Over 75 % of the terrestrial territory in the Northern Hemisphere is subjected to seasonally freezing and thawing cycles. The naturally occurred soil freezing processes induce the migration of soil water from unfrozen underlying depths towards the freezing front under gradients of matric potential, temperature and vapor concentration/pressure. The upward moving soil water and vapor change to ice near unfrozen-frozen interfaces, which increases the total water content in the frozen layers. Although a portion of the migrated water redistributes during soil thawing, in general, a gain in shallow total soil water content (GSTSWC). The GSTSWC can be utilized by crops in dry and cold regions, where rainfall limits agricultural and ecosystem productivity. However, there is a knowledge gap on how much water migrates to increase the total shallow soil water content under various land uses and soil conditions. To assess the amount of GSTSWC under various driving factors, a meta-analysis and structural equation model (SEM) were performed using 774 paired observations compiled from 61 studies worldwide. The results indicate a hierarchical order of GSTSWC, with bare land exhibiting the highest GSTSWC value (17 %), followed by rangeland (13 %), forest land (7 %), and agricultural land (3 %). The GSTSWC exhibits an inverse relationship with initial soil water content (SWC). The implementation of straw and plastic film mulching practices exerts a significant effect on soil insulation and water retention, causing a notable postponement and prolongation of the soil thawing process. Consequently, GSTSWC in the 50–100 cm soil layer increases by 2 % for straw mulching and 3 % for plastic film mulching. The SEM demonstrated that mean annual precipitation and initial SWC directly affect GSTSWC. It can assist in formulating recommendations for soil water management in seasonally-frozen soil regions.

中文翻译：

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冻结诱导土壤水分再分配 综述与全球荟萃分析


北半球超过 75% 的陆地领土受到季节性冻融循环的影响。自然发生的土壤冻结过程诱导土壤水在基质电位、温度和蒸汽浓度/压力梯度下从未冻结的底层深度迁移到冻结前沿。向上移动的土壤水和蒸汽在未冻结-冻结界面附近变为冰，这增加了冻结层中的总含水量。尽管一部分迁移的水在土壤解冻过程中重新分布，但一般来说，浅层土壤总含水量 （GSTSWC） 会增加。GSTSWC 可用于干旱和寒冷地区的作物，这些地区的降雨限制了农业和生态系统的生产力。然而，在各种土地利用和土壤条件下，对于增加浅层土壤总含水量，有多少水迁移存在知识差距。为了评估各种驱动因素下 GSTSWC 的量，使用从全球 61 项研究汇编的 774 个配对观察结果进行了荟萃分析和结构方程模型 （SEM）。结果表明 GSTSWC 的层次结构顺序，裸地的 GSTSWC 值最高 （17 %），其次是牧场 （13 %）、林地 （7 %） 和农业用地 （3 %）。GSTSWC 与初始土壤含水量 （SWC） 呈负关系。秸秆和塑料薄膜覆盖措施的实施对土壤保温和保水产生了显着影响，导致土壤解冻过程显着推迟和延长。因此，秸秆覆盖和 3% 塑料薄膜覆盖相比，50-100 cm 土层的 GSTSWC 增加了 2%，塑料薄膜覆盖增加了 3%。 SEM 表明，年平均降水量和初始 SWC 直接影响 GSTSWC。它可以帮助制定季节性冻土区域的土壤水分管理建议。