New genotype of avian bornavirus in wild geese and trumpeter swans in Canada     

Delnatte P  Berkvens C  Kummrow M  Smith DA  Campbell D  Crawshaw G  Ojkic D  DeLay J 《The Veterinary record》2011,169(4):108

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Management of bovine tuberculosis in Michigan wildlife: current status and near term prospects     

O'Brien DJ  Schmitt SM  Fitzgerald SD  Berry DE 《Veterinary microbiology》2011,151(1-2):179-187

Surveillance and control activities for bovine tuberculosis (bTB) in free-ranging Michigan white-tailed deer (Odocoileus virginianus) have now been underway for over a decade. Significant progress has been made, lowering apparent prevalence in deer in the core area by >60%, primarily via reduction of deer densities through hunting, and restrictions on public feeding and baiting of deer. These broad strategies of the Michigan Department of Natural Resources (MDNR), implemented with the cooperation of Michigan deer hunters, halved the deer population in the bTB endemic area. However, as hunters see fewer deer, their willingness to sustain aggressive harvests has waned, and public resentment of control measures has grown. During the past four years, apparent prevalence in core area deer has held approximately steady just below 2%. After bottoming out in 2004 at an estimated 10-12 deer/km(2), deer numbers have since rebounded by ～ 30%. Public compliance with baiting and feeding restrictions has been variable. In general, hunters in the core area do not perceive bTB as a problem, in spite of 13 years of MDNR outreach. To date, MDNR has expended more than US$23 million on TB-related activities. Of late, a substantial portion of that funding has been diverted to support other programs which have suffered from budget shortfalls. Livestock herd breakdowns continue to occur sporadically, averaging 3-4 per year 2005 to present. In total, 46 cattle and 4 captive deer herds have been diagnosed bTB positive statewide, the majority yielding only 1 positive animal. Five cattle herds were twice infected, one thrice. Michigan Department of Agriculture (MDA) policy emphasis has shifted towards obtaining producer support for wildlife risk mitigation and farm biosecurity. Funding has proven a limiting factor, with the majority of the US$63 million spent to date devoted to whole herd testing. Nevertheless, some initiatives justify cautious optimism. Promising research to support eventual vaccination of wild deer continues. Some hunters and landowners have begun to recognize the costs of high deer densities and supplemental feeding. A peninsula-wide ban on baiting and feeding was enacted. Some cattle producers, recognizing their precarious circumstances, have begun work to change long-held prevailing opinions among their peers about farm biosecurity. Yet formidable challenges remain, and evidence suggests that eradication of bTB, if it can be achieved, will take decades, and will require greater public and political resolve than has been demonstrated thus far.  相似文献   

Responses of transpiration and canopy conductance to partial defoliation of Eucalyptus globulus trees     

Audrey G. Quentin  Anthony P. O’Grady  Christopher L. Beadle  Dale WorledgeElizabeth A. Pinkard 《Agricultural and Forest Meteorology》2011,151(3):356-364

Partial defoliation has been shown to affect the water relations and transpiration (gas exchange) of plants. Over one growing season, the water relations in response to partial (∼45%) defoliation were examined in four-year-old Eucalyptus globulus trees in southern Australia. Daily maximum transpiration rates (E_max), maximum canopy conductance (GCmax), and diurnal patterns of tree water-use were measured over a period of 215 days using the heat-pulse technique in adjacent control (non-defoliated) and defoliated trees. Sap-flux measurements were used to estimate canopy conductance and soil-to-leaf hydraulic conductance (K_P); leaf water potential (Ψ) and climate data were also collected. Following the removal of the upper canopy layer, defoliated trees exhibited compensatory responses in transpiration rate and canopy conductance of the remaining foliage. Defoliated E. globulus had similar predawn but higher midday Ψ_l, transpiration rates (E), canopy conductance (G_C) and K_P compared to the non-defoliated controls, possibly in response to increased water supply per unit leaf area demonstrated by higher midday Ψ_l. Higher E in defoliated E. globulus trees was the result of higher G_C in the morning and early afternoon. This paper also incorporates the cumulative effect of defoliation, in a phenomenological model of maximum canopy conductance of E. globulus. These results contribute to a mechanistic understanding of plant responses to defoliation, in particular the often observed up-regulation of photosynthesis that also occurs in response to defoliation.  相似文献   

Macronutrient uptake,translocation, and tissue concentration of soybeans infested with the soybean cyst nematode and elemental composition of cysts isolated from roots 1     

Dale G. Blevins  Victor H. Dropkin  Virgil D. Luedders 《Journal of plant nutrition》2013,36(3):579-591

The soybean cyst nematode (SCN, Heterodera glycines Ichinohe) is a major pest of soybeans (Glycine max L. Merrill) in the central and southern United States. Soybean cyst nematode causes stunted top growth, root pruning and symptoms of mineral element deficiency in soybeans. The objective of this study was to determine the effect of two selections of SCN (I selected on PI209332 and IV selected on PI 89772) on macronutrient uptake, translocation, and tissue concentrations of soybean and to determine the elemental composition of cysts isolated from roots. Soybeans were grown in plastic tubes in the greenhouse where the middle one‐third of the Hodge fine sand (Typic Udipsamment) contained 0, 25,000, or 50,000 SCN eggs. After 35 days, plants were harvested and tissue nutrient element concentrations were determined. Plants infested with both SCN selections were smaller and had much less root volume than controls. Dry weight of each plant tissue decreased as SCN population was increased. Root concentration of potassium (K) and magnesium (Mg) was decreased, whereas root calcium (Ca) and phosphorus (P) concentrations were increased with SCN treatments. Leaf Mg and Ca concentrations increased with SCN treatment. Magnesium uptake per unit root volume was decreased, but Mg translocation (% of total plant content in aerial portion) was increased with SCN treatment. Calcium uptake per unit of root volume was increased, but translocation was unchanged by SCN treatment. The Ca and P concentration of cysts isolated from the soybean roots was high. This high concentration of Ca in cysts is interesting based on the greater root Ca concentration and uptake per unit of root volume in SCN infested plants. Since total uptake and root concentrations of both K and Mg were decreased by SCN treatment, infested soybeans might require very high levels of K and Mg fertilization. These results indicate that K and Mg fertility should be followed closely in SCM‐infested soybean fields.  相似文献   

The use of additives,temperature, and plant position to increase efficacy of dinoseb for potato (Solanum tuberosum) vine desiccation     

Dale R. Mutch  Donald Penner  Frank Roggenbuck  Richard W. Chase 《American Journal of Potato Research》1984,61(9):577-586

Chemical vine desiccation is an important management practice for late season potatoes (Solanum tuberosum L.) in Michigan. A number of desiccants are registered; however, most Michigan growers apply dinoseb (2-sec- butyl-4,6-dinitrophenol). Greenhouse experiments were initiated to evaluate the potential of ammonium salts and ethephon (2-chloroethyl)phosphonic acid) to increase the efficacy of the chemical harvest aids dinoseb and endothall (7-oxabicyclo[2,2,1]heptane-2,3-dicarboxylic acid) on potato vines. Temperature and potato vine position were evaluated to determine their influence on vine desiccation. All treatments with endothall applied at 0.6 kg/ha resulted in unsatisfactory potato vine desiccation. Ethephon and ammonium sulfate increased efficacy of dinoseb. High temperature both before and after treatment contributed to greater dinoseb efficacy. The horizontal placing of potato vines resulted in the desired desiccation rating of 9.0 or greater using the combination of dinoseb at 2.8 kg/ha, plus ammonium sulfate at 9 kg/ha plus 2.4 L/ha X-77 surfactant.³  相似文献   

Evolution of the Minangkabau's shifting cultivation in the West Sumatra highland OF Indonesia and its strategic implications for dynamic farming systems     

A. Dendi  G. P. Shivakoti  R. Dale  S. L. Ranamukhaarachchi 《Land Degradation \u0026amp; Development》2005,16(1):13-26

This paper explores the evolution of the shifting cultivation of the Minangkabau , the biggest matrilineal society in Indonesia, and examines factors underlying the instability and vulnerability of farmers' livelihoods and the degradation of their resource base using an extended factor analysis technique, in order to understand how development strategies might be modified towards a more dynamic farming system. The study distinguished three main phases of the farming system's changes and found that these changes highly corresponded with the emerging market and institutional incentives. Furthermore, the factor analysis generated a six‐factor model suggesting strategic interventions to foster the improvement of farmers' livelihoods and environment in future. In addition, consistent with the results of these factors analysis, we argue that, provided land tenure is conducive, there are substantial possibilities for policies and interventions that focus first on agricultural diversification and then on organization building, to assist in dealing with farmers' vulnerability and environmental degradation in the uplands. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Stem dimensional fluctuation in Jeffrey pine from variation in water storage as influenced by thinning and prescribed fire     

Robert M. Fecko  Roger F. Walker  Wesley B. Frederick  Watkins W. Miller  Dale W. Johnson 《Annals of Forest Science》2008,65(2):201-201

Forest thinning utilizing cut-to-length and whole-tree harvesting systems with subsequent underburning were assessed for their impacts on water storage in the extensible tissues of dominant and codominant trees in an uneven-aged Jeffrey pine (Pinus jeffreyi Grev. & Balf.) stand on the east slope of the Sierra Nevada. Prior to the onset of the third growing season following thinning and the second season after burning, manual band dendrometers were installed at breast height on the selected trees and readings of diurnal fluctuation in stem circumference, an indication of bole water status, were taken monthly for one year. Diameter and relative diameter fluctuation were calculated from the circumference measurements. Overall, thinning had a positive influence on stem water recharge capacity, with the most pronounced effects evident in the latter part of the growing season. During this period, bole contraction in thinned stand portions was 49 to 55% greater than in the unthinned control, suggesting that both a greater volume of stored water was available for transpiration and was transpired in trees of the former treatment. There was no clear evidence that harvesting method affected stem water storage and influences of underburning were also absent entirely. Seasonal effects on diurnal changes in stem diameter were prominent, as the extent to which boles contracted generally increased over the course of the growing season, whereas fluctuations were at a minimum during the colder months. The magnitude of stem dimensional flux was found to be negatively correlated with initial tree DBH in one instance, while negative relationships between the former and live crown length as well as percentage were also revealed, albeit infrequently. Changes in bole size were positively correlated with residual basal area in some cases. These results suggest that improvement in water relations can be realized from density management in a dry site forest type with no apparent compromise of this benefit by broadcast underburning.  相似文献   

魁北克省多日龄猪接种FLEX系列茵格发(R)猪圆环病毒疫苗预防猪圆环病毒相关疾病(PCVAD)的初步结果     

Dorine Tremblay  Robert Tremblay  Dale Polson  黄念 《湖北畜牧兽医》2010,(2)

人们认为猪圆环病毒2型(PCV2)是发生断奶仔猪多系统衰竭综合征的一个必要因素.目前断奶仔猪多系统衰竭综合征在欧洲称作猪圆环病毒病(PCVD),在北美称作猪圆环病毒相关疾病(PCVAD).  相似文献   

Indices of landscape pattern   总被引：171，自引：1，他引：170  

R. V. O'Neill  J. R. Krummel  R. H. Gardner  G. Sugihara  B. Jackson  D. L. DeAngelis  B. T. Milne  M. G. Turner  B. Zygmunt  S. W. Christensen  V. H. Dale  R. L. Graham 《Landscape Ecology》1988,1(3):153-162

Landscape ecology deals with the patterning of ecosystems in space. Methods are needed to quantify aspects of spatial pattern that can be correlated with ecological processes. The present paper develops three indices of pattern derived from information theory and fractal geometry. Using digitized maps, the indices are calculated for 94 quadrangles covering most of the eastern United States. The indices are shown to be reasonably independent of each other and to capture major features of landscape pattern. One of the indices, the fractal dimension, is shown to be correlated with the degree of human manipulation of the landscape.  相似文献   

Evaluation of 3 Assays for Failure of Passive Transfer in Calves   总被引：2，自引：1，他引：1  

Jeff W. Tyler  Dale D. Hancock  Steven M. Parish  Douglas E. Rea  Thomas E. Besser  Sean G. Sanders  Leilani K. Wilson 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1996,10(5):304-307

This study examined the sensitivity, specificity, predictive values, and classification accuracy of 3 commonly used screening tests for failure of passive transfer: the sodium sulfite turbidity test, the zinc sulfate turbidity test, and re-fractometry relative to serum immunoglobulin G₁, (IgG₁) concentrations determined by radial immunodiffusion. Serum samples were obtained from 242 calves ranging from 1 to 8 days of age. Using a serum concentration of 1,000 mg/dL IgG₁ to define adequate passive transfer, the zinc sulfate test had a sensitivity of 1.00 and a specificity of 0.52 in the detection of inadequate passive transfer. The endpoint of the test appeared to be higher than desired; calves testing negative had mean serum IgG₁ concentration of 955 mg/dL and a large proportion of calves with adequate passive transfer were misclassified as positive for failure of passive transfer. Using the qualitative zinc sulfate test, the percentage of calves correctly classified with regard to passive transfer status was less than that observed with either the sodium sulfite test or refractometry. The sensitivity of the sodium sulfite assay was 0.85 at a 1+ endpoint and 1.00 at a 2 or 3+ endpoint. The specificity of the sodium sulfite assay varied from 0.87 at a 1+ endpoint and 0.56 at a 2+ endpoint. The sensitivity and specificity of refractometry varied from 0.01 to 1.00 depending on the choice of endpoint. Refractometry correctly classified the largest proportion of calves with regard to their passive transfer status at test endpoints of 5.0 and 5.5 g/dL, 83% and 82% respectively. The highest percentages of calves correctly classified occurred with the sodium sulfite test using a 1+ endpoint (86.30%) and refractometry using a 5.0 g/dL endpoint (83.00%). A regression equation was developed that permitted calculation of an optimal endpoint for refractometric determinations of total serum protein concentration. A serum protein concentration of 5.2 g/dL was equivalent to 1,000 mg/dL serum IgG₁. Optimal selection of tests for passive transfer status in calves will be governed by the prevalence of failure of passive transfer, test performance, and the anticipated costs of classification errors.  相似文献