黑河中游农田荒漠过渡带土壤冻融过程中水热动态

Soil Water and Heat Dynamics in Soil Freezing-Thawing Processes of Farmland-Desert Transitional Zone in Middle Reach of Heihe River

以黑河中游典型农田荒漠过渡带为例,对过渡带3种景观单元冻融期土壤水热动态进行了野外定位监测。结果表明:(1)土壤温度随气温剧烈变化,变幅随土壤深度的增加而减小,3种景观单元土壤温度变幅由剧烈到平缓的顺序为:荒漠>农田>防护林,并依次形成60,100和80cm深的冻土层;(2)受土壤性质和地表覆盖的影响,冻融过程中,农田、防护林土壤含水量变化明显,且农田土壤水分含量4月初达到最大值,而荒漠土壤含水量则基本保持不变;(3)土壤水分变化滞后于土壤温度的变化,防护林土壤水和温度变化较农田缓慢;(4)浅层地下水位在冻结期下降,融化期回升,且回升速率大于下降速率。冻融过程可有效减小土壤水分的蒸发和渗漏,冻后聚墒明显,利于下层土壤水分的保持,对于来年植物生长具有一定的意义。

A typical farmland-desert transitional zone in the Heihe River Basin was selected to explore soil water and heat dynamics in soil freezing-thawing processes under different landscapes. The main results were as follows：（1） Soil temperature was in response to air temperature quickly, but its amplitudes de-creased with the increasing soil depth. The variation of soil temperature were ordered as. desert〉farmland〉 shelterbelt, whereas the soil frost depth was ordered as ： farmland（100 cm） 〉shelterbelt（80 cm） 〉desert（60 cm）; （2） Due to the soil properties and surface cover, the soil moisture content of farmland and shelterbelt changed greatly, and the maximum occurred in early April, while soil moisture content of desert was almost invariant; （3） Changes of soil moisture laged behind that of soil temperature, soil water and temperature changes of shelter forest is slower than that of farmland; （4） Shallow groundwater level dropped during the freezing period, and rose during the thawing period, and the rise rate was greater than the drop rate. The soil freezing and thawing process could effectively reduce soil moisture evaporation and seepage by lifting subsoil moisture upward, and therefore help to conserve water in the deep soil, which has great significance to plants of the following year.