疏勒河源区含砂砾石土壤水热实验

Hydraulic and thermal experiment of soil with gravel in the source region of Shule River

对疏勒河源区的翻耕补播地、围栏封育地和围栏外草地这3种砂砾石含量不同的草地为研究对象,对其饱和导水率、冻融状态下的导热率进行测定,分析了饱和导水率、导热率与不同样地、土层深度、及土壤物理性质的关系。结果表明:1)3种样地不同土层的砂砾石含量有较大差异,翻耕补播地100~160 cm砂砾石含量达到73%。2)土壤饱和导水率和导热率随着样地类型和土层深度的不同而变化,疏勒河源区上游高寒草地饱和导水率和导热率具有空间异质性。3)砂砾石含量对饱和导水率和导热率有显著影响,今后的研究中需考虑砂砾石对土壤水热属性的影响。

[Background]The Qinghai-Tibetan Plateau( QTP) is sensitive to climate change and human disturbance. There is large amount of gravel in the soil of the QTP due to the weak chemical and biological processes. However,few attentions have been paid to the thermal and hydraulic properties of soil with gravel. Gravel in soil affects soil composition,water content,soil bulk density,soil thermal conductivity and other soil properties. The study on hydrothermal properties of gravel was few. The widely used parameterization schemes of soil water and thermal properties only considers the sandy,silt and clay soil,the understanding of the importance of gravel is not enough. [Methods]According to the different content of gravel in soil,three types of grassland were selected as the research object. In each type,three plots were selected,totally 9 plots. A 1. 6 m deep soil profile was dug in each plot. Each profile was divided into four layers,namely: 0-20,20-40,60-100,and 100-160 cm. Soil samples were taken from each soil layer and brought to the laboratory. The saturated hydraulic conductivity of soil samples was measured by constant-head permeameter and variable-head permeameter in the laboratory. The thermal conductivity of soil samples in the study area was analyzed by thermal characteristic analyzer( KD2 Pro,DECAGON,USA). The relationship between saturated hydraulic conductivity,thermal conductivity and gravel content was analyzed by origin software. and the significance was tested by SPSS.[Results]The saturated hydraulic conductivity increases sharply when the content of gravel is more than60%. The saturated hydraulic conductivity reaches 1. 5 cm/s when the content of gravel reaches 80%.Saturated hydraulic conductivity of tillage and supplementary sowing land increases with the increase of gravel content. For all soil layers,the thermal conductivity is basically the same under two conditions when the soil moisture is zero. The thermal conductivity of frozen soil is lower than that of unfrozen soil.With the increase of soil moisture,the thermal conductivity of frozen soil is higher than that of unfrozen soil at about 10%-20%. In addition,when the moisture content of soil samples is approximately the same,the thermal conductivity of frozen and unfrozen soil samples with larger proportion of gravel is higher than that of soil samples with smaller proportion of gravel. The saturated hydraulic conductivity of soil,the unfrozen and frozen thermal conductivity of soil at saturation are positively correlated with soil density,the content of gravel with particle size larger than 2 mm,and negatively correlated with porosity and the content of non-gravel with particle size smaller than 2 mm. [Conclusions]The content of gravel has a significant effect on the saturated hydraulic conductivity and thermal conductivity,and future studies need to consider the effect of gravel on the soil water and heat properties.