Postfire Succession in Big Sagebrush Steppe With Livestock Grazing     

Jonathan D. Bates  Edward C. Rhodes  Kirk W. Davies  Robert Sharp 《Strength and Conditioning Journal》2009,62(1):98-110

Prescribed fire in rangeland ecosystems is applied for a variety of management objectives, including enhancing productivity of forage species for domestic livestock. In the big sagebrush (Artemisia tridentata Nutt.) steppe of the western United States, fire has been a natural and prescribed disturbance, temporarily shifting vegetation from shrub–grass codominance to grass dominance. There is limited information on the impacts of grazing to community dynamics following fire in big sagebrush steppe. This study evaluated cattle grazing impacts over four growing seasons after prescribed fire on Wyoming big sagebrush (Artemisia tridentata subsp. Wyomingensis [Beetle & Young] Welsh) steppe in eastern Oregon. Treatments included no grazing on burned and unburned sagebrush steppe, two summer-grazing applications after fire, and two spring-grazing applications after fire. Treatment plots were burned in fall 2002. Grazing trials were applied from 2003 to 2005. Vegetation dynamics in the treatments were evaluated by quantifying herbaceous canopy cover, density, annual yield, and perennial grass seed yield. Seed production was greater in the ungrazed burn treatments than in all burn–grazed treatments; however, these differences did not affect community recovery after fire. Other herbaceous response variables (cover, density, composition, and annual yield), bare ground, and soil surface litter did not differ among grazed and ungrazed burn treatments. All burn treatments (grazed and ungrazed) had greater herbaceous cover, herbaceous standing crop, herbaceous annual yield, and grass seed production than the unburned treatment by the second or third year after fire. The results demonstrated that properly applied livestock grazing after low-severity, prescribed fire will not hinder the recovery of herbaceous plant communities in Wyoming big sagebrush steppe.  相似文献   

Equine amnionitis and fetal loss: The case definition for an unrecognised cause of abortion in mares     

KH Todhunter  NR Perkins  RM Wylie  C Chicken  AJ Blishen  DJ Racklyeft  G Muscatello  MC Wilson  PL Adams  JR Gilkerson  WL Bryden  AP Begg 《Australian veterinary journal》2009,87(1-2):35-38

A series of abortions occurred in mares in New South Wales during 2004 that involved similar and unusual findings on post mortem examination of aborted fetuses and fetal membranes. The term Equine Amnionitis and Fetal Loss (EAFL) was developed to describe the condition. This form of abortion had not been previously recognised in Australia. The pathology alone is not specific for EAFL and diagnosis requires demonstration of a combination of certain pathological and bacteriological features. The purpose of this paper is to describe patterns considered consistent with EAFL cases as a working case definition for use by veterinarians and veterinary pathologists in identifying future cases of EAFL. More detailed papers are in preparation to fully describe the epidemiological, histopathological, and microbiological aspects of EAFL.  相似文献   

Analysis of changes in organic carbon in mineral soils across England and Wales using a simple single‐pool model     

G. J. D. Kirk  P. H. Bellamy 《European Journal of Soil Science》2010,61(3):406-411

We use a simple single‐pool model of soil carbon turnover to evaluate possible explanations for the widespread changes in the organic carbon contents of mineral soils across England and Wales, measured in the National Soil Inventory between 1978 and 2003. We provide a means of quantifying the changes in rates of soil organic carbon decomposition in relation to inputs from vegetation required to explain the results. We find that neither changes in decomposition resulting from the effects of climate change on soil temperature and moisture, nor changes in input, could by themselves account for the overall trends. Past changes in land use and management were more likely explanations. Any climate‐change signal is masked by these other changes.  相似文献   

Diffusion of strongly sorbed solutes in soil: a dual-porosity model allowing for slow access to sorption sites and time-dependent sorption reactions     

M. Ptashnyk    T. Roose  & G. J. D. Kirk 《European Journal of Soil Science》2010,61(1):108-119

We use homogenization techniques to derive a dual (or double) porosity model of solute diffusion and reaction in soil, allowing for slow access to sorption sites within micro-aggregates and time-dependent sorption reactions. We give a means for determining the conditions in which micro-scale concentration gradients affect macro-scale gradients and fluxes. We present equations for a unit volume of soil represented as a series of uniformly-spaced, porous spherical particles, containing and surrounded by solution through which solutes diffuse. The methods we use can, in principle, be applied to more complex geometries. We compare the model's predictions with those of the equivalent single porosity model for commonly used boundary conditions. We show that failure to allow for slow access to reaction sites can lead to seriously erroneous results. Slow access has the effect of decreasing the sorption of solute into soil from a source or desorption from soil to a sink. As a result of slow access, the diffusion coefficients of strongly-sorbed solutes measured at the macro-scale will be time-dependent and will depend on the method of measurement. We also show that slow access is more often likely to limit macro-scale diffusion than rates of slow chemical reactions per se . In principle, the unimportance of slow reactions except at periods longer than several weeks of diffusion simplifies modelling because, if slow access is correctly allowed for, sorption can be described with equilibrium relations with an understanding of speciation and rapid sorption-desorption reactions.  相似文献   

Anesthetic effects of different volumes of lidocaine for spermatic cord block in cattle     

Ana C. Neves  Juracy CB. Santos Júnior  Rodrigo L. Marucio  Monica Midon  Stelio PL. Luna 《Veterinary anaesthesia and analgesia》2017,44(2):375-378

Objective

To evaluate three volumes of lidocaine for spermatic cord block to perform castration in cattle.

Study design

Randomized blinded clinical study.

Animals

Thirty mixed-breed Nellore cattle, aged 28–40 months and weighing 395 ± 21 (352–452) kg [mean ± standard deviation (range)].

Methods

Cattle were restrained in a chute and allowed to stand without sedation. Three milliliters of 2% lidocaine without epinephrine were infiltrated subcutaneously at each site of scrotal incision in all animals. The animals were allocated to three groups of 10 animals each. Lidocaine 2% was injected into each spermatic cord using a volume of 2, 3 or 4 mL in groups A, B, or C, respectively. The total volumes of lidocaine used were 10, 12, and 14 mL in groups A, B, and C, respectively. The duration of surgery and the retraction of the testicle (scored as positive or negative according to retraction of the testicle) during the procedure were recorded. The data were statistically analyzed by one-way anova followed by Tukey’s and chi-square tests. Differences were considered significant when p < 0.05.

Results

The mean surgical time was shorter in group C than in groups A and B (p < 0.001). In groups A, B and C, 90%, 60% and 10% of the animals showed retraction of the testicle, respectively. Fewer animals retracted the spermatic cord in group C than in group A (p = 0.002) and B (p = 0.02).

Conclusions and clinical relevance

Optimal spermatic cord block was achieved by injection of 4 mL of 2% lidocaine 5 minutes before castration and following incisional infiltration of lidocaine, in adult cattle weighing about 400 kg.  相似文献   

Sage Grouse Groceries: Forb Response to Piñon-Juniper Treatments     

Jonathan D. Bates  Kirk W. Davies  April Hulet  Richard F. Miller  Bruce Roundy 《Strength and Conditioning Journal》2017,70(1):106-115

Juniper and piñon coniferous woodlands have increased 2- to 10-fold in nine ecoregions spanning the Intermountain Region of the western United States. Control of piñon-juniper woodlands by mechanical treatments and prescribed fire are commonly applied to recover sagebrush steppe rangelands. Recently, the Sage Grouse Initiative has made conifer removal a major part of its program to reestablish sagebrush habitat for sage grouse (Centrocercus urophasianus) and other species. We analyzed data sets from previous and ongoing studies across the Great Basin characterizing cover response of perennial and annual forbs that are consumed by sage grouse to mechanical, prescribed fire, and low-disturbance fuel reduction treatments. There were 11 sites in western juniper (Juniperus occidentalis Hook.) woodlands, 3 sites in singleleaf piñon (Pinus monophylla Torr. & Frém.) and Utah juniper (Juniperus osteosperma [Torr.] Little), 2 sites in Utah juniper, and 2 sites in Utah juniper and Colorado piñon (Pinus edulis Engelm). Western juniper sites were located in mountain big sagebrush (A. tridentata ssp. vaseyana) steppe associations, and the other woodlands were located in Wyoming big sagebrush (A. tridentata ssp. wyomingensis) associations. Site potential appears to be a major determinant for increasing perennial forbs consumed by sage grouse following conifer control. The cover response of perennial forbs, whether increasing (1.5- to 6-fold) or exhibiting no change, was similar regardless of conifer treatment. Annual forbs favored by sage grouse benefitted most from prescribed fire treatments with smaller increases following mechanical and fuel reduction treatments. Though forb abundance may not consistently be enhanced, mechanical and fuel reduction conifer treatments remain good preventative measures, especially in phase 1 and 2 woodlands, which, at minimum, maintain forbs on the landscape. In addition, these two conifer control measures, in the short term, are superior to prescribed fire for maintaining the essential habitat characteristics of sagebrush steppe for sage grouse.  相似文献   

Efficacy of Azithromycin and Compounded Atovaquone for Treatment of Babesia gibsoni in Dogs          下载免费PDF全文

S.K. Kirk  J.K. Levy  P.C. Crawford 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2017,31(4):1108-1112

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Vegetation Characteristics of Mountain and Wyoming Big Sagebrush Plant Communities in the Northern Great Basin     

Kirk W. Davies  Jon D. Bates 《Strength and Conditioning Journal》2010,63(4):461-466

Dominant plant species are often used as indicators of site potential in forest and rangelands. However, subspecies of dominant vegetation often indicate different site characteristics and, therefore, may be more useful indicators of plant community potential and provide more precise information for management. Big sagebrush (Artemisia tridentata Nutt.) occurs across large expanses of the western United States. Common subspecies of big sagebrush have considerable variation in the types of sites they occupy, but information that quantifies differences in their vegetation characteristics is lacking. Consequently, wildlife and land management guidelines frequently do not differentiate between subspecies of big sagebrush. To quantify vegetation characteristics between two common subspecies of big sagebrush, we sampled 106 intact big sagebrush plant communities. Half of the sampled plant communities were Wyoming big sagebrush (A. tridentata subsp. wyomingensis [Beetle & A. Young] S. L. Welsh) plant communities, and the other half were mountain big sagebrush (A. tridentata subsp. vaseyana [Rydb.] Beetle) plant communities. In general, mountain big sagebrush plant communities were more diverse and had greater vegetation cover, density, and biomass production than Wyoming big sagebrush plant communities. Sagebrush cover was, on average, 2.4-fold higher in mountain big sagebrush plant communities. Perennial forb density and cover were 3.8- and 5.6-fold greater in mountain compared to Wyoming big sagebrush plant communities. Total herbaceous biomass production was approximately twofold greater in mountain than Wyoming big sagebrush plant communities. The results of this study suggest that management guidelines for grazing, wildlife habitat, and other uses should recognize widespread subspecies as indicators of differences in site potentials.  相似文献   

Postoperative analgesic effects of intravenous,intramuscular, subcutaneous or oral transmucosal buprenorphine administered to cats undergoing ovariohysterectomy     

Tatiana Giordano  Paulo VM Steagall  Tatiana H Ferreira  Bruno W Minto  Sílvia Elaine Rodolfo De Sá Lorena  Juliana Brondani  Stelio PL Luna 《Veterinary anaesthesia and analgesia》2010,37(4):357-366

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Estimation of leaf area index in cereal crops using red–green images     

Kristian Kirk  Hans Jrgen Andersen  Anton G. Thomsen  Johannes R. Jrgensen  Rasmus N. Jrgensen 《Biosystems Engineering》2009,104(3):308-317

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