基于火历史的滇西北亚高山主要针叶林对火的适应机制研究

Northwestern Yunnan province is one of the most important hotspots of global biodiversity, due to abundant species, beautiful natural and human landscapes, and well-known continuous distribution of sub-alpine coniferous forests. However, this eco-functional area, whose ecological environment is vulnerable, suffering from many disasters, especially, seasonal forest fires. It is very important and necessary to reconstruct fire history of this area and to know how the main coniferous forests adapt to it. First, use the methods such as remote sensing, field surveying, fire-scar and dendrochronology to get the fire history of this area, including fire patterns or regimes, fire frequency, fire seasons, fire intensity and fire losses. Second, use the following indexes: fire acres and fire intensity, in order to quantificate the spatial differentiation. Combined with natural and human factors, especially the climate change, the mechanism of fire history could be obtained. By using knowledge of forestry, plant physiology as well as ecology and focusing on coniferous forests' rebirth, seasonal aspects, construction and function of the forest after the fire could lead to the mechanism of main coniferous forests' adaption to it. The aim of this study is to break through the theory which relates to the history of the fire and main coniferous forests' adaption to the fire in sub-alpine area. The results of this research will help to master the rules of the fire occuring, spreading and extinguishing, the temporal and spatial characteristics of the fire, to deeply understand these main species' processes of updating, growing and developing, as well as to asses and adjust forest fire policy, improve the levels of fire control and management by modifying the measurements of operation and management, and promote sustainable forest development.

滇西北是全球重要的生物多样性热点地区之一，物种极其丰富，自然、人文景观极其优美，连续分布的亚高山针叶林在世界同类森林中非常少见，但由于生境异常脆弱，经常遭受森林火灾的威胁。综合研究区的林火资料，结合遥感影像和野外调查，运用火疤-树木年轮年代法重建滇西北亚高山主要针叶林的火历史（火格局，火频率，火季节和火强度、火损失等），量化滇西北亚高山火格局的时间、空间变异特征，结合自然人文因子分析其机理，并运用林学、植物生理、生态学等来解析主要针叶林对火的适应及响应机制，包括结构、功能和火后更新方式、季相等。预期得到该区域主要针叶林的火历史格局特征以及对火的响应机制。研究结果有助于把握该区域森林火灾发生时间、空间发展规津，火与植被变化特征，有助于深入了解该地区主要树种的更新生长发育过程，评估、调整并改进林火管理政策，改进森林抚育、经营管理措施，提高该林区的林火管理水平，促进林业的可持续发展。

滇西北是全球重要的生物多样性热点地区之一，物种极其丰富，自然、人文景观极其优美，连续分布的亚高山针叶林在世界同类森林中非常少见，但由于生境异常脆弱，经常遭受森林火灾的威胁。综合研究区的林火资料，结合遥感影像和野外调查，运用火疤-树木年轮年代法重建滇西北亚高山主要针叶林的火历史（火频率，火季节和火强度等），量化滇西北亚高山火格局的时间、空间变异特征，结合自然人文因子分析其机理，并运用林学、植物生理、生态学等来解析主要针叶林对火的适应及响应机制，包括结构、功能和火后更新方式、季相等。.结果表明：（1）火格局：森林火灾主要集中在2-5月份，3，4月份的火险等级最高，易发生重大森林火灾，主要发生在高山峡谷区，尤其是山谷、陡坡、鞍形场、悬崖和山脊线等。（2）主要针叶林燃烧性：①华山松纯林地表可燃物是低强度火，具有小坡度燃烧特征，相对稳定、平缓，火焰高度、火强度较小。但野外地表可燃物里有部分半分解的树桩和大枝条，在适宜条件下，能死灰复燃，危险性高。枯枝含水率极低，载量不大，但易燃，一旦发生火灾，能形成树冠火。②以草类为主的云南松纯林地可燃物火焰高度都在50 cm 以下，温度近600 ℃，热辐射低于8 kW/m2，火强度在405 kW/m 以下，烧除率60%，低强度火烧，难以形成树冠火，烧除间隔期应为3 年左右。③枯死紫茎泽兰载量积累较多，超过1.0kg/m2，呈丛生状，连续、致密且高度一致，着火后迅速蔓延，可能引起树冠火。同时，也是过火通道，利于水平蔓延。（3）火适应主要包括：芽的保护与植物的存活，树皮对芽的保护，火后萌发；火刺激开花；种子在植株上的保存及火烧促进种子开裂；土壤种子库/贮存的种子与火对发芽的刺激作用等。.研究结果有助于把握该区域森林火灾发生时间、空间发展规律，火与植被变化特征，有助于深入了解该地区主要树种的更新生长发育过程，评估、调整并改进林火管理政策，改进森林抚育、经营管理措施，提高该林区的林火管理水平，促进林业的可持续发展。