Abstract:

In order to investigate the effects of different intensity rainfall process on soil moisture in typical steppe of Northern China, based on the hourly soil moisture automatic observation data and daily precipitation data in Xilinhot weather station of Inner Mongolia from 2013 to 2015, the variation characteristics of soil moisture before and after the rainfall process were analyzed. The results showed that the variation characteristics of each layer soil moisture at different stages after the rainfall process ended were different with the increase of precipitation. There was binomial regression relationship between soil moisture increment and precipitation at 0-10 cm and 10-20 cm depth soil layers. The precipitations were at least 10.0 mm, 17.0 mm, 25.5 mm and 29.0 mm to cause the stable increase of soil moisture at 0-10 cm, 10-20 cm, 20-30 cm and 30-40 cm depth soil layers, respectively, while the extreme precipitation could cause the stable increase of soil moisture below 40 cm depth soil layer, which indicated that the precipitation causing the stable rising of soil moisture increased gradually with the increase of soil depth. Moreover, the average soil moisture increment gradually decreased with the increase of soil depth during the rainfall process with precipitation more than 5.0 mm, and that was almost closed to 0% at 70-80 cm and 90-100 cm depth soil layers, which indicated that the effect of natural rainfall on the soil moisture below 60 cm depth was less.

Key words: natural rainfall process, soil moisture, typical steppe

摘要：

利用内蒙古锡林浩特气象站2013—2015年生长季自动土壤水分逐时观测数据及逐日降水量数据，分析北方典型草原降雨过程前后各层土壤水分的变化特征。结果表明，随着雨量的增加，各层土壤水分变化规律不同。0—10 cm、10—20 cm土层土壤水分增量与降雨量之间存在二项式回归关系，要使这两层土壤水分稳定增加，至少分别需要约10.0 mm、17.0 mm的降雨量；＞25.5 mm的降雨过程才能引起20—30 cm土层土壤水分的稳定增加；29.0 mm以上的降雨过程能使30—40 cm土层的土壤水分稳定增加；极端降水过程（70.2 mm）能引起40 cm以下土层土壤水分的稳定增加。对5.0 mm以上降水过程的统计分析表明，随着土层的加深，各层平均土壤水分增量呈减少趋势，60 cm以下土层土壤水分受天然降水的影响较小。

关键词: 自然降雨过程, 土壤水分, 典型草原