东北黑土区土壤剖面地温和水分变化规律

Variation of soil temperature and soil moisture on black soil profile in seasonal frozen area of Northeast China

东北黑土区土壤侵蚀的结果使土壤在坡面上发生再分配,土壤腐殖质层厚度的空间变异增大。腐殖质层厚度的变化又引起地温和土壤水分等土壤物理性质的变化,地温和水分是影响和反映冻融侵蚀作用的重要因子,也是影响地表和土壤剖面物质运移的重要因素。本文通过实测不同厚度腐殖质层剖面的地温和土壤水分,分析了地温和水分随时间和土壤剖面深度的变化规律。结果显示腐殖质层厚度对土壤温度和含水量有显著影响,腐殖质层较厚的剖面解冻速度比薄层黑土区要慢,不同深度土层温度到达0℃的日期也不相同,腐殖质层较厚的剖面冻结时间要滞后1周左右。同时,腐殖质层较厚的黑土区土壤含水量明显大于薄层黑土区,土壤水分运移的深度范围也大。

Soil erosion in black soil region in Northeast China leads to soil redistribution on a slope and great spatial variance in the thickness of soil humus layer. Changes of humus layer thickness will result in such physical properties variations as soil moisture and soil temperature. And soil moisture and soil temperature are important factors for freeze-thaw erosion, besides they can affect soil particles and chemical elements movement on the surface and soil profile. In order to explore the law of changes of soil moisture and soil tem- perature by time and depth of soil profile, two field monitoring points A and B were select- ed to monitor soil moisture and soil temperature simultaneously. At site A, soil humus layer is about 60 era, and at site B, soil humus layer is about 130 era. Soil temperature was recorded with a thermistor thermometer at eight o＇clock a.m. everyday from 10 April to 14 June and twice a week from 23 January to 7 April. Soil moisture was monitored with an oven after sampling by drills. Soil moisture and temperature were measured at an interval of 10 cm from the surface to 150 cm deep on two profiles in the paper. Results show that the thickness of humus layer has significant influences on soil moisture and soil temperature. The thicker the humus layer is, the slower the rate of thaw. At site A, the rate of thaw was 2.4cm/day, however, it was 2. lcm/day at site B. Furthermore, the freeze time lags a week or so. At the same time, soil moisture of thicker humus layers is more than that of thinner humus layers in black soil region, as well as the moving extent of soil moisture is deeper. The humus layer has a great impact on the distribution of soil moisture on the profile. As a result, runoff rate during a rainstorm will occur differently from place to place because of the diversity in humus layer depth on a slope.