Water is usually considered to be a key limiting factor for the growth and reproduction of steppe plants in the Xilin River Basin, Nei Mongol. Foliar δ13C values, an indicator of long term intercellular carbon dioxide concentration and thus of water use efficiency (WUE) in plants, were measured on Leymus chinensis (Trin.) Tzvel. and Cleistogenes squarrosa (Trin.) Keng.in six communities of different habitats in the Xilin River Basin. The foliar δ13C values of both species tended to increase with decreasing soil water content (SWC) and a significant negative correlation was found between foliar δ13C values and SWC in different soil layers, indicating that the two species could change WUE according to water availability. We also found relatively constant leaf water contents (LWC) of the two species in different habitats. Our results implied that the two steppe species might have adapted to different soil water regimes either through adjusting stomatal conductance to get a proper WUE, or through enhancing the osmosis regulating ability to keep a relatively stable LWC. Our findings could partially explain why the two plant species have a wide distribution range and become dominant in the Xilin River Basin.
内蒙古锡林河流域不同植物群落中羊草和糙隐子草水分利用效率的变异
陈世苹 白永飞 韩兴国*
（中国科学院植物研究所植被数量生态学开放研究实验室，北京100093）
摘要： 用稳定性同位素技术,研究了锡林河流域不同群落和生境下羊草(Leymus chinensis ( Trin.) Tzvel.)和糙隐子草(Cleistogenes squarrosa (Trin.) Keng.)叶片δ13C值及其水分利用效率的变化.结果表明,在不同生境下,羊草和糙隐子草叶片δ13C 值随土壤水分含量的降低而增大,并与不同土层土壤水分含量均表现出极显著的线性负相关关系;而二者的叶片水分含量与土壤水分含量无显著的相关关系.这一结果说明,羊草和糙隐子草的水分利用效率均随土壤水分含量的降低而提高,而叶片水分含量保持相对稳定.这两种植物可能通过调节气孔导度、提高水分利用效率和增强渗透调节能力等生理生态机制适应水分状况不同的生境,从而使它们能够在锡林河流域不同植物群落中广泛分布并成为建群种或优势种.
关键词： 锡林河流域；羊草；糙隐子草；水分利用效率：δ13C 值
通讯作者。E-mail: <xghan @ ns.ibcas.ac.cn>
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