Abstract: This study investigated the plant community composition and plant diversity of mixed-seeding artificial grassland in winter pastures in the plateau continental climate zone (DDM),summer pastures in the plateau continental climate zone (DXM) and winter pastures in the plateau cold climate zone (HDM) of Qinghai Province. The aims were to investigate the changing characteristics of the community structure of artificial mixed-seeding grassland in the high cold area and provide theoretical basis for the establishment of the artificial mixed-seeding grassland in the high cold area. Results showed that the artificial grassland significantly increased the cover and aboveground biomass compared with the control plot in all three study sites,among which the highest increment of cover was in HDM (P<0.01),but the highest increment of aboveground was in DDM (P<0.01). Mixed-seeding significantly altered the plant community composition and species important values in all sites,and the ratios of Poaceae significantly increased,especially in DXM (P<0.01). In addition,the ratios of weeds in all sites decreased after mixed-seeding,especially in HDM (P<0.01). Mixed-seeding also changed the specie richness,Shannon-Weiner index,Pielou index,Simpson index. In summary,artificial mixed planting was an effective measure for the restoration of degraded grassland in “black beach” land in alpine regions,but the restoration effect was different in different regions. Therefore,the planting of artificial grassland in the Qinghai-Tibetan plateau should be based on local conditions and the climatic status to achieve the sustainable management.

Key words: Three Rivers Source Region, Mixed-seeding, Plant community composition, Plant diversity, Black beach, Qinghai-Tibetan plateau

摘要： 本试验对青海省三江源区人工混播草地（海南州贵南县森多乡高原大陆性气候冬季牧场（记为DDM）2014年混播草地、果洛州玛沁县大武镇高原寒冷气候冬季牧场（记为HDM）2015年混播草地和海南州贵南县森多乡高原大陆性气候夏季牧场（记为DXM）2016年混播草地）的植被群落结构特征物种进行多样性调查，旨在探讨高寒区人工混播草地群落结构的变化特征，为高寒区人工混播草地建植提供理论依据。试验结果表明：混播第2年，DDM，DXM和HDM草地的植被盖度和地上生物量均有所提高，HDM人工草地的植被盖度与DDM和DXM相比，差异极显著（P<0.01），DDM人工草地的地上生物量与DXM和HDM相比，差异极显著（P<0.01）。从物种组成上来看，3个试验样地在混播后，植被群落组成及物种重要值均发生了显著变化，其中禾本科牧草所占比例均显著上升，DXM与DDM和HDM相比，上升较为明显（P<0.01）。另外，各个样地的杂类草比例均显著下降，HDM与DDM和DXM相比，下降最为明显（P<0.01）。此外，人工混播措施显著降低了3个样地的物种丰富度、Shannon-Weiner指数、Pielou指数、Simpson指数。综上所述，人工混播是高寒区黑土滩退化草地修复的一种有效措施，但在不同区域的恢复效果不同，因此在青藏高原建植人工草地时要因地制宜，综合考虑不同区域的气候特征，最终达到人工草地的可持续性经营。

关键词: 三江源区, 混播, 群落结构, 物种多样性, 黑土滩, 青藏高原