中文摘要：

刈割是内蒙古草原的主要利用方式之一。当植物面对刈割干扰时,可以通过繁殖策略的调节适应变化的环境。研究刈割干扰下植物繁殖策略的调节对于揭示植物的适应与进化机制具有重要意义。为此,选择内蒙古典型草原的大针茅（Stipa grandis）和糙隐子草（Cleistogenes squarrosa）,在1979年围封的羊草（Leymus chinensis）样地（对照）和毗邻的长期刈割区对其繁殖策略进行了研究。结果显示：1）长期刈割干扰下,大针茅的种群生物量与对照区无显著差异,由于其株丛生物量显著降低,大针茅种群生物量的维持得益于种群密度的显著增加。糙隐子草的种群生物量比对照区显著提高,由于其株丛生物量与对照区无显著差异,糙隐子草种群生物量的增加也是因为密度的显著提高。因此,密度调节是两种植物应对长期刈割干扰的重要的调节机制。2）长期刈割干扰下,两种植物在无性繁殖和有性繁殖过程所采取的密度调节策略并不相同。大针茅种群生殖株丛的密度无显著变化,非生殖株丛的密度显著提高,导致其非生殖株丛的相对密度显著增加,而生殖株丛的相对密度显著降低。因此刈割干扰下大针茅种群在密度调节上采取了保持有性繁殖株丛密度,增加无性繁殖株丛密度的策略。糙隐子草种群非生殖株丛的密度显著增加,但生殖株丛的密度增加幅度更大,导致其非生殖株丛的相对密度显著降低,而生殖株丛的相对密度显著提高。因此刈割干扰下糙隐子草种群在密度调节上采取了增加无性繁殖株丛密度的同时,更大幅度地增加有性繁殖株丛密度的策略。3）长期刈割干扰下,两种植物对生物量生殖分配的调节采取了不同的策略。大针茅株丛生物量向生殖枝分配的比例无显著变化,通过降低生殖枝向穗的生物量分配比例,降低了对有性生殖过程的生物量分配的投入;而糙隐子草

英文摘要：

Aims Stipa grandis and Cleistogenes squarrosa are two important bunchgrass species in Inner Mongolia typical steppe.Stipa grandis is a dominant species in undisturbed communities,while C.squarrosa becomes the dominant species in degraded communities.It is important to understand the regulation mechanisms of the two populations under mowing disturbance,especially those regulating sexual and asexual reproduction.We addressed four questions：1） Do the two populations exhibit density-dependent regulation under mowing disturbance？ 2） If so,how do they regulate sexual and asexual reproduction？ 3） Do the species modify their biomass allocation patterns under mowing disturbance,and,if so,how do they change their allocation patterns？ 4） Does mowing disturbance affect plant basal area and tiller number？ Methods This study was conducted in a long-term fenced site and a long-term mowed site at the Inner Mongolia Grassland Ecosystem Research Station of Chinese Academy of Sciences in 2007.We examined the density regulation and resource allocation regulation of S.grandis and C.squarrosa under different management regimes.Important findings Under mowing disturbance,S.grandis exhibited no significant change in population biomass,while C.squarrosa significantly increased.Because mean plant biomass of S.grandis decreased significantly and that of C.squarrosa did not change,density increase plays an important role for the two species in population biomass production.The two species exhibited different strategies in density-dependent regulation of asexual and sexual reproductive processes.For S.grandis,density increased in non-reproductive plants,but was unchanged in reproductive plants under mowing disturbance,which led to relative density increasing in non-reproductive plants and decreasing in reproductive plants.For C.squarrosa,the densities of both reproductive and non-reproductive plants increased significantly at the mowed site.The relative density increased in reproductive plants,but decreased in non-reproduct