关键词: 水分胁迫, 土壤水分, 变化特征, 典型草原

Abstract: Adequate understanding of water stress influences on the temporal-spatial variations of soil moisture is crucial for studying water consumption and drought identification in grasslands. Based on soil volumetric water content data monitored in multi-layer soil under two water supply conditions during 2016-2017, soil water status, the seasonal variations and the vertical distribution in the typical steppe in Xilinhot of Inner Mongolia were investigated. The results show that soil water showed distinct seasonal variations in a normal year with dual peaks curve. That was, soil volumetric water content reached the peak in the spring green-up and the rainy season (July), and then it decreased and reached the minimum value in the late of May and the early of September. Soil water content of top 50 cm layer also exhibited marked variation, especially for 0-30 cm layer. The water stress changed the seasonal dynamics of soil moisture (i.e. reduction in the amplitude). More importantly, serious water stress caused that the dual peaks curve failed (becoming smooth), and the water consumption happened in the deeper layer. Moreover, the sensitive area of soil water change extended to the 60-80 cm soil layer. The results highlight that seasonal variations in soil moisture and soil depth are two valuable factors analyzing the interactions between water stress and ecosystem as well as soil drought index.

Key words: water stress, soil moisture, seasonal variation, vertical distribution, typical steppe