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1.
Ecol Appl ; 27(7): 2013-2030, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-28644577

RESUMO

Following changes in vegetation structure and pattern, along with a changing climate, large wildfire incidence has increased in forests throughout the western United States. Given this increase, there is great interest in whether fuels treatments and previous wildfire can alter fire severity patterns in large wildfires. We assessed the relative influence of previous fuels treatments (including wildfire), fire weather, vegetation, and water balance on fire-severity in the Rim Fire of 2013. We did this at three different spatial scales to investigate whether the influences on fire severity changed across scales. Both fuels treatments and previous low to moderate-severity wildfire reduced the prevalence of high-severity fire. In general, areas without recent fuels treatments and areas that previously burned at high severity tended to have a greater proportion of high-severity fire in the Rim Fire. Areas treated with prescribed fire, especially when combined with thinning, had the lowest proportions of high severity. The proportion of the landscape burned at high severity was most strongly influenced by fire weather and proportional area previously treated for fuels or burned by low to moderate severity wildfire. The proportion treated needed to effectively reduce the amount of high severity fire varied by spatial scale of analysis, with smaller spatial scales requiring a greater proportion treated to see an effect on fire severity. When moderate and high-severity fire encountered a previously treated area, fire severity was significantly reduced in the treated area relative to the adjacent untreated area. Our results show that fuels treatments and low to moderate-severity wildfire can reduce fire severity in a subsequent wildfire, even when burning under fire growth conditions. These results serve as further evidence that both fuels treatments and lower severity wildfire can increase forest resilience.


Assuntos
Agricultura Florestal/métodos , Tempo (Meteorologia) , Incêndios Florestais , California , Incêndios Florestais/classificação
2.
PLoS One ; 11(5): e0147688, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27196621

RESUMO

Quantifying historical fire regimes provides important information for managing contemporary forests. Historical fire frequency and severity can be estimated using several methods; each method has strengths and weaknesses and presents challenges for interpretation and verification. Recent efforts to quantify the timing of historical high-severity fire events in forests of western North America have assumed that the "stand age" variable from the US Forest Service Forest Inventory and Analysis (FIA) program reflects the timing of historical high-severity (i.e. stand-replacing) fire in ponderosa pine and mixed-conifer forests. To test this assumption, we re-analyze the dataset used in a previous analysis, and compare information from fire history records with information from co-located FIA plots. We demonstrate that 1) the FIA stand age variable does not reflect the large range of individual tree ages in the FIA plots: older trees comprised more than 10% of pre-stand age basal area in 58% of plots analyzed and more than 30% of pre-stand age basal area in 32% of plots, and 2) recruitment events are not necessarily related to high-severity fire occurrence. Because the FIA stand age variable is estimated from a sample of tree ages within the tree size class containing a plurality of canopy trees in the plot, it does not necessarily include the oldest trees, especially in uneven-aged stands. Thus, the FIA stand age variable does not indicate whether the trees in the predominant size class established in response to severe fire, or established during the absence of fire. FIA stand age was not designed to measure the time since a stand-replacing disturbance. Quantification of historical "mixed-severity" fire regimes must be explicit about the spatial scale of high-severity fire effects, which is not possible using FIA stand age data.


Assuntos
Incêndios , Florestas , Pinus ponderosa , Traqueófitas , América do Norte
3.
Anesth Analg ; 95(3): 512-6, table of contents, 2002 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-12198027

RESUMO

UNLABELLED: In this study, we examined the utility of preoperative dobutamine stress echocardiograms (DSE) obtained for 85 patients in accordance with guidelines published by the American College of Cardiology (ACC) and the American Heart Association (AHA). The medical record of each patient was reviewed to identify the clinical criteria that indicated the need for a DSE, the DSE results, therapeutic interventions rendered as a result of the DSE, and any perioperative cardiac morbidity. The DSE was positive for inducible ischemia in 4 patients (4.7%), negative in 74 (87.1%), and nondiagnostic in 7 (8.2%). DSEs that were obtained for 48 patients because of a history of diabetes mellitus, mild angina, or "minor clinical predictors" produced only negative results. Of the four patients with positive DSE results, three underwent coronary angiography, and one of those three underwent bypass grafting before surgery. An additional 29 patients received a preoperative DSE but were excluded from the study because the criteria for ordering the DSE did not meet the ACC/AHA guidelines. No patient had any perioperative morbidity related to myocardial ischemia. The total patient charge for the 85 DSEs obtained at our institution was US$104,635. Use of the ACC/AHA guidelines for preoperative DSEs does not appear to be cost-effective. However, the current algorithm could be significantly improved by altering the criteria for obtaining preoperative DSEs. IMPLICATIONS: This study was a retrospective review of 85 patient charts that found a low cost-effectiveness of using American College of Cardiology/American Heart Association guidelines for obtaining preoperative dobutamine stress echocardiograms. Suggested modifications of these guidelines should improve their specificity with no loss in sensitivity.


Assuntos
Agonistas Adrenérgicos beta , Dobutamina , Eletrocardiografia/efeitos dos fármacos , Teste de Esforço/métodos , Cuidados Pré-Operatórios/economia , Procedimentos Cirúrgicos Operatórios , Agonistas Adrenérgicos beta/economia , Algoritmos , Dobutamina/economia , Teste de Esforço/economia , Humanos , Valor Preditivo dos Testes , Estudos Retrospectivos , Medição de Risco
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