Soil Freeze-Thaw and Water Transport Characteristics Under Different Vegetation Types in Seasonal Freeze-Thaw Areas of the Loess Plateau

Abstract

In the arid and semi-arid regions of the Loess Plateau, seasonal freezing and thawing influence soil water movement, and water movement directly influences vegetation growth. However, currently, research with regard to freezing and thawing processes under various vegetation types and the mechanism of soil water movement is lacking. Therefore, the present study explored soil water migration characteristics of two typical vegetation types [arbor land (AL) and shrub land (SL)] on the Loess Plateau during seasonal freezing and thawing processes using bare land (BL) as a control. We used field measured data for hourly soil temperature (ST) and soil water content (SWC) at a depth of 100 cm below the soil surface from November 2017 to March 2018. Freezing and thawing process was divided into three stages based on ST change (initial freezing period, stable freezing period, and thawing period). Compared with previous studies in this area, ST is lower than expected, and SWC migration characteristics are also different. The results revealed that: 1) the maximum freezing depth of AL and SL was 60 cm, which was 30 cm less than that of BL. The freezing date of each soil layer in BL was the earliest and average ST value was the lowest. BL had the highest degree of freezing. The freezing of all soil layers in AL occurred at a later date than that of SL. ST and the minimum soil freezing temperatures were higher than those of SL, and the capacity of AL to resist freezing was higher; 2) the SWCs in AL and BL at depths of 0–10 cm and 10–30 cm decreased, whereas SWCs of AL and BL at a depth of 60 cm increased by 152 and 146%, respectively. The SWCs of SL at soil depths of 0–10 cm, 10–30 cm, and 30–60 cm increased by 46.3, 78.4 and 205%, respectively. The amount and distribution of soil moisture in SL were optimum when compared to those of AL and BL. The results of the present study could provide a scientific basis for vegetation restoration in arid and semi-arid areas of the Loess Plateau.

Seasonal freeze-thaw characteristics of soil carbon pools under different vegetation restoration types on the Longzhong Loess Plateau

“…Seasonal freeze-thaw (FT) is a physical and geological natural phenomenon in which soil water undergoes more frequent phase changes during seasonal transitions due to cyclical changes in ambient temperature (Chou and Wang, 2021). It is widespread at mid to high latitudes and altitudes around the world and is particularly pronounced at high altitudes in northeast and northwest China (Bo et al, 2021;Huang et al, 2021). As an abiotic stress in soils (Cheng and Wu, 2007), FT first occurs in the topsoil and gradually extends to the subsoil (Liang et al, 2021).…”

“…This process has a potentially important impact on the carbon cycle of the soil (Guo et al, 2018;Huang et al, 2021). Vegetation plays an important role in the terrestrial carbon cycle (Malcolm et al, 2009;Wilkinson and Sherratt, 2016), but seasonal FT processes affect soil moisture distribution and directly influence vegetation growth activity (Bo et al, 2021). Studies have shown differences in the buffering effect of vegetation types on soil FT phenomena (Xiao et al, 2019;Bo et al, 2021).…”

“…Vegetation plays an important role in the terrestrial carbon cycle (Malcolm et al, 2009;Wilkinson and Sherratt, 2016), but seasonal FT processes affect soil moisture distribution and directly influence vegetation growth activity (Bo et al, 2021). Studies have shown differences in the buffering effect of vegetation types on soil FT phenomena (Xiao et al, 2019;Bo et al, 2021). Among them, forest systems had a higher buffering adaptation capacity to soil temperature under FT than grassland (Bo et al, 2021), and forest SOC was more sensitive than grassland in response to FT (Xiao et al, 2019).…”

“…Studies have shown differences in the buffering effect of vegetation types on soil FT phenomena (Xiao et al, 2019;Bo et al, 2021). Among them, forest systems had a higher buffering adaptation capacity to soil temperature under FT than grassland (Bo et al, 2021), and forest SOC was more sensitive than grassland in response to FT (Xiao et al, 2019). Also, FT processes in the soil significantly increased anaerobic respiration in soils (Koponen et al, 2006), inhibited the mineralization of OC in soils (Bo and Brandt, 2003), and further increased soil DOC content and reduced soil MBC content (Li et al, 2019).…”

Optimal Allocation of Slope Ecological Restoration for the Climate Change Mitigation and Natural Function Improvement

“…Slope ecological restoration is an important measure for the construction of Nature-Enriched-Attributes-Coordinated-Watershed (Yan et al, 2017;. On the one hand, it directly affects vertical hydrological processes such as the atmospheric water vapor flux (Fathizadeh et al, 2017;Ghimire et al, 2017;Liu J. et al, 2018b), soil water movement (Wu et al, 2017;Huang et al, 2017;Yu et al, 2018;Bo et al, 2021;Xu M. et al, 2021), and evapotranspiration (Li et al, 2016;Wang et al, 2018). On the other hand, the canopy structure and community succession of vegetation indirectly affect the horizontal hydrological processes such as runoff generation and confluence on the slope (Amenu and Kumar, 2008;Yang et al, 2010;Dong et al, 2021) by changing the underlying surface conditions and the surface roughness.…”