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

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 temperature by time and depth of soil profile,two field monitoring points A and B were selected to monitor soil moisture and soil temperature simultaneously.At site A,soil humus layer is about 60 cm,and at site B,soil humus layer is about 130 cm.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 2.1cm/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.