Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “wildfires”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13

Decadal-scale recovery of carbon stocks after wildfires throughout the boreal forests

Boreal forests store 30% of the world's terrestrial carbon (C). Consequently, climate change mediated alterations in the boreal forest fire regime can have a significant impact on the global C budget. Here, we synthesize the effects of forest fires on the stocks and recovery rates of C in boreal forests from 368 plots from 16 long-term (= 100 years) fire chronosequences spread throughout the boreal zone. The mean annual temperature varied from -9.5°C to +5.2°C and annual precipitation from 295 mm to 824 mm in the study sites. Total C stocks decreased on average by 60% (range from <10% to >80%) because of forest fires, primarily due to large declines in the living trees and O-layer C stocks. C emissions of fires ranged from 0.1 to 11.4 kg m-2, and in most cases, the emissions were < 4 kg m-2. Total C stocks increased with time since fire following a sigmoidal shape Gompertz function, and it took 125 years until an average asymptote of 8.1 kg C m-2 was reached. Total C stocks accumulated at a rate of 2–60 g m-2 yr-1 during the first 100 years. We found that potential evapotranspiration (PET) was significantly correlated with C stocks and their post-fire recovery, likely because it integrates temperature, radiation and the length of the growing season. If the fire return interval shortens to under 100 years in the future, this suggests that many boreal forests will be prevented from reaching their full C storage potential. However, our results suggest that climate warming-induced increases in PET may also speed up the post-fire recovery of C stocks.

carbon accumulation, carbon pools, chronosequence,↗

Wildfire Smoke Demonstrates Significant and Predictable Black Carbon Light Absorption Enhancements

Abstract Black carbon (BC) is estimated to have the second largest anthropogenic radiative forcing in earth‐systems models (ESMs), but there is significant uncertainty in its impact due to complex mixing with organics. Laboratory‐generated particles show that co‐mixed non‐absorbing material enhances absorption by BC by a factor of 2–3.5 as predicted by optical models. However, weak or no enhancements are often reported for field studies. The cause of lower‐than‐expected absorption is not well understood and implies a lower radiative impact of BC compared to how many ESMs currently treat aerosols. By analyzing BC aerosol particle‐by‐particle we reconcile observed and expected absorption for ambient smoke plumes varying in geographic origin, fuel types, burn conditions, atmospheric age and transport. Although particle‐by‐particle tracking is computationally prohibitive for sophisticated ESMs we show that realistic BC absorption is reliably estimated by bulk properties of the plume providing a suitable parameterization to constrain black carbon radiative forcing.

54 ENVIRONMENTAL SCIENCES↗

Woodland wildfire enables fungal colonization of encroaching Douglas‐fir

Abstract Self‐reinforcing differences in fire frequency help closed‐canopy forests, which resist fire, and open woodlands, which naturally burn often, to co‐occur stably at landscape scales. Forest tree seedlings, which could otherwise encroach and overgrow woodlands, are killed by regular fire, yet fire has other effects that may also influence these feedbacks. In particular, many forest trees require symbiotic ectomycorrhizal fungi in order to establish. By restructuring soil fungal communities, fire might affect the availability of symbionts or the potential for symbiont sharing between encroaching trees and woodland vegetation. To investigate this possibility, we performed a soil bioassay experiment using inoculum from burned and unburned oak woodlands and Douglas‐fir forests. We examined how fire, ecosystem type, and neighboring heterospecific seedlings affect fungal root community assembly of Douglas‐firs and oaks. We asked whether heterospecific seedlings facilitated fungal colonization of seedling roots in non‐native soil, and if so, whether fire influenced this interaction. External fungal colonization of oak roots was more influenced by fire and ecosystem type than by the presence of a Douglas‐fir, and oaks increased the likelihood that Douglas‐fir roots would be colonized by fungi in oak woodland soil. Yet, fire increased colonization of Douglas‐fir in oak soil, diminishing the otherwise crucial role played by oak facilitation. Fire also strengthened the positive effect of Douglas‐firs on oak root‐associated fungal diversity in Douglas‐fir forest soil. Prior work shows that fire supports woodland ecosystems by stemming recruitment of encroaching seedlings. Here, we find evidence that it may contrastingly reduce fungal limitation of invasive seedling growth and establishment, otherwise relieved only by facilitation. Future work can investigate how these opposing effects might contribute to the net impact of changes in fire regime on landcover stability. Read the free Plain Language Summary for this article on the Journal blog.

54 ENVIRONMENTAL SCIENCES↗