中文摘要：

地下生物量实测数据的缺乏严重影响草地地下碳库的精确估计，本文以苏尼特右旗小针茅荒漠草原为研究对象，通过野外实地调查。选取6个样地，采集2160份根系样品，进行室内试验分析，获得小针茅荒漠草原生长季5--9月地下生物量数据，分析了小针茅草原植被地下生物量的季节动态。结果表明：（1）小针茅草原植被地下生物量季节动态表现为N型变化规律，最高值出现在7月下旬，最低值出现在8月下旬。狭叶锦鸡儿-小针茅＋无芒隐子草草地各月的地下生物量均高于小针茅＋无芒隐子草草地类型。（2）小针茅草原不同层次地下部分生物量的季节变化不同，0—10cm的地下生物量表现出很大的波动性，与总地下生物量的变化趋势基本一致；10cm以下的变化曲线逐渐平缓。（3）5—9月生长季小针茅草原0～60cm土层地下生物量与土壤有机碳含量无显著相关性，0—10cm土层地下生物量与土壤有机碳呈显著正相关。（4）小针茅草原每月地下生物量和月降水量与月平均气温的相关性都不明显。（5）小针茅草原不同深度土壤含水量与地下生物量存在显著正相关，总地下生物量受0—10cm土壤含水量影响较大。

英文摘要：

The lack of measured data on belowground biomass seriously affects the accurate estimation of grassland belowground carbon pool. By taking stipa klemenzii steppe as the research object, six sample plots were selected, and 2160 root samples were collected for further experimental analysis via wild plots investigation, the seasonal dynamics of belowground biomass from May to September was analyzed. The results show that （1） The change trend of belowground biomass appears a N type, and the peak value appears in late July, and the lowest value appears in late August, the belowground biomass of grassland type of Caragana stenophylla Pojark-Stipa klemenzii＋Cleistogenes songorica in each month is higher than that of grassland type of Stipa klemenzii＋Cleistogenes songorica. （2） The seasonal dynamics of belowground biomass in different soil layers of Stipa klemenzii steppe is different, belowground biomass in the layer of 0-10cm appears a large fluctuation, which is consistent with the trend of total belowground biomass. Curve below the layer of 10cm is steadily stable. （3） There is no obvious correlation between below-biomass and soil organic carbon content in the soil layer of 0 -60cm. However, in the layer of 0-10cm, the soil organic carbon content is significant positive correlated with belowground biomass from May to July. （4） There is no obvious correlation between belowground biomass and monthly precipitation or monthly average temperature. （5） Belowground biomass in different soil layers has a significant positive relation with soil moisture; total belowground biomass is greatly influenced by soil moisture in the layer of 0-10cm.