Palynological study of Holocene sediments from Lake Doirani in northern Greece     

Nikolaos Athanasiadis  Spassimir Tonkov  Juliana Atanassova  Elissaveta Bozilova 《Journal of Paleolimnology》2000,24(3):331-342

A palynological investigation was conducted on two cores with Holocene sediments collected from the northeastern littoral part of the border Lake Doirani in northern Greece. The radiocarbon dates indicated that the analyzed sediments accumulated during the last 5000 yrs. The pollen-stratigraphic record revealed the environmental changes in the catchment area, starting from a natural undisturbed landscape to one modified by increasing anthropogenic influences. The tree vegetation dominated by Quercus woods in the lowlands and byPinus, Abies, and Fagus at higher altitudes, lasted for the period 2900 - 830 cal. B.C. Subsequently it was replaced by xerothermic herb and tree vegetation as a result of intensive human activity - and farming and stock-breeding. The accumulation of sediments with more sand and gravel in historical time was the result of increased erosion.  相似文献   

Quantification of displacement and particle crushing around a penetrometer tip     

Eshan Ganju  Fei Han  Monica Prezzi  Rodrigo Salgado  Juliana Spohr Pereira 《地学前缘(英文版)》2020,(2):389-399

Particle crushing occurs near the tip of a penetrometer and influences the development of the tip resistance.To study particle crushing near a penetrometer tip,a cone penetrometer was monotonically jacked and then load-tested in medium dense and dense silica sand samples prepared in a halfcylindrical calibration chamber with viewing windows.During the tests,images of the advancing penetrometer and the surrounding soil were taken using digital cameras and analyzed to obtain the displacement and strain fields around the penetrometer using the Digital Image Correlation(DIC)technique.Subsequently,soil samples were collected near the tip of the penetrometer using a novel agarimpregnation technique and digitized using an X-ray microscope.The digitized samples were analyzed to reconstruct the three-dimensional models of individual particles,generating the gradation and relative breakage parameters of the sand around the cone penetrometer.  相似文献   

Characterization of Non-Gaussian Geologic Facies Distribution Using Ensemble Kalman Filter with Probability Weighted Re-Sampling     

Siavash Nejadi  Juliana Leung  Japan Trivedi 《Mathematical Geosciences》2015,47(2):193-225

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Consuming space. Placing consumption in perspective – Edited by Michael K Goodman,David Goodman and Michael Redclift     

Juliana Mansvelt 《New Zealand geographer》2011,67(3):228-229

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Floods control the influence of environmental gradients on the diversity of zooplankton communities in a neotropical floodplain     

Nadson Ressyé Simões  Juliana Déo Dias  Clarice Maria Leal  Louizi de Souza Magalhães Braghin  Fábio Amodêo Lansac-Tôha  Cláudia Costa Bonecker 《Aquatic Sciences - Research Across Boundaries》2013,75(4):607-617

Floodplains show a high biodiversity due to their spatial heterogeneity and temporal variability, which are governed by environmental dynamics resulting from the flood pulse. We evaluated the importance of this driving force, the flood pulse, in the structuring of environmental gradients that influence species diversity in a neotropical floodplain. Gamma (γ) and alpha (α) zooplankton diversities were higher in the year with a typical flood pulse (2010), indicating that flood dynamics contributed to high diversity component values. We found significant relationships between α- and β-diversity and local environmental gradients, indicating that in years with a flood pulse, environmental filters might be the dominant mechanisms that structure the zooplankton community. Additive partitioning of γ-diversity showed that even in 2000 with atypical flood conditions, zooplankton diversities showed non-random patterns of spatial distribution and temporal variation in the floodplain. Our results indicate that the driving force of a floodplain can determine the spatial distribution of α- and β-diversity of aquatic communities owing to its primary effect on environmental filters. Therefore, if human activities that influence this driving force, such as water regulation, affect those environmental filters, floodplain biodiversity may decline.  相似文献   

Tourism Today: A Geographical Analysis by Douglas Pearce     

Juliana Mansvelt 《New Zealand geographer》1998,54(2):55a-56

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Evolution of the deep Atlantic water masses since the last glacial maximum based on a transient run of NCAR-CCSM3     

Juliana M. Marson  Lawrence A. Mysak  Mauricio M. Mata  Ilana Wainer 《Climate Dynamics》2016,46(3-4):865-877

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Trace metal distribution in white shrimp (<Emphasis Type="Italic">Litopenaeus schmitti</Emphasis>) tissues from a Brazilian coastal area     

Juliana Ribeiro Nascimento  Edison Dausacker Bidone  Denise Rolão-Araripe  Karina Annes Keunecke  Elisamara Sabadini-Santos 《Environmental Earth Sciences》2016,75(11):990

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Reconstructing pre-colonial oyster demographics in the Chesapeake Bay, USA     

Roger Mann  Juliana M. Harding  Melissa J. Southworth 《Estuarine, Coastal and Shelf Science》2009,85(2):217-222

Recent estimates of growth and mortality rates in extant Chesapeake Bay, USA oyster (Crassostrea virginica) populations are used to quantify changes in both population abundance (dN/dT) and shell accretion (dS/dT) associated with modern population demographics. The demographics of oyster populations that would be required to maintain reef accretion rates commensurate with sea level rise over geological time frames are examined using estimates of oyster longevity in pre-colonial (pre -1600) times combined with parallel estimates of pre-disease endemic mortality. The analysis demonstrates that modern populations, with their disease related, age-truncated demographics, are generally not capable of maintaining and building biogenic reefs through accretion. Estimates of filtration rates associated with Chesapeake Bay oyster populations prior to 1600 considerably underestimate actual benthic-pelagic coupling during that period. Pristine oyster populations would have supported water column turnover rates on the order of minutes to hours. Thus, the spatial footprint of oyster reefs was limited by available productivity in the estuary. Accretion rate calculations for pristine (pre-1600) oyster reefs describe the intimate relationship between benthic-pelagic coupling and the presence or absence of oyster reefs and the associated communities.  相似文献   

Temporal variation and patchiness of zooplankton around a restored oyster reef     

Juliana M. Harding 《Estuaries and Coasts》2001,24(3):453-466

Zooplankton abundance and distribution patterns were determined for six seasonally important invertebrate taxa (bivalve veligers, gastropod veligers, polychaete larvae, barnacle nauplii, calanoid copepod adults and nauplii) and a diurnally important taxon (decapod zoea) around a restored oyster reef in the Piankatank River, Virginia. Data were collected on spatial scales of hundreds of meters and seasonal (May through October), diel (day-night), and tidal (3 h) temporal scales. Significant seasonal and diel patterns in abundance were observed for all taxa. Tidal influences alone appear to be less important than seasonal and diel patterns for most taxa but the interation of tidal and diel cues may have caused the observed diel zooplankton distribution patterns in both June and August 1996. Zooplankton taxa around the oyster reef were distributed non-randomly (patchily) regardless of their horizontal location with regard to the reef. Seasonal pulses in zooplankton abundance relate directly to life history patterns and reproductive cycles for individual taxa. Reef benthic fauna have the capacity to directly influence the composition and absolute abundance of the overlying zooplankton community and indirectly influence oyster reef community trophic dynamics.  相似文献