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The level of protection to fauna provided by tree cavities during wildland fires is not well understood. Here we present a model for estimating the transport of combustion gases into cylindrical, single-entrance cavities during exposures caused by different wildland fire scenarios. In these shelters, the entrance occurs near the top of the cavity. This empirical model was developed from a suite of numerical experiments using the National Institute of Standards and Technology’s Fire Dynamics Simulator, which spanned a range of entrance diameters, wind speeds, gas temperatures, and vertical angles of incidence. To evaluate the model’s predictions, it was used to replicate, with great accuracy, a time series of carbon monoxide (CO) concentrations in a controlled experiment where a fabricated cylindrical cavity was exposed to combustion products. The time constant for cavity filling is proportional to the ratio of cavity volume to entrance area. Hot gases lead to significant stratification within the cavity during exposures. To demonstrate the model’s potential use in predicting faunal exposures in the context of land management, we show that the model can be used to estimate dosage within red-cockaded woodpecker (Picoides borealis Vieillot, 1809) cavities without requiring temporally detailed, local measurements of wind speed and combustion product concentrations.
