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Abstract In semi‐arid regions where drought and wildfire events often co‐occur, such as in Southern California chaparral, relationships between plant hydration, drought‐ and fire‐adapted traits may explain landscape‐scale wildfire dynamics. To examine these patterns, fire scientists and plant physiologists quantify hydration in plants via mass‐based metrics of water content, including live fuel moisture, or pressure‐based metrics of physiological status, such as xylem water potential; however, relationships across these metrics, plant traits and flammability remain unresolved.To determine the impact of hydration on tissue‐level flammability (leaves and stems), we conducted laboratory dehydration tests across wet and dry seasons in which we simultaneously measured xylem water potential, live fuel moisture and flammability. We tested two widespread chaparral shrubs,Adenostoma fasciculatumandCeanothus megacarpus.Live fuel moisture showed a threshold‐type relationship with tissue flammability (increased ignitability and combustibility at specific hydration levels) that aligned with drought‐response traits (turgor loss point) and fire behaviour (increased fire likelihood and spread) identified at the landscape scale. Water potential was the better predictor of flammability in linear statistical models.A. fasciculatumwas more flammable thanC. megacarpus, and both species were more flammable during the wet growing season, suggesting seasonal growth or drought‐related tissue characteristics other than moisture content, such as lignin or chemical content, are critical for determining flammability.Our results suggest a mechanism for landscape‐scale increases in flammability at specific levels of drought stress. Integration of drought‐related traits, such as the turgor loss point, might improve models of wildfire risk in drought‐ and fire‐prone systems. Read the freePlain Language Summaryfor this article on the Journal blog.
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A Comparison of Fire Weather Indices with MODIS Fire Days for the Natural Regions of Alaska
Research Highlights: Flammability of wildland fuels is a key factor influencing risk-based decisions related to preparedness, response, and safety in Alaska. However, without effective measures of current and expected flammability, the expected likelihood of active and problematic wildfires in the future is difficult to assess and prepare for. This study evaluates the effectiveness of diverse indices to capture high-risk fires. Indicators of drought and atmospheric drivers are assessed along with the operational Canadian Forest Fire Danger Rating System (CFFDRS). Background and Objectives: In this study, 13 different indicators of atmospheric conditions, fuel moisture, and flammability are compared to determine how effective each is at identifying thresholds and trends for significant wildfire activity. Materials and Methods: Flammability indices are compared with remote sensing characterizations that identify where and when fire activity has occurred. Results: Among these flammability indicators, conventional tools calibrated to wildfire thresholds (Duff Moisture Code (DMC) and Buildup Index (BUI)), as well as measures of atmospheric forcing (Vapor Pressure Deficit (VPD)), performed best at representing the conditions favoring initiation and size of significant wildfire events. Conventional assessments of seasonal severity and overall landscape flammability using DMC and BUI can be continued with confidence. Fire models that incorporate BUI in overall fire potential and fire behavior assessments are likely to produce effective results throughout boreal landscapes in Alaska. One novel result is the effectiveness of VPD throughout the state, making it a potential alternative to FFMC among the short-lag/1-day indices. Conclusions: This study demonstrates the societal value of research that joins new academic research results with operational needs. Developing the framework to do this more effectively will bring science to action with a shorter lag time, which is critical as we face growing challenges from a changing climate.
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- PAR ID:
- 10166155
- Date Published:
- Journal Name:
- Forests
- Volume:
- 11
- Issue:
- 5
- ISSN:
- 1999-4907
- Page Range / eLocation ID:
- 516
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/f11050516
