Abstract:

Prediction of fuel moisture content based timelag and equilibrium moisture content is a accurate method, which is commonly employed in the American National Fire Danger Rating System and the Canadian Forest Fire Danger Rating System. The timelag and equilibrium moisture content constants vary with fuel types and structure. A preliminary study was conducted on the effects of fuelbed structure features on these parameters in desorption process of fuelbeds composed of Scots pine needles. The results indicated that with the Catchpoles method, the fuel moisture was well modelled with errors within 0.01, which approved the validity of the estimated parameters. Further analysis revealed that fuelbed depth and load affected these parameters: timelag and constant b of Nelson(1984) model were positively, and constant a of the model was negatively, correlated with these features. Models established for predicting these parameters from these fuelbed structure features overestimated timelag and constant b but underestimate constant a. There exist some uncertainty in the analysis, and futher research is needed on both desorption and absorption processes with other equilibrium moisture models and under broader weather conditions.

Key words: fuel, moisture content, timelag, equilibrium moisture content, Scots Pine, structure