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61.
The contribution of bioturbation to downslope soil transport is significant in many situations, particularly in the context of soil formation, erosion and creep. This study explored the direct flux of soil caused by Aphaenogaster ant mounding, vertebrate scraping and tree‐throw on a wildfire‐affected hillslope in south‐east Australia. This included the development of methods previously applied to Californian gopher bioturbation, and an evaluation of methods for estimating the volume of soil displaced by tree‐throw events. All three bioturbation types resulted in a net downslope flux, but any influence of hillslope angle on flux rates appeared to be overshadowed by environmental controls over the spatial extent of bioturbation. As a result, the highest flux rates occurred on the footslope and lower slope. The overall contribution of vertebrate scraping (57.0 ± 89.4 g m?1 yr?1) exceeded that of ant mounding (36.4 ± 66.0 g m?1 yr?1), although mean rates were subject to considerable uncertainty. Tree‐throw events, which individually cause major disturbance, were limited in their importance by their scarcity relative to faunalturbation. However, tree‐throw might be the dominant mechanism of biotic soil flux on the mid‐slope provided that it occurs at a frequency of at least 2–3 events ha?1 yr?1. Although direct biotic soil flux appears to be geomorphologically significant on this hillslope, such transport processes are probably subordinate to other impacts of bioturbation at this site such as the enhancement of infiltration following wildfire. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
62.
T.G. Measham L. BrakeC.J. Robinson S. LarsonC. Richards T.F. Smith 《Journal of Arid Environments》2011,75(10):968-973
The management of dryland environments involves the interaction of multiple government agencies and citizens, and is required to respond to a wide range of responsibilities and aspirations for a given region. This paper focuses on the characteristics of engagement between management agencies and citizens in a dryland region, presented here as a series of success factors. These factors are based on empirical research carried out in the Lake Eyre Basin in Australia, one of the world’s largest inwardly draining basins. The results reinforce generic and dryland-specific factors supporting successful community engagement. The former, such as building trust, working in partnership, supporting community champions, and maintaining transparency, are necessary but insufficient for achieving successful community engagement in the case study region. In addition, community engagement in the case study region also required respecting the extreme conditions and extraordinary variability of the Basin and committing to longer timeframes even if the outcomes of community engagement are slow to accrue, in order to take advantage of opportunities in more prosperous times. 相似文献
63.
The Çöpler epithermal Au deposit and related subeconomic porphyry Cu–Au deposit is hosted by the middle Eocene Çöpler–Kabata? magmatic complex in central eastern Anatolia. The intrusive rocks of the complex were emplaced into Late Paleozoic–Mesozoic metamorphosed sedimentary basement rocks near the northeastern margin of the Tauride-Anatolide Block. Igneous biotite from two samples of the magmatic complex yielded 40Ar/39Ar plateau ages of 43.75?±?0.26 Ma and 44.19?±?0.23, whereas igneous hornblende from a third sample yielded a plateau age of 44.13?±?0.38. These ages closely overlap with 40Ar/39Ar ages of hydrothermal sericite (44.44?±?0.28 Ma) and biotite (43.84?±?0.26 Ma), and Re–Os ages from two molybdenite samples (44.6?±?0.2 and 43.9?±?0.2 Ma) suggesting a short-lived (<1 my) magmatic and hydrothermal history at Çöpler. No suitable minerals were found that could be used to date the epithermal system, but it is inferred to be close in age to the precursor porphyry system. The Çöpler–Kabata? intrusive rocks show I-type calc-alkaline affinities. Their normalized trace element patterns show enrichments in large ion lithophile and light rare earth elements and relative depletions in middle and heavy rare earth elements, resembling magmas generated in convergent margins. However, given its distance from the coeval Eocene Maden–Helete volcanic arc, the complex is interpreted to be formed in a back-arc setting, in response to Paleocene slab roll-back and upper-plate extension. The tectonomagmatic environment of porphyry-epithermal mineralization at Çöpler is comparable to some other isolated back-arc porphyry systems such as Bajo de la Alumbrera (Argentina) or Bingham Canyon (USA). 相似文献
64.
A reconnaissance traverse across Victoria yields 160 K‐Ar dates on igneous rocks from 94 localities. These are supplemented by Rb‐Sr dating in critical cases, and major‐element analyses (some new) on a proportion of the samples. All dates quoted in text and tables, new and previously‐published, have been revised in terms of the latest decay‐constant conventions. The dates range from Early Ordovician (480 Ma) in the west to Late Devonian (360 Ma) among the high‐level intrusives of Central Victoria. The relatively complex age pattern, and the petrochemical character of the rocks, are compared with the published chronology of neighbouring States, and are interpreted in terms of a long‐duration regime of westwards compression, which began in the deformations of the Adelaide System of South Australia, and continued until the Mid‐Devonian Tabberabberan Movement. 相似文献
65.
James U.L. Baldini Frank McDermott Dirk L. Hoffmann David A. Richards Nicholas Clipson 《Earth and Planetary Science Letters》2008,272(1-2):118-129
Cave air PCO2 at two Irish sites varied dramatically on daily to seasonal timescales, potentially affecting the timing of calcite deposition and consequently climate proxy records derived from stalagmites collected at the same sites. Temperature-dependent biochemical processes in the soil control CO2 production, resulting in high summer PCO2 values and low winter values at both sites. Large Large-amplitude, high-frequency variations superimposed on this seasonal cycle reflect cave air circulation. Here we model stalagmite growth rates, which are controlled partly by CO2 degassing rates from drip water, by considering both the seasonal and high-frequency cave air PCO2 variations. Modeled hourly growth rates for stalagmite CC-Bil from Crag Cave in SW Ireland reach maxima in late December (0.063 μm h− 1) and minima in late June/early July (0.033 μm h− 1). For well-mixed ‘diffuse flow’ cave drips such as those that feed CC-Bil, high summer cave air PCO2 depresses summer calcite deposition, while low winter PCO2 promotes degassing and enhances deposition rates. In stalagmites fed by well-mixed drips lacking seasonal variations in δ18O, integrated annual stalagmite calcite δ18O is unaffected; however, seasonality in cave air PCO2 may influence non-conservative geochemical climate proxies (e.g., δ13C, Sr/Ca). Stalagmites fed by ‘seasonal’ drips whose hydrochemical properties vary in response to seasonality may have higher growth rates in summer because soil air PCO2 may increase relative to cave air PCO2 due to higher soil temperatures. This in turn may bias stalagmite calcite δ18O records towards isotopically heavier summer drip water δ18O values, resulting in elevated calcite δ18O values compared to the ‘equilibrium’ values predicted by calcite–water isotope fractionation equations. Interpretations of stalagmite-based paleoclimate proxies should therefore consider the consequences of cave air PCO2 variability and the resulting intra-annual variability in calcite deposition rates. 相似文献
66.
Michael P.RICHARDS 《中国科学D辑(英文版)》2009,52(1):85-92
Despite great achievements in the origins of domestic pigs made by the methods of zooarchaeology and molecular biology, how
to scientifically distinguish the domesticated pigs from wild boars during the early stage of pig domestication is still poorly
understood. Compared to wild boar’s diets which come from the natural environment, the diets of domestic pigs are more easily
influenced by human feeding activities. Therefore, in principle, exploration of the dietary differences among pigs and under-standing
the impact on pig diets fed by humans can have great potential to differentiate between wild boars and domesticated pigs.
To reveal dietary differences among pigs and distinguish the domesticated pigs from wild boars based on comparison with the
diets of humans and other animals, we analyzed the carbon and nitrogen stable isotopes of human bones from Xiaojingshan Site
and animal bones from Yuezhuang Site, both of which belong to Houli Culture in Shandong Province and date to about 8500-7500
years ago. The mean δ13C value ((−17.8 ± 0.3)‰) and δ15N value ((9.0±0.6)‰) in human collagen indicate that although millet agriculture began it was not the main subsistence strategy
as millets are typical of C4 plants and that humans made a living mainly by gathering, hunting or raising some domesticated animals. The δ13C value (−16.1‰) and δ15N value (6.9‰) in the bovine suggest that C3 plants were dominant in its diet with some C4 plants complemented. The fish has lower δ13C value (−24.9‰) and higher δ15N value (8.8‰) than the bovine, which is the characteristic of the isotopic values from Eurasian freshwater fish. Based on
the differences in carbon and nitrogen isotope values, the pigs can be divided into three groups. A group, composed of two
pigs, has low δ13C values (−18.1‰, −20.0‰) and low δ15N values (4.7‰, 6.0‰). B group, only one pig, has the highest δ13C value (−10.6‰) and mediate δ15N value (6.4‰). As for the C group, also only one pig, low δ13C value (−19.0‰) and the highest δ15N value (9.1‰) are observed. Previous studies on the stable isotopes from modern or ancient wild boars’ bones have suggested
that C3 plants are predominated in their diets and that their δ15N values are close to those in herbivores and far from those in carnivores. Based on the comparison with the isotope values
from humans, the wild boars and the domestic pigs from Xipo Site in Henan 6000-5500 years ago and Kangjia Site in Shaanxi
4500-4000 years ago, we conclude that A pig group belongs to wild boars while B and C groups can be attributed to domesticated
pigs.
Supported by Max-Planck Society and Chinese Academy of Sciences, Knowledge Innovation Program of the Chinese Academy of Sciences
(Grant No. KJCX3.SYW.N12), National Natural Science Foundation of China (Grant No. 40702003) and President Funding of Graduate
University of Chinese Academy of Sciences 相似文献
67.
D.L. Tucker S. Kent M.W. Richmond J. Annis J.A. Smith S.S. Allam C.T. Rodgers J.L. Stute J.K. Adelman‐McCarthy J. Brinkmann M. Doi D. Finkbeiner M. Fukugita J. Goldston B. Greenway J.E. Gunn J.S. Hendry D.W. Hogg S.‐I. Ichikawa
. Ivezi G.R. Knapp H. Lampeitl B.C. Lee H. Lin T.A. McKay A. Merrelli J.A. Munn E.H. Neilsen H.J. Newberg G.T. Richards D.J. Schlegel C. Stoughton A. Uomoto B. Yanny 《Astronomische Nachrichten》2006,327(9):821-843
The photometric calibration of the Sloan Digital Sky Survey (SDSS) is a multi‐step process which involves data from three different telescopes: the 1.0‐m telescope at the US Naval Observatory (USNO), Flagstaff Station, Arizona (which was used to establish the SDSS standard star network); the SDSS 0.5‐m Photometric Telescope (PT) at the Apache Point Observatory (APO), NewMexico (which calculates nightly extinctions and calibrates secondary patch transfer fields); and the SDSS 2.5‐m telescope at APO (which obtains the imaging data for the SDSS proper). In this paper, we describe the Monitor Telescope Pipeline, MTPIPE, the software pipeline used in processing the data from the single‐CCD telescopes used in the photometric calibration of the SDSS (i.e., the USNO 1.0‐m and the PT). We also describe transformation equations that convert photometry on the USNO‐1.0m u ′g ′r ′i ′z ′ system to photometry the SDSS 2.5m ugriz system and the results of various validation tests of the MTPIPE software. Further, we discuss the semi‐automated PT factory, which runs MTPIPE in the day‐to‐day standard SDSS operations at Fermilab. Finally, we discuss the use of MTPIPE in current SDSS‐related projects, including the Southern u ′g ′r ′i ′z ′ Standard Star project, the u ′g ′r ′i ′z ′ Open Star Clusters project, and the SDSS extension (SDSS‐II). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
68.
69.
Full-orbit H observations have been analyzed to determine the two-dimensional distribution of the circumstellar gas in the four short-period Algols, U Sge, U CrB, RS Vul, and SW Cyg. In these systems, the gas stream resulting from Roche-lobe overflow directly impacts the mass-gaining star and feeds material into a structure known as a transient accretion disk. The accretion regions observed in these systems include a transient accretion disk that at least partially surrounds the mass gainer, the gas stream, and possibly a chromospheric component associated with the magnetically active cool star. 相似文献
70.