草原火的热状况及其对植物的生态效应

The Heat Regimes of Steppe Fire and Their Ecological Effects on Plants

探讨了草原火的热状况及其对植物的生态效应。国外的实验研究结果表明，在草原火烧过程中，土壤表面的平均温度一般变化于１０２℃～３８８℃之间；在土壤表面以下，温度随着土层深度的增加而急骤下降，火烧的影响深度一般为０．６４ｃｍ以上的土壤范围，在０．３～０．６４ｃｍ上层中，土壤温度多为６６℃～７９℃；在土壤表面以上５～１５ｃｍ高度上，温度上升非常迅速，温度的高低取决于燃烧物的数量和风速．草原植物的种子对热辐射有非常强的耐受力，火对禾草休眠种子的死亡率影响甚微，但维管植物的组织却容易被热辐射杀死，其致死温度一般为６０℃左右，经过火烧以后，草原群落中不同植物种类的生长状况与生物量的增减变化与这些植物的生长型及其生长点所处的位置密切相关．

he literature of the heat regimes of steppe fire and their ecological effects on plants has beenreviewed.The average soil surface temperature generally ranges from 102 ℃ to 388 ℃ duringsteppe fire.Below the mineral soil surface,temperatures decrease sharply.The soil depth influ-cenced by fire is above 0.64 cm. The soil temperatures at depths of 0.3 to 0.64 cm range from 66℃to 79 ℃. Above the soil surface, up to a height of 5 to 15 cm,tempratures of steppe fire are ris-ing very rapidly. The degrees of temperatures depend on the amounts of fine fuels and wind veloc-ity. The seeds of steppe species are very tolerant to heat.Grass fire would probably have only aslight effect on the mortality of dorment seeds.Vascular plants tissues are easily killed by heat,temperature of 60℃ is usually given as the thermal death point for most plants tissues.Afterburning,the changes of the growth and biomass of different species are related to their growthforms and the location of their growing points.