The re-emergence of indigenous forest in an urban environment, Christchurch, New Zealand   总被引：4，自引：0，他引：4  

Glenn H. Stewart  Maria E. Ignatieva  Colin D. Meurk  Richard D. Earl 《Urban Forestry & Urban Greening》2004,2(3):149-158

Christchurch, the second largest city in New Zealand is a planned city on a coastal plain on the east coast of the South Island. The birth of the city and the subsequent century of development was characterised by colonial values and tree and garden planting with familiar European species along with those from Australia, North America, and eventually all other continents. The image of an “English garden city” with classical parks of oaks and willow-lined rivers became the accepted norm and the way in which the city has been promoted to potential tourists. Gardening is one of the top two recreational activities and exotic species greatly outnumber native species in the flora and in gardens. This has had serious consequences for the highly fragmented and degraded indigenous vegetation and its co-adapted wildlife. A few hardy indigenous species continued to regenerate through this period, but since the 1970s, there has been a progressive change of attitude and interest in reclaiming the natural heritage of the city, manifest in widespread private and public planting of indigenous species and active habitat restoration. In this article we examine the indigenous and exotic shrub and tree components of the Christchurch flora as planted street trees, in domestic gardens, and in parks. We also present data on shrub and tree regeneration in parks and domestic gardens in the city. Indications are that the more sensitive, less intrusive management of urban environments, combined with the greater density of indigenous seed sources, has allowed regeneration of a wide range of indigenous species across a broad spectrum of habitats – from neglected gardens to pavement cracks to exotic plantations. This is despite the competition from the prodigious seed banks and density of exotic trees, shrubs, and ground covers and albeit minimal impacts of introduced browsing and seed eating mammals. If the present trends continue through appropriate management and facilitation, these tentative signs of native forest regeneration should eventually proliferate into a sustainable mixed origin urban forest that resurrects and preserves the natural character of the region.  相似文献   

Pocono mesic till barrens in retreat: topography,fire and forest contagion effects     

Maurice  Keith R.  Welch  Joan M.  Brown  Christopher P.  Latham  Roger Earl 《Landscape Ecology》2004,19(6):603-620

The Pocono mesic till barrens (PMTB) are a unique assemblage of fire-maintained shrub communities that support numerous rare species. Historically these barrens covered a large area in the vicinity of Long Pond, Pennsylvania, USA. However, due largely to regional fire suppression instituted in the early 1960s, over 70% of the area covered by barrens succeeded to fire-intolerant forest that does not support the rare species. We investigated the influence of forest proximity on barrens succession across three geomorphic types during periods of high fire frequency and fire suppression, testing the hypothesis that forest processes such as seed rain, shading, and detrital enrichment of soils enhances barrens succession through a contagion effect. Evidence of a forest contagion effect should be shown by increased rates of barrens succession with increasing proximity to the nearest forest edge. In order to detect a forest contagion effect, barrens persistence and barrens succession were modeled in proximity zones of 0-50 m, 50-100 m, 100-200 m, and greater than 200 m from the nearest forest edge. We used existing GIS data layers for fire, geomorphology, and vegetation distribution in 1938, 1963, and 1992. The layers were modified and overlain using ArcView software to determine persistence and succession rates for each unique combination of layers in each proximity zone from 1938 to 1963 (pre-fire suppression) and 1963 to 1992 (post-fire suppression). ANCOVA results indicate that proximity to the nearest forest edge significantly affected barrens persistence rates in both time periods, but succession rates were significantly affected in 1938 to 1963 only. Twenty-eight percent of the 1938 barrens succeeded to forest by 1963; 56% of the 1963 barrens became forest by 1992. Results support previous findings that barrens persistence is enhanced by increased fire frequency, and that barrens persist longer where they overlie flat glacial till than on other geomorphology types.  相似文献   

Tall fescue forage mass in a grass-legume mixture: predicted efficiency of indirect selection     

Blair L. Waldron  Michael D. Peel  Steven R. Larson  Ivan W. Mott  J. Earl Creech 《Euphytica》2017,213(3):67

High fertilizer prices and improved environmental stewardship have increased interest in grass-legume mixed pastures. It has been hypothesized, but not validated, that the ecological combining ability between grasses and legumes can be improved by breeding specifically for mixture performance. This experiment examined the predicted efficiency of selection in a grass monoculture environment to indirectly improve tall fescue (Lolium arundinaceum (Schreb.) Darbysh.) forage mass in a grass-legume mixture. Heritability, genetic and rank correlations, and selection efficiencies were estimated for forage mass in a tall fescue half-sib population grown as spaced-plants overseeded with either turf-type tall fescue (monoculture) or alfalfa (mixture). Heritability for tall fescue forage mass in monoculture ranged from 0.32 to 0.70 and were always similar or greater than those in mixture (range 0.27–0.55) for four successive harvests and annual total. Genetic correlations between monoculture and mixture tall fescue forage mass varied with values of 0.48, 0.92, ?0.31, 0.70, and 0.25 in June, July, August, October, and annual total, respectively. Indirect selection efficiencies exceeded or approached direct selection for mixtures only in July and October (1.29, and 0.73, respectively). Whereas, indirect selection efficiencies were low in June, August, and annual forage mass (0.58, ?0.31, and 0.28, respectively). Moreover, low Spearman’s rank correlations (?0.03 to 0.35) indicated differing half-sib family performance between the monoculture and mixture environments. Results indicate that direct selection should be used to improve tall fescue forage mass in a grass-legume mixture, and support the hypothesis of increasing ecological combining ability by breeding for mixtures per se.  相似文献   

Diagnosis and treatment of a selective immunoglobulin M glomerulonephropathy in a quarter horse gelding     

Mcsloy A  Poulsen K  Fisher PJ  Armien A  Chilton JA  Peek S 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2007,21(4):874-877

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Applications of single-strand conformation polymorphism (SSCP) to taxonomy, diagnosis, population genetics and molecular evolution of parasitic nematodes.   总被引：2，自引：0，他引：2  

R B Gasser  N B Chilton 《Veterinary parasitology》2001,101(3-4):201-213

The analysis of genetic variation in parasitic nematodes has important implications for studying aspects of taxonomy, diagnosis, population genetics, drug resistance and molecular evolution. This article highlights some applications of PCR-based single-strand conformation polymorphism (SSCP) for the analysis of sequence variation in individual parasites (and their populations) to address some of these areas. It also describes the principles and advantages of SSCP, and provides some examples for future applications in parasitology.  相似文献   

Osteomyelitis of the pelvis caused by Rhodococcus equi in a two-year-old horse     

Clark-Price SC  Rush BR  Gaughan EM  Cox JH 《Journal of the American Veterinary Medical Association》2003,222(7):969-72, 952-3

A 2-year-old female Quarter Horse was evaluated for hind limb lameness, fever (40 degrees C [104 degrees F]), and lethargy of 2 weeks' duration. Hypoproteinemia characterized by hypoalbuminemia and hyperfibrinogenemia was detected. Abdominal ultrasonography revealed thickening of the right dorsal colon wall. Treatment was instituted for putative right dorsal coliis. Lameness evaluation localized signs of pain to the lumbar vertebrae or pelvis. Radiography performed with the horse standing and nuclear scintigraphy revealed no abnormalities. Ventrodorsal pelvic radiography revealed a focal area of bony lysis and proliferation involving the cranial portion of the pubic symphysis. Aspiration yielded purulent exudate containing Rhodococcus equi, which was susceptible to erythromycin. Treatment included surgical debridement of the abscess and oral administration of erythromycin and rifampin. The horse's hind limb lameness completely resolved within 20 days. Infections of the pubic symphysis should be considered when lameness localized to the pelvis is associated with fever and an inflammatory leukogram.  相似文献   

Is AZT/3TC therapy effective against FIV infection or immunopathogenesis?     

Arai M  Earl DD  Yamamoto JK 《Veterinary immunology and immunopathology》2002,85(3-4):189-204

In vitro and in vivo prophylactic and therapeutic efficacy of AZT/3TC treatment was evaluated against feline immunodeficiency virus (FIV) infection. In vitro studies utilized FIV-infected peripheral blood mononuclear cells (PBMCs) or FIV-infected T-cell lines treated with AZT (azidothymidine) alone, 3TC alone, or AZT/3TC combination and tested for anti-FIV activity and drug toxicity. AZT/3TC combination had additive to synergistic anti-FIV activities in primary PBMC but not in chronically infected cell lines. In vivo studies consisted of four treatment groups (n=15) of SPF cats receiving AZT/3TC combination (5-75 mg/kg/drug PO BID for 8 or 11 weeks) and one control group (n=9) receiving oral placebo. Group I (n=6, 150 mg/kg/drug/day) was treated starting 3 days pre-FIV inoculation, whereas Group II (n=3, 150 mg/kg/drug/day) and Group III (n=3, 100 mg/kg/drug/day) treatments were simultaneous with FIV inoculation. Group IV treatment (n=3, 100 mg/kg/drug/day) was initiated 2 weeks post-FIV inoculation. All cats were monitored for drug toxicity and FIV infection. Eighty-three percent of cats in Group I and 33% of cats in Groups II and III were completely protected from FIV infection. A significant delay in infection and antibody seroconversion was observed in all unprotected cats from Groups I, II and III. Group IV cats had only a slight delay in FIV antibody seroconversion. Adverse drug reactions (anemia and neutropenia) were observed at high doses (100-150 mg/kg/drug/day) were reversible upon lowering the dose (20 mg/kg/drug/day). In contrast, AZT/3TC treatment had no anti-FIV activity in chronically infected cats. Furthermore, severe clinical symptoms caused by adverse drug reactions were observed in some of these cats. Overall, AZT/3TC treatment is effective for prophylaxis but not for therapeutic use in chronically FIV-infected cats.  相似文献   

Geo-referenced spatiotemporal analysis of the urban citrus canker epidemic in Florida     

Gottwald TR  Sun X  Riley T  Graham JH  Ferrandino F  Taylor EL 《Phytopathology》2002,92(4):361-377

ABSTRACT Five areas in urban Miami were identified to study the spread of Xanthomonas axonopodis pv. citri to determine if the practice of removing exposed citrus trees within 38.1 m of trees affected by citrus canker was adequate to curtail further bacterial spread. To accomplish this, 18,769 trees in dooryards were surveyed, geo-referenced by differential global positioning systems (GPS), and assayed for disease severity, age of infection, citrus cultivar, location of infection in tree, and canopy size. For each tree, the date the tree became infected was estimated and used to separate trees into contiguous 30-day categories. For each area studied, distance measurements between focal trees and newly infected trees were calculated for various temporal periods of 30, 60, 90, and 120 days in duration, corresponding to intervals of inspection survey. A visual basic application was used to calculate the distances between each newly diseased tree and all prior focal trees. The nearest distance was used because it was considered the most conservative estimate possible. It is therefore likely to be an underestimate of spread but is a good estimate of the minimum possible distances of spread. For the first four 30-day periods among the five study areas, calculated maximum distances of spread ranged from 12 to 3,474 m, indicating a broad continuum of distance for bacterial spread was possible. Disease increased during the first two-thirds of the time studied and reached an asymptote due to dry conditions in the final one-third of the duration of the study. Cross correlation analysis indicated that disease was best visualized 107 days following rainstorms with wind. Analysis of regional spatial point patterns was performed temporally for each 30-day period via a modified Ripley's K-function. Spatiotemporal analyses between periods over areas larger than previously examined were accomplished via spatiotemporal semivariogram analysis. These methods in combination demonstrated rapid increases in range of spatial dependency and range of spatiotemporal dependency for all study sites. This corresponded to rapid spread of disease across the regions studied in response to rainstorms with wind followed by a "filling in" of disease on remaining noninfected susceptible trees through time by less intense rain events. A stochastic quadratization technique demonstrated that disease incidence and disease severity were not greatly affected by urban host density but were positively correlated to host susceptibility within local 0.25-km(2) quadrats.  相似文献   

Experimental transmission of bovine anaplasmosis (caused by Anaplasma marginale) by means of Dermacentor variabilis and D. andersoni (Ixodidae) collected in western Canada          下载免费PDF全文

Murray W. Lankester  W. Brad Scandrett  Elizabeth J. Golsteyn-Thomas  Neil C. Chilton    Alvin A. Gajadhar 《Canadian journal of veterinary research》2007,71(4):271-277

Canadian cattle are free of bovine anaplasmosis, with the exception of 4 isolated incursions since 1968, which were eradicated. It is not known why the disease has not become established in regions of Canada adjacent to the United States where it is endemic. To assess the vector competence of wild-caught ticks in cattle-rearing regions, Dermacentor variabilis and D. andersoni were collected in western Canada and fed on calves experimentally infected with Anaplasma marginale (St. Maries strain). The 2 tick species were equally competent in transmitting A. marginale to splenectomized calves, all 15 tick-exposed calves becoming infected. The prepatent periods in 13 calves ranged from 18 to 26 d and did not vary in relation to the numbers of ticks fed or the duration of transmission feedings. The unusually long prepatent periods in 2 calves (45 and 55 d) were probably due to concomitant Eperythrozoon infection. This study clearly demonstrated that tick species present in western Canada are competent vectors of bovine anaplasmosis. Potential barriers, including climate, must be considered in developing strategies to prevent A. marginale from becoming established in anaplasmosis-free regions.  相似文献   

Sectional notes     

E. Marx  C. H. Metzger  B. A. Brown  Eugene W. Whitman  H. R. Talmage  Frank W. Hussey  H. A. Reiley  Marx Koehnke  J. C. Campbell  E. V. Hardenburg  Karl H. Fernow  Earl B. Tussing  E. R. Jackman  C. A. Henderson  O. D. Burke  K. W. Lauer  John Noonan  H. L. Bailey  Chas D. Gaines  W. N. Keenan  R. E. Goodin 《American Journal of Potato Research》1943,20(8):224-236

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