The Fine Fuel Moisture Code (FFMC) of the Canadian Forest Fire Weather Index System is modified to apply to the top layers of reindeer lichen (Cladina rangiferina [L.] Nyl.). While the basic assumption for FFMC, i.e., exponential drying in constant weather influenced by relative humidity, air temperature, and wind, is retained in the calculation of the reindeer lichen moisture code, actual drying in the model is accelerated by isolation. The equilibrium moisture content (E) of sun-exposed reindeer lichen is 3-4% lower than that for shaded fuels. Rainfall causes a more rapid rise of moisture content in reindeer lichen than in FFMC, and the change is proportional to the initial Mo) and saturation Ms) moisture contents of the lichen, and the amount of rain (R). The model postulates that after rain the moisture content of the lichen (Mr) is: Mr = Mo + [a(Ms - Mo)/(a + Mo)][1 - e-b(Ms-Mo)R]. Comparison of experimental measurements with calculated values suggests that the model represents moisture content in the top 3-4 cm layer of reindeer lichen.
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