Simulation of Soil Freeze-thaw Process and Water Balance in Shrubland Meadow in Shallow Mountain Area of Qilian Mountains

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  • 1. Key Laboratory of Ecological Safety and Sustainable Development in Arid LandsNorthwest Institute of Eco-Environment and ResourcesChinese Academy of Sciences. Lanzhou 730000GansuChina
    2. University of Chinese Academy of Sciences. Beijing 100049BeijingChina

Online published: 2024-10-21

Abstract

Soil water-heat dynamics are pivotal in influencing regional hydrological processes. Understanding the dynamics of soil thermal and moisture changes during freezing and thawing processes is essential for assessing water balance in high-altitude regions. This study utilizes meteorological and soil water-heat observational data from a typical shallow mountainous catchment in the Qilian Mountains to simulate the water-heat dynamics of subalpine shrub meadow soil using the SHAW modelanalyzing the changes in water balance during the soil freezing and thawing process. The results indicate that the SHAW model effectively simulates the temporal and vertical variations in soil temperature and moisture in subalpine shrub meadow soils. The findings demonstrates that the Nash-Sutcliffe EfficiencyNSEfor simulated soil temperature at various depths exceeded 0. 88with ae correlation coefficientRgreater than 0. 97and a Root Mean Square ErrorRMSEless than 1. 89 ℃. For soil moisturethe correlation coefficientRwas greater than 0. 94NSE was greater than 0. 88. and the RMSE was less than 0. 05 m³·m⁻³. Overallthe simulation of soil temperature is more accurate than that of soil moistureespecially in deeper soil layers. The soil freezing and thawing periodsdelineated by temperature profilesrevealed a distinct unidirectional freezing and thawing characteristic of the subalpine shrub meadow soilwith the longest duration in the complete freezing period and the shortest in the freezing period. The trends in temperature and moisture across the soil profile exhibit a "U" shapeindicating higher soil temperatures and moisture during the thawing period compared to the freezing periodwith significant fluctuations in surface soil moisture and relative stability at deeper layers. The water balance characteristics are significantly varied across different soil freezing and thawing periods. During the freezing periodthe precipitation input is 4. 28 mmwith the main expenditure of water is deep percolation at 9. 06 mm. In the complete freezing periodthe precipitation input is 28. 69 mmwith the main expenditure of water is surface runoff at 17. 90 mm. During the thawing period and the complete thawing periodthe precipitation input is 106. 29 mm and 207. 31 mm respectivelywith the major water output through evapotranspirationwhere plant transpiration accounted for 78. 11% and 71. 54% respectively. The soil moisture shows a negative balance during the freezing and complete thawing periodsindicating a net loss of moisture. Converselythe soil moisture exhibits a positive balance during the complete freezing and thawing periodssignifying a net increase in moisture. This study may provide empirical data and theoretical support for the formation and transformation of water resources in the Qilian Mountain region.

Cite this article

LU Tiaoxue, YANG Linshan, WANG Jingru, ZOU Xingyi, HE Wanghan . Simulation of Soil Freeze-thaw Process and Water Balance in Shrubland Meadow in Shallow Mountain Area of Qilian Mountains[J]. Plateau Meteorology, 0 : 1 . DOI: 10. 7522/j. issn. 1000-0534. 2024. 00077

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