimate ET0 using the PM and the Priestley–Taylor (PT) equations on the Tibetan Plateau. Moreover, the Hargreaves (Harg) equation that requires only air temperature was also applied to estimate ET0 . Comparisons of three methods were conducted and the results showed that the PT method overestimated daily ET0 with respect to PM– ET0 and the Harg method underestimated it at all meteorological stations. The PT method was more sui...

Determination of seismic failure frequencies for storage tanks in Hungary

A newly developed technique is presented to estimate site specific seismic failure frequencies of several types of storage tanks. Seismic failure is a failure event triggered by an earthquake leading to material release and serious damages. The present method is based on the convolution of site specific seismic hazard curves and component dependent fragility curves. Fragility curves are calculated with the help of probit coefficients originated from the analysis of historical data of earthquake damage. The calculation considers only the filling level, pressure and the damage state of storage tanks, and neglects the shape, volume, material and other parameters. Determination of seismic failure frequencies for storage tanks is done for three different Hungarian plant sites (Paks, Püspökszilágy, Csömör) using seismic hazard curves. In contrast of the simplifications the obtained frequency values represent a conservative estimation of failure frequencies triggered by earthquakes, and in comparison to international failure data the calculated values indicate significant frequencies. Therefore, the results imply that despite of the moderate seismic activity in Hungary, the effects of earthquakes on major-accident hazards should be considered in quantitative risk assessment.

Radiation calibration of FAO56 Penman–Monteith model to estimate reference crop evapotranspiration in China

The standardized FAO56 Penman–Monteith model, which has been the most reasonable method in both humid and arid climatic conditions, provides reference crop evapotranspiration (ET o) estimates for planning and efficient use of agricultural water resources. Net radiation is an important and site-specific component to determine ET o. The empirical radiation estimation in FAO56 Penman–Monteith model was calibrated by observed solar radiation of 81 meteorological stations over China during 1971–2000, and measurements of net longwave radiation in the Tibetan Plateau. Results showed that Ångström formula based on simple annual linear regression coefficients of 0.20 and 0.79 yielded the least error for the preserved 30 validation stations, and are thus recommended for estimating solar radiation in China. The optimal calibration of net longwave radiation was based on Penman estimation combined with the minimum and maximum temperatures. The calibrated net radiation served as the basis to estimate ET o accurately, which would be overestimated by about 27% if no local calibration is performed on the FAO56 Penman–Monteith model in China. The average ET o was 769 mm yr −1 based on calibrated radiation model in China during 1971–2000.

Component carbon fluxes and their contribution to ecosystem carbon exchange in a pine forest: an assessment based on eddy covariance measurements and an integrated model.

We used a combination of eddy flux, canopy, soil and environmental measurements with an integrated biophysical model to analyze the seasonality of component carbon (C) fluxes and their contribution to ecosystem C exchange in a 50-year-old Scots pine forest (Pinus sylvestris L.) in eastern Finland (62 degrees 47' N, 30 degrees 58' E) over three climatically contrasting years (2000-2002). Eddy flux measurements showed that the growing Scots pine forest was a sink for CO2, with annual net C uptakes of 131, 210 and 258 g C m-2> year-1 in 2000, 2001 and 2002, respectively. The integrated process model reproduced the annual course of daily C flux above the forest canopy as measured by the eddy covariance method once the site-specific component parameters were estimated. The model explained 72, 66 and 68% of the variation in daily net C flux in 2000, 2001 and 2002, respectively. Modeled annual C loss by respiration was 565, 629 and 640 g C m-2 year-1, accounting for 77, 77 and 65% of annual gross C uptake, respectively. Carbon fluxes from the forest floor were the dominant contributors to forest ecosystem respiration, with the fractions of annual respiration from the forest floor, foliage and wood being 46-62, 27-44 and 9-10%, respectively. The wide range in daily net C uptake during the growing season was largely attributable to day-to-day fluctuations in incident quantum irradiance. During just a few days in early spring and late autumn, ecosystem net C exchange varied between source and sink as a result of large daily changes in temperature. The forest showed a greater reduction in gross C uptake by photosynthesis than in C loss by respiration during the dry summer of 2000, indicating that interannual variability in ecosystem net C uptake at this site was modified mostly by summer rainfall and vapor pressure deficit.

Variability patterns of microphytoplankton communities along the French coasts

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 242:39-50 (2002) - doi:10.3354/meps242039 Variability patterns of microphytoplankton communities along the French coasts I. Gailhard1,*, Ph. Gros1, J. P. Durbec2, B. Beliaeff3, C. Belin3, E. Nézan4, P. Lassus3 1IFREMER, BP 70, 29280 Plouzané, France 2COM, Faculté des Sciences de Luminy, Case 901, 13288 Marseille Cedex 09, France 3IFREMER, BP 21105, 44311 Nantes Cedex 3, France 4IFREMER, 29187 Concarneau Cedex, France *E-mail: igailhar@ifremer.fr ABSTRACT: Microalgal populations along French coasts (English Channel, Bay of Biscay and Mediterranean Sea) have been sampled twice a month since 1987 within the context of the French Phytoplankton and Phycotoxin Monitoring Network (REPHY). This study used these data to characterize the large-scale geographical structures of microphytoplankton communities and to determine whether ŒhomogeneousŒ geographical areas exist in which microalgal populations display similar temporal variability schemes. Once the temporal variability component shared by all sampled coastal sites was identified, the ŒresidualŒ site-specific component was analyzed. Multivariate ordination methods were used to determine seasonal and inter-annual variability. The expected temporal pattern common to all sites was identified and the seasonal cycle of the most frequently observed phytoplankton communities along French coasts was described. The between-site analysis, using multitable comparison methods (RV-coefficient and multidimensional scaling), allowed the identification of 3 large areas (western English Channel, Bay of Biscay and Mediterranean Sea) according to the temporal variability patterns of microphytoplankton populations. The results, despite the coastal locations of REPHY sampling sites, indicate that the hydrodynamic characteristics of the different areas play a major role in the geographical structure of microalgal populations in French coastal waters. KEY WORDS: Microphytoplankton · French coast · Geographical structure · Temporal variability · RV coefficient · Multidimensional scaling Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 242. Online publication date: October 25, 2002 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2002 Inter-Research.

Estimating the long-term trend in the extreme values of tropospheric ozone using a multivariate approach.

This paper deals with the identification and estimation of the long-term trend in the extreme values of tropospheric ozone after allowing for the confounding effects of meteorological conditions. The U. S. Environmental Protection Agency's (EPA's) National Ambient Air Quality Standard for ozone is stated in terms of exceedances of a specified threshold level. Therefore, the EPA is concerned with the long-term trend in the probability of an exceedance. A multivariate nonparametric probit regression model estimated within the framework of a hierarchical Bayes model is used to model the probability of an exceedance after allowing for the effects of changing meteorological conditions. There are three advantages to using this model. First, the trends estimated at each site in a region can be separated into a city-wide component that is common to all sites and a site-specific component that is unique to the individual site. Second, the hierarchical Bayes framework allows for combining information across monitoring sites to increase the information available regarding the trend at each individual site. Third, the nonparametric model does not require the a priori specification of the functional forms relating the probability of an exceedance to the meteorological variables. Ozone data from four Houston, Texas monitoring sites for the period 1981-1997 are analyzed. We find that there is a downward trend in the probability of an exceedance in the 1980s followed by a relatively flat trend in the 1990s.