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361.
362.
Seed passage through the gut of vertebrates is critical for endozoochorus seed dispersal because it may influence seed viability and germination capacity. Foxes are important fruit-eaters and presumed seed dispersers in the Chaco ecoregion. We experimentally assessed the seed passage time (SPT) and its effect on seed viability and germination in two fox species (Pseudalopex gymnocercus and Cerdocyon thous) that occur in the Chaco. Passage time was measured using both artificial seeds of three sizes and wild seeds of four native fleshy-fruit species commonly consumed by foxes (Ziziphus mistol, Acacia aroma, Celtis tala, and Syagrus romanzoffiana). The average SPT was 6.8 h for the Pampa fox and 7.7 h for the crab-eating fox. Passage time did not differ either among seeds of different sizes or between fox species. Passage through digestive tract of both fox species did not affect seed survival, whereas germination rate was slightly improved. Our data suggest that both fox species are legitimate seed dispersers of the four species studied, having a positive effect on both germination rate and dispersal distance from the parent plant. 相似文献
363.
Racism has become a fact of life in Australia over the past decade or so, yet there are relatively few studies of its nature or extent, and still fewer on its geography. Using a social constructivist approach, this study draws on a survey of 5056 respondents to investigate attitudes to racism and cultural diversity in New South Wales and Queensland, and of perceptions of out-groups as instances of ‘strangers in our midst’. On racism, results show the presence of a continuum of attitudes ranging from generally tolerant to generally intolerant, a presence which cuts across compositional (social or aspatial) characteristics to emphasise the existence of a distinctive geography, an everywhere different nature to racist and non-racist attitudes which transcends urban–rural and traditional social layers. On the other hand, perceptions of out-groups are not uniformly correlated with presence or absence of cultural diversity. In many cases, the ability to make judgements about significant ‘others’ or out-groups has been shown to relate more to abstract notions of self and national identity, reproduced in public by mainstream news media and political leaders. In particular, it may reflect an Anglo (or Anglo-Celtic) view on nationalism, which is a hallmark of the ‘new racism’: an assimilationist or ethnocultural view of Australian society which is different from the ‘civic nation’ ideal envisaged by multiculturalism. That the geography of attitudes and perceptions people have towards and about different cultural groups is so ‘everywhere different’ has important implications for attempts to address and redress issues of intolerance in Australia. 相似文献
364.
Thomas O. Graff 《The Professional geographer》2006,58(1):54-64
The three largest discount chains, Kmart, Target, and Wal‐Mart, have adopted the supercenter format for expansion. This article examines the locations of and the competition among these supercenters. Wal‐Mart has the greatest number of supercenters and is driving the expansion of the supercenter format. Both Kmart and Target have clustered their supercenters in a small number of metropolitan markets. In contrast to Wal‐Mart and Kmart, Target has focused on a middle‐class rather than a blue‐collar clientele. Now Kmart is struggling following a declaration of bankruptcy. Wal‐Mart has largely defeated its supercenter competitors and now is confronting the major grocery chains for grocery sales. 相似文献
365.
Sven O. Franz Lorenz Schwark Cathrin Brüchmann Burkhard Scharf Ralf Klingel Jon D. Van Alstine Namık Çagatay Umut B. Ülgen 《Journal of Paleolimnology》2006,35(4):715-736
A limnogeological reconnaissance study was carried out on Lake Iznik, located in the southeast of the Marmara region of Turkey,
involving a seismic survey and collection of short sediment cores. This lake is located on the middle branch of the North
Anatolian Fault Zone (NAFZ), a transform plate boundary between the Eurasian and Anatolian Plates. It is, therefore, tectonically
active and offers an opportunity to investigate the interplay of sedimentary and seismo-tectonic processes, as well as climate
change and human impact in the region. Short cores of the three sub-basins, maximum length of 35.5 cm, recovered non-laminated,
blackish clays and silts with varying amounts of biogenic and minerogenic (allochthonous, autochthonous) material, which documented
almost the last 80 years of deposition and environmental history. High sedimentation rates in the deeper core sections are
accompanied by changes in land use (conversion of woodland to farmland) in the northern areas of Lake Iznik, which caused
the deposition of more weathered material (high K/Na ratios) and higher contents of Mn in the lake. A tendency towards eutrophic
conditions within the last 20 years is indicated by high nutrient content (N, TOC, P), decreasing C/N-ratios, and characteristic
diatom and cladoceran associations. Also increased pollution is revealed by higher Pb, Cu, and Zn contents and increased supply
of human and animal faeces (high coprostanol content) during the last two decades. But simultaneous lower sedimentation rates
towards the core tops complicate the reconstruction of recent and past eutrophication and pollution states of Lake Iznik.
This requires an extension of the pilot study and deeper sediment cores, to recover non-anthropogenic influenced sediment
levels. 相似文献
366.
367.
368.
Brian Emmerson James Jackson Dan McKenzie Keith Priestley 《Geophysical Journal International》2006,167(3):1233-1272
369.
370.
The rotation of the solar corona is analyzed using the original database on the brightness of the FeXIV 530.3 nm coronal green line covering six recent activity cycles. The rate of the differential rotation of the corona depends on the cycle phase. In decay phases, there are only small differences in the rotation, which are similar to that of a rigid body. The differences are more significant (though less pronounced than in the photosphere) during rise phases, just before maxima, and sometimes at maxima. The total rate of the coronal rotation is represented as a superposition of two, i.e., fast and slow modes. The synodic period of the fast mode is approximately 27 days at the equator and varies slightly with time. This mode displays weak differences in rotation and is most pronounced in the middle of decay phases. The slow mode is manifested only at high latitudes during the rise phases of activity, and displays a mean period of 31 days. The relative contribution of each mode to the total rotational rate is determined as a function of time and heliographic latitude. These results indicate that the structure of the velocity field in the convective zone must also vary with time. This conclusion can be verified by helioseismology measurements in the near future. 相似文献