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1）

摘要

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 11.36-140.0 cm and air temperature was 13.10℃ , and the temperature diversity between snow-bottom and snow-surface was6 .89℃, however, when the depth of snow reached up to 275.-30 cm and the air temperature lowered to -30.20℃, then, the temperature diversity between snow-bottom and snow-surface 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 grea-ter difference of temperature-gradient, when the snow depth was 132.5 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 .%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。