Land surface fuel load and influencing factors of Pinus tabuliformis and Platycladus orientalis plantations

  Objective  This paper aims to study the land surface fuel load and influencing factors of typical coniferous forests in Beijing, and to establish a fuel load model, so as to provide research basis for the scientific management of fuel.

  Method  Based on stand factors (DBH, tree height, canopy density, crown width, height of the first living branch) and terrain factors (altitude and slope degree), representative Pinus tabuliformis and Platycladus orientalis forests were selected in 7 districts and counties of Beijing. 42 sample plots were set for each forest type to investigate and measure the fuel load of two coniferous forests (upper dead leaves, lower dead leaves, shrubs, herbs, 1 h time-lag dead branches,10 h time-lag dead branches), redundancy analysis (RDA) was used to study the relationship between land surface fuel load and stand factors and terrain factors, and the total fuel load model was established by multiple linear regression.

  Result  (1) The average total fuel load of Pinus tabuliformis forest and Platycladus orientalis forest were 14.31 and 9.78 t/ha, respectively. The lower dead leaf load accounted for the largest proportion of total fuel load of the two coniferous forests. (2) Redundancy analysis (RDA) showed that the fuel load of upper dead leaves and shrubs was positively correlated with DBH, and that of lower dead leaves was positively correlated with canopy density and slope degree. The dead leaf load of upper and lower layers of Platycladus orientalis was positively correlated with tree height and crown width, and negatively correlated with altitude. The fuel load of shrub was positively correlated with tree height and canopy density, and negatively correlated with altitude. The total fuel load, 1 h time-lag, 10 h time-lag dead branch load of the two coniferous forests were positively correlated with DBH, and the herbage fuel load was positively correlated with altitude. (3) The model showed that DBH, tree height and crown width can calculate the total fuel load of Pinus tabuliformis forest, and the first living branch height, crown width and slope degree can calculate the total fuel load of Platycladus orientalis forest.

  Conclusion  Pinus tabuliformis forest has the possibility of developing into a larger forest fire. According to the land surface fuel load, we should focus on the management of forest litter and fuel, timely clean up the fuel under the forest, and reduce the potential forest fire risk. The relationship between fuel load of different forest types, stand factors and terrain factors is different. In fuel management, we should choose reasonable and appropriate measures according to local conditions.