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International Journal of Wildland Fire International Journal of Wildland Fire Society
Journal of the International Association of Wildland Fire
RESEARCH ARTICLE

Relating fuel loads to overstorey structure and composition in a fire-excluded Sierra Nevada mixed conifer forest

Jamie M. Lydersen A E , Brandon M. Collins A B , Eric E. Knapp C , Gary B. Roller D and Scott Stephens D
+ Author Affiliations
- Author Affiliations

A USDA Forest Service, Pacific Southwest Research Station, 1731 Research Park Dr., Davis, CA 95618, USA.

B Center for Fire Research and Outreach, College of Natural Resources, University of California, Berkeley, USA.

C USDA Forest Service, Pacific Southwest Research Station, 3644 Avtech Parkway, Redding, CA 96002, USA.

D Department of Environmental Science, Policy and Management, University of California, Berkeley, 130 Mulford Hall, MC#3114, Berkeley, CA 94720, USA.

E Corresponding author. Email: jmlydersen@fs.fed.us

International Journal of Wildland Fire 24(4) 484-494 https://doi.org/10.1071/WF13066
Submitted: 19 April 2013  Accepted: 6 November 2014   Published: 5 March 2015

Abstract

Although knowledge of surface fuel loads is critical for evaluating potential fire behaviour and effects, their inherent variability makes these difficult to quantify. Several studies relate fuel loads to vegetation type, topography and spectral imaging, but little work has been done examining relationships between forest overstorey variables and surface fuel characteristics on a small scale (<0.05 ha). Within-stand differences in structure and composition would be expected to influence fuel bed characteristics, and thus affect fire behaviour and effects. We used intensive tree and fuel measurements in a fire-excluded Sierra Nevada mixed conifer forest to assess relationships and build predictive models for loads of duff, litter and four size classes of downed woody fuels to overstorey structure and composition. Overstorey variables explained a significant but somewhat small percentage of variation in fuel load, with marginal R2 values for predictive models ranging from 0.16 to 0.29. Canopy cover was a relatively important predictor for all fuel components, although relationships varied with tree species. White fir abundance had a positive relationship with total fine woody fuel load. Greater pine abundance was associated with lower load of fine woody fuels and greater load of litter. Duff load was positively associated with total basal area and negatively associated with oak abundance. Knowledge of relationships contributing to within-stand variation in fuel loads can increase our understanding of fuel accumulation and improve our ability to anticipate fine-scale variability in fire behaviour and effects in heterogeneous mixed species stands.

Additional keywords: fine fuels, forest structure, fuel model, overstorey composition, woody debris.


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