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91.
Driving forces of tropical deforestation: The role of remote sensing and spatial models 总被引:2,自引:0,他引:2
Rinku Roy Chowdhury 《Singapore journal of tropical geography》2006,27(1):82-101
Remote sensing technologies are increasingly used to monitor landscape change in many parts of the world. While the availability of extensive and timely imagery from various satellite sensors can aid in identifying the rates and patterns of deforestation, modelling techniques can evaluate the socioeconomic and biophysical forces driving deforestation processes. This paper briefly reviews some emerging spatial methodologies aimed at identifying driving forces of land use change and applies one such methodology to understand deforestation in Mexico. Satellite image classification, change analysis and econometric modelling are used to identify the rates, hotspots and drivers of deforestation in a case study of the southern Yucatán peninsular region, an enumerated global hotspot of biodiversity and tropical deforestation. In particular, the relative roles of biophysical and socioeconomic factors in driving regional deforestation rates are evaluated. Such methodological approaches can be applied to other regions of the forested tropics and contribute insights to conservation planning and policy. 相似文献
92.
93.
This article discusses the involvement of older women and men in voluntary work in rural communities in the Netherlands. Gender,
ageing and civil society form the core concepts in the article. Politicians and policy makers in the Netherlands are worried
about the perceived decline of civil society and about the consequences of this decline for specific categories of older women
in terms of well-being and social exclusion. The paper presents the results of two surveys of involvement of older women and
men in civic organisations, voluntary work and local actions. The surveys indicate high levels of involvement of both women
and men. No gender differences are found in activity level. However, the data demonstrate the gendered nature of civil society.
Women are more engaged in informal voluntary work and informal local actions, while men are more active in formal organisations
and functions. This gender segmentation is not absolute, however. Many older women and men transgress the traditional feminine–masculine
boundaries. The surveys highlight the involvement of women and men in rural communities, but indicate lower activity levels
in urban areas. 相似文献
94.
P. K. Joshi G. S. Rawat H. Padaliya P. S. Roy 《Journal of the Indian Society of Remote Sensing》2005,33(3):371-380
The remote sensing technology has been widely used for mapping the vegetation types in the tropical landscapes. However, in
the temperate and alpine arid regions of India very few studies have been conducted using this technique. In the mountainous
temperate arid conditions the vegetation is largely confined to marsh meadows, streams courses, river valleys and moist pockets
close to snowfields. The ground truth collection in these zones are physically challenging due to tough terrain and restricted
mobility. The detailed mapping of vegetation and other land use classes in these areas is therefore, extremely difficult.
This paper describes the use of IRS-ID LISS III sensor for deciphering land cover details Nubra Valley, northern portion of
Ladakh Autonomous Hill Council, Jammu & Kashmir (India). This analysis essentially emphasizes in bringing out various vegetation
classes (speciallyHippophae rhamnoides and other medicinal plant communities) along the narrow river valleys. 相似文献
95.
A two-dimensional global climate model is used to assessthe climatic changes associated with the new IPCC SRES emissions scenarios and to determine which kind of changes in total solar irradiance and volcanic perturbations could mask the projected anthropogenic global warming associated to the SRES scenarios. Our results suggest that only extremely unlikely changes in total solar irradiance and/or volcanic eruptions would be able to overcome the simulated anthropogenic global warming over the century. Nevertheless, in the critical interval of the next two decades the externally-driven natural climate variability might possibly confuse the debate about temperature trends and impede detection of the anthropogenic climate change signal. 相似文献
96.
Generalized equations using fractional-flow dimensions were derived to estimate the Darcy and seepage velocities obtained
from the point-dilution and the single-well injection-withdrawal field tests conducted in fractured-rock aquifers. Seepage
velocities can only be estimated from single-well tests if the hydraulic conductivity and the hydraulic gradient are known
a priori. However, if a radial-convergent test is also performed between two boreholes, the kinematic porosity can be estimated
and be used to estimate the seepage velocity from the single-well test results.
To apply the generalized equations, the flow dimension and the extent of the flow region must be known. Therefore, the generalized
radial flow (GRF) model of Barker (1988; a generalized radial flow model for hydraulic tests in fractured rock. Water Resour
Res 24(10):1796–1804) is used to estimate the flow dimension because of its wide range of applications. A pumping test performed
on the boreholes will yield an estimate of the fractional-flow dimension by applying the GRF model.
Electronic Publication 相似文献
97.
S. Siegesmund H. Jelsma J. Becker G. Davies P. Layer E. van Dijk L. Kater M. Vinyu 《International Journal of Earth Sciences》2002,91(1):20-34
In order to constrain the temporal relationship between granite (sensu lato) emplacement and metamorphism, isotope work was carried out on the minerals zircon and apatite (U-Pb), garnet (Pb-Pb) and hornblende (Ar-Ar) from wall rock samples in the Shamva area in Zimbabwe. The area, encompassing parts of the Chinamora and Murehwa batholiths and a wedge-shaped greenstone belt segment in between, is commonly quoted in the literature as an example illustrating pluton emplacement processes and deformational models for the Archean. New U-Pb dating of apatite from a boudinaged pegmatite within mafic schists in the batholith-greenstone contact zone has yielded an age of 2619 +28/-24 Ma. This age is interpreted as the best estimation of the intrusion age of this unit, depending on the assumed closure temperature, and provides an upper age limit for the syntectonic emplacement of the now gneissic granites. Pb-Pb dating of late kinematic garnets in cordierite-bearing rocks within the greenstone belt wall rocks gives an age of 2623NJ Ma. Together, this timing of relatively late, syntectonic plutonism and metamorphic mineral growth at ca. 2.62 Ga compares well with existing zircon crystallization ages for felsic volcanics (2645dž Ma, 2643NJ Ma) and post-tectonic porphyritic monzogranites (2601ᆢ Ma). Ar-Ar hornblende ages for mafic schists from different areas within the greenstone belt wall rocks range between 2621 and 2498 Ma and have been interpreted to indicate mixing between metamorphic ages and cooling ages. The data support a geological model whereby volcanism and sedimentation are associated with an early phase of regional deformation at ca. 2.64 Ga, which may have started earlier and lasted longer, and evolves into the voluminous emplacement of granites (now gneissic granites) in the batholiths at approximately 2.62 Ga. Emplacement of post-tectonic tabular monzogranites takes place at ca. 2.60 Ga. 相似文献
98.
The political turning point in the former GDR and the transformation processes that have been observed since then have significantly
affected economic and social structures in the new Federal States. Gender roles, however, were subjected to even more dramatic
changes. Whilst many women experienced the employment policies of the GDR era as beneficial, social researchers often designate
them as the losers of unification nowadays. This is largely because the abundance of State support measures for employed women
and mothers has been drastically reduced and women as a group have been hit hardest by the crisis on the East German labour
market. Using two cases (Mecklenburg-Westpommerania and Thuringia), this paper aims to illustrate the impact of the transformation
process on the everyday (working) lives of women. We are particularly concerned with a comparative analysis of how women experience
and deal with regional disparities in East Germany.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
99.
Evidence for compressionally induced high subsidence rates in the Kurile Basin (Okhotsk Sea) 总被引:1,自引:0,他引:1
Boris V. Baranov Reinhard Werner Kaj A. Hoernle Ira B. Tsoy Paul van den Bogaard Igor A. Tararin 《Tectonophysics》2002,350(1)
A combined volcanological, geochemical, paleo-oceanological, geochronological and geophysical study was undertaken on the Kurile Basin, in order to constrain the origin and evolution of this basin. Very high rates of subsidence were determined for the northeastern floor and margin of the Kurile Basin. Dredged volcanic samples from the Geophysicist Seamount, which were formed under subaerial or shallow water conditions but are presently located at depths in excess of 2300 m, were dated at 0.84±0.06 and 1.07±0.04 Ma with the laser 40Ar/39Ar single crystal method, yielding a minimum average subsidence rate of 1.6 mm/year for the northeast basin floor in the Quaternary. Trace element and Sr–Nd–Pb isotope data from the volcanic rocks show evidence for contamination within lower continental crust and/or the subcontinental lithospheric mantle, indicating that the basement presently at 6-km depth is likely to represent thinned continental crust. Average subsidence rates of 0.5–2.0 mm/year were estimated for the northeastern slope of the Kurile Basin during the Pliocene and Quaternary through the determination of the age and paleo-environment (depth) of formation of sediments from a canyon wall. Taken together, the data from the northeastern part of the Kurile Basin indicate that subsidence began in or prior to the Early Pliocene and that subsidence rates have increased in the Quaternary. Similar rates of subsidence have been obtained from published studies on the Sakhalin Shelf and Slope and from volcanoes in the rear of the Kurile Arc. The recent stress field of the Kurile Basin is inferred from the analysis of seismic activity, focal mechanism solutions and from the structure of the sedimentary cover and of the Alaid back-arc volcano. Integration of these results suggests that compression is responsible for the rapid subsidence of the Kurile Basin and that subsidence may be an important step in the transition from basin formation to its destruction. The compression of the Kurile Basin results from squeezing of the Okhotsk Plate between four major plates: the Pacific, North American, Eurasian and Amur. We predict that continued compression could lead to subduction of the Kurile Basin floor beneath Hokkaido and the Kurile Arc in the future and thus to basin closure. 相似文献
100.
Delphine PaillerEdouard Bard Frauke RostekYan Zheng Richard MortlockAlexander van Geen 《Geochimica et cosmochimica acta》2002,66(5):849-865
Authigenic metals (uranium, cadmium, and molybdenum), organic carbon (OC) and total C37 alkenone (totC37) concentrations were measured for the last 350 kyr in core MD900963, located in the eastern equatorial Arabian Sea. Authigenic metal concentrations on a carbonate-free basis range between 1 and 17 ppm, 0.5 and 6 ppm, and 0.5 and 4 ppm for U, Cd, and Mo, respectively. The profiles are characterized by well-defined 23 kyr cycles between oxic and mildly suboxic conditions. The redox-sensitive metal profiles also follow variations in the concentrations of OC (0.2-0.9%) and alkenones (0.2-6.7 ppm). The coupled variations in inorganic and organic constituents are attributed to a 23-kyr cycle in primary production above site MD900963, as suggested by clear correlations with independent micropaleontologic proxies (primary productivity indices based on foraminifera and coccoliths and fragmentation of foraminiferal shells). The 23-kyr cycles do appear to be primarily driven by productivity rather than changes in bottom water oxygen. Comparison with other records indicates that if this interpretation is correct, productivity variations across much of the Indian Ocean have been dominated by precessional forcing, with high productivity in phase with low summer insolation in the Northern Hemisphere. This interpretation contrasts with the traditional attribution of enhanced productivity in the Indian Ocean with periods of high summer insolation. 相似文献