Relationships between rocky desertification and spatial pattern of land use in typical karst area,Southwest China   总被引：7，自引：4，他引：3  

Yongjun Jiang  Linli Li  Chris Groves  Daoxian Yuan  Pat Kambesis 《Environmental Earth Sciences》2009,59(4):881-890

Karst rocky desertification is a typical type of land degradation in the Southwest China. An attempt was made to study quantitatively the relationships between rocky desertification and spatial pattern of land use through applying spatial analysis of Geographical Information System in Nandong underground river system, a typical karst area, Southwest China. The spatial distribution of rocky desertification and spatial pattern of land use were obtained from interpreting Landsat Images in Nandong area in 2007 by supervised classifications, and verified and rectified through field survey. The results indicate that: (1) the total land deserted area covers 378.3 km², or 23.4% of the total area, of which intense, moderate and slight rocky desertification covers 269.46, 54.2, and 54.63 km², respectively, in Nandong area. (2) There is an obvious effect of spatial pattern of land use on rocky desertification. With the increase of elevation and slope, there is a higher occurrence ratio of rocky desertification in the cultivated land and grass land. Also, more than half of total rocky desertification was dominated within the areas of 4 km from the construction land, and 97% of total rocky desertification was dominated within the areas of 10 km from the construction land in Nandong area. And what can be known from the data is that the primary effect distance of human on rocky desertification from the construction land is 4 km, and the farthest effect distance of human on rocky desertification from the construction land is 10 km in Nandong area.  相似文献   

Reappraising the P–T evolution of the Rogaland–Vest Agder Sector,southwestern Norway     

Eleanore Blereau  Tim E. Johnson  Chris Clark  Richard J.M. Taylor  Peter D. Kinny  Martin Hand 《地学前缘(英文版)》2017,8(1):1-14

The Rogaland-Vest Agder Sector of southwestern Norway comprises high-grade metamorphic rocks intruded by voluminous plutonic bodies that include the ~1000 km~2 Rogaland Igneous Complex(RIC).New petrographic observations and thermodynamic phase equilibria modelling of three metapelitic samples collected at various distances(30 km,10 km and ~ 10 m) from one of the main bodies of RIC anorthosite were undertaken to assess two alternative P-T-t models for the metamorphic evolution of the area.The results are consistent with a revised two-phase evolution.Regional metamorphism followed a clockwise P-T path reaching peak conditions of ~ 850-950 ℃ and ~7-8 kbar at ~1035 Ma followed by high-temperature decompression to ~5 kbar at ~950 Ma,and resulted in extensive anatexis and melt loss to produce highly residual rocks.Subsequent emplacement of the RIC at ~930 Ma caused regional-scale contact metamorphism that affected country rocks 10 km or more from their contact with the anorthosite.This thermal overprint is expressed in the sample proximal to the anorthosite by replacement of sillimanite by coarse intergrowths of cordierite plus spinel and growth of a second generation of garnet,and in the intermediate(10 km) sample by replacement of sapphirine by coarse intergrowths of cordierite,spinel and biotite.The formation of late biotite in the intermediate sample may suggest the rocks retained small quantities of melt produced by regional metamorphism and remained at temperatures above the solidus for up to 100 Ma.Our results are more consistent with an accretionary rather than a collisional model for the Sveconorwegian Orogen.  相似文献   

The benefits of climate change mitigation in integrated assessment models: the role of the carbon cycle and climate component   总被引：1，自引：1，他引：0  

Andries F. Hof  Chris W. Hope  Jason Lowe  Michael D. Mastrandrea  Malte Meinshausen  Detlef P. van Vuuren 《Climatic change》2012,113(3-4):897-917

Integrated Assessment Models (IAMs) are an important tool to compare the costs and benefits of different climate policies. Recently, attention has been given to the effect of different discounting methods and damage estimates on the results of IAMs. One aspect to which little attention has been paid is how the representation of the climate system may affect the estimated benefits of mitigation action. In that respect, we analyse several well-known IAMs, including the newest versions of FUND, DICE and PAGE. Given the role of IAMs in integrating information from different disciplines, they should ideally represent both best estimates and the ranges of anticipated climate system and carbon cycle behaviour (as e.g. synthesised in the IPCC Assessment reports). We show that in the longer term, beyond 2100, most IAM parameterisations of the carbon cycle imply lower CO₂ concentrations compared to a model that captures IPCC AR4 knowledge more closely, e.g. the carbon-cycle climate model MAGICC6. With regard to the climate component, some IAMs lead to much lower benefits of mitigation than MAGICC6. The most important reason for the underestimation of the benefits of mitigation is the failure in capturing climate dynamics correctly, which implies this could be a potential development area to focus on.  相似文献   

Interacting effects of vegetation, soils and management on the sensitivity of Australian savanna rangelands to climate change     

Nicholas P. Webb  Chris J. Stokes  Joe C. Scanlan 《Climatic change》2012,112(3-4):925-943

There is an increasing need to understand what makes vegetation at some locations more sensitive to climate change than others. For savanna rangelands, this requires building knowledge of how forage production in different land types will respond to climate change, and identifying how location-specific land type characteristics, climate and land management control the magnitude and direction of its responses to change. Here, a simulation analysis is used to explore how forage production in 14 land types of the north-eastern Australian rangelands responds to three climate change scenarios of +3°C, +17% rainfall; +2°C, ?7% rainfall; and +3°C, ?46% rainfall. Our results demonstrate that the controls on forage production responses are complex, with functional characteristics of land types interacting to determine the magnitude and direction of change. Forage production may increase by up to 60% or decrease by up to 90% in response to the extreme scenarios of change. The magnitude of these responses is dependent on whether forage production is water or nitrogen (N) limited, and how climate changes influence these limiting conditions. Forage production responds most to changes in temperature and moisture availability in land types that are water-limited, and shows the least amount of change when growth is restricted by N availability. The fertilisation effects of doubled atmospheric CO₂ were found to offset declines in forage production under 2°C warming and a 7% reduction in rainfall. However, rising tree densities and declining land condition are shown to reduce potential opportunities from increases in forage production and raise the sensitivity of pastures to climate-induced water stress. Knowledge of these interactions can be applied in engaging with stakeholders to identify adaptation options.  相似文献   

Is an onset vortex important for monsoon onset over Kerala?     

M. R. Ramesh Kumar  Syam Sankar  Chris Reason 《Theoretical and Applied Climatology》2012,110(1-2):209-227

Inter-annual variability in the formation of the mini warm pool [sea-surface temperature (SST)>30°C] over the south eastern Arabian Sea (SEAS) and its role in the formation of the monsoon onset vortex (MOV) has been examined using two independent SST data sets. The role of SST, convection, integrated columnar water vapour and the low-level jet in the setting up of the monsoon onset over Kerala (MOK) is examined. It is found that the MOV which forms over the SEAS region upsets the delicate balance between convection, buildup of moisture and strengthening and deepening of the westerlies over the SEAS that is needed for the setting up of the MOK. Thus, the formation over the SEAS of an MOV is not necessarily conducive for MOK. Furthermore, it is shown that a mini warm pool over the southeastern Arabian Sea is not a sufficient condition for the formation of an MOV because such a warm pool is present over this region during most of the years, but an MOV does not necessarily form over there.  相似文献   

On the direction of Rossby wave breaking in blocking     

Chris Weijenborg  Hylke de Vries  Reindert J. Haarsma 《Climate Dynamics》2012,39(12):2823-2831

The direction of Rossby wave breaking at the onset of large-scale atmospheric blocking events is shown to relate closely to its position relative to the location of the climatological storm tracks. Using ERA-Interim reanalysis data from October 1989 to March 2009 and a dynamically-based blocking index, Rossby wave breaking is shown to occur preferentially cyclonically to the north, and anticyclonically to the south of the average storm tracks location. Therefore the results support existing theory on the relation between Rossby wave breaking direction and barotropic shear of the background wind. The further away from the storm tracks the breaking occurs, the stronger this preference in breaking direction. Regional differences can also be explained. For the European region on average 70?% of the detected blocking took place after anticyclonic Rossby wave breaking event that occurred on average 6° south of the climatological storm tracks position. Over Western Pacific wave breaking prior to blocking occurs predominantly cyclonically and on average 6° north of the storm tracks. Differences in blocking duration and intensity are found to be within estimated error margins at most longitudes, except for the Atlantic-Europe sector where the blocking events following anticyclonic blocking are also the strongest.  相似文献   

Constraints on the genesis of gold mineralization at the Homestake Gold Deposit, Black Hills, South Dakota from rhenium–osmium sulfide geochronology     

Ryan M. Morelli  Chris C. Bell  Robert A. Creaser  Antonio Simonetti 《Mineralium Deposita》2010,45(5):461-480

The Homestake gold deposit, located in the Black Hills, South Dakota, USA, is one of the largest known hydrothermal gold deposits globally, with total mining production exceeding 40 Moz Au. Rhenium–osmium geochronology of ore-associated arsenopyrite and pyrrhotite was performed in an effort to delineate the timing of gold mineralization in relation to known tectonothermal events in the northern Black Hills. Arsenopyrite yields a rhenium–osmium (Re–Os) age of 1,736 ± 8 Ma (mean squared weighted deviation = 1.6), consistent with existing age constraints for gold mineralization, whereas Re–Os pyrrhotite data are highly scattered and do not yield a meaningful mineralization age. This is taken to indicate that the Re–Os arsenopyrite chronometer is robust to at least 400°C, whereas the Re–Os pyrrhotite chronometer is likely disturbed by temperatures of 300–350°C. The Re–Os arsenopyrite age and initial Os ratio (0.28 ± 0.15) are interpreted to indicate that gold was introduced at ca. 1,730 Ma, coincident with the onset of exhumation of crustal blocks and, possibly, the earliest intrusive phases of Harney Peak granite magmatism. New in situ U–Pb monazite analyses from an aplite dike in the east-central Black Hills indicate that granite magmatism was a protracted event, persisting until at least ca. 1,690 Ma.  相似文献   

Middle Holocene Bison diet and mobility in the eastern Great Plains (USA) based on δC, δO, and Sr/Sr analyses of tooth enamel carbonate     

Chris Widga  J. Douglas Walker  Lisa D. Stockli 《Quaternary Research》2010,73(3):449-463

During the Holocene, bison (Bison bison) were key components of the Great Plains landscape. This study utilizes serial stable isotope analyses (tooth enamel carbonate) of 29 individuals from five middle Holocene (∼ 7–8.5 ka) archaeological sites to address seasonal variability in movement patterns and grazing behavior of bison populations in the eastern Great Plains. Stable carbon isotopes (δ¹³C) indicate a bison diet that is similar to the C3/C4 composition of modern tallgrass prairies, while ⁸⁷Sr/⁸⁶Sr values generally indicate very little seasonal movement (< 50 km) and relatively limited inter-annual movement (< 500 km) over the course of 4–5 yr. Analyses of variability in serial stable oxygen isotope samples (δ¹⁸O) further substantiate a model of localized bison herds that adhered to upland areas of the eastern Plains and prairie–forest border.  相似文献   

Transient currents in the global electric circuit due to cloud-to-ground and intracloud lightning     

Chris R. Maggio  Thomas C. Marshall  Maribeth Stolzenburg 《Atmospheric Research》2009,91(2-4):178-183

Intracloud (IC) and cloud-to-ground (CG) lightning flashes produce transient changes in the electric field (E) above a thundercloud which drive transient currents in the global electric circuit (GEC). Using in-cloud and above-cloud E data from balloons, ground-based E data, and Lightning Mapping Array data, the above-cloud charge transfers due to lightning transients are estimated for five IC and five CG flashes from four thunderstorms that occurred above the mountains in New Mexico, USA, in 1999. For the five CG flashes (which transferred − 4 to − 13 C to the ground), the transient currents moved + 1 to + 5 C of charge upward from cloudtop toward the ionosphere, with an average transient charge transfer of about 35% of the charge transferred to ground. For the five IC flashes (which neutralized 6 to 21 C inside the cloud), the transient currents moved − 0.7 to − 3 C upward, with an average transient charge transfer of about 12% of the lightning charge. Estimates for three thunderstorms indicate that the transient currents made only a small GEC contribution compared to the quasi-stationary Wilson currents because of the offsetting effects of IC and CG flashes in these storms. However, storms with extreme characteristics, such as high flash rates or predominance of one flash type, may make a significant GEC contribution via lightning transients.  相似文献   

Sustainable Household Capability: which households are doing the work of environmental sustainability?   总被引：2，自引：2，他引：0  

Gordon Waitt  Peter Caputi  Chris Gibson  Carol Farbotko  Lesley Head  Nick Gill 《The Australian geographer》2012,43(1):51-74

This paper presents a framework for analysing which households are doing ‘their bit’ for sustainability in an era of climate change, using a two-stage cluster analysis of sustainable household capabilities. The framework segments households by their reported level of commitment to ‘pro-sustainability’ practices common to conventional government policies. Results are presented from a large-scale survey of Wollongong households, New South Wales, Australia. Results illustrate the importance of approaching household sustainability through everyday practices. Attention is drawn to the wide variation in participation in specific household sustainability practices. Investigation into sustainable household capability by household segments shows the limits of even the most committed households. Results show the importance of socio-cultural contexts in differentiating sustainable household capabilities—with women, suburban-detached households and lower income segments of the population ultimately doing most of the work of being sustainable.  相似文献