Abstract: Potential population leaf area index(1AI)of Leymus chinensis is evaluated on the basis ofcommunity water balance and Leymus chinensis'water use strategy.The whole experiment period contains adrought stage and a wet one,before or after several rains.L.chinensis deVeloped distinctive diurnal coursecharacters of transpiration rate,leaf behavior of transpiration and water use efficiency at these two stages,Compared with Potentilla tanacetifolia,an important companion species in the community.L.chinensis ex-hibits similar diurnal course character of transpiration rate and resembles leaf behavior of transpiration,but kept a lower transpiration rate and a higher water usage efficiency.In the experiment period,the precipita-tion was 69.6 millimeter.Community evapotranspirated 43.07 millimeter.Soil water storage had a surplusof 26.53 millimeter.Soil evaporation exhausted 40% evapotranspiration.Leymus chinensis population ex-hausted 30%,while other species in the community used the rest 30%.The population's LAI of Leymuschinensis in the natural community studied is 0.983,far little from the maximum value permitted by the re-gion water condition,which equal to 2.16(LAI)from the point of view of community water balance.

Key words: Leymus chinensis, Water use strategy, Water balance, Population growth potential

摘要： 本文结合羊草群落的水分平衡状况分析了羊草的水分利用对策,推测了羊草种群在实验期间的生长潜力。实验期分为旱期和湿期。不同期间,羊草在蒸腾速率特点、叶片蒸腾行为以及水分利用效率等方面采用不同的水分利用对策。同群落中与占优势的伴生种菊叶委陵菜相比,在蒸腾速率特点和叶片蒸腾行为方面具有相似性,但羊草具有较低的蒸腾速率和较高的水分利用效率。实验期间,降水69.6mm,群落蒸散43.07mm,土壤储水盈余26.53mm。土壤蒸发占总蒸散40%,羊草种群蒸腾耗水占总蒸散30%,其它植物利用30%。天然羊草群落中羊草种群叶面积指数为0.983,远未达到环境水资源所允许的最大容纳量(3.09),如果其它植物的用水考虑在内,当时羊草种群的叶面积指数可达216。

关键词: 羊草, 水分利用对策, 水平衡, 生长潜力