Spread rate and parameter correction of surface fuel in Pinus koraiensis plantation based on Rothermel model

  Objective  Based on laboratory simulation burning experiment, this paper aims to measure the spread rate of surface fuel in Pinus koraiensis plantation under different slopes and water contents, compared with the spread rate calculated by Rothermel model, and modify the parameter of Rothermel model to increase the applicability in Korean pine plantation.

  Method  Taking surface fuel of Pinus koraiensis plantation as experimental materials, according to the field conditions of sample plots, the fuel bed was established with different water contents and slopes. 30 times burning experiments were conducted under no slope and no wind conditions, 5°, 10°, 15° and 20° each for 15 times, in a total of 90 time experiments. The calculation of spread rate was based on thermocouple, its location data, and fit the parameters of Rothermel model in no slope and no wind conditions to obtain the optimal model, and correct slope coefficient of Rothermel model.

  Result  In all experiments, the maximum spread rate was 0.631 m/min, and the minimum spread rate was 0.114 m/min. The mean average absolute error was 0.059 m/min, and the range was 0.003−0.241 m/min, and the average relative error was 27.4%, which was calculated by Rothermel model, and the range was 2.40%−152.6%. On the basis of re-correcting the fuel characteristic parameter β_op of the Rothermel model with the burning test data under flat ground and no wind, the slope correction parameters were corrected based on the burning test data under the conditions of 5°−20°, and the mean value of average absolute error for Rothermel model after the correction had reduced by 0.024 m/min, which was 0.035 m/min, the range was 0.003−0.102 m/min, and the average relative error had reduced by 10.44% , being 17.0%, and the range was 1.8%−65.5%; R² was 0.913 5 between measured spread rate and predicted value after parameter correction.

  Conclusion  The Rothermel model cannot be directly used to predict the spread rate of surface fuel in Pinus koraiensis plantation under the slope of 0°−20°, the fuel characteristic parameter and slope coefficient parameter need to be corrected. After parameter correction, the prediction error is significantly reduced, and the prediction accuracy is significantly improved. Then it is possible to predict the surface fuel spread rate in Pinus koraiensis plantation under low slope conditions in China.