祁连山大通河源多年冻土区浅层土壤水热时空变化特征

在大通河源不同草甸生态系统中建立浅层土壤水热监测网络. 2010-2011年监测结果表明：土壤温度和水分均具有明显的冻融交替和空间梯度变化格局. 在沼泽化草甸和典型草甸区，土壤融化和冻结末期分别出现在5月底、6月初和11月中下旬；而退化草甸区对应的时间则出现在4月底、5月初和11月中上旬. 在沼泽化草甸和典型草甸土壤温度变化曲线上有明显的“零点幕”时期，而退化草甸则不太明显. 土壤温度曲线的阶段划分结果表明，沼泽化草甸和典型草甸各阶段不存在显著差异，二者阶段划分曲线基本重合，均可以划分为6个阶段：春季升温阶段、春季“零点幕”阶段、夏季升温阶段、秋季降温阶段、秋季“零点幕”阶段和冬季降温阶段. 对于退化草甸而言，春季和秋季“零点幕”时期不明显，阶段划分曲线与前二者具有较大差异. 退化草甸温度曲线“零点幕”时期不显著对应于下伏多年冻土临近岛状多年冻土边缘，是最易于受环境影响变化而发生退化的区域. 3个监测场地浅层土壤水热格局一定程度上指示了下伏多年冻土的空间分布格局.

Spatial and temporal variations of the superficial hydro-thermal characteristics in permafrost regions in the source areas of the Datong River,Qilian Mountains

The superficial hydro-thermal characteristics within 0-20 cm in depth at different meadow-dominated eco-systems were monitored during 2010-2011 in the source areas of the Datong River in the northeastern section of the Qilian Mountains. A freezing-thawing cycle and spatial gradient varying were found in the edaphic hydro-thermal characteristics. For the swamp meadow and typical meadow, the terminations of soil thawing and freezing occurred at the end of May to the beginning of June and the mid-to-late November, respectively, while the corresponding dates for degradation meadow eco-system occurred at the end of April to the beginning of May and the early-to-mid November. A zero-curtain effect was observed in the temperature curve for the swamp meadow and the typical meadow eco-systems, while it was insignificant in the temperature curve for the degradation meadow eco-system. The variations of soil temperature in a year can be divided into six periods：rising temperature in spring, zero-curtain effect in spring, rising temperature in summer, decreasing temperature in autumn, zero-curtain effect in autumn and decreasing temperature in winter. There was no remarkable difference between the two temperature curves of the swamp meadow and the typical meadow. In contrast, there was no significant period of zero curtain effect in degradation meadow, which corresponded spatially well to the edge of underlying permafrost. The measured ground temperatures at the other two monitoring sites indicated that there was permafrost. The spatial patterns of superficial hydro-thermal variations at the three meadow eco-systems corresponded to the gradient patterns of underlying permafrost.