Moisture and Fine Forest Fuel Response


H E. Anderson

Document Type

Contribution to Book

Journal/Book Title/Conference

Proceedings of the 8th Conference on Fire and Forest Meteorology

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The dynamics of the fine forest fuel's response to moisture changes have not been fully recognized. Fire behavior systems now in use consider all fine fuels to have a 1-hour response time. Experimental results of testing a wide range of fine fuels show the change in moisture content does follow a negative exponential in time. In addition, there is great variability in the desorption and adsorption response times of recently cast and weathered materials. Fuels such as cheatgrass stems and leaves, rockhair lichens, and Cladonia spp. have response times of 1 hour or less. However, other needle fuels such as lodgepole pine, Douglas-fir, and Engelmann spruce have response times greater than 15 hours. Adsorption response times are generally longer than desorption. Weathering for 1 year does shorten response times, but they still remain longer than 1 hour. The effect of a weather diurnal cycle is demonstrated.


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