Abstract:

Ansai County and Jingchuan County are respectively located in the semiarid and semihumid region of the Loess Plateau of China. By using soil coring method,the seasonal dynamics of surface area of fine roots and soil water content in Robinia pseudoacacia forests were investigated in Ansai County and Jingchuan County. The results showed that the vertical distribution of fine roots,the fine root surface area of R. pseudoacacia and its seasonal dynamics were different between Ansai County and Jingchuan County. Around 86.5% of total fine root surface area was in the 0-200 cm soil layer in Ansai County,while the 87.6% of total fine root surface area was distributed in the 0-150 cm soil layer in Jingchuan County. In the growing season in 2007,the highest value of fine root surface area was observed in April in Jingchuan County,while it was in June in Ansai County. The difference of total fine root surface area between Ansai and Jingchuan was not significant in June. By comparing the characteristic of fine root surface area in Ansai County with the characteristic of fine root surface area in Jingchuan County,the R. pseudoacacia in Ansai County reduced the density of fine root surface area,however increased the vertical depth of fine root distribution to maintain the total fine root surface area for tree growth.

Key words: Robinia pseudoacacia, fine root, arid climate, Loess Plateau, soil water content