Characteristics and the driving factors of vapor condensation in different soil textures

Vapor condensation is important for dryland ecosystems. However, the effects of soil type and texture on vapor condensation are not well quantified. In this study, five typical soils were chosen to investigate the influence of soil texture on vapor condensation at a field site on the southern Loess Plateau in Shaanxi, China, using an array of on-site micro-observation cylinders and devices for meteorological measurements. Results showed that: (1) The average daily condensation on gravel, coarse sand, medium sand, loamy sand, and silty loam, showed an increasing trend with the fineness of the soil from 0.133, 0.176, 0.214, 0.309 to 0.609 mm∙d-1, respectively, with significant differences (p < 0.01); (2) The response of different textures to relative air humidity and ground temperature to dewpoint difference varied. With the increasing relative humidity and decreasing ground temperature to dewpoint difference, the condensation increased in different soils; (3) The ratio of condensation in a certain soil to that in the coarse sand (/) is positively and logarithmically related to the soil’s silt-to-sand ratio (Kf) (p < 0.05), with a general fitting equation being , which can be used to estimate the amount of vapor condensation in different soils and provide a reference for the evaluation of dew amount in a soil texture.

水汽凝结对于干旱地区生态系统至关重要。然而，土壤类型与质地对水汽凝结的影响尚未得到充分量化。本研究选取了五种典型土壤，以探讨土壤质地对陕西南部黄土高原某实地观测点的土壤水汽凝结作用。研究采用了现场微观测圆柱体和气象测量设备。研究结果表明：（1）在砾石、粗砂、中砂、壤砂和粉砂质壤土上的日均凝结量，随着土壤细度的增加呈上升趋势，分别为0.133、0.176、0.214、0.309至0.609 mm∙d-1，差异显著（p < 0.01）；（2）不同质地土壤对相对空气湿度和地面温度至露点差变化的响应各异。随着相对湿度的增加和地面温度至露点差的降低，不同土壤的凝结量均有所增加；（3）特定土壤的凝结量与粗砂凝结量的比值（/）与土壤的粉砂与砂的比值（Kf）呈正相关且对数关系（p < 0.05），一般拟合方程为 ，可用于估算不同土壤中的水汽凝结量，并为土壤质地中露水量评价提供参考。