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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #387310

Research Project: Development of Management Strategies for Livestock Grazing, Disturbance and Climate Variation for the Northern Plains

Location: Livestock and Range Research Laboratory

Title: Weather and fuel as modulators of grassland fire behavior in the northern Great Plains

item McGranahan, Devan
item ZOPFI, MEGAN - University Of North Dakota
item YURKONIS, KATHRYN - University Of North Dakota

Submitted to: Environmental Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/3/2022
Publication Date: 12/16/2022
Citation: McGranahan, D.A., Zopfi, M.E., Yurkonis, K.A. 2022. Weather and fuel as modulators of grassland fire behavior in the northern Great Plains. Environmental Management. 71:940-949.

Interpretive Summary: Safe and effective prescribed fire management requires knowledge of how vegetation and weather conditions affect fire behavior, but little such information is available in the Northern Great Plains. We report temperatures and rates of spread for prescribed burns in grazed pastures in central and southwestern North Dakota. Higher winds caused fires to move more quickly, but not necessarily to burn hotter. Rather, flame temperatures increased with higher fuel loads and lower moisture content.

Technical Abstract: Fuel and fire weather conditions interact to affect wildland fire behavior, but little is known about how these variables affect fire behavior in the northern Great Plains of North America. Data that are available consist mostly of reports based on temperature-time data from thermocouples, and neither consider rate of spread or statistically test the influence of fire environmental variables. We measured fuel load and fuel moisture ahead of prescribed fires in southwestern and central North Dakota, USA, and used a unique multi-channel thermocouple array to measure rate of spread, soil surface temperature, and flame temperature in the plant canopy, which we compared with fire weather data taken from nearby weather stations. Canopy temperatures averaged 225oC during spring burns in central North Dakota and 250oC during fall burns in southwestern North Dakota. Surface temperatures averaged just above 100oC, although 50% of observations were 60oC or less. Regression analysis indicated that wind speed drove faster rates of spread while higher fuel loads and lower fuel moisture produced higher canopy temperatures. None of our measurements explained variability in soil surface temperature, likely because ground-level heating remained low. We highlight the differential responses among fire behavior metrics to different components of the wildland fire environment. These results can help wildland fire managers better match burn conditions to desired outcomes and fire ecologists match measurements to specific ecological responses. We also discuss knowledge gaps that remain in understanding how land management and ignition patterns interact to effect variability in fire behavior, and what fire scientists need to learn about the relationships between atmospheric moisture and fuel curing in grassland systems.