云南松林飞火形成的火环境研究

Fire environment of spot fires in a Pinus yunnanensis forest

分析了云南省安宁市1971年至2000年的气象资料和基础地形数据,结合2006年＂3.29＂重大森林火灾典型案例,并调查火烧迹地,得到云南松Pinus yunnanensis林飞火发生的火环境特征。结果表明：①干季的气象条件有利于飞火形成,特别是3月份,气温逐渐上升,平均相对湿度、最小相对湿度都达到最小值,分别为53%和3%;最大平均风速、平均风速、大风日数都达到一年中的最大值,分别为29.0 m.min-1,16.3 m.min-1和16.3 d,而降水量不足20 mm,蒸发量高达263 mm;②地形、地势有利于产生飞火,全市相对高差为200~1 000 m的面积占了总面积的60.7%,山高坡陡;③其他因素,云南松林区冬、春季受到西风环流南支急流的控制,又正是云南松及其林下灌丛、草本的休眠期,燃烧性强,可燃物丰富。

By collecting 30 years of meteorological information from 1971 to 2000,by surveying fire sites of spot fires,and by gathering local topographic data,environmental characteristics of spot fires for a Pinus yunnanensis forest were gained.Results showed that meteorological factors during the dry season,especially in March,were favorable for spot fires.During March,air temperature increased with relative humidity（53%） and the minimal relative humidity（3%） being lowest for the year;however,average wind speed（29 m·min-1）, maximal average wind speed（16.3 m·min-1）,and gale days（16.3 d） reached the annual maximum.In addition, average precipitation in March was less than 20 mm;whereas,evaporation was 263 mm for the second highest monthly rate of the year.Topography and terrain were also beneficial to forming spot fires with the relative elevation between 200 to 1 000 m in the Anning City area being very steep（60.7%）.Also,climate increased chances of spot fires.The distribution of Pinus yunnanensis was confined to southern branch of western circumfluence during spring and winter,which was the dormant period for Pinus yunnanensis trees,shrubs, and herbs.Thus,combustibility was too weak to easily ignite,spread,and form spot fires.