Land-use and climate change within assessments of biodiversity change: A review   总被引：1，自引：0，他引：1  

Jacqueline de Chazal  Mark D.A. Rounsevell 《Global Environmental Change》2009,19(2):306-315

Projected changes in biodiversity are likely inadequately estimated when climate and land-use change effects are examined in isolation. A review of studies of the effects of these drivers singly and in combination highlights little discussed complexities in revising these estimates. In addition to considering interactions, different characterisations of climate change, land-use change and biodiversity greatly influence estimates. Habitat loss leading to decreased species richness is the most common land-use change and biodiversity relationship considered with less attention being given to other land-use changes (e.g. other conversions, fragmentation, different management intensities) and biodiversity characterisations and responses (e.g. selected groups of species, increased species richness). Characterisations of more complex relationships between climate change, land-use change and biodiversity however are currently limited by a lack of process understanding, data availability and inherent scenarios uncertainties.  相似文献   

Transformation of meta-stable calcium silicate hydrates to tobermorite: reaction kinetics and molecular structure from XRD and NMR spectroscopy     

Jacqueline R Houston  Robert S Maxwell  Susan A Carroll 《Geochemical transactions》2009,10(1):1-14

Understanding the integrity of well-bore systems that are lined with Portland-based cements is critical to the successful storage of sequestered CO₂ in gas and oil reservoirs. As a first step, we investigate reaction rates and mechanistic pathways for cement mineral growth in the absence of CO₂ by coupling water chemistry with XRD and NMR spectroscopic data. We find that semi-crystalline calcium (alumino-)silicate hydrate (Al-CSH) forms as a precursor solid to the cement mineral tobermorite. Rate constants for tobermorite growth were found to be k = 0.6 (± 0.1) × 10^-5 s^-1 for a solution:solid of 10:1 and 1.6 (± 0.8) × 10^-4 s^-1 for a solution:solid of 5:1 (batch mode; T = 150°C). This data indicates that reaction rates for tobermorite growth are faster when the solution volume is reduced by half, suggesting that rates are dependent on solution saturation and that the Gibbs free energy is the reaction driver. However, calculated solution saturation indexes for Al-CSH and tobermorite differ by less than one log unit, which is within the measured uncertainty. Based on this data, we consider both heterogeneous nucleation as the thermodynamic driver and internal restructuring as possible mechanistic pathways for growth. We also use NMR spectroscopy to characterize the site symmetry and bonding environment of Al and Si in a reacted tobermorite sample. We find two ^[4]Al coordination structures at δ _iso = 59.9 ppm and 66.3 ppm with quadrupolar product parameters (P_Q) of 0.21 MHz and 0.10 MHz (± 0.08) from ²⁷Al 3Q-MAS NMR and speculate on the Al occupancy of framework sites by probing the protonation environment of Al metal centers using ²⁷Al{¹H}CP-MAS NMR.  相似文献   

Structural and mineralogical study of active and inactive hydrothermal fluid discharges in Panarea,Italy     

Richard Stanulla  Thomas Pohl  Christin Müller  Jacqueline Engel  Mandy Hoyer  Broder Merkel 《Environmental Earth Sciences》2017,76(11):404

The isle of Panarea (Aeolian Arc, Italy) is an active hydrothermal system, characterized by different types of fluid emissions, which cause various types of unique hydrothermal structures that are typical for hydrothermal fluid discharges. Such fluid discharge structures at shallow depths of less than 30 m have not been described in marine hydrothermal systems until now to the authors’ knowledge. The focus of the investigations was set on morphological, mineralogical, geochemical, and structural analyses. A broad variety of analytical methods was applied to gain as much information as possible. In addition to geological and sedimentological documentation and standard methods like making and analyzing thin and polished sections, optical microscopy or X-ray fluorescence analysis, the samples were investigated by X-ray computer tomography and scanning electron microscopy, including energy-dispersive X-ray spectroscopy. Because discharge features occur in various settings, a general classification of the features in the hydrothermal system was performed with special focus on their preservability in geological archives. In total, nine different facies types were distinguished based on genetic and/or morphological differences. All samples show laminated structures from µm to cm scale. The single laminae vary in shape and material witnessing various chemical compositions.  相似文献   

Radiometric dating of late proterozoic ophiolites: Meaning,correlations and problems     

Jacqueline Desmons 《Precambrian Research》1982,16(4):A15

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Hydrogeologic Behavior of an Alluvial Aquifer,Salta Province,Argentina: Simulations of Hydraulic Conductivity Field,Groundwater Flow,and Chloride Migration     

Köhn  Jacqueline  Kruse  Eduardo E.  Santos  Juan E. 《Natural Resources Research》2002,11(3):157-166

This work was designed to analyze the hydrogeological behavior of an alluvial aquifer in the River Mojotoro basin site in the Province of Salta, Argentina. The study area presents coarse-grained sediments with high infiltration capacity. The hydraulic conductivity field is affected by the physical heterogeneity of the medium and a geostatistical method, kriging, was used to construct this field from local measurements. The groundwater flow velocity field is computed using a hybrid mixed finite-element method and small variations in the flow directions were determined. Given the existence of a point source of chloride in the region under study, the spatial distribution of the generated plume in the saturated zone is analyzed. The advection-diffusion equation describing the transport of chloride in vertical and horizontal cross-sectional planes of the aquifer is discretized employing a method of characteristics combined with a mixed finite-element procedure, which provides an efficient method to eliminate spurious numerical oscillations and handle the convective term in the equation. The migration of chloride shows patterns, which are affected by the litologic heterogeneities of the aquifer and the regional groundwater flow.  相似文献   

Oxygen and hydrogen isotope compositions of eclogites and associated rocks from the Eastern Sesia zone (Western Alps,Italy)     

Jacqueline Desmons  James R. O'Neil 《Contributions to Mineralogy and Petrology》1978,67(1):79-85

Oxygen and hydrogen isotope analyses have been made of mineral separates from eclogites, glaucophanites and glaucophane schists from the eastern Sesia zone (Italian Western Alps). Regularities in (1) hydrogen isotope compositions, (2) order of ¹⁸O enrichment among coexisting minerals, and (3) ¹⁸O (quartz-rutile) and ¹⁸O (quartz-phengite) imply attainment of a high degree of isotopic equilibrium. However, some scattering of ¹⁸O values of individual minerals indicates that the eclogitic assemblage did not form in the presence of a thoroughly pervasive fluid. Minerals from an eclogitic lens enclosed in marble have ¹⁸O values distinctly different from those measured in the other rocks. The ¹⁸O values are high in comparison with other type C eclogites of the world, and it is proposed that the fluid present during the high pressure metamorphism has to a large extent been inherited from the precursor rocks of amphibolite facies.An average formation temperature of 540 ° C is inferred from the oxygen isotope fractionations between quartz and rutile and between quartz and white mica. This temperature is in accordance with petrologic considerations and implies subduction of the precursor rocks into the upper mantle to achieve the high pressures required.  相似文献   

Diffusion processes in resorbed garnets     

Pierre de Béthune  Dominique Laduron  Jacqueline Bocquet 《Contributions to Mineralogy and Petrology》1975,50(3):197-204

Mn- (and Ca-) enriched border fringes around resorbed garnets, and Mn-enriched zones along cracks in resorbed garnets and along intergranular boundaries in resorbed sievegarnets, indicate a limited diffusion of Mn (and some Ca) into the garnet structure.  相似文献   

Temporal dynamics and spatial scales: Modeling deforestation in the southern Yucatán peninsular region     

Jacqueline Geoghegan  Laura Schneider  Colin Vance 《GeoJournal》2004,61(4):353-363

Two spatially explicit econometric land use change models are presented, focusing on tropical deforestation caused by agricultural expansion in the southern Yucatán peninsula, Mexico. The two models developed are both based on conceptually similar theoretical models of farmer behavior. However, there are different empirical specifications of this theoretical model according to the scale of the analysis as well as the availability of temporal data on the observation of deforestation. For both models, the unit of observation for the dependent variable of deforestation is the TM pixel from satellite data. However, the socio-economic explanatory variables are derived from different sources. The first econometric model links the satellite data for the entire study region with aggregate census data at the village level. This model is estimated using a discrete choice logit model over a single time period. The second econometric model uses individual household survey data for a small random sample of the region, linked to satellite data for the plots of each household over multiple time periods. This model is estimated using a dynamic hazard model that estimates the risk of a specific pixel converting from forest to agricultural use. Both estimated models are used to predict deforestation and the results of the two modeling approaches are compared.  相似文献   

The Impact of Climate on Holiday Destination Choice   总被引：2，自引：1，他引：2  

Andrea Bigano  Jacqueline M. Hamilton  Richard S. J. Tol 《Climatic change》2006,76(3-4):389-406

The holiday destination choice is analysed for tourists from 45 countries, representing all continents and all climates. Tourists are deterred by distance, political instability and poverty, and attracted to coasts. Tourists prefer countries with a sunny yet mild climate, shun climates that are too hot or too cold. A country's tourists' aversion for poverty and distance can be predicted by that country's average per capita income. The preferred holiday climate is the same for all tourists, independent of the home climate. However, tourists from hotter climates have more pronounced preferences.  相似文献   

U–Pb dating of plutonic rocks involved in the nappe tectonic in southern Cameroon: consequence for the Pan-African orogenic evolution of the central African fold belt     

Sadrack Felix Toteu  Rose Yongue Fouateu  Joseph Penaye  Jacqueline Tchakounte  Aubin Ciriaque Seme Mouangue  William Randall Van Schmus  Etienne Deloule  Henrik Stendal 《Journal of African Earth Sciences》2006,44(4-5):479

TIMS-ID and SIMS U–Pb dating on zircons from metaplutonic rocks involved in the Pan-African nappe of southern Cameroon allow definition of three groups of subduction-related intrusions: group-I intrusions represented by the Masins metagabbro in the Lomie region yielded 666 ± 26 Ma; group-II intrusions represented by the Mamb metasyenogabbro and the Yaoundé pyriclasite yielded ca. 620 Ma and are broadly coeval with the deposition of the Yaoundé metasediments; group-III intrusions represented by the Elon augen metagranite and the Ngaa Mbappe metamonzodiorite yielded ca. 600 Ma. The onset of the nappe tectonics occurred under high-grade conditions in the range 616 to 610 Ma and continued around 600 Ma with the emplacement of the shallowest nappes. Finally, the construction of southern Cameroon proceeded by a multi-stage evolution characterized by a long-lived development of magmatic arcs associated with rapid opening and closure of sedimentary marginal basins in relation to a northward subduction.  相似文献