中文摘要：

以内蒙古贝加尔针茅（Stipa baicalensis）草原3种主要植物贝加尔针茅、羊草（Leymus chinensis）和冷蒿（Artemisia frigida）为对象,采用分解袋法研究了3种不同植物器官（叶、茎、根）凋落物的分解速率和养分动态变化过程.结果表明：3种主要植物凋落物分解速率存在明显差异,贝加尔针茅叶凋落物分解快于根凋落物,羊草和冷蒿根凋落物分解快于叶和茎凋落物;3种主要植物凋落物分解季节动态呈单峰型曲线,在8月份时达最大值;羊草和冷蒿茎凋落物初始N含量与其分解速率成显著正相关,3种主要植物凋落物C含量和C/N与各器官凋落物分解速率成显著负相关.

英文摘要：

Litter decomposition is one of the key processes of energy flow and nutrient cycling in grassland ecosystems. The objectives of the present study are to explore the seasonal dynamics of both root and shoot litter decompositions of Stipa baicalensis , Leymus chinensis and Artemisia frigida in the Stipa ba- icalensis grassland of Inner Mongolia, China. The root tissues and aboveground litters （leaves and stems） of three different species were covered with litterbags. The litterbags were collected after 295, 356 and 417 days, then the mass losses and C, N, P and K contents of remaining litters were determined. The decom- position rates of litters had significant difference among tested plants. The decomposition of aboveground litter of S. baicalensis was faster than that of root tissue, whereas the decompositions of root tissues of both L. chinensis and A. frigida were slower than that of aboveground litters. The seasonal dynamics of decomposition rate of tested litters showed a single-peak curve with the maximum value in August. The decomposition rate of stem litter had significantly positive correlation with initial nitrogen, significantly negative correlation with initial carbon content and C/N ratio.