大兴安岭北部白桦次生林林内积雪及浅层土壤温度分布特征

Characteristics of Temperature in Snow-cover and Shallow-soil in Betula platyphylla Secondary Forests in the Northern Daxing'an Mountains

以大兴安岭北部白桦次生林林内积雪为研究对象,通过野外定位观测,分析了积雪及浅层土壤温度分布特征。结果表明：1）积雪内部温度差异随着积雪厚度的增加而逐渐增大,积雪厚度在11.36～14.00 cm,气温为-13.10℃时,雪底与雪表温差为6.89℃,而积雪厚度增到27.50～30.00 cm,气温降到-30.20℃时,雪底与雪表温差高达18.87℃,在气温骤降17.10℃过程中,雪表温度相差17.31℃,而雪底温度仅相差5.34℃,这说明一定厚度的积雪具有缓冲冷空气和保持雪底温度的作用,且积雪越厚其保温性越强。2）积雪上层和下层的温度梯度差异随着积雪厚度的增加而增大,当积雪厚度在13.25 cm时,积雪上层和下层的温度梯度相差0.17℃/cm,而当积雪厚度在29.80 cm时,温度梯度相差达0.65℃/cm,说明冷空气穿透上层积雪后对下层积雪的降温作用变缓。3）积雪的覆盖延缓了冷空气向下层土壤的传导,积雪深度11.36～14.00 cm时,气温降低6℃,浅层土壤温度降低2.59℃,而当积雪深度在26.00～34.80 cm时,气温降低8℃,而浅层土壤温度仅降低2.63℃。4）积雪层越厚滞缓冷空气对土壤侵袭效应越明显,12.46 cm积雪覆盖条件下,0～10 cm土层温度梯度为0.26℃/cm,20～30 cm土层是0.13℃/cm,积雪厚度达到30.22 cm时,0～10 cm土层温度梯度为0.31℃/cm,而20～30 cm土层仅为0.12℃/cm。

We studied the characteristics of temperature in snow-cover and shallow-soil by locating observation in Betula platyphylla secondary forest in the northern Daxing＇an Mountains. With the increasing of the snow depth,snow-cover had greater difference of temperature,when the snow depth was in 11.36-14.00 cm and air temperature was 13.10 ℃,and the temperature diversity between snow-bottom and snow-surface was 6.89 ℃,however,when the depth of snow reached up to27. 5-30 cm and the air temperature lowered to-30.20 ℃,then,the temperature diversity between snow-bottom and snowsurface got to 18.87 ℃. As air temperature cooled to 17.10 ℃,the snow-surface temperature cooled 17.31 ℃,snow-bottom temperature only cooled 5.34 ℃,which showed that certain thick snow had thermal effect on snow-bottom temperature,and the thicker the snow was,the greater insulated effect became. With the increasing of the snow depth,snow-cover had greater difference of temperature-gradient,when the snow depth was 13.25 cm,the temperature-gradient diversity between the upper and lower was 0.17 ℃ / cm,nevertheless,when the depth of snow reached up to 29.80 cm,the temperature-gradient difference soared to 0.65 ℃ / cm,which showed that when cold air passed through the topsnow,and showed the cooling effect on subsnow. The snow-cover delayed the transmission of cold air to the subsoil,when the depth of snow was 11.36-14 cm,shallow-soil cooled 2.59 ℃ on condition that air temperature cooled 6 ℃; when the depth of snow rose go up to 26.00-34.80 cm,shallow-soil merely cooled 2.63 ℃ on condition that air temperature cooled 8 ℃. The thicker snow-cover was,the more obvious snow-cover sluggished the invasion of cold air to soil. Under 12.46 cm snow-cover,the temperature-gradient were 0.26 ℃ / cm and 0.13 ℃ / cm in soil-layers of 0-10 cm and 20-30 cm,respectively. When the snow depth was 30.22 cm,the temperature-gradients of 0-10 cm and 20-30 cm soil-layers were 0.31 and 0.12 ℃ / cm,respectively.