四川西昌云南松林地表可燃物载量及影响因素研究

Surface fuel load and influencing factors of Pinus yunnanensis forest in Xichang City,Sichuan Province of southwestern China

【目的】研究西昌市云南松林地表可燃物载量及影响因素,为科学管理可燃物,降低森林火险等级提供依据。【方法】以四川省西昌市云南松林为研究对象,依据林分因子(树高、胸径、郁闭度、平均活枝高)和地形因子(海拔、坡度、坡向、坡位)设置16块20 m×30 m标准地,调查样地内不同类型地表可燃物(草本、灌木、地表枯叶、1时滞枯枝、10时滞枯枝、100时滞枯枝),结合室内实验结果计算可燃物载量,运用冗余分析明确可燃物载量与林分因子和地形因子的响应关系,运用多元线性回归分析进一步确定各类地表可燃物载量的主要影响因素。【结果】(1)云南松林地表总可燃物载量范围为7.82~33.53 t/hm^(2),平均为22.25 t/hm^(2),易燃可燃物载量平均为10.68 t/hm^(2),占地表总可燃物载量的48.00%。(2)冗余分析结果表明:云南松林地表总可燃物载量与郁闭度呈正相关(P<0.01),与海拔呈负相关(P<0.05),阴坡云南松地表总可燃物和易燃可燃物载量高于阳坡(P<0.01)。(3)多元线性回归分析表明:云南松林地表总可燃物和易燃可燃物载量的主要影响因素均为坡向。【结论】云南松林可燃物载量受到以坡向和海拔为主的地形因子和以郁闭度为主的林分因子的共同作用影响。西昌市云南松飞播林区地表总可燃物载量高,易燃可燃物占比大,存在较大的火灾隐患。

[Objective]This paper aims to study the surface fuel load and influencing factors of Pinus yunnanensis forest in Xichang City,Sichuan Province of southwestern China to provide a basis for the scientific fuel management and reduce forest fire risk level.[Method]P.yunnanensis forest in Xichang City was taken as the research object.A typical and representative P.yunnanensis forest was selected to set up 16 standard plots with the size of 20 m×30 m,and the surface load of different type fuels(herbs,shrubs,surface withered leaves,1 h time-lag dead twigs,10 h time-lag dead twigs,100 h time-lag dead twigs)were investigated in the sample plots.RDA redundancy analysis and multivariable linear regression analysis were used to determine the relationship between fuel load and stand factors(DBH,tree height,average undershoot height,canopy density)and topographic factors(altitude,slope,slope aspect,slope position),and to determine the key influencing factors of surface fuel load.[Result](1)The total surface fuel load of P.yunnanensis forest was 7.82−33.53 t/ha,with an average of 22.25 t/ha.The average combustible load was 10.68 t/ha,accounting for 48.00%of the total surface fuel load.(2)RDA analysis showed that total fuel load was positively correlated with canopy density(P<0.01),and negatively correlated with altitude(P<0.05).The total and flammable fuel load of P.yunnanensis on shady slope was higher than that on sunny slope(P<0.01).(3)Multivariate linear regression analysis showed that slope aspect was the main factor affecting the total combustible and combustible load of P.yunnanensis.[Conclusion]The fuel load of P.yunnanensis forest was affected by both the topographic factors,mainly including slope aspect,and altitude and the stand factors mainly including canopy density.In the aerial seeding forest area of P.yunnanensis in Xichang City,the total surface fuel load is high,and the proportion of combustible fuel is large,so there is a large fire hazard.