Variability of Soil Water Heat and Energy Transfer Under Different Cover Conditions in a Seasonally Frozen Soil Area

Fanxiang Meng,Tianxiao Li,Renjie Hou,Qiang Fu

doi:10.3390/su12051782

Abstract

In a seasonally frozen soil area, there is frequent energy exchange between soil and environment, which changes the hydrological cycle process, and then has a certain impact on the prediction and management of agricultural soil moisture. To reveal the effects of different modes of regulation on the energy budget of soil in a region with seasonally frozen soil, four treatments, including the regulation of bare land (BL), biochar (CS), and straw (JS), and the combined regulation of biochar and straw (CJS), were used in field experiments. The variations in the soil temperature, liquid water content, and total water content were analyzed, the energy budget of the soil was calculated, the response functions of the soil energy were determined, and the mechanism of soil energy transfer was elucidated. The results showed that, during the freezing period, the JS treatment reduced the amplitudes of the variations in the soil temperature and liquid water content and increased the water content at the soil surface. During the thawing period, the CJS treatment effectively improved the soil hydrothermal conditions. During the freezing period, the heat absorbed by the CS and JS treatments reduced the fluctuation of the soil energy budget. At a soil depth of 10 cm, the spectral entropy of a time series of the soil net energy was 0.837 under BL treatment, and the CS, JS, and CJS treatments decreased by 0.015, 0.059, and 0.045, respectively, compared to the BL treatment. During the thawing period, the CS treatment promoted energy exchange between the soil and the external environment, and the spectral entropy of a time series of the soil net energy was increased; the JS treatment had the opposite effect. The CJS treatment weakened the impact of environmental factors on the soil energy budget during the freezing period, while it enhanced the energy exchange between the soil and the environment during the thawing period. This study can provide important theoretical and technical support for the efficient utilization of soil hydrothermal resources on farmland in cold regions.

Highlights

It is generally known that seasonally frozen soil, as part of the Soil–Plant–Atmosphere Continuum system, frequently alternates between freezing and thawing and is the main location of energy–water–gas exchange between the atmosphere and land surfaces in cold regions [1,2,3]
During the freezing period, under the bare land (BL) treatment, the variation amplitude of the soil temperature at a soil depth of 20 cm was 22.21 ◦C; With the increase of soil depth, the variation amplitude of the soil temperature decreased in order
The comparative analysis showed that, during the freezing period, the average total water content at a depth of 20 cm under the JS treatment was increased by 2.31%, 1.85%, and 0.56% compared to that under the BL, CS, and CJS treatments, respectively, which is consistent with the research conclusions of San et al [33]

Summary

Introduction

It is generally known that seasonally frozen soil, as part of the Soil–Plant–Atmosphere Continuum system, frequently alternates between freezing and thawing and is the main location of energy–water–gas exchange between the atmosphere and land surfaces in cold regions [1,2,3]. The energy transfer between soil and environment affects the interaction effect of water and heat in soil [11,12,13]. Xu et al [18] simulated the dynamic change and transfer of water and heat in frozen soil by establishing a one-dimensional numerical model. Yang et al [19] studied the effects of mulching coverage and double coverage on the temperature in the profile of frozen–thawed soil and proposed that regulating the surface cover affected the net radiation obtained by the soil, which, in turn, affected the evolution of the hydrothermal environment in soil. Most of the above studies focused on the regulation effects of covering on soil hydrothermal conditions during the freezing–thawing cycle, while neglecting the energy transfer process between the soil and the environment under changing environments

Objectives

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Results

Discussion

Conclusion