内蒙古地区羊草草原植被对温度变化的动态响应

 1981～1994年连续14年内蒙古羊草草原温度随时间变化结果显示，该区域温度变化具有不对称性，冬季最低均温升高明显，而最高温及平均温度无明显增加趋势。羊草草原气候的变化主要表现在冬季最低温的增加，而不是平均温度的增加。羊草群落的结构和功能对冬季最低均温变化的响应研究表明，随着冬季最低均温的升高，阿尔泰狗哇花(Heteropappus altaicus)和冰草(Agropyron michnoi)的重要值及地上初级生产力将明显增加，而寸草苔(Cares duriuscula)则呈下降趋势，作为群落主要优势种的羊草(Leymus chinensis)和大针茅(Stipa grandis)及其它优势植物对冬季最低均温变化反应不明显。同时，群落的生物多样性指数(Simpson指数、Shannon-Wiener指数)、物种饱和度及地上初级生产力对冬季最低均温也均无显著相关，14年间冬季最低均温的变化并没有对群落的结构和功能产生明显影响。然而，因寸草苔和冰草等少数优势植物对冬季最低均温变化反应的敏感，温度变化的幅度增加或时间延续很可能造成少数优势种在群落中地位的改变，进而可能导致羊草群落结构和功能的变化。这表明在进行气候变化的模拟和模型研究时，不能仅简单地考虑平均温度增加的情况，而应确定主导影响因子，从而了解草原生态系统对全球变化的响应，选取适宜的模型参数。

RESPONSE OF LEYMUS CHINENSIS GRASSLAND VEGETATION IN INNER MONGOLIA TO TEMPERATURE CHANGE

Global temperatures are increasing, and, in particular, global minimum temperatures are increasing faster than maximum temperatures. Because temperature is a key factor hat controls the growth and distribution of vegetation, and there is no a priori reason to assume that ecosystems will respond similarly to changes in minimum and maximum temperatures, it is very important to explore the ecological consequences of global warming on terrestrial communities. The Leymus chinensis grassland is a dominant ecosystem of Inner Mongolia, and this region is very vulnerable to global climate change. We analyzed a long term climate and vegetation data base (1981-1994) for Inner Mongolia to examine the characteristics and the ecological consequences of temperature changes on Leymus chinensis grasslands. The results showed that temperatures increased and minimum temperatures, especially winter minimum temperatures, increased faster than maximum and average temperatures. There were no significant relationships between winter minimum temperatures and diversity indices (Simpson index and Shannon-wiener index), species saturation, and aboveground net primary productivity (ANPP) at the community scale. At the species level, the importance value and ANPP of most species had no significant relationship with winter minimum temperatures, except for Agropyron michnoi, Heteropappus altaicus and Carex duriuscula, all of which showed significant negative relationships. Because these are important species in this grassland community, the results suggest that the structure and function of the L. chinensis grassland community could be altered if winter minimum temperatures continue to increase. Thus, the identification of key elements of temperature change is very important for understanding and predicting the impacts of global warming to L. chinensis grassland communities.