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1.
The starting dates of the pre-summer rainy season during historical times （1736- 1911） in Fuzhou and Guangzhou of South China, were determined and reconstructed on the basis of historical documents in the Yu-Xue-Fen-Cun archive, together with observed features of precipitation during the pre-summer rainy season. In addition, starting dates of the pre-summer rainy season from 1953 in Fuzhou and from 1952 in Guangzhou were reconstructed for the instrumental period. These data allowed for analyses of inter-annual and inter-decadal changes in the starting dates of the pre-summer rainy season in South China over the past 300 years. Results show that the mean starting date of the pre-summer rainy season in South China was the first pentad of May; in addition, periodicities in the starting dates of 2-3 years, 10 years, and 40 years were detected during the period 1736-1911, and of 2-3 years, 10 years, and 22 years during the instrumental period. From 1736 to 1911, the earliest starting dates at Fuzhou and Guangzhou both occurred at the fourth pentad of April, while the latest starting dates were at the sixth pentad of May in Fuzhou and the first pentad of June in Guangzhou. During the instrumental period, the earliest and latest starting dates were at the fourth pentad of April and the first pentad of June, respectively, in both Fuzhou during 1953-2010 and Guangzhou during 1952-2010. The maximum difference between neighboring decades during 1736-1911 was 2.2 and 1.6 pentads in Fuzhou and Guangzhou, respectively, and during the instrumental period it was 2.5 and 2.4 pentads in Fuzhou and Guangzhou, respectively. 相似文献
2.
Sedimentation rates in the Wanggang salt marshes, Jiangsu 总被引：1，自引：0，他引：1
WANGAijun GAOShu JIAJianjun PANShaoming 《地理学报(英文版)》2005,15(2):199-209
1 IntroductionLand-ocean interaction in coastalzone is one of the key m atters of the International G eosphereand Biosphere Program (IG BP). The key problem s of the second phase in the next decadeinclude the m aterial cycle, the system evolution process … 相似文献
3.
In order to study the element contents and distribution of various mosses collected in the Antarctica, we analyzed the heavy elements of 3 species of Polytri-chum in the Fildes Peninsula, P. alpinum, P. juniperinum and P. alpestre, by synchrotron radiation X-ray fluorescence ( SR-XRF). The result shows that the elements, such as K, Ca, Mn, Fe, Cu, Zn and Sr, are nearly the same in Potytrichum. The peak intensity of K is higher than that of Ca, and the peak intensity of Ca is higher than that of Fe in P. alpinum. In P. juniperinum, the peak intensity of K is higher than that of Ca, and the peak intensity of Ca is close to that of Fe. The peak intensity of K is nearly equal to those of Ca and Fe in P. alpestre. Therefore, the habitats of 3 species of Polytrichum are similar in the Fildes Peninsula. By XRF analyzing of different parts of P. alpestre, we found that the peak intensities of relative concentration of elements are obviously different. The peak intensity of K in apical-bud is the highest in orga 相似文献
4.
S.J. Davies S.E. Metcalfe A.B. MacKenzie A.J. Newton G.H. Endfield J.G. Farmer 《Journal of Paleolimnology》2004,31(1):77-98
Lago de Zirahuén (19° 26 N, 101° 44 W) lies within a montane basin in highland Michoacán, Mexico at 2075 m a.s.l. The lake basin has high recreational value and is promoted as a tourist attraction. Four short (<1 m), sediment–water interface cores were used to investigate Late Holocene environmental change. The cores span approximately the last 1000 years, based on 210Pb dating, AMS 14C dating and tephrochronology. Cesium-137, Americium-241 and tephra layers from Volcan Paricutín (AD 1943–1952) and Volcan Jorullo (AD 1759–1774) provide independent age markers. Cores were analysed for diatoms, magnetic susceptibility and heavy metals (iron, lead, manganese, copper and zinc). Drier climate around 1000 years BP is tentatively inferred from the diatom assemblage and is concordant with other regional records. Increased soil erosion between ca. AD 1100 and AD 1550 may be associated with Pre-Hispanic settlement in the basin, but there is no archaeological evidence to support this. A period of catchment stability occurred during the early Colonial Period, ca. AD 1550–1750. The dramatic decline in the indigenous population following the Spanish Conquest in 1521 may have promoted vegetation recovery on the basin slopes. After the mid-18th century, a significant change in diatom species composition is observed along with an increase in soil erosion, as inferred from the magnetic susceptibility profile. Concentrations of copper and lead also increased. These changes are associated with the establishment of a copper smelting industry in the basin and increased Colonial agricultural development. Recently, tourist developments and commercial agriculture have impacted on the basin. The diatom flora has changed dramatically in the last 20 years, apparently in response to the onset of cultural eutrophication. The palaeoenvironmental evidence suggests that the lake is responding rapidly to land use intensification in the basin, which may have implications for future developments. 相似文献
5.
This article presents a large-scale analysis of the trajectories of individual cities and regions in the world city network between 2000 and 2012. The methodology used to examine cities' evolving network centralities is based on advanced producer services firms “interlocking” cities through their worldwide distribution of offices. We do not limit our analysis to a limited set of putative world cities, but incorporate 157 cities from all world regions into this global urban analysis. Absolute and relative measures of change are developed to reveal the major dimensions of change. The most notable finding is that significant connectivity gains have been limited to a small set of cities (Dubai, Shanghai, Beijing, and Moscow in particular) in the face of persisting core–periphery patterns at the level of the global economy, with New York and London remaining firmly at the apex. At the same time, overall levels of connectivity in the world city network have clearly risen, suggesting an increasingly integrated network. In geographical terms, a west-to-east shift is discernible, albeit uneven. 相似文献
6.
Michael Gentile 《Urban geography》2013,34(10):1455-1464
ABSTRACTDespite the recent planetary turn that has swept through gentrification research, the theoretical barycentre remains pegged to a few strongholds located in the global north-west. Against this background, this essay offers a provincialized account of three gentrification-like trends – tele-urbanization, Schengtrification and colour-splashing – which are currently taking place in Tbilisi, Riga and Kiev. It is proposed that these processes are supported by an underlying logic that is not pinned to these cities’ specific (“post-communist”) contexts, raising questions about the avowedly universal validity of theories of gentrification stemming from the global northwest, and particularly those developed within the more critical scholarly tradition. 相似文献
7.
Nicholas L. Balascio Stephen Wickler 《Norsk geografisk tidsskrift. Norwegian journal of geography》2018,72(3):146-160
Integrated archaeological and paleoenvironmental investigations provide long-term perspectives on human–environment interactions. In the North Atlantic region, early human settlements were established in marginal agricultural environments and were susceptible to various environmental stressors. The Lofoten Islands have had an important role in the history of this region, particularly during the Iron Age, when Lofoten developed from pioneering agricultural settlements to a prominent node of power and trade under Viking chieftains. Iron Age developments in Lofoten were concurrent with significant natural environmental changes, including variations in climate and sea level. However, there has not been a comprehensive investigation of their influence on early settlements. The purpose of the study is to review Iron Age cultural developments in Lofoten using published archaeological data and paleoenvironmental records of past climate and sea-level change, and to present specific examples of the intersection of early human development and natural environmental changes. The findings show that climate changes probably influenced agricultural phases and that relative sea-level variations had important impacts on maritime developments. In conclusion, the findings demonstrate that human–environment interactions were significant factors in Lofoten’s history and the authors suggest specific areas for future research. 相似文献
8.
WANG Xiaodi LI Yongsheng ZHANG Lijuan SONG Shuaifeng PAN Tao REN Chong TAN Yulong 《地理学报(英文版)》2022,32(2):225-240
With the advent of climate change,winter temperatures have been steadily in-creasing in the middle-to-high latitudes of the world.However,we have not found a corre-sponding decrease in the number of extremely cold winters.This paper,based on Climatic Research Unit (CRU) re-analysis data,and methods of trend analysis,mutation analysis,correlation analysis,reports on the effects of Arctic warming on winter temperatures in Hei-longjiang Province,Northeast China.The results show that:(1) during the period 1961-2018,winter temperatures in the Arctic increased considerably,that is,3.5 times those of the Equator,which has led to an increasing temperature gradient between the Arctic and the Equator.An abrupt change in winter temperatures in the Arctic was observed in 2000.(2) Due to the global warming,an extremely significant warming occurred in Heilongjiang in winter,in particular,after the Arctic mutation in 2000,although there were two warm winters,more cold winters were observed and the interannual variability of winter temperature also increased.(3)Affected by the warming trend in the Arctic,the Siberian High has intensified,and both the Arctic Vortex and the Eurasian Zonal Circulation Index has weakened.This explains the de-crease in winter temperatures in Heilongjiang,and why cold winters still dominate.Moreover,the increase in temperature difference between the Arctic and the Equator is another reason for the decrease in winter temperatures in Heilongjiang. 相似文献
9.
Karin Holmgren Jan Risberg Johan Freudendahl Mussa Achimo Anneli Ekblom Joao Mugabe Elin Norstr?m Sandra Sitoe 《Journal of Paleolimnology》2012,48(2):311-322
Stratigraphic variations in diatom composition and phytolith abundance in a sediment core from a small, hydrologically isolated waterbody, Lake Nhauhache, Mozambique, provide evidence of water-level fluctuations over the past ~2,300?years. Ten AMS radiocarbon dates on bulk sediment samples show that the lake came into existence about 2,300?years ago and that it has dried out since then, but only for brief time periods. Changes in the diatom assemblage composition indicate that lake level fluctuated in response to shifting humidity conditions. The changes reflect wetter conditions ca. 300 BC?CAD 800, more variable conditions between AD 800 and 1150, a distinct dry phase within the time span AD 1150?C1700 and a return thereafter to more humid conditions until present. There is general agreement between the Lake Nhauhache record and other records from the Southern Hemisphere summer rainfall region. This suggests that sediments from small interdunal lakes, which are abundant along the coast of southern Africa, provide reliable, regional paleoenvironmental information about an area from which more such data are needed. 相似文献
10.
Using the observed data from 184 stations over the Yunnan-Guizhou Plateau (YGP) from 1961 to 2005, the long-term trends in sunshine duration, cloud amount, dry visibility (Vd), dry extinction, and water vapor over the YGP are analyzed. The results show that 85% of the stations recorded shortening annual sunshine duration, with the decrease rates between ?12.2 and ?173.7 h/10yr. Results of Mann-Kendall tests indicate that, among the stations with decreasing sunshine duration, 63.7% of them experienced an abrupt change that started in the 1970s and peaked in the 1980s. This decreasing trend has reversed in the early years of the 21st century. The cloud cover and water vapor content in the mid and lower levels over the YGP had no obvious changes during the study period. The annual averages of Vd declined from 34 km in the 1960s to 27 km at present. The annual mean dry extinction coefficient trended upward, from 0.176 to 0.190, on the YGP from 1980 to 2005. Analyses of cloud cover, water vapor, atmospheric visibility, and dry extinction coefficient revealed that emitted tropospheric aerosols (including air pollutants) resulting from increased energy consumption over the YGP could be a major factor influencing the reductions of sunshine duration and atmospheric visibility. 相似文献
11.
Ramesh Dhussa 《The Professional geographer》2013,65(2):312-313
In this article, we first replicate and then adapt an existing index of social vulnerability to hazard developed for the United States to a non-U.S. context. We construct indexes for Norwegian municipalities, describe the adjustment process, and compare the replicated and adapted assessments. Our results indicate only a moderate correlation between the replicated and adapted vulnerability indexes and for several municipalities the difference between the indexes is considerable. This demonstrates that context matters and that indexes of vulnerability need to be adapted rather than replicated. To facilitate such adaption processes, we identify three types of accommodation: conceptual, technical, and geographic. 相似文献
12.
Supported by MSS images in the mid and late 1970s,TM images in the early 1990s and TM/ETM images in 2004,grassland degradation in the＂Three-River Headwaters＂region （TRH region）was interpreted through analysis on RS images in two time series,then the spatial and temporal characteristics of grassland degradation in the TRH region were analyzed since the 1970s.The results showed that grassland degradation in the TRH region was a continuous change process which had large affected area and long time scale,and rapidly strengthen phenomenon did not exist in the 1990s as a whole.Grassland degradation pattern in the TRH region took shape initially in the mid and late 1970s.Since the 1970s,this degradation process has taken place continuously,obviously characterizing different rules in different regions.In humid and semi-humid meadow region,grassland firstly fragmentized, then vegetation coverage decreased continuously,and finally＂black-soil-patch＂degraded grassland was formed.But in semi-arid and arid steppe region,the vegetation coverage decreased continuously,and finally desertification was formed.Because grassland degradation had obviously regional differences in the TRH region,it could be regionalized into 7 zones, and each zone had different characteristics in type,grade,scale and time process of grassland degradation. 相似文献
13.
This article presents some of the findings of a multi-indicator investigation of the history of vegetational changes and land degradation in the Lake Baringo basin, Kenya, East Africa, during the Late Holocene. 14C- and 210Pb-dated record of the lithostratigraphy is used to reconstruct the paleoenvironment in the region of the lake. The stratigraphic record from Lake Baringo reveals the presence of two abrupt dry episodes at ca. AD 1650 and AD 1720 in east Africa that led to drying up of the lake. The record also shows evidence of a third period of desiccation at ca. AD 1880, which resulted in lowering of the lake level and is corroborated by oral tradition from the area. This article shows the potential of how the paleoenvironmental record can be combined with the historical record to understand East Africa's paleoenvironment. 相似文献
14.
In this paper, stable isotope(δ~(18)O, δD) investigations were completed in ground ice from a deep borehole in the Beiluhe Basin on northern Qinghai-Tibet Plateau to unravel the isotopic variations of ground ice and their possible source water. The δ~(18)O and δD of ground ice show distinctive characteristics compared with precipitation and surface water. The near-surface ground ice is highly enriched in heavier isotopes(δ~(18)O and δD), which were gradually depleted from top to bottom along the profile. It is suggestive of different origin and ice formation process. According to isotopic variations, the ice profile was divided into three sections: the near-surface ground ice at 2.5 m is frozen by the active-layer water which suffered evaporation. It is possible that ground ice between 3 and 4.2 m is recharged by the infiltration of snowmelt. From 5 to 6 m, the ground ice show complex origin and formation processes. Isotopic variations from 6 to 11.1 m and 20.55 m indicate different replenishment water. The calculated slope of freezing line(S=6.4) is larger than the experimental value(5.76), and is suggestive of complex origin and formation process of ground ice. 相似文献
15.
Heike Jöns 《The Professional geographer》2017,69(4):670-682
This article examines the role of early female academics at the University of Cambridge in the production and dissemination of knowledge between 1926 and 1955. A statistical comparison of women's use of academic leave of absence with that of their male colleagues reveals that, across disciplines, women were less integrated into (inter)national knowledge networks and thus less visible in their epistemic communities than men because women focused their academic leaves more on research, rarely attended conferences, traveled overseas less often than men, and went more frequently to destinations within Europe than the United States as the new economic hegemon. Biographical case studies of these early female academics demonstrate the importance, variously, of their upper middle-class background, academic excellence, and familial and nonfamilial patronage in developing their careers, overcoming multiple hurdles, and producing intellectual contributions of equal quality to that of their male peers. Conceptually, this article calls for the inclusion of academic travelers from disciplines other than geography into feminist histories of geographical knowledge and argues that rather than stereotyping gender differences, greater comparative research on the experiences of female and male academics is needed to understand the mechanisms of gender inequality within the university. 相似文献
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17.
Seed germination was compared among wild, in situ-managed (wild plants let standing in areas cleared for agriculture), and cultivated populations of the columnar cacti Stenocereus pruinosus, Polaskia chichipe, Myrtillocactus schenckii, and Polaskia chende, species representing a gradient from higher to lower management intensity, respectively. We hypothesized that seeds from cultivated populations have higher water requirements to germinate than seeds of other populations, and that such difference is stronger in species more intensely managed. Germination was evaluated under water potential treatments at 0.0, ?0.2, and ?0.4 MPa. Interspecific differences were identified; germination rates markedly decreased in S. pruinosus and P. chichipe as water potential reduced. M. schenckii seeds germinated better at ?0.2 MPa, and seeds of P. chende in all treatments. Seed germination of wild and cultivated populations was similar in all cases and, therefore, at the population level domestication does not appear to have influenced variations in germination of the studied cacti species. However, experiments to test whether germination of seeds from plants with clear signs of domestication differs with seeds from other plants and their differential germination and seedling survival in wild, in situ-managed and cultivated environments could help to precise the influence of domestication on these plants. 相似文献
18.
The formal opportunity to learn geography in the United States is unevenly distributed across space, creating possible geography deserts. Data on the number of exams taken in Advanced Placement Human Geography (APHG) and bachelor’s degrees earned in geography are mapped at the state and regional scales. Normalized rates are ranked and grouped into quintiles. For APHG exams, states in the southeastern region of the United States are in the uppermost quintiles while states in the northeastern region are in the lowermost quintiles. The pattern for bachelor’s degrees in geography is somewhat the spatial inverse of that for APHG. 相似文献
19.
《The Journal of geography》2012,111(6):217-225
Abstract This article situates geospatial technologies as a constructivist tool in the K-12 classroom and examines student experiences with real-time authentic geospatial data provided through a hybrid adventure learning environment. Qualitative data from seven student focus groups demonstrate the effectiveness of using real-time authentic data, peer collaboration, and geospatial technologies in learning geography. We conclude with recommendations about geospatial technology curricula, geospatial lesson design, providing preservice teachers with geographic technological pedagogical content knowledge, and encouraging further research to investigate the impact, affordances, and pedagogical implications of geospatial technologies and data in the K–12 classroom. 相似文献