中文摘要：

以内蒙古典型草原羊草Leymus chinensis和大针茅Stipa grandis群落为研究对象,于2006年7月、8月进行了群落组成调查和生物量测定,并采样测定了各植物种热值,按各种的干质量权重计算了群落水平的热值。测定分析结果表明,在观测期羊草热值平均为18.99 kJ/g;大针茅热值平均为19.16 kJ/g;羊草和大针茅无论样地间还是种间差异都不显著。在观测期内,羊草和大针茅的热值均表现出一定的随季节略微增加的变化特征,羊草热值的季节变化以二次多项式拟合的效果较好,大针茅热值的季节变化以线性拟合更好。群落水平上,羊草群落和大针茅群落热值最高的均是大针茅,分别为19.03和19.28 kJ/g,热值最小的植物种在羊草群落中为轴藜Axyris amaranthoides和灰绿藜Chenopodium glaucum,在大针茅群落中为猪毛菜Salsola collina。羊草群落干质量加权热值为18.73 kJ/g,大针茅群落为18.43 kJ/g。整个观测期群落地上部分、根系、凋落物及立枯物热值结果说明,地上部分热值高于地下部分,群落热值随时间和群落结构变化而有略微波动,群落水平热值与种及器官水平上的热值有着一定差异。

英文摘要：

The caloric values of two typical steppe communities （Leymus chinensis and Stipa grandis） in Inner Mongolia were measured and analyzed on the scale of community in July and August 2006, meanwhile, the plant composition and biomass of community were investigated. The caloric value of L. chinensis was 19.03 kJ/g （CV= 1.61%） ; and the value of S. grandis was 19. 13 kJ/g （CV= 1.33%）. The analysis of variance showed that the caloric values of two species were not significantly different whether they were from same plot or not, and same season or not. The values value showed an increasing trend in observing period along with the season, and might be described with 2-order polynomial model for L. chinensis, and better with linear model for S. grandis. At the community level, S. grandis had the higher caloric values that were 19.03 kJ/g and 19.28 kJ/g respectively in two communities. The species with the low value were Axyris arnaranthoides and Chenopodiurn glau- cum in L. chinensis community （15.04 kJ/g）, and Salsola collina in S. grandis community （12.75 kJ/g）. The caloric value of L. chinensiscornmunity （18.73 kJ/g） was higher than that of S. grandis community （18.43 kJ/g）. The caloric value of aboveground biomass was higher than underground biomass and the species from gramineae family was higher than those from other families. The caloric value slightly varied with the growing season and community structure.