Human influence on the abundance and connectivity of high-risk fuels in mixed forests of northern Wisconsin,USA   总被引：2，自引：1，他引：1  

Sturtevant  Brian R.  Zollner  Patrick A.  Gustafson  Eric J.  Cleland  David T. 《Landscape Ecology》2004,19(3):235-253

Though fire is considered a natural disturbance, humans heavily influence modern wildfire regimes. Humans influence fires both directly, by igniting and suppressing fires, and indirectly, by either altering vegetation, climate, or both. We used the LANDIS disturbance and succession model to compare the relative importance of a direct human influence (suppression of low intensity surface fires) with an indirect human influence (timber harvest) on the long-term abundance and connectivity of high-risk fuel in a 2791 km² landscape characterized by a mixture of northern hardwood and boreal tree species in northern Wisconsin. High risk fuels were defined as a combination of sites recently disturbed by wind and sites containing conifer species/cohorts that might serve as ladder fuel to carry a surface fire into the canopy. Two levels of surface fire suppression (high/current and low) and three harvest alternatives (no harvest, hardwood emphasis, and pine emphasis) were compared in a 2×3 factorial design using 5 replicated simulations per treatment combination over a 250-year period. Multivariate analysis of variance indicated that the landscape pattern of high-risk fuel (proportion of landscape, mean patch size, nearest neighbor distance, and juxtaposition with non fuel sites) was significantly influenced by both surface fire suppression and by forest harvest (p > 0.0001). However, the two human influences also interacted with each other (p < 0.001), because fire suppression was less likely to influence fuel connectivity when harvest disturbance was simultaneously applied. Temporal patterns observed for each of seven conifer species indicated that disturbances by either fire or harvest encouraged the establishment of moderately shade-tolerant conifer species by disturbing the dominant shade tolerant competitor, sugar maple. Our results conflict with commonly reported relationships between fire suppression and fire risk observed within the interior west of the United States, and illustrate the importance of understanding key interactions between natural disturbance, human disturbance, and successional responses to these disturbance types that will eventually dictate future fire risk.This revised version was published online in May 2005 with corrections to the Cover Date.  相似文献   

Isolation of Jamestown Canyon virus (California virus group) from vesicular lesions of a horse.     

S P Sahu  J Landgraf  N Wineland  D Pedersen  D Alstad  G Gustafson 《Journal of veterinary diagnostic investigation》2000,12(1):80-83

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Technology assessment, soviet style     

Gustafson T 《Science (New York, N.Y.)》1980,208(4450):1343-1348

The Soviet Union is actively considering two plans to divert large northern lakes and rivers to the south of the country. If adopted, these would rank among the most expensive and complicated engineering projects ever undertaken, with unforeseeable but possibly far-reaching environmental effects. The plans, now at an advanced stage, have aroused a spirited public controversy, providing an unusual glimpse of Soviet policy-making and technology assessment. Major decisions are due by 1985. The question is, what will happen to the quality and openness of this debate as the political stakes rise and the time of decision draws near?  相似文献   

The works of living social insects as pseudofossils and the age of the oldest known metazoa     

Cloud P  Gustafson LB  Watson JA 《Science (New York, N.Y.)》1980,210(4473):1013-1015

Living organisms are known to create structures in ancient rocks that are indigenous but not primary and that have been mistaken for fossils. Examination of burrows recently reported as fossils from 10(9)-year-old sedimentary rocks indicates that they are not the same age as the rocks but were probably made by termites working down after water. The burrows are partially filled with material from a modern lateritic surface from which they descend into steeply dipping, decomposed silt-stones of the Zambian Copperbelt. In fact, no authentic record of Metazoa that are demonstrably coeval with rocks older than 680 million years is known.  相似文献   

Wheat Substitutions in Hexaploid Triticale*     

J. P. Gustafson  J. E. Dille  B. Skovmand 《Plant Breeding》1989,102(2):109-112

Crosses between octoploid and hexaploid triticales have been made m breeding programs for several years, From an analysis of the progeny of such crosses where selections for an octoploid-like phenotype had been made, it was established that 149 out of 150 lines were hexaploid in chromosome number, C-banding and in situ hybridization demonstrated that all but five of the 62 lines analyzed in detail contained visible chromosomes or segments from the D genome. Only four lines had D-genome chromosome replacing rye chromosomes. All of the remaining 53 D-genome substitutions involved the replacing of wheat chromosomes from either the A or B genomes. This establishes the ease with which D-genome genes can be placed into triticale without the loss of rye chromosomes.  相似文献   

Drug dose and drug choice: Optimizing medical therapy for veterinary cancer     

Douglas H. Thamm  Daniel L. Gustafson 《Veterinary and comparative oncology》2020,18(2):143-151

Although novel agents hold great promise for the treatment of animal neoplasia, there may be room for significant improvement in the use of currently available agents. These improvements include altered dosing schemes, novel combinations, and patient‐specific dosing or selection of agents. Previous studies have identified surrogates for “individualized dose intensity,”, for example, patient size, development of adverse effects, and pharmacokinetic parameters, as potential indicators of treatment efficacy in canine lymphoma, and strategies for patient‐specific dose escalation are discussed. Strategies for treatment selection in individual patients include conventional histopathology, protein‐based target assessment (eg, flow cytometry, immunohistochemistry, and mass spectrometry), and gene‐based target assessment (gene expression profiling and targeted or global sequencing strategies). Currently available data in animal cancer evaluating these strategies are reviewed, as well as ongoing studies and suggestions for future directions.  相似文献   

The influence of haemocyte number on the resistance of the freshwater crayfish, Pacifastacus leniusculus Dana, to the parasitic fungus Aphanomyces astaci     

M. PERSSON  L. CERENIUS  K. SÖDERHÄLL 《Journal of fish diseases》1987,10(6):471-477

Abstract. The number of circulating haemocytes in crayfish, Pacifastacus leniusculus Dana, was reduced after injection of yeast cell walls (Zymosan) into the animals. Crayfish harbouring the parasitic fungus A. astaci as a 'latent' infection in melanized areas in the cuticle died due to unrestricted growth of unmelanized hyphae when they were injected with Zymosan. The β–1,3–gIucan laminaran, introduced into the haemocoel of P. leniusculus harbouring A. astaci hyphae in the cuticle, also caused a decrease in the total haemocyte counts (THC), but these animals survived the treatment and no unmelanized hyphae of A, astaci were found. The recovery of THC was found to be more rapid after laminaran injection than after Zymosan injection, which could explain why laminaran treated crayfish retained their resistance and could combat the A. astaci hyphae in the cuticle. The importance of the number of haemocytes in defence and well-being of crayfish is discussed.  相似文献   

Rapid introduction of disease resistance from rye into common wheat by anther culture of a 6x triticale × nulli-tetrasomic wheat     

X. Q. Zhang    X. P. Wang    K. Ross    H. Hu  J. P. Gustafson  C. O. Qualset 《Plant Breeding》2001,120(1):39-42

Powdery mildew (caused by Erysiphe graminis) and yellow rust (caused by Puccinia striiformis) are the two most serious wheat diseases found in China. Rye chromosomes, carrying genes for resistance to these diseases, were introduced into common wheat in two generations using chromosome engineering and anther culture. The F₁ hybrids from a cross involving a hexaploid triticale (×Triticosecale Wittmack) בChinese Spring’ nulli‐tetrasomic N6DT6A wheat aneuploid line were anther cultured and doubled‐haploid plants were regenerated. Using genomic in situ hybridization, C‐banding and biochemical marker analyses, one of the anther‐cultured lines (ZH‐1)studied in detail, proved to be a doubled‐haploid with one rye chromosome pair added (1R) and a homozygous 6R/6D substitution (2n= 44). The line was tested for expression of disease resistance and found to be highly resistant to powdery mildew and moderately resistant to yellow rust.  相似文献   

Early determination of genotypes for apple scab resistance by forced flowering of test cross progenies   总被引：1，自引：0，他引：1  

Herb S. Aldwinckle  H. L. Gustafson  R. C. Lamb 《Euphytica》1976,25(1):185-191

Summary Apple selections with different major genes for resistance to apple scab (Venturia inaequalis) derived from Malus floribunda and M. pumila were crossed with each other. The progenies were screened as young seedlings for their reaction to V. inaequalis race 1. A gene for resistance from M. pumila, causing stellate necrotic (SN) lesions, was epistatic to a second gene for resistance from M. floribunda, causing irregular chlorotic (Chl) lesions. Although in most cases SN, Chl and susceptible phenotypes were clearly distinct, occasionally reactions were difficult to characterize or varied from one inoculation to another. Selected seedlings showing resistant or susceptible reactions were forced to flower in 16–20 months in the greenhouse and test crossed with susceptible cultivars. Test cross seedlings were screened for scab reaction. The presence of both genes for resistance in a resistant plant was indicated by presence of both Chl and SN resistant phenotypes in the test cross progeny. Chi-square analysis of four large progenies produced a good fit to the expected ratio. The use of the forced flowering technique to determine scab resistance genotypes in 28 months demonstrated its value in breeding apples with multiple disease resistance.  相似文献   

Pharmacokinetics of ceftiofur and metabolites after single intravenous and intramuscular administration and multiple intramuscular administrations of ceftiofur sodium to sheep   总被引：1，自引：0，他引：1  

A. L. Craigmill  S. A. Brown  S. E. Wetzlich  C. R. Gustafson  & T. S. Arndt 《Journal of veterinary pharmacology and therapeutics》1997,20(2):139-144

Twenty-four sheep (38.0–54.1 kg body wt) were allocated into four treatment groups and dosed with ceftiofur sodium at 1.1 mg ceftiofur free acid equivalents (CFAE)/kg or 2.2 CFAE/kg using a complete two-route (intravenous, i.v.; intramuscular, i.m.), two-period crossover design, with a two-week washout between injections. After another two-week washout period, 12 sheep were selected and dosed with ceftiofur sodium i.m. for five consecutive days at either 1.1 or 2.2 mg CFAE/kg. After all injections, blood samples were obtained serially for determination of serum concentrations of ceftiofur and metabolites. The terminal phase half-lives derived from the last 3–5 concentration-time points were 350 and 292 min (harmonic means) after i.v. doses of 1.1 and 2.2 mg/kg, respectively, and 389 and 459 min after i.m. doses of 1.1 and 2.2 mg/kg, respectively. The i.m. bioavailability of ceftiofur sodium in sheep was 100%, and the area under the curve from time 0 to the limit of quantitation ( AUC _0–LOQ) was dose-proportional from 1.1–2.2 mg CFAE/kg body wt in sheep. After 5 daily i.m. doses of ceftiofur sodium at either 1.1 or 2.2 mg CFAE/kg there was minimal accumulation of drug in serum as assessed by the observed maximum serum concentration ( C _max), and serum concentrations were dose-proportional after the multiple dosing regimen.  相似文献