Effects of soil water and heat relationship under various snow cover during freezing-thawing periods in Songnen Plain, China

Qiang Fu,Renjie Hou,Tianxiao Li,Ruiqi Jiang,Ziao Ma,Peiru Yan,Zhaoqiang Zhou

doi:10.1038/s41598-018-19467-y

Abstract

In this study, the spatial variations of soil water and heat under bare land (BL), natural snow (NS), compacted snow (CS) and thick snow (TS) treatments were analyzed. The relationship curve between soil temperature and water content conforms to the exponential filtering model, by means of the functional form of the model, it was defined as soil water and heat relation function model. On this basis, soil water and heat function models of 10, 20, 40, 60, 100, and 140 cm were established. Finally, a spatial variation law of the relationship effect was described based on analysising of the differences between the predicted and measured results. During freezing period, the effects of external factors on soil were hindered by snow cover. As the snow increased, the accuracy of the function model gradually improved. During melting period, infiltration by snowmelt affected the relationship between the soil temperature and moisture. With the increasing of snow, the accuracy of the function models gradually decreased. The relationship effects of soil water and heat increased with increasing depth within the frozen zone. In contrast, below the frozen layer, the relationship of soil water and heat was weaker, and the function models were less accurate.

Highlights

Frozen soil is widespread in northeastern, northwestern and northern China
Fu19 studied the interactions between soil water and heat beneath snow cover of various depths during freezing and thawing periods and concluded that the relationship between soil water and heat gradually strengthened with increased snow cover during freezing periods
In the seasonally frozen soil region, soil freezing and melting processes were accompanied by water and heat migration

Summary

Materials and Methods

The water contents (i.e., liquid moisture contents) and soil temperatures at depths of 10, 20, 40, 60, 100, and 140 cm were measured during freezing and melting periods. During the freezing and melting processes, the fitting function models of soil temperature and water content under the different treatment conditions were similar and can be approximated as follows[28,29]: θv = Ac/{1 + exp[B(T − ΔT0)]} + Δθ0,. The MATLAB (2010b) data regression analysis toolbox was used to develop the function model relating soil moisture content at point No 1 and temperature under the four treatment conditions at depths of 10, 20, 40, 60, 100, and 140 cm, respectively. According to the soil moisture content data of the No.[2] test points, the soil temperature was calculated by the mathematical function model constructed above. Where xi is the predicted value, xi′ is the measured value, and x is the average of the measured values

Results and Discussion

Discussion

Conclusions