The aftermath of megafaunal extinction: ecosystem transformation in Pleistocene Australia     

Rule S  Brook BW  Haberle SG  Turney CS  Kershaw AP  Johnson CN 《Science (New York, N.Y.)》2012,335(6075):1483-1486

Giant vertebrates dominated many Pleistocene ecosystems. Many were herbivores, and their sudden extinction in prehistory could have had large ecological impacts. We used a high-resolution 130,000-year environmental record to help resolve the cause and reconstruct the ecological consequences of extinction of Australia's megafauna. Our results suggest that human arrival rather than climate caused megafaunal extinction, which then triggered replacement of mixed rainforest by sclerophyll vegetation through a combination of direct effects on vegetation of relaxed herbivore pressure and increased fire in the landscape. This ecosystem shift was as large as any effect of climate change over the last glacial cycle, and indicates the magnitude of changes that may have followed megafaunal extinction elsewhere in the world.  相似文献   

Aggregation of a soil with different cropping histories following the addition of organic materials     

C.W. Watts  W.R. Whalley  D.J. Longstaff  R.P. White  P.C. Brook  A.P. Whitmore 《Soil Use and Management》2001,17(4):263-268

Abstract. Soil management studies show that intensive arable agriculture can lead to a decline in both organic matter levels and the stability of the soil structure. It is a priority to understand how soil structure responds when fresh organic materials are added to poor quality degraded arable soils. This is of particular interest because of its implication for carbon sequestration. We investigate whether the addition of organic materials can form stable aggregates in a degraded soil. Grass or peat residues were added to samples of soil obtained from the continuous grassland and arable plots of the long-term experiment at highfield, IACR-Rothamsted (UK) and incubated at 2° and 24°C, for upto 8 weeks at -5 kPa. At 1 day and at 2, 4 and 8 weeks the soil was slaked in de-ionised water and the aggregate size distributions were measured. The data was used to calculate mean weight diameters (MWD). The treatments with added grass showed increased aggregated relative to the control; the treatments with added peat did not. At 24°C the value of MWD increased with the incubation period, but at 2°C there was no further aggregation beyond week two. Respiration measurements were made and the samples that released the most CO₂ were also those which re-aggregated the most. This suggests that the process of aggregation is microbiologically mediated. The results are discussed within the broader context of the implications of soil organic matter content on soil management.  相似文献   

Spectroscopy application for soil differentiation in urban landscape     

Daniella Kopel  Anna Brook  Lea Wittenberg  Dan Malkinson 《Journal of Soils and Sediments》2016,16(11):2557-2567

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Assessing the impact of small dams on vector borne disease   总被引：1，自引：0，他引：1  

R. C. Carter  J. M. Brook  J. M. Jewsbury 《Irrigation and Drainage Systems》1990,4(1):1-16

The creation of vector habitats and the increased incidence of malaria, schistosomiasis and other diseases following the construction of surface water reservoirs in hot climates are well known. Little attempt has been made however to quantify the health impact of such water resource development projects. It has been suggested recently (Jewsbury & Imevbore 1988) that small dams may pose a greater disease risk than large structures. In view of the fact that small projects are attractive for a number of important reasons (Carter 1989), this conclusion gives rise to some concern.The paper reviews the ecology of the mosquito vectors and the snail intermediate hosts of the major water related diseases, malaria and schistosomiasis. As a result of this review the reservoir surface area from the shore to a depth of 2 m is proposed as a measure of Vector Habitat Potential (VHP). It is then shown how a simple spreadsheet model can be used to quantify the VHP for a proposed reservoir site at any chosen water-level or as a time-series. This reservoir model is demonstrated using data for a proposed dam in Burkina Faso, West Africa. Finally it is shown how the reservoir model must be combined with studies of vector biology and human behaviour in order to quantify the disease risk of any proposed dam site. The full model will enable various sites (large and small) to be compared, or, for a single site, the effects of different water management strategies to be evaluated.  相似文献   

Fundamentals of endodontics.   总被引：1，自引：0，他引：1  

Brook A Niemiec 《Veterinary Clinics of North America: Small Animal Practice》2005,35(4):837-68, vi

Endodontic disease is a highly prevalent (>10% of all dogs) and insidiously painful process that can have significant local and systemic effects. The root canal system is a delicate organ and is prone to inflammation, infection, and partial and complete necrosis. Vital pulp therapy must be performed quickly, gently, and meticulously if it is to be effective. The relatively high rate of failure in direct pulp capping makes regular follow-up radiographs of critical importance to ensure patient health. Once a tooth is dead, there are often no obvious clinical signs; therefore, clinicians must be educated in the diagnosis of the disease processes. Once properly educated, the practitioner must remain vigilant for subtle signs of the disease process. Standard root canal therapy is an effective method of removing the inflammation, infection, and associated discomfort of the endodontically diseased tooth while maintaining its function. Endodontic failure most likely remains hidden unless dental radiology is used. Follow-up radiographs at regular intervals throughout the patient's life are critical for ensuring the long-term success of any endodontic therapy.  相似文献   

Temporal effects of plasmapheresis on serum proteins in horses.     

K G Magdesian  D Brook  S J Wickler 《American journal of veterinary research》1992,53(7):1149-1153

The temporal response of blood and serum proteins to chronic plasmapheresis was determined in 8 horses used in a commercial antibody enterprise. Plasmapheresis of between 4 and 11 L induced significant decreases in total protein, albumin, and IgG values. With the exception of a high hematocrit value for the first postplasmapheresis blood sample, there were no changes in erythrocyte or leukocyte measurements, and no changes in the proportions of serum protein in an electrophoretic profile. Regression equations generated for recovery of proteins after plasmapheresis indicated a return to preplasmapheresis values of total protein and albumin at approximately 1 month. Complications of repeated plasmapheresis were not detected when plasma extractions were done between 7 and 19 times at 30-day intervals.  相似文献   

Citizens' juries give verdict on whether private practice veterinarians should attend unvaccinated Hendra virus suspect horses     

EJ Annand  PA Reid  J Johnson  GL Gilbert  M Taylor  M Walsh  MP Ward  A Wilson  C Degeling 《Australian veterinary journal》2020,98(7):273-279

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Unfolding the diagnosis of subspectacular fluid opacity in a corn snake (Pantherophis guttatus)     

Allison M. Cleymaet  EJ Ehrhart  Miranda J. Sadar  Matthew Johnston  Kathryn Wotman  Michala de Linde Henriksen 《Veterinary ophthalmology》2020,23(4):754-759

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An unusual lightning flash at kennedy space center   总被引：1，自引：0，他引：1  

Uman MA  Beasley WH  Tiller JA  Lin YT  Krider EP  Weidmann CD  Krehbiel PR  Brook M  Few AA  Bohannon JL  Lennon CL  Poehler HA  Jafferis W  Gulick JR  Nicholson JR 《Science (New York, N.Y.)》1978,201(4350):9-16

A lightning flash that struck the 150-meter weather tower at Kennedy Space Center was studied by several research groups using varioul techniques. The flash had unusually large peak currents and a stepped leader of relatively short duration. The charged regions neutralized by the three return strokes were located within a horizontal layer between heights of about 6 and 8 kilometers, where environmental temperatures were about -10 degrees to -20 degrees C. The charge source for the first return stroke coincided with a vertical shaft of precipitation inferred to have been graupel or hail. Charge sources for subsequent strokes were near the edge of the detectable precipitation echo. The overall channel length was about 10 kilometers. A Vertically oriented intracloud discharge occurred after the three return strokes.  相似文献   

GRASSLAND IN THE RESTORATION OF OPENCAST COAL SITES IN YORKSHIRE     

D. S. Brook  F. Bates 《Grass and Forage Science》1960,15(2):116-123

In the rehabilitation of land disturbed by opencast coal workings, the place of grass and clover is an important one, and is two-fold. In the first place, the sward is of value as a soil improver, and, secondly, under the right conditions, grassland can contribute substantially to the economic farming of this land. In Yorkshire, we feel that both these factors can operate so that well-farmed grassland can improve the physical condition of the soil, and, at the same time give the farmer, when his land is returned to him, a reasonable profit in retum for his endeavours and extra financial outlay.  相似文献