Climate and fire impacts on tree recruitment in mixed conifer forests in northwestern Mexico and California.

Frequent-fire forests were once heterogeneous at multiple spatial scales, which contributed to their resilience to severe fire. While many studies have characterized historical spatial patterns in frequent-fire forests, fewer studies have investigated their temporal dynamics. We investigated the influences of fire and climate on the timing of conifer recruitment in old-growth Jeffrey pine-mixed conifer forests in the Sierra San Pedro Martir (SSPM) and the eastern slope of the Sierra Nevada. Additionally, we evaluated the impacts of fire exclusion and recent climate change on recruitment levels using statistical models with realized as well as fire suppression and climate change-free counterfactual scenarios. Excessive soil drying from anthropogenic climate change resulted in diminished recruitment in the SSPM but not in the Sierra Nevada. Longer fire-free intervals attributable to fire suppression and exclusion resulted in greater rates of recruitment across all sites but was particularly pronounced in the Sierra Nevada, where suppression began >100 years ago and recruitment was 28 times higher than the historical fire return interval scenario. This demonstrates the profound impact of fire's removal on tree recruitment in Sierra Nevada forests even in the context of recent climate change. Tree recruitment at the SSPM coincided with the early-20th-century North American pluvial, as well as a fire-quiescent period in the late 18th and early 19th centuries. Episodic recruitment occurred in the SSPM with no "average" recruitment over the last three centuries. We found that temporal heterogeneity, in conjunction with spatial heterogeneity, are critical components of frequent-fire-adapted forests. Episodic recruitment could be a desirable characteristic of frequent-fire-adapted forests, and this might be more amenable to climate change impacts that forecast more variable precipitation patterns in the future. One key to this outcome would be for frequent fire to continue to shape these forests versus continued emphasis on fire suppression in California.

Intravenous Fluid Bag as a Substitute for Gel Standoff Pad in Musculoskeletal Point-of-care Ultrasound.

INTRODUCTION: Point-of-care ultrasound (POCUS) is a tool undergoing expanding use in military medicine, including routine inpatient, outpatient, and operational environments. Specific musculoskeletal POCUS examinations require additional equipment in the form of a standoff assist device to maximize image acquisition. These devices may not be readily available to POCUS users in more austere or resource-constrained environments. We devised a study to determine if intravenous fluid bags of various volumes could be substituted for standard standoff devices in musculoskeletal POCUS. MATERIALS AND METHODS: Sequential images of a soft tissue foreign body model, an interphalangeal joint, and a chest wall were taken using a gel standoff pad or water bath and compared to images acquired using three different sizes of intravenous fluid bags after removing excess air from the bags. Images were de-identified and scored for quality using a visual analog scale. We used a two-factor analysis of variance without replication to analyze the differences in image quality between standoff devices, with a P-value less than.05 considered statistically significant. RESULTS: We performed 13 POCUS studies and had a group of eight POCUS-trained physicians and physician assistants score these studies, resulting in 104 total quality scores. There was no significant difference in image quality between standoff devices for chest (P-value.280) and hand (P-value 0.947) images. We found a significant difference in image quality between standoff devices for the soft tissue foreign body model (P-value 0.039), favoring larger intravenous fluid bag standoff over standard devices. CONCLUSIONS: In the absence of a standard commercial gel standoff device or water bath, intravenous fluid bags of 50, 100, and 250 mL can facilitate quality image acquisition for musculoskeletal POCUS.

Changes in fire behavior caused by fire exclusion and fuel build-up vary with topography in California montane forests, USA.

Wildfire sizes and proportions burned with high severity effects are increasing in seasonally dry forests, especially in the western USA. A critical need in efforts to restore or maintain these forest ecosystems is to determine where fuel build-up caused by fire exclusion reaches thresholds that compromise resilience to fire. Empirical studies identifying drivers of fire severity patterns in actual wildfires can be confounded by co-variation of vegetation and topography and the stochastic effects of weather and rarely consider long-term changes in fuel caused by fire exclusion. To overcome these limitations, we used a spatially explicit fire model (FlamMap) to compare potential fire behavior by topographic position in Lassen Volcanic National Park (LAVO), California, a large (43,000 ha), mountainous, unlogged landscape with extensive historical and contemporary fuels data. Fuel loads were uniformly distributed and incrementally increased across the landscape, meaning variation in fire behavior within each simulation was due to topography and among simulations, to fuels. We analyzed changes in fire line intensity (FLI) and crown fire potential as surface and canopy fuels increased from historical to contemporary levels and with percentile and actual wildfire weather conditions. Sensitivity to the influence of fuel build-up on fire behavior varied by topographic position. Steep slopes and ridges were most sensitive. At lower surface fuel loads, under pre-exclusion and contemporary canopy conditions, fire behavior was comparable and remained surface-type. As fuels increased, FLI and passive crown fire increased on steep slopes and ridgetops but remained largely unchanged on gentle slopes. Topographic variability in fire behavior was greatest with intermediate fuels. At higher surface fuel loads, under contemporary canopy fuels, passive crown fire dominated all topographic positions. With LAVO's current surface fuels, the area with potential for passive crown fire during actual fire weather increased from 6% pre-exclusion to 34% due to canopy fuel build-up. For topographically diverse landscapes, the results highlight where contemporary fire characteristics are most likely to deviate from historical patterns and may help managers prioritize locations for prescribed burning and managed wildfire to increase fire resilience in fuel rich landscapes.

Immersive Virtual Reality Medical Simulation: Autonomous Trauma Training Simulator.

Background Medical and traumatic emergencies can be intimidating and stressful. This is especially true for early-career medical personnel.Training providers to respond effectively to medical emergencies before being confronted with a real scenario is limited by unnatural or high-cost training modalities that fail to realistically replicate the stress and gravity of real-world trauma management. Immersive virtual reality (IVR) may provide a unique training solution.  Methods We created a working group of 10 active duty or former military emergency medicine physicians and two technical experts. We hosted 10 meetings to facilitate the development process. The program was developed with financial support from the Telemedicine and Advanced Technology Research Center (TATRC), through the primary vendor Exonicus, Inc, with support from Anatomy Next Inc, and Kitware, Inc. Development was completed using an agile project management style, which allowed our team to review progress and provide immediate feedback on previous milestones throughout its completion. The working group completed the resulting four simulation scenarios to evaluate perceived realism and training potential. Finally, testing of the technology platform off the network in a deployed role 3 was conducted. Results Upon completion, we created four IVR scenarios based on the highest mortality battlefield injuries: hemorrhage, tension pneumothorax, and airway obstruction. The working group unanimously indicated a high level of realism and potential training usefulness. Throughout this process, there have been a number of lessons learned and we present those here to show what we have created as well as provide guidance to others creating IVR training solutions.  Conclusion Our team developed trauma scenarios that, to our knowledge, are the only IVR trauma scenarios to run autonomously without instructor input. Furthermore, we provide a potential template for the creation of future autonomous IVR training programs. This framework may offer a dynamic starting point as more teams seek to leverage the capabilities IVR offers.

Socioecological transitions trigger fire regime shifts and modulate fire-climate interactions in the Sierra Nevada, USA, 1600-2015 CE.

Large wildfires in California cause significant socioecological impacts, and half of the federal funds for fire suppression are spent each year in California. Future fire activity is projected to increase with climate change, but predictions are uncertain because humans can modulate or even override climatic effects on fire activity. Here we test the hypothesis that changes in socioecological systems from the Native American to the current period drove shifts in fire activity and modulated fire-climate relationships in the Sierra Nevada. We developed a 415-y record (1600-2015 CE) of fire activity by merging a tree-ring-based record of Sierra Nevada fire history with a 20th-century record based on annual area burned. Large shifts in the fire record corresponded with socioecological change, and not climate change, and socioecological conditions amplified and buffered fire response to climate. Fire activity was highest and fire-climate relationships were strongest after Native American depopulation-following mission establishment (ca. 1775 CE)-reduced the self-limiting effect of Native American burns on fire spread. With the Gold Rush and Euro-American settlement (ca. 1865 CE), fire activity declined, and the strong multidecadal relationship between temperature and fire decayed and then disappeared after implementation of fire suppression (ca. 1904 CE). The amplification and buffering of fire-climate relationships by humans underscores the need for parameterizing thresholds of human- vs. climate-driven fire activity to improve the skill and value of fire-climate models for addressing the increasing fire risk in California.

Accuracy of trans-abdominal ultrasound in a simulated massive acute overdose.

INTRODUCTION: Toxic ingestions are a common cause of morbidity and mortality in the United States. In 2013, there were nearly 2 million reported ingestions and nearly 1000 deaths from poisonings. There is no well-validated imaging study for confirming the presence of pills in the stomach of an overdose patient. There are case reports of ultrasound used for confirmation of pills in the stomach, and we are aware of one prospective trial to evaluate sonography for this application. OBJECTIVE: To determine the sensitivity and specificity of transabdominal ultrasound for visualization of ingested pills. METHODS: Randomized, blinded, placebo-controlled study. Twenty Subjects were randomized to one of two groups. The experimental group ingested 50 enteric-coated placebo capsules with 1 liter of fluid. The control group ingested only 1 liter of fluid. At time 0, 60, and 90 minutes after ingestion, expert sonographers performed transabdominal ultrasound in an attempt to visualize pills in the stomach. RESULTS: At time 0, 60, and 90 minutes post-ingestion, ultrasound had a sensitivity of 62.5% (41.1%, 81.9%), 20.8% (4.6%, 37.1%), and 25% (7.7%, 42.3%) respectively. The specificity at time 0, 60, and 90 minutes post-ingestion were 58.3% (21.9%, 61.4%), 79.1% (62.9%, 95.5%), and 70.8% (52.6%, 89.0%) respectively. CONCLUSION: There is poor sensitivity and specificity for ultrasound detection of pills in the stomach at time 0; these values fell substantially at 60 and 90 minutes post-ingestion. In this pilot study, we did not find ultrasound to be a useful screening tool for detecting pills in the stomach.

Comparison of Preloaded Bougie versus Standard Bougie Technique for Endotracheal Intubation in a Cadaveric Model.

INTRODUCTION: We compared intubating with a preloaded bougie (PB) against standard bougie technique in terms of success rates, time to successful intubation and provider preference on a cadaveric airway model. METHODS: In this prospective, crossover study, healthcare providers intubated a cadaver using the PB technique and the standard bougie technique. Participants were randomly assigned to start with either technique. Following standardized training and practice, procedural success and time for each technique was recorded for each participant. Subsequently, participants were asked to rate their perceived ease of intubation on a visual analogue scale of 1 to 10 (1=difficult and 10=easy) and to select which technique they preferred. RESULTS: 47 participants with variable experience intubating were enrolled at an emergency medicine intern airway course. The success rate of all groups for both techniques was equal (95.7%). The range of times to completion for the standard bougie technique was 16.0-70.2 seconds, with a mean time of 29.7 seconds. The range of times to completion for the PB technique was 15.7-110.9 seconds, with a mean time of 29.4 seconds. There was a non-significant difference of 0.3 seconds (95% confidence interval -2.8 to 3.4 seconds) between the two techniques. Participants rated the relative ease of intubation as 7.3/10 for the standard technique and 7.6/10 for the preloaded technique (p=0.53, 95% confidence interval of the difference -0.97 to 0.50). Thirty of 47 participants subjectively preferred the PB technique (p=0.039). CONCLUSION: There was no significant difference in success or time to intubation between standard bougie and PB techniques. The majority of participants in this study preferred the PB technique. Until a clear and clinically significant difference is found between these techniques, emergency airway operators should feel confident in using the technique with which they are most comfortable.

Perceived effectiveness of teaching methods for point of care ultrasound.

BACKGROUND: Point of care ultrasound (POCUS) is a rapidly expanding aspect of both the practice and education of emergency physicians. The most effective methods of teaching these valuable skills have not been explored. OBJECTIVE: This project aimed to identify those methods that provide the best educational value as determined by the learner. METHODS: Data was collected from pre- and post-course surveys administered to students of the introductory POCUS course provided to emergency medicine residents each year at our facility. Data were collected in 2010 and 2011. Participants were asked to evaluate the effectiveness of small- vs. large-group format, still images vs. video clips, and PowerPoint slides vs. live demonstration vs. hands-on scanning. RESULTS: Students felt the most effective methods to be small-group format, video-clip examples, and hands-on scanning sessions. Students also rated hands-on sessions, still images, and video images as more effective in post-course surveys as compared with pre-course surveys. CONCLUSIONS: The methods perceived as most effective for POCUS education are small-group format, video-clip examples, and hands-on scanning sessions.

Impact of decontamination therapy on ultrasound visualization of ingested pills.

INTRODUCTION: Acute toxic ingestion is a common cause of morbidity and mortality. Emergency physicians (EP) caring for overdose (OD) patients are often required to make critical decisions with incomplete information. Point of care ultrasound (POCUS) may have a role in assisting EPs manage OD patients. We evaluated the impact of different liquid adjuncts used for gastric decontamination on examiners' ability to identify the presence of tablets using POCUS, and assessed examiners' ability to quantify the numbers of tablets in a simulated massive OD. METHODS: This prospective, blinded, pilot study was performed at an academic emergency department. Study participants were volunteer resident and staff EPs trained in POCUS. Five nontransparent, sealed bags were prepared with the following contents: 1 liter (L) of water, 1 L of water with 50 regular aspirin (ASA) tablets, 1 L of water with 50 enteric-coated aspirin tablets (ECA), 1 L of polyethylene glycol (PEG) with 50 ECA, and 1 L of activated charcoal (AC) with 50 ECA. After performing POCUS on each of the bags using a 10-5 MHz linear array transducer, participants completed a standardized questionnaire composed of the following questions: (1) Were pills present? YES/NO; (2) If tablets were identified, estimate the number (1-10, 11-25, >25). We used a single test on proportions using the binomial distribution to determine if the number of EPs who identified tablets differed from 50% chance. For those tablets identified in the different solutions, another test on proportions was used to determine whether the type of solution made a difference. Since 3 options were available, we used a probability of 33.3%. RESULTS: Thirty-seven EPs completed the study. All (37/37) EP's correctly identified the absence of tablets in the bag containing only water, and the presence of ECA in the bags containing water and PEG. For Part 2 of the study, most participants - 25/37 (67.5%) using water, 23/37 (62.1%) using PEG, and all 37 (100%) using AC - underestimated the number of ECA pills in solution by at least 50%. CONCLUSION: There may be a potential role for POCUS in the evaluation of patients suspected of acute, massive ingested OD. EPs accurately identified the presence of ECA in water and PEG, but underestimated the number of tablets in all tested solutions.

Carbon dynamics in the future forest: the importance of long-term successional legacy and climate-fire interactions.

Understanding how climate change may influence forest carbon (C) budgets requires knowledge of forest growth relationships with regional climate, long-term forest succession, and past and future disturbances, such as wildfires and timber harvesting events. We used a landscape-scale model of forest succession, wildfire, and C dynamics (LANDIS-II) to evaluate the effects of a changing climate (A2 and B1 IPCC emissions; Geophysical Fluid Dynamics Laboratory General Circulation Models) on total forest C, tree species composition, and wildfire dynamics in the Lake Tahoe Basin, California, and Nevada. The independent effects of temperature and precipitation were assessed within and among climate models. Results highlight the importance of modeling forest succession and stand development processes at the landscape scale for understanding the C cycle. Due primarily to landscape legacy effects of historic logging of the Comstock Era in the late 1880s, C sequestration may continue throughout the current century, and the forest will remain a C sink (Net Ecosystem Carbon Balance > 0), regardless of climate regime. Climate change caused increases in temperatures limited simulated C sequestration potential because of augmented fire activity and reduced establishment ability of subalpine and upper montane trees. Higher temperatures influenced forest response more than reduced precipitation. As the forest reached its potential steady state, the forest could become C neutral or a C source, and climate change could accelerate this transition. The future of forest ecosystem C cycling in many forested systems worldwide may depend more on major disturbances and landscape legacies related to land use than on projected climate change alone.

Randomized controlled study on the use of multiple-dose activated charcoal in patients with supratherapeutic phenytoin levels.

INTRODUCTION: We conducted a prospective randomized controlled study on the influence of multiple doses of activated charcoal (MDAC) in patients with supratherapeutic serum phenytoin levels; METHODS: Patients with serum phenytoin levels greater than 30 mg/L upon presentation to the ED were recruited from two urban teaching hospitals. Patients enrolled were older than 18, nonpregnant, able to tolerate activated charcoal by mouth and able to give written consent. They were randomized to receive 50 g activated charcoal by mouth every 4 hours or no activated charcoal. They continued in the study until the patient was discharged or the serum level was <25 mg/L. Serum levels were drawn every 6 hours initially, then every 24 hours after the 1st day. The presence of gait abnormalities and nystagmus was recorded and mini-mental status exam (MMSE) scores were collected from each patient enrolled. Time to reach subtoxic levels was recorded; RESULTS: Seventeen patients were enrolled in the study. Seven patients received MDAC, eight patients served as controls and two patients who were initially enrolled as controls inadvertently received one dose of activated charcoal and were excluded from the analysis. Both groups were comparable in age and all were male. The median time to reach a subtoxic level was 41.1 hours (range, 11.6-196) and 19.3 hours (range, 13-33) in the control and charcoal groups, respectively (p = 0.049). The median and range peak serum levels were 40.0 hours (range, 32.0-47.6) and 35.6 hours (range, 32.5-40.0) in the control and charcoal groups, respectively (p = 0.082). The median and range MMSE scores were 20 points (range, 12-30) and 19.5 points (range, 16-29) in the control and charcoal groups, respectively; CONCLUSION: Further study is needed to determine if MDAC decreases the time to reach a subtoxic level of phenytoin in patients with supratherapeutic phenytoin levels.

Three cases of "spice" exposure.

INTRODUCTION: We describe three cases with confirmed exposure to "spice" by detection of the metabolites JWH-018 and/or JWH-073 in urine. All cases had a negative urine drug screen. Case 1. A 25-year-old male with possible seizure, tachycardia, acidosis, and unresponsiveness, presented to a local emergency department (ED) after smoking a "spice" product. His symptoms resolved with benzodiazepines, fluid, and observation. His urine tested positive for JWH-018 and negative for JWH-073 metabolites. Case 2. A 21-year-old male was found unresponsive after smoking "spice." He had hypertension, was agitated, and had a Glasgow Coma Score of 7; the patient was intubated. The skin was warm and dry. His symptoms resolved with IV fluids and he was discharged home after 24 h. His urine tested positive for metabolites of JWH-018 and JWH-073. Case 3. A 19-year-old male was brought to the ED 1 h after smoking a "spice" product and having paranoia and delusions. His urine tested positive for JWH-018 and JWH-073 metabolites. He was discharged asymptomatic after observation for a few hours. DISCUSSION: Spice products are new and abused for their psychogenic effects and mood alteration. These cases exhibited changes consistent with either an anticholinergic or sympathomimetic agent that resolved following general supportive care.

Holocene forest development and maintenance on different substrates in the Klamath Mountains, northern California, USA.

The influence of substrate on long-term vegetation dynamics has received little attention, and yet nutrient-limited ecosystems have some of the highest levels of endemism in the world. The diverse geology of the Klamath Mountains of northern California (USA) allows examination of the long-term influence of edaphic constraints in subalpine forests through a comparison of vegetation histories between nutrient-limited ultramafic substrates and terrain that is more fertile. Pollen and charcoal records spanning up to 15000 years from ultramafic settings reveal a distinctly different vegetation history compared to other soil types. In non-ultramafic settings, the dominant trees and shrubs shifted in elevation in response to Holocene climate variations resulting in compositional and structural changes, whereas on ultramafic substrates changes were primarily structural, not compositional. Fire activity was similar through most of the Holocene with the exception of declines over the last 4000 years on ultramafic substrates, likely due to the reduction of understory fuels and cooler wetter conditions than in the middle Holocene. These results suggest that the tree and shrub distributions were more responsive to past climate changes on non-ultramafic substrates compared to those on ultramafic substrates. The combination of these dynamics may help explain high levels of plant diversity in the Klamath Mountains and provide insights for managing these complex ecosystems.

Understanding common statistical methods, Part I: descriptive methods, probability, and continuous data.

Statistical methods are pervasive in medical research and general medical literature. Understanding general statistical concepts will enhance our ability to critically appraise the current literature and ultimately improve the delivery of patient care. This article intends to provide an overview of the common statistical methods relevant to medicine.

Review of multi-person exposure calls to a regional poison control center.

OBJECTIVE: Poisoning events, including exposures to hazardous materials, can involve multiple victims. Regional poison centers often are contacted in such events involving multiple victims. METHODS: We searched our poison center database over a nine-year time period for all calls involving a poisoning event in which more than two people were exposed to the same substance. We then matched each product to the generic category used by the National Poison Data System. We analyzed this data to find the most frequent substances reported as primary substances in the multiple exposures. RESULTS: We identified 6,695 calls between 2000 and 2008 that had more than two people exposed to the same substance. In these calls, 25,926 people were exposed (3.6% of the 715,701 human exposure calls for this period). These calls involved 64 of the 67 NPDS substance group codes. Some substances were much more commonly involved than others. The top three categories causing the most exposures were Fumes/Gases/Vapors, Food Products/Food Poisoning and Pesticides. Of the patients exposed, 69.4 % were not followed due to minimal effects possible or judged as nontoxic, 0.3% had major effects, 8.6% had no effects, and 9.3% had minimal to moderate effects. Eight people expired. CONCLUSION: Fumes, gases, and vapors make up the majority of multi-exposure calls. The overall mortality from multi-exposures, based on our data, is low. Analysis of these calls can help poison centers better understand these events and direct training.

Melamine toxicity.

Melamine contamination of infant formula in China and its health effects highlight the safety of the global food supply especially as it relates to formula-fed infants. Melamine is a widely used industrial chemical not considered acutely toxic with a high LD(50) in animals. The data available on acute and chronic human exposure to melamine have been limited and extrapolated from animal data. Pet food contamination in 2004 and 2007 showed stone formation and illness in animals when melamine was co-ingested with cyanuric acid. The recent outbreak in infants showed that melamine ingested in large doses may cause stones and illness without significant ingestion of cyanuric acid or other melamine-related chemicals. This may be due to increased uric acid excretion in infants and formation of melamine-uric acid stones. Diagnosis and treatment of infants exposed to melamine requires further study. Clinical signs and symptoms in infants are nonspecific. The stones may be radiolucent and are not consistently seen on ultrasound. The use of alkalinization of the urine for treatment has been proposed, but is of unproven benefit. The FDA and other regulatory agencies have recommended acceptable levels of melamine in foods for consumption. Melamine ingestion has been implicated in stone formation when co-ingested with cyanuric acid, but will cause urinary stones in infants when large amounts of melamine alone are ingested.

The National Fire and Fire Surrogate study: effects of fuel reduction methods on forest vegetation structure and fuels.

Changes in vegetation and fuels were evaluated from measurements taken before and after fuel reduction treatments (prescribed fire, mechanical treatments, and the combination of the two) at 12 Fire and Fire Surrogate (FFS) sites located in forests with a surface fire regime across the conterminous United States. To test the relative effectiveness of fuel reduction treatments and their effect on ecological parameters we used an information-theoretic approach on a suite of 12 variables representing the overstory (basal area and live tree, sapling, and snag density), the understory (seedling density, shrub cover, and native and alien herbaceous species richness), and the most relevant fuel parameters for wildfire damage (height to live crown, total fuel bed mass, forest floor mass, and woody fuel mass). In the short term (one year after treatment), mechanical treatments were more effective at reducing overstory tree density and basal area and at increasing quadratic mean tree diameter. Prescribed fire treatments were more effective at creating snags, killing seedlings, elevating height to live crown, and reducing surface woody fuels. Overall, the response to fuel reduction treatments of the ecological variables presented in this paper was generally maximized by the combined mechanical plus burning treatment. If the management goal is to quickly produce stands with fewer and larger diameter trees, less surface fuel mass, and greater herbaceous species richness, the combined treatment gave the most desirable results. However, because mechanical plus burning treatments also favored alien species invasion at some sites, monitoring and control need to be part of the prescription when using this treatment.

Fire treatment effects on vegetation structure, fuels, and potential fire severity in western U.S. forests.

Forest structure and species composition in many western U.S. coniferous forests have been altered through fire exclusion, past and ongoing harvesting practices, and livestock grazing over the 20th century. The effects of these activities have been most pronounced in seasonally dry, low and mid-elevation coniferous forests that once experienced frequent, low to moderate intensity, fire regimes. In this paper, we report the effects of Fire and Fire Surrogate (FFS) forest stand treatments on fuel load profiles, potential fire behavior, and fire severity under three weather scenarios from six western U.S. FFS sites. This replicated, multisite experiment provides a framework for drawing broad generalizations about the effectiveness of prescribed fire and mechanical treatments on surface fuel loads, forest structure, and potential fire severity. Mechanical treatments without fire resulted in combined 1-, 10-, and 100-hour surface fuel loads that were significantly greater than controls at three of five FFS sites. Canopy cover was significantly lower than controls at three of five FFS sites with mechanical-only treatments and at all five FFS sites with the mechanical plus burning treatment; fire-only treatments reduced canopy cover at only one site. For the combined treatment of mechanical plus fire, all five FFS sites with this treatment had a substantially lower likelihood of passive crown fire as indicated by the very high torching indices. FFS sites that experienced significant increases in 1-, 10-, and 100-hour combined surface fuel loads utilized harvest systems that left all activity fuels within experimental units. When mechanical treatments were followed by prescribed burning or pile burning, they were the most effective treatment for reducing crown fire potential and predicted tree mortality because of low surface fuel loads and increased vertical and horizontal canopy separation. Results indicate that mechanical plus fire, fire-only, and mechanical-only treatments using whole-tree harvest systems were all effective at reducing potential fire severity under severe fire weather conditions. Retaining the largest trees within stands also increased fire resistance.