Astrocytoma arising at the optic disc in a dog.          下载免费PDF全文

J Caswell  C Curtis    B Gibbs 《The Canadian veterinary journal. La revue veterinaire canadienne》1999,40(6):427-428

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AN EVALUATION OF AN ELECTRONIC INSTRUMENT FOR PASTURE YIELD ESTIMATION     

H. L. Back  F. E. Alder  † B. G. Gibbs 《Grass and Forage Science》1969,24(2):168-172

In situations where yield is variable but in which it is not desirable to take too large a cut sample, e.g. on grazed plots, the pasture-yield estimator can be used to improve the accuracy of yield estimation. An outline of the theory and examples of the use of the method are given.  相似文献   

Global consequences of land use   总被引：83，自引：0，他引：83  

Foley JA  Defries R  Asner GP  Barford C  Bonan G  Carpenter SR  Chapin FS  Coe MT  Daily GC  Gibbs HK  Helkowski JH  Holloway T  Howard EA  Kucharik CJ  Monfreda C  Patz JA  Prentice IC  Ramankutty N  Snyder PK 《Science (New York, N.Y.)》2005,309(5734):570-574

Land use has generally been considered a local environmental issue, but it is becoming a force of global importance. Worldwide changes to forests, farmlands, waterways, and air are being driven by the need to provide food, fiber, water, and shelter to more than six billion people. Global croplands, pastures, plantations, and urban areas have expanded in recent decades, accompanied by large increases in energy, water, and fertilizer consumption, along with considerable losses of biodiversity. Such changes in land use have enabled humans to appropriate an increasing share of the planet's resources, but they also potentially undermine the capacity of ecosystems to sustain food production, maintain freshwater and forest resources, regulate climate and air quality, and ameliorate infectious diseases. We face the challenge of managing trade-offs between immediate human needs and maintaining the capacity of the biosphere to provide goods and services in the long term.  相似文献   

High and dry in days gone by: Life-history theory predicts Appalachian mountain stream fish assemblage transformation during historical drought     

Eric W. Malone  Joshuah S. Perkin  William Keith Gibbs  Matthew Padgett  Matthew Kulp  Stephen E. Moore 《Ecology of Freshwater Fish》2022,31(1):29-44

Understanding the ecological dimensions of drought is critical for predicting how humans and nature will be affected by the expected increased prevalence of drought in the future. We tested life-history-based predictions for fish assemblage responses to drought using retrospective analysis of long-term (1986–2003) fish surveys from two streams in the Appalachian Mountains of North America. We hypothesised that (1) fish assemblage composition would correlate with wet and dry hydrologic conditions as assemblages fluctuated within a loose equilibrium and (2) life-history traits of fishes would correlate with dry versus wet periods such that opportunistic life-history strategists would dominate during drought. Results showed fish assemblage changes in Little River and Cataloochee Creek correlated with drought severity measured one year prior to fish surveys. Fish assemblages at all three sampling sites in Little River and two sites in Cataloochee Creek fluctuated within a loose equilibrium, while the remaining two sites in Cataloochee Creek indicated directional change. Life-history traits for fishes in Cataloochee Creek correlated with one-year time lag fluctuations in drought caused by opportunistic species being dominant during drought and periodic/equilibrium species dominant during wet periods. Time series plots of fish abundances aggregated by life-history strategy revealed dominance of opportunistic species emerged at the onset of a multi-year drought spanning 1998–2004, particularly for the two sites undergoing directional change. Our work provides empirical evidence for theoretical linkages between life history and environmental fluctuations and can ultimately be used to predict stream fish community response to future drought regimes.  相似文献