Land Changes Fostering Atlantic Forest Transition in Brazil: Evidence from the Paraíba Valley     

Ramon Felipe Bicudo da Silva  Mateus Batistella  Emilio Federico Moran  Dengsheng Lu 《The Professional geographer》2017,69(1):80-93

The Atlantic Forest biome has only 13 percent of its pristine vegetation cover left. This article analyzes the consequences of land changes on forest cover in the Paraíba Valley, São Paulo state, Brazil, from 1985 to 2011. Multitemporal satellite image classifications were carried out to map eight land use and land cover classes. The forest cover increased from 2,696 km² in 1985 to 4,704 km² in 2011, mostly over areas of degraded pastures. The highest rates of afforestation were observed within protected areas around eucalyptus plantations. On the other hand, deforestation processes were concentrated on areas covered by secondary forests. Socioeconomic changes taking place in particular Brazilian settings, such as industrialization and agricultural modernization, allied to the Paraíba Valley's natural biophysical constraints for agricultural production, have led the region to experience a remarkable case of forest transition.  相似文献   

Shallow-level differentiation of phonolitic lavas from Sumaco Volcano,Ecuador     

Jennifer?M.?GarrisonEmail authorView author&#;s OrcID profile  Kenneth?W.?W.?Sims  Gene?M.?Yogodzinski  Ricardo?D.?Escobar  Sean?Scott  Patricia?Mothes  Minard?L.?Hall  Patricio?Ramon 《Contributions to Mineralogy and Petrology》2018,173(1):6

Sumaco Volcano is located in the rear-arc of Ecuador and produces phonolitic alkaline lavas hosting a unique assemblage of minerals including haüyne and titanaugite. The most mafic lavas are picrobasalts that contain titanaugite as the primary mineral phase; the most evolved tephri-phonolite lavas contain titanaugite?+?anorthoclase?+?haüyne. Titanaugite forms at middle to deep crustal pressures, whereas haüyne is only stable at shallow depths in highly oxidizing conditions. The Sumaco mineral assemblages and geochemistry indicate that fractionation of the titanaugite- and haüyne-bearing assemblage took place over a range of pressures from 5 to 25 kbar (14–75 km), with at least 50% of differentiation taking place at shallow crustal levels. Minerals record multiple cycles of recharge and mixing accompanied by an increase in fO₂ and sulfur concentration during differentiation. Mantle-like Sr and Nd isotope values (⁸⁷Sr/⁸⁶Sr = 0.70406–0.70423; ¹⁴³Nd/¹⁴⁴Nd = 0.512880–0.512913) indicate minimal crustal assimilation. Sumaco’s unique geochemical composition is not observed in the nearby volcanoes Antisana, Pan de Azucar or El Reventador suggesting that its unique magma source is confined to this volcano. The high temperature and sulfate-saturated conditions at shallow depths suggest that magma ascends rapidly to a shallow reservoir where the majority of crystallization and recharge takes place prior to eruption. An important conclusion of this research is that Sumaco does not represent typical rear-arc subduction processes, and caution should be used when using Sumaco as an end-member to evaluate across-arc processes in the Northern Volcanic Zone.  相似文献   

InSAR datum connection using GNSS-augmented radar transponders     

Pooja Mahapatra  Hans van der Marel  Freek van Leijen  Sami Samiei-Esfahany  Roland Klees  Ramon Hanssen 《Journal of Geodesy》2018,92(1):21-32

Deformation estimates from Interferometric Synthetic Aperture Radar (InSAR) are relative: they form a ‘free’ network referred to an arbitrary datum, e.g. by assuming a reference point in the image to be stable. However, some applications require ‘absolute’ InSAR estimates, i.e. expressed in a well-defined terrestrial reference frame, e.g. to compare InSAR results with those of other techniques. We propose a methodology based on collocated InSAR and Global Navigation Satellite System (GNSS) measurements, achieved by rigidly attaching phase-stable millimetre-precision compact active radar transponders to GNSS antennas. We demonstrate this concept through a simulated example and practical case studies in the Netherlands.  相似文献   

Molecular approach to determine contributions of the protist community to particle flux     

Jessica Amacher  Susanne Neuer  Ian Anderson  Ramon Massana 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(12):2206-2215

The importance of key taxonomic groups of eukaryotic phytoplankton as contributors to downward particle flux was evaluated near the European time-series station (ESTOC) in the eastern subtropical North Atlantic in March 2005. For the first time, molecular (cloning and sequencing) techniques were used to compare plankton communities from various depths in the euphotic zone with clone libraries from surface-tethered particle traps. Analyses of 18S rDNA clone libraries revealed compositional differences between the phytoplankton assemblages in the photic zone and those retrieved from shallow particle traps below, suggesting that not all phytoplankton contribute equally to particle flux. Contrary to expectations, our study also showed that it is not diatoms, despite their high abundance in the water column, but rather small phytoplankton taxa that dominated sequences recovered from trap material. We provide here first observational evidence that large taxa with mineral tests may not necessarily contribute more to export production than do smaller taxa even if the former are abundant in the water column.  相似文献   

Seasonal and interannual dynamics in diatom production in the Cariaco Basin,Venezuela     

Oscar E. Romero  Robert C. Thunell  Yrene Astor  Ramon Varela 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(4):571-581

We examine the diatom flux collected between November 1996 and April 1998, and between January and October 1999 at the time-series study site in the Cariaco Basin, off Venezuela. The temporal dynamics of the total diatom flux mainly reflect seasonal, trade wind-driven changes in surface hydrographic conditions, including changes associated with the El Niño/Southern Oscillation (ENSO). Highest diatom fluxes (>1.8×10⁷ valves m^?2 d^?1) coincided with the upwelling season in boreal winters 1997 and 1999. Changes in the composition of the diverse diatom community reflect variations in hydrographic and atmospheric conditions, as well as nutrient availability. Cyclotella litoralis, a neritic diatom typical of nutrient-rich waters, along with resting spores of several Chaetoceros spp., dominate during periods of high diatom flux, following trade wind-driven upwelling. During the boreal summers of 1997 and 1999, nutrient-depleted surface waters resulted in low diatom fluxes (<5.2×10⁶ valves m^?2 d^?1). The seasonal pattern of high diatom production was altered from July 1997 through April 1998, when the ENSO affected the Caribbean Sea. The occurrence of ENSO during boreal winter 1997–1998 caused a major change in the qualitative composition of the diatom assemblage: the highly diverse diatom assemblage was composed of a mixture of pelagic (Nitzschia bicapitata, Thalassionema nitzschioides var. inflata, T. nitzschioides var. parva, Azpeitia tabularis) and coastal species (C. litoralis, resting spores of Chaetoceros, T. nitzschioides var. nitzschioides). The simultaneous occurrence of neritic and open-ocean diatoms during boreal summers reflects the fact that the Cariaco Basin is influenced by both offshore and coastal waters, with considerable short-term variability in hydrographic conditions and nutrient availability.  相似文献   

Consistent grain size distribution of pedogenic maghemite of surface soils and Miocene loessic soils on the Chinese Loess Plateau     

Junsheng Nie  Yougui Song  John W. King  Ramon Egli 《第四纪科学杂志》2010,25(3):261-266

There is agreement that ultrafine maghemite grains (<100 nm) are responsible for the magnetic enhancement of Chinese loess. Recent studies show that grain size distribution of ultrafine pedogenic maghemite grains within the aeolian sequences on the central Chinese Loess Plateau deposited in the last 8 Ma is consistent. However, whether the observed grain size distribution of ultrafine pedogenic maghemite grains can be observed in the western Chinese Loess Plateau and modern soils is not entirely clear. Here we find that young surface soil samples across the Chinese Loess Plateau and early Neogene loessic soils from the western Chinese Loess Plateau also show consistent grain size distribution with that of ultrafine pedogenic maghemite grains on the central Chinese Loess Plateau. The fact that young surface soil samples show apparent magnetic enhancement suggests that the ultrafine pedogenic maghemite grains derive from oxidation of ultrafine magnetite grains. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

A new concept for the combination of optical interferometers and high-resolution spectrographs     

Simon Albrecht  Andreas Quirrenbach  Robert N. Tubbs  Ramon Vink 《Experimental Astronomy》2010,27(3):157-186

The combination of high spatial and spectral resolution in optical astronomy enables new observational approaches to many open problems in stellar and circumstellar astrophysics. However, constructing a high-resolution spectrograph for an interferometer is a costly and time-intensive undertaking. Our aim is to show that, by coupling existing high-resolution spectrographs to existing interferometers, one could observe in the domain of high spectral and spatial resolution, and avoid the construction of a new complex and expensive instrument. We investigate in this article the different challenges which arise from combining an interferometer with a high-resolution spectrograph. The requirements for the different sub-systems are determined, with special attention given to the problems of fringe tracking and dispersion. A concept study for the combination of the VLTI (Very Large Telescope Interferometer) with UVES (UV-Visual Echelle Spectrograph) is carried out, and several other specific instrument pairings are discussed. We show that the proposed combination of an interferometer with a high-resolution spectrograph is indeed feasible with current technology, for a fraction of the cost of building a whole new spectrograph. The impact on the existing instruments and their ongoing programs would be minimal.  相似文献   

The Astronomy and Astrophysics Review introduces article citation-id     

Ramon Khanna  Thierry J.-L. Courvoisier 《Astronomy and Astrophysics Review》2011,19(1):36-2

  相似文献   

The Quaternary glacial sequence in Ecuador: a reinterpretation of the work of Walter Sauer     

Chalmers M. Clapperton  Ramon Vera 《第四纪科学杂志》1986,1(1):45-56

The Quaternary glacial sequence proposed for the Ecuadorian Andes by Walter Sauer is critically reviewed. Examination of his field evidence at sections exposing Quaternary sediments east of Quito has led to a fundamental reinterpretation. Deposits which Sauer considered as glacial, glacio-fluvial, glacio-lacustrine and pluvio-glacial in origin appear to have been formed mainly by volcanic, volcano-loessic, laharic, fluvial, colluvial and pedogenic processes.  相似文献   

Effects of 17beta-estradiol exposure in the mussel Mytilus galloprovincialis     

Janer G  Lavado R  Thibaut R  Porte C 《Marine environmental research》2004,58(2-5):443-446

Mussels Mytilus galloprovincialis were exposed to different concentrations of estradiol (20, 200, and 2000 ng/l) in a semi-static regime (1-day dosing intervals) for up to 7 days in an attempt to see how mussels dealt with exogenous estrogenic compounds. Sex hormone levels were determined in whole tissue. Free-estradiol was only significantly elevated at the highest exposure dose (up to 10-fold). Most of the estradiol was in the tissues as fatty acid esters (> 78%), which sharply increased in a dose-dependent manner (from 4 ng/g in controls to 258 ng/g at the high exposure group). In contrast, neither free nor esterified testosterone levels showed significant differences between control and exposure groups. The results suggest the existence of mechanisms that allow mussels to maintain their hormonal status, and the important role that fatty acid esterification may play within those mechanisms. Synthesis and conjugation rates of estradiol were further investigated by measuring the activity of P450 aromatase, and palmitoyl-CoA:estradiol acyltransferase, in digestive gland microsomal fractions. Overall, the study contributes to the better knowledge of molluscan endocrinology, and defines new mechanisms of regulation of free steroid-levels in mussels.  相似文献