Based on a 3-year field experiment (2015-2017) with two treatments, annual whole-film mulching (PM) and uncovered (CK), we analyzed the relationship between soil temperature, moisture, and soil hydrothermal movement in semi-arid area. The results showed that freezing-thawing processes under both PM and CK were one-way freezing and two-way melting. Compared with CK, the freezing period in PM treatment was lagged, freezing rate was slowed down, freezing depth was 20 cm shallower, but melting rate was faster, and melting period was shortened by 6-7 days. In freezing period, soil temperature gradients of PM and CK were positive, with heat being transmitted toward top soil layer, and the conduction strength in PM treatment was greater than CK. During the melting period, soil temperature gradient of PM was also positive, with heat being transmitted toward upper soil layer, and that of CK was conversed. Soil water in PM treatment transported to upper soil layer during freezing-thawing period, but it appeared a "down-up-down" movement mode under CK in freezing period, "up-down" in thawing period. There was positively correlation between temperature and moisture gradient in the freezing period under both PM and CK treatments, with closer correlation in PM than CK. During melting period, soil temperature and moisture gradient was positively correlated in PM treatment with soil heat and moisture moved upward synchronously, while that in CK was negatively correlated with soil heat and moisture simultaneously moved to the lower layer soil. Driven by soil temperature and moisture gradient, soil temperature in 0-10 cm, 10-20 cm and 20-30 cm layers increased by 1.13-1.34 ℃, 0.96-1.24 ℃ and 0.89-1.32 ℃, while average soil water content increased by 3.4%-5.6%, 1.4%-2.2% and 6.7%-7.8%, respectively in PM treatment before sowing. Our results indicated that PM could provide water and heat protection for re-greening of winter crop and sowing, emergence and seedling of spring-sown crops in semi-arid areas.
依托3年大田定位试验(2015—2017),设置周年全膜覆盖(PM)和裸地(CK)2个处理,分析半干旱冷凉区土壤温湿度梯度和水热运动的关系。结果表明: PM和CK冻融过程均为单向冻结、双向融通。与CK相比,PM冻结期滞后,冻结速率减慢,冻结深度浅20 cm,但融化速率加快,融化期缩短6～7 d。冻结期PM和CK土壤温度梯度均为正值,热量向上层土壤传导,但PM传导强度大于CK;融化期PM温度梯度为正值,热量向上层传导,而CK则相反。土壤水分运移表现为:PM在整个冻结期向上运动,CK则表现为“向下-向上-向下”的运动方式;融化期PM水分向上层运移,而CK融化初期向上层运移,融化中后期则向下层运移。在冻结期PM和CK的土壤温度梯度与湿度梯度均呈正相关,但PM相关性大于CK,融化期PM土壤温度梯度与湿度梯度间呈正相关,土壤热量、水分同时向上层运动,CK呈负相关,土壤热量、水分同时向下层运动。在土壤温、湿度梯度驱动下,融通-播前PM 0～10、10～20和20～30 cm土壤温度分别较CK平均提高1.13～1.34、0.96～1.24和0.89～1.32 ℃,土壤含水量分别平均提高3.4%～5.6%、1.4%～2.2%和6.7%～7.8%。可见,PM可为半干旱冷凉区越冬作物返青和春播作物播种、出苗和保苗提供水热保障。.
Keywords: annual whole-film mulching; soil freezing-thawing characteristics; soil moisture and temperature distribution; soil moisture gradient; soil temperature gradient.