预防华山松树冠火的最低修枝高度探讨

The Lowest Pruning Heights of Preventing Crown Fire of Pinus armandii Trees

为确定可以阻止华山松林地表火向树冠火转化的最低修枝高度,测定了华山松针叶的着火点,在自行设计的燃烧床上对不同载量的华山松林细小可燃物进行了5次燃烧试验,通过分析可燃物地表火过程中垂直方向上的温度变化,将燃烧区域垂直方向上最高温度等于着火点处的高度确定为华山松的最低安全修枝高度。经推算,可燃物载量为1.77 kg/m2、2.37 kg/m22、.96 kg/m23、.55 kg/m23、.84 kg/m2时,华山松人工林的最低安全修枝高度分别为0.82 m、0.92 m、1.13 m1、.20 m1、.22 m。讨论了风、可燃物层的密实度、立地条件对最低安全修枝高度的影响,并分析了不同气象和立地条件下最低修枝高度计算方法。

To determine the lowest pruning heights of Pinus arrnandii trees which could prevent forest crown fire conversion from surface fire, combustion experiments of fine fuel were tested by 5 times with experimental equipment designed by the authors and ignition temperature were measured. The lowest pruning height of Pinus armandii trees from the aspect of preventing crown fire, namely the height that the highest temperature of the height in combustion field equaled ignition temperature, were put forward based on the temperature curves of different heights on combustion field in experimental course. The results showed that the lowest pruning heights of Pinus armandii trees were 0.82 m, 0. 92 m, 1.13 m,1.20 m,1.22 re,while forest fuel loads were 1.77 kg/m^2 and 2. 37 kg/m^2,2. 96 kg/m^2,3.55 kg/m^2 and 3.84 kg/m^2, respectively. The effect of wind, dense degree of forest fuel layers, site condition on the lowest pruning heights of Pinus arrnanclii trees was discussed and the computing method was put forward based on conditions of meteorology and site.