Integrating plant physiology into simulation of fire behavior and effects.

Wildfires are a global crisis, but current fire models fail to capture vegetation response to changing climate. With drought and elevated temperature increasing the importance of vegetation dynamics to fire behavior, and the advent of next generation models capable of capturing increasingly complex physical processes, we provide a renewed focus on representation of woody vegetation in fire models. Currently, the most advanced representations of fire behavior and biophysical fire effects are found in distinct classes of fine-scale models and do not capture variation in live fuel (i.e. living plant) properties. We demonstrate that plant water and carbon dynamics, which influence combustion and heat transfer into the plant and often dictate plant survival, provide the mechanistic linkage between fire behavior and effects. Our conceptual framework linking remotely sensed estimates of plant water and carbon to fine-scale models of fire behavior and effects could be a critical first step toward improving the fidelity of the coarse scale models that are now relied upon for global fire forecasting. This process-based approach will be essential to capturing the influence of physiological responses to drought and warming on live fuel conditions, strengthening the science needed to guide fire managers in an uncertain future.

Compositional data analysis of smoke emissions from debris piles with low-density polyethylene.

Data describing the composition of smoke are inherently multivariate and always non-negative parts of a whole. The data are relative and the information is contained in the ratios between parts of the composition. A prior analysis of smoke emissions produced from the burning of manzanita wood mixed with low-density polyethylene plastic applied traditional statistical methods to the compositional data and found no effect. The current paper applies compositional data techniques to these smoke emissions to determine if the prior analysis was accurate. Analysis of variance of the isometric log-ratios showed that LDPE significantly affected the CO2 emission ratio for 8 of the 191 trace gases; this analysis showed none of the gases identified in the previous analysis were affected by LDPE. LDPE did not affect the CO2 emission ratios for the alkanes, alkenes, alkynes, aldehydes, cycloalkanes, cycloalkenes, diolefins, ketones, MAHs, and PAHs. Compositional data analysis should be used to analyze smoke emissions data. Burning contaminant-free LDPE should produce emissions like wood. Implications Reanalysis of impact of burning LDPE plastic in silvicultural debris piles using appropriate statistical techniques confirmed previously published results from inappropriate techniques that LDPE did not change the composition of the smoke emissions. Being able to dispose of these LDPE-covered forest debris by burning can save thousands of dollars in labor costs annually. Disposal of pesticide-free agricultural LDPE plastic by burning should only produce wood-like smoke emissions. This applies to LDPE/total mass ratios of 0.25- 2.5% as studied.

Wind Tunnel Experiments to Study Chaparral Crown Fires.

The present protocol presents a laboratory technique designed to study chaparral crown fire ignition and spread. Experiments were conducted in a low velocity fire wind tunnel where two distinct layers of fuel were constructed to represent surface and crown fuels in chaparral. Chamise, a common chaparral shrub, comprised the live crown layer. The dead fuel surface layer was constructed with excelsior (shredded wood). We developed a methodology to measure mass loss, temperature, and flame height for both fuel layers. Thermocouples placed in each layer estimated temperature. A video camera captured the visible flame. Post-processing of digital imagery yielded flame characteristics including height and flame tilt. A custom crown mass loss instrument developed in-house measured the evolution of the mass of the crown layer during the burn. Mass loss and temperature trends obtained using the technique matched theory and other empirical studies. In this study, we present detailed experimental procedures and information about the instrumentation used. The representative results for the fuel mass loss rate and temperature filed within the fuel bed are also included and discussed.

Soil Respiration of the Dahurian Larch (Larix gmelinii) Forest and the Response to Fire Disturbance in Da Xing'an Mountains, China.

Despite the high frequency of wildfire disturbances in boreal forests in China, the effects of wildfires on soil respiration are not yet well understood. We examined the effects of fire severity on the soil respiration rate (Rs) and its component change in a Dahurian Larch (Larix gmelinii) in Northeast China. The results showed that Rs decreased with fire burning severity. Compared with the control plots, Rs in the low burning severity plots decreased by 19%, while it decreased by 28% in the high burning severity plots. The Rs decrease was mainly due to a decreased autotrophic respiration rate (Ra). The temperature sensitivity (Q 10) of Rs increased after the low severity fire disturbances, but it decreased after the high severity fire disturbance. The Rs were triggered by the soil temperature, which may explain most of the Rs variability in this area. Our study, for the first time, provides the data-based foundation to demonstrate the importance of assessing CO2 fluxes considering both fire severity and environmental factors post-fire in boreal forests of China.

Increases in generative concern among older adults following reminders of mortality.

According to terror management theory, people are motivated to protect themselves from the potential for anxiety resulting from awareness of mortality. It was hypothesized that increased concern for future generations, and the symbolic immortality this produces, may be particularly important to older adults when awareness of their mortality is increased. In two studies, older and younger adults' generative concern was examined following mortality or control primes. As hypothesized, older adults' generative concern and preference for pro-social over pro-self generativity were greater following reminders of mortality, whereas neither effect was observed among younger adults. For both studies, age differences were only observed when mortality salience was heightened; older and younger adults' generative concern did not differ in control conditions. Results provide support for the hypothesis that younger and older adults differ in their responses to increased awareness of mortality and suggest that older adults respond to death reminders by adopting a more pro-social generative orientation.

Increases in generative concern among older adults following reminders of mortality.

According to terror management theory, people are motivated to protect themselves from the potential for anxiety resulting from awareness of mortality. It was hypothesized that increased concern for future generations, and the symbolic immortality this produces, may be particularly important to older adults when awareness of their mortality is increased. In two studies, older and younger adults' generative concern was examined following mortality or control primes. As hypothesized, older adults' generative concern and preference for pro-social over pro-self generativity were greater following reminders of mortality, whereas neither effect was observed among younger adults. For both studies, age differences were only observed when mortality salience was heightened; older and younger adults' generative concern did not differ in control conditions. Results provide support for the hypothesis that younger and older adults differ in their responses to increased awareness of mortality and suggest that older adults respond to death reminders by adopting a more pro-social generative orientation.

Effect of low-density polyethylene on smoke emissions from burning of simulated debris piles.

UNLABELLED: Low-density polyethylene (LDPE) plastic is used to keep piled debris from silvicultural activities--activities associated with development and care of forests--dry to enable efficient disposal by burning. The effects of inclusion of LDPE in this manner on smoke emissions are not well known. In a combustion laboratory experiment, 2-kg mixtures of LDPE and manzanita (Arctostaphylos sp.) wood containing 0, 0.25, and 2.5% LDPE by mass were burned. Gaseous and particulate emissions were sampled in real time during the entire flaming, mixed combustion phase--when the flaming and smoldering phases are present at the same time--and during a portion of the smoldering phase. Analysis of variance was used to test significance of modified combustion efficiency (MCE)--the ratio of concentrations of fire-integrated excess CO2 to CO2 plus CO--and LDPE content on measured individual compounds. MCE ranged between 0.983 and 0.993, indicating that combustion was primarily flaming; MCE was seldom significant as a covariate. Of the 195 compounds identified in the smoke emissions, only the emission factor (EF) of 3M-octane showed an increase with increasing LDPE content. Inclusion of LDPE had an effect on EFs of pyrene and fluoranthene, but no statistical evidence of a linear trend was found. Particulate emission factors showed a marginally significant linear relationship with MCE (0.05 < P-value < 0.10). Based on the results of the current and previous studies and literature reviews, the inclusion of small mass proportions of LDPE in piled silvicultural debris does not appear to change the emissions produced when low-moisture-content wood is burned. In general, combustion of wet piles results in lower MCEs and consequently higher levels of emissions. IMPLICATIONS: Current air quality regulations permit the use of burning to dispose of silvicultural piles; however, inclusion of low-density polyethyelene (LDPE) plastic in silvicultural piles can result in a designation of the pile as waste. Waste burning is not permitted in many areas, and there is also concern that inclusion of LDPE leads to toxic air emissions.

Interpersonal politics: the role of terror management and attachment processes in shaping political preferences.

Research on terror management theory (TMT) indicates that reminders of death affect political attitudes, but political orientation only sometimes moderates these effects. We propose that secure relationships are associated with values of tolerance and compassion, thus orienting people toward liberalism; insecure attachments are associated with more rigid and absolutist values that orient people toward conservatism. Given that attachment relationships become especially active when security needs are heightened, we predicted that mortality salience would be an important factor in understanding the relationship between attachment processes and political orientation. Supporting these ideas, Study 1 showed that after a mortality-salience manipulation, securely attached participants increased their support for a liberal presidential candidate, and less securely attached participants increased their support for a conservative presidential candidate. In Study 2, a secure-relationship prime following a mortality-salience manipulation engendered a less violent approach to the problem of terrorism than did a neutral-relationship prime. We discuss the interaction of TMT processes and individual differences in attachment in shaping political preferences.