生物防火林带技术的科学基础和发展前景

生物防火林带技术是将特定常绿阔叶树种呈带状密植到易燃的植物群落中,用以预防和阻隔地表火及树冠火蔓延。研究表明,生物防火林带的防隔火功能不只是来自于植物叶片间可燃性的差异,更多源于常绿阔叶树的树冠结构以及相对密植构成的独特林分。通过抑制带内地表可燃物的生长,实现对地表火的阻隔;在遭受树冠火袭击时,以其树冠较弱的可燃性和分层特性消减火势(强度),降低火蔓延过程中热量输运的效率,使火蔓延自动终止。与传统的防火隔离带(生土带)相比,该项技术在阻挡火焰辐射、飞火以及保持水土和生态维护等方面拥有绝对优势。由于缺乏对其抵抗树冠火规模的量化认识,也没有建立起量化的技术性能指标以及细化的实施规范,生物防火林带技术仍处于经验型阶段。对该项技术的进一步发展与完善,不仅可以确保其在森林防火分隔实践中的应用效果,还可以在森林和城镇结合部等火灾多发地域发挥更大的作用。

Scientific Basis and Prospects of Biological Fire-prevention-belt Technique

Biological fire-prevention-belt technique is specific to the relatively dense plantation of evergreen broad-leaf species in highly-flammable coniferous communities in the form of a belt, for the purpose of preventing and blocking the spread of surface and crown fire. Research indicates that the functions of fire prevention and blockage not solely come from poor flammability of the plant leaves, but more importantly are originated from the individual crown structure of evergreen broad-leaf species and the stands formed as a result of relatively dense plantation. By inhibiting the growth of surface fuels in the belt, the surface fire can be isolated. During the attack of a crown fire, the fire intensity is lessened by the poor combustibility and layered feature of the plant crown. This rapidly reduces the efficiency of heat transfer during the fire spread, leading to the automatic termination of fire spread. Compared to the conventional fuel breaks, this technique has obvious advantages in the efficiency of blocking flame radiation and firebrands sourced from an external fire and in conserving local soil and water as well as maintaining the local ecology. So far, there is a lack of the understanding on its quantitative capacity in resisting the crown fire intensity, and no technical performance indexes and detailed implementation specifications have been established; thus, this technique remains at an empirical stage. Further development and improvement of this technique not only can ensure its effectiveness in the forest fire separation practice, but also make it available to maximize its utilization in other fire-prone areas such as the wildland and urban interface.