Abstract: Under the conditions of drought and waterlogging,the dynamic of root dry weight and its distribution were studied with the method of root cutting collection in shajiang black soil. The result showed that root dry weight and its distribution were largely affected by drought and waterlogging,especially the later. During a drought,root dry weight of maize per plant was higher, and the time of root dry weight increase and decrease were earlier, the speed of roots spreading into deep soil were quicker and many roots were distributed in deeper soil layer. While during a waterlogging, the result was contrary to the above.

Key words: soil organic carbon, root biomass, soil moisture content, interspecific relationship, arid area, Elacagnus angustifolia-Achnatherum splendens community.