A leakiness index for assessing landscape function using remote sensing   总被引：2，自引：0，他引：2  

Ludwig  John A.  Eager  Robert W.  Bastin  Gary N.  Chewings  Vanessa H.  Liedloff  Adam C. 《Landscape Ecology》2002,17(2):157-171

The cover, number, size, shape, spatial arrangement and orientation of vegetation patches are attributes that have been used to indicate how well landscapes function to retain, not ‘leak’, vital system resources such as rainwater and soil. We derived and tested a directional leakiness index (DLI) for this resource retention function. We used simulated landscape maps where resource flows over map surfaces were directional and where landscape patch attributes were known. Although DLI was most strongly related to patch cover, it also logically related to patch number, size, shape, arrangement and orientation. If the direction of resource flow is multi-directional, a variant of DLI, the multi-directional leakiness index (MDLI) can be used. The utility of DLI and MDLI was demonstrated by applying these indices to three Australian savanna landscapes differing in their remotely sensed vegetation patch attributes. These leakiness indices clearly positioned these three landscapes along a function-dysfunction continuum, where dysfunctional landscapes are leaky (poorly retain resources). This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Occurrence of Mirafiori Lettuce Virus and Lettuce Big-vein Virus in Relation to Development of Big-vein Symptoms in Lettuce Crops     

Piero Roggero  Hervé Lot  Sylvie Souche  Riccardo Lenzi  Robert G. Milne 《European journal of plant pathology / European Foundation for Plant Pathology》2003,109(3):261-267

Big-vein disease (BV) of lettuce has been attributed to infection by Lettuce big-vein virus (LBVV), vectored by the soil fungus Olpidium brassicae. The finding of a second soil-borne virus in lettuce, Mirafiori lettuce virus (MiLV), led to a re-investigation of the role of LBVV in big-vein disease, with evidence emerging that both MiLV and LBVV are vectored by O. brassicae, and that MiLV, not LBVV, is the cause of BV (Lot et al. (2002), Phytopathology 92: 288–293). The two viruses have coat proteins of similar size but have different morphologies and are serologically unrelated. We tested individual lettuce plants in BV-prone fields and protected crops in France and Italy for the presence of the two viruses, using DAS-ELISA and antisera specific for each virus. Both MiLV and LBVV were found at high incidence, often together but sometimes separately. Symptoms were frequently found to be associated with MiLV alone or both viruses, but rarely LBVV alone. However, no absolute correlation emerged, because sometimes MiLV was present in the absence of symptoms, and vice versa. To clarify the situation, individual lettuce plants were examined over a period of time in two further surveys. In surveys of protected crops in France, plants with big-vein were always ELISA-positive for MiLV, or else symptomless plants positive for MiLV were later seen to develop big-vein symptoms. Presence or absence of LBVV appeared to have no effect on symptom development. In surveys of open fields in Italy, all combinations were found: presence of both viruses, apparent absence of both viruses, or presence of each one alone, in plants that developed BV. At the end of the observation period, nearly all plants had BV and contained both viruses.  相似文献   

Zusammenfassende Auswertung von Versuchen zur biologischen Wirksamkeit von Pflanzenschutzmitteln im Apfelanbau bei grobtropfiger Applikation     

Reinhard Frießleben  Arno Fried  Eckart Lange  Klaus Schmidt  Hans-Georg Funke  Heribert Koch  Horst Knewitz  Gerhard Palm  Reinhold Stadler  Robert Heinkel 《Gesunde Pflanzen》2003,55(3):77-84

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Quantifying patch distribution at multiple spatial scales: Applications to wildlife-habitat models     

Johnson  Chris J.  Boyce  Mark S.  Mulders  Robert  Gunn  Anne  Gau  Rob J.  Cluff  H. Dean  Case  Ray L. 《Landscape Ecology》2004,19(8):869-882

Multiscale analyses are widely employed for wildlife-habitat studies. In most cases, however, each scale is considered discrete and little emphasis is placed on incorporating or measuring the responses of wildlife to resources across multiple scales. We modeled the responses of three Arctic wildlife species to vegetative resources distributed at two spatial scales: patches and collections of patches aggregated across a regional area. We defined a patch as a single or homogeneous collection of pixels representing 1 of 10 unique vegetation types. We employed a spatial pattern technique, three-term local quadrat variance, to quantify the distribution of patches at a larger regional scale. We used the distance at which the variance for each of 10 vegetation types peaked to define a moving window for calculating the density of patches. When measures of vegetation patch and density were applied to resource selection functions, the most parsimonious models for wolves and grizzly bears included covariates recorded at both scales. Seasonal resource selection by caribou was best described using a model consisting of only regional scale covariates. Our results suggest that for some species and environments simple patch-scale models may not capture the full range of spatial variation in resources to which wildlife may respond. For mobile animals that range across heterogeneous areas we recommend selection models that integrate resources occurring at a number of spatial scales. Patch density is a simple technique for representing such higher-order spatial patterns.  相似文献   

Book Review: Monitoring Ecosystems     

Potts  Robert 《Landscape Ecology》2004,19(5):561-562

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West Nile virus infection in free-ranging squirrels in Illinois.     

Kathleen M Heinz-Taheny  John J Andrews  Michael J Kinsel  Allan P Pessier  Marie E Pinkerton  Karin Y Lemberger  Robert J Novak  George J Dizikes  Eric Edwards  Nicholas Komar 《Journal of veterinary diagnostic investigation》2004,16(3):186-190

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Pharmacokinetics of carfentanil and naltrexone in domestic goats (Capra hircus).     

Adrian Mutlow  Ramiro Isaza  James W Carpenter  David E Koch  Robert P Hunter 《Journal of zoo and wildlife medicine》2004,35(4):489-496

Using a crossover study design, the pharmacokinetics of carfentanil and naltrexone after i.v., i.m., and s.c. administration were determined in eight domestic goats (Capra hircus). Serial blood samples were taken up to 120 hr after carfentanil administration, and the plasma drug concentrations were determined using liquid chromatography and mass spectroscopy. All goats were immobilized with 40 microg/kg carfentanil i.m., although the resulting neurologic effects varied considerably. Plasma profiles showed rapid carfentanil absorption and a simple biphasic decline for 12-48 hr. Naltrexone given at 100 mg naltrexone/mg carfentanil 30 min after carfentanil administration produced rapid reversal of immobilization after all routes of administration. Variable fluctuations in the naltrexone plasma concentrations during the first 2.5-3.5 hr were observed, followed by a more consistent biphasic decline. The time to standing was significantly shorter after i.v. compared with s.c. naltrexone, although the time difference (1 min) had little clinical relevance. No statistically significant differences between the naltrexone pharmacokinetic parameters measured for the three routes of naltrexone administration were identified, although the recoveries after i.m. administration were, subjectively, the smoothest. The carfentanil half-life did not differ significantly in the goats given naltrexone by different routes. Although it is currently recommended that the naltrexone dose be divided into s.c. and i.v. portions, this practice does not appear to offer any benefit.  相似文献   

Endoscopic sex determination and gonadal manipulation in Gulf of Mexico sturgeon (Acipenser oxyrinchus desotoi).     

Stephen J Hernandez-Divers  Robert S Bakal  Brian H Hickson  Clarence A Rawlings  Heather G Wilson  MaryAnn Radlinsky  Sonia M Hernandez-Divers  Samuel R Dover 《Journal of zoo and wildlife medicine》2004,35(4):459-470

Seventeen Gulf of Mexico sturgeons (Acipenser oxyrinchus desotoi) underwent endoscopic sex determination, gonadal biopsy, and various reproductive surgeries as part of a conservation development plan. The fish were anesthetized with tricaine methanesulfonate (MS-222) buffered with sodium bicarbonate and maintained on a recirculating water anesthesia circuit. A 6-mm Ternamian EndoTip Cannula, placed through the ventral midline, midway between pectoral and pelvic fins, permitted the introduction of a 5-mm telescope. Swim bladder aspiration and CO2 insufflation of the coelomic cavity provided excellent observation. Second and third cannulae were placed under direct visual control, lateral and cranial or caudal to the telescope cannula. Sex determination was successfully performed in all fish; however, five of 17 sturgeons (29%) required endoscopic gonadal biopsy to confirm sex. Bilateral ovariectomy or orchidectomy was successfully performed in three males and four females. Unilateral ovariectomy and bilateral ligation of the müllerian ducts using an extracorporeal suturing technique was accomplished in an additional three females. No apparent morbidity was associated with the anesthesia or endoscopic surgery in any fish. The ability to safely perform minimally invasive reproductive surgery in fish may have important management and conservation benefits.  相似文献   

Evaluation of individual low‐dose dexamethasone suppression test patterns in naturally occurring hyperadrenocorticism in dogs          下载免费PDF全文

Michael Bennaim  Robert E. Shiel  Christopher Forde  Carmel T. Mooney 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2018,32(3):967-977

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Incidence and risk factors for neurological signs after attenuation of single congenital portosystemic shunts in 253 dogs          下载免费PDF全文

Rhiannon Strickland BVetMed  Michael S. Tivers BVSc  PhD  DipECVS  Sophie E. Adamantos BVSc  DACVECC  DECVECC  Tom R. Harcourt‐Brown MA  VetMB  DipECVN  Robert C. Fowkes BSc  PhD  Victoria J. Lipscomb MA  VetMB  DipECVS 《Veterinary surgery : VS》2018,47(6):745-755

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