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21.
A palaeoecological approach was undertaken to investigate the last 400 years of change in vegetation, fire, nutrient mobility, lake productivity and erosion associated with Aboriginal and European land-use practices in a forested environment in eastern Victoria. Melaleuca ericifolia scrub, although present prior to European settlement, has expanded around Lake Curlip in the last 200 years, primarily due to the action of fire on a forest already weakened by drought. A fern understorey has declined in extent and a more open aspect has developed in the forest. Fire has been a major component of vegetation dynamics in the historical period. Erosion rates were comparatively low and associated with fire during prehistoric times, but after European settlement its increase is more closely related to land clearance and flooding than fire. The response of vegetation to both anthropogenic and natural influences changed during the historical period. Although fire is an integral part of vegetation change, it is not an over-riding effect at Lake Curlip. Drain construction in the swamp has reduced the impact that any accumulation of pasture improvement chemicals may have had on eutrophication of the lake. 相似文献
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Three rare Himyaritic coins found in the territory of the ancient Hadramawt kingdom are published for the first time. Two of the coins bear the name of the king,'Amdan Bayyin, while the third has the name of Tha'ran Ya'ub. 相似文献
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An attempt has been made to relate steatite artifacts to the source of rock from which they were manufactured, using the distribution patterns of rare earth elements. Radiochemical- and instrumental-neutron activation analyses of Shetland steatites suggest that the use of rare earth elements in artifact provenancing may be unreliable. Concentrations of rare earth elements in many Shetland steatites are too low to be measured reliably by a cost effective method. The relative importance of primary igneous and secondary metasomatic processes in controlling steatite rare earth element geochemistry is discussed and geological arguments against the existence of unique rare earth ‘fingerprints’ for steatite are presented. 相似文献
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'Ali Perwāz SR 《Indian journal of history of science》1986,21(4):297-314
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