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KEVIN TIMONEY GEORGE PETERSON PAT FARGEY MURRAY PETERSON STEVE McCANNY ROSS WEIN 《Climatic change》1997,35(4):463-483
A historic record of spring ice-jam floods of the Peace-Athabasca Delta was analyzed for the years 1826–1995. The temporal pattern of flooding is non-random. The likelihood of a flood following a flood, or a non-flood following a non-flood, is greater than expected by chance. Probability analysis of flood occurrence reveals that the period 1860–1880 was a time of unusually few floods, and the period 1915–1950 was a time of unusually frequent floods. The long-term flood frequency is 1 flood in 6.25 years. Changes in flood frequency over the record reveal a pattern of oscillation described by a sine-based model that is correlated with the long-term (Gleissberg) cycle of solar activity. Monte Carlo simulation was used to test a Bennett Dam Model and a Cyclic Model. The Bennett Dam Model is unlikely to have generated the observed flood history (p=0.04). The observed flood history shows a better fit to the Cyclic Model (p=0.65). No correlations between floods and ENSO cold or warm events was detected. The most recent wet period began about 1900 and ended in the early 1960's prior to completion of the W. A. C. Bennett Dam in British Columbia. As independent corroboration of climatically-driven changes in flood frequency we present three additional lines of evidence. The pattern of annual muskrat returns (95 year record) reveals both 10 year cycles and long-term patterns that agree well with the observed flood cycle. The annual area burned in Wood Buffalo National Park is inversely related to flood occurrence. Incised channels and dendritic drainage patterns in the bed of Lake Mamawi provide probable evidence of a previous dry period in the delta. Climatic change or oscillation likely underlies the drying trend observed in recent decades in the Peace-Athabasca Delta. 相似文献
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ABSTRACT. The conceptualization of alien invasive species conflates two axes of variability that have become unhelpfully blurred. The nativeness/alienness axis refers to the presumed belonging of a species in ecological or social space. Invasiveness refers to the behavior of the species in question, particularly in relation to other species. The overlay of nation introduces further variability. Teasing these axes apart is important for more effective environmental management. We examine these concepts using two influential forms of ecological knowledge: the biogeographical and ecological literature and the vernacular experiences of suburban backyarders. Three case studies, the invasive native Pittosporum undulatum and two invasive exotics, Lantana camara and Cinnamomum camphora, illustrate the complex and contingent nature of human interactions with such species and the potential for human interactions to increase and/or reduce the propagation of plant species. 相似文献
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PAT HUTCHINGS 《海洋学报(英文版)》1986,5(4):603-613
INTRODUCTION Cryptofaunal communities consist of the animals and plants living within dead coral.As a very large part of a coral reef is composed of dead coral,the biomasses of crypto-faunal communities on a reef must be significant.And as many of the cryptofaunal animalsreproduce at regular intervals,rates of turnover of the community are also high and thusare major contributors to the productivity of coral reefs.Grassle(1973)collected a 4.7 相似文献
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ABSTRACT. Gardens have been an important site of environmental engagement in Australia since the British colonization. They are places where immigrant people and plants have carried on traditions from their homelands and have worked out an accommodation with new social and biophysical environments. We examined the backyard gardens of three contemporary migrant groups—Macedonian, Vietnamese, and British born—in suburban Australia and a group of first‐generation Australians with both parents born overseas. In Macedonian backyards, emphasis was strong on the production of vegetables; in Vietnamese backyards, on herbs and fruit. British backyards were more diverse, some focusing on non‐native ornamental flowers and others favoring native plants. The cohesiveness of the respective groups was partly an artifact of our sampling strategy. The Macedonian and Vietnamese migrants shared an affinity for productive, humanized landscapes that reflected their rural, subsistence backgrounds and crossed over into their attitudes toward the broader environment and national parks. The rural and village backgrounds help explain why intensive backyard food production has broken down among the next generation in (sub)urban Australia, becoming part of heritage rather than everyday practice. 相似文献
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