中文摘要：

选取内蒙古锡林郭勒典型草原区的糙隐子草占优势的退化草地进行氮素添加实验（添加梯度为0，30，50，80g·m^-2），以研究在退化草地中糙隐子草根系特征对氮素添加的响应。结果显示，随着氮素添加量的增加，糙隐子草根系长度和根系表面积没有显著变化，根系直径和根系体积在50g·m^-2的处理情况下显著高于其他3个处理，而0，30，80g·m^-2处理之间无显著差异，这表明退化样地中土壤氮素的适量增加会显著促进优势种糙隐子草根系的增粗生长，而对根系增长生长没有影响，且氮素对于糙隐子草根系的影响存在阈值。糙隐子草根系的长度、直径、表面积、体积与氮素添加量之间都没有显著相关性。

英文摘要：

In order to study the response of root characters of Cleistogenes squarrosa to N addition in degraded grassland, a degraded grassland that dominated by Cleistogenes squarrosa was select- ed in Xilingol typical grassland region of Inner Mongolia, and 2 - year N addition experiment was performed（ addition gradient 0,30,50,80g/m2 ）. The results show ： with the increase of ni- trogen adding rates, the response of root system length and area of Cleistogenes squarrosa is not sensitive, the volume and diameter of root at 50 g/m2 nitrogen adding rates are significantly higher than those of the other three treatments, and there are not significant differences among 0, 30, 80 g/m2 nitrogen adding rates, it is indicated that the moderate soil N addition will sig- nificantly promote, and it is beneficial to enlarge root - diameter of the dominant species Cleisto- genes squarrosa under moderate soil N addition in degraded grassland, but not to root elongation, and there is a threshold of the response of Cleistogenes squarrosa root system to nitrogen adding rates. There are not significantly correlations between length, diameter, surface area, volume of root and nitrogen adding rates.