满归地区兴安落叶松林火灾历史及其与干旱的关系

摘要

A 257-year forest fire chronology was built by using 16 cross-dated tree-ring fire scar discs of Larix gmelinii in Mangui of the northern Daxing' an Mountains, China. All fire-scar data were input and analyzed using software FHX2. Results showed that the mean fire interval of L. gmelinii forest in Mangui was 26.3 a, and the number of years per fire was 44.8 a. The major type of forest fires in this area was earlywood fire, which accounts for 86.3% of all fires. The proportion attributed to latewood fire and dormant fire was rather small, only 13.7%. Furthermore, the climate-driven mechanism of forest fires in Mangui was analyzed. Palmer Drought Severity Index ( PDSI) was significant at the 95% confidence interval at fire year by using superposed epoch analysis. In other words, the possibility of forest fire occurrences in Mangui increased as climates became dry. The relatively humid climates in the years before fires were also a prerequisites for fire occurrences. Moreover, a long-term drought might lead to a huge forest fire. Anthropogenic activities and national policies would also affect fire regime in long-term scales.%主要利用树木年轮年代学方法,以大兴安岭北部满归林业局16个兴安落叶松(Larix gmelinii)树轮为基础,依据树轮火疤,通过交叉定年重建了该地区257 a的火灾历史,并用火历史分析软件FHX2得出满归地区兴安落叶松的火灾间隔期为26.3 a,火灾轮回期为44.8a.林火主要以早材火为主,占该地区火灾总数的86.3％,晚材火和休眠火所占比例极小,仅为13.7％.进而对满归地区林火发生的气候驱动机制进行了分析研究,结果表明:帕默尔干旱指数(Palmer Drought Severity Index,PDSI)与火灾发生当年的叠加点事件分析(Superposed Epoch Analysis,SEA)达到在95％的显著水平,即气候越干旱,满归地区火灾发生的可能性越大.火灾前几年相对湿润的气候条件也为林火发生提供了必要条件,而且连续的干旱可能导致森林大火的发生.此外,长时间尺度的国家政策或人为干扰也对火灾发生频度也有影响.