中文摘要：

为揭示白羊草（Bothriochloa ischaemum）种群地带性分布与水热梯度的关系,试验于2005年-2009年,采用野外调查与定位监测相结合的研究方法,分析了黄土高原半干旱-半湿润区水热梯度对白羊草群落分布与生态幅的影响。结果表明,受海拔高度的影响,白羊草的垂直分布已由适宜生长的500 m-1700 m海拔范围扩展到海拔1950 m的上界,种群密度达3-4株/m^2,生殖枝数为12株/丛,生物量为12 g/丛;受降水梯度等影响,白羊草的水平分布范围已由森林草原地带的建群种或优势种扩展到了典型草原地带,并从伴生种上升为优势种。在荒漠草原地带的沟谷阳坡也常呈偶见种出现,并从年降雨500 mm-800 mm的适宜区扩大到300 mm-900 mm范围的降雨区。因此表明,在全球气候变化背景下,典型指示植物-白羊草种群受区域水热环境的影响,生态幅逐渐扩大,但其稳定性有待长期研究。

英文摘要：

To find out the relationship between the zonal distribution of Bothriochloa ischaemum population and the Hydrothermal gradient,the effects of the hydrothermal gradient on the zonal and ecological amplitude of Bothriochloa ischaemum population in the semi-arid and semi-humid region of Loess Plateau with field survey and position monitoring were studied from 2005 to 2009.The elevation gradient affected Bothriochloa ischaemum extend from its optimal vertical elevation of 500 m-1700 m above sea level to 1950 m above sea level.With population density within 3 to 4 plants/m2,its reproductive branches were 12 per cluster and its biomass reached 12 g per cluster.And the rainfall gradient made Bothriochloa ischaemum horizontal distribution from forest steppe zones to the typical grassland zone,which means it became the dominate species instead of the companion species.Also,it appeared as the occasional species on the south-facing lands of the gullies and valleys in the forest steppe zone and its optimal rainfall limits changed from 500 mm-800 mm to 300 mm-900 mm.Furthermore,the conclusion indicated that under global climate changes,Bothriochloa ischaemum as a typical indicting plant gradually widened its ecological amplitude.