中文摘要：

油蒿（Artermisia ordosica）是中国干旱、半干旱地区广泛生长的优良固沙种,研究干旱区不同区域油蒿种群的种内竞争可为天然油蒿种群的保护与恢复提供科学依据。选择同处于干旱地区的宁夏中卫市沙坡头、甘肃古浪县鸣沙咀和民勤县扎子沟这3个油蒿天然林分布区,利用Hegyi单木竞争模型对油蒿种内竞争进行分析。结果表明：干旱区天然油蒿种群种内竞争的最适宜竞争范围为6m;随着对象木冠幅的增加,其平均竞争指数呈减小的趋势,且对象木冠幅面积在0.08m2以下时竞争指数均比较大,当对象木冠幅面积大于0.08m2时,平均竞争指数迅速减小;不同样地的油蒿种群种内竞争强度存在差异,其大小顺序为鸣沙咀固定沙地〉沙坡头〉鸣沙咀半固定沙地〉扎子沟;用幂函数可以较好的表达油蒿种内竞争与油蒿冠幅之间的关系。

英文摘要：

Artermisia ordosica has been highly regarded as a sand fixation plant in arid and semi-arid area of China. The research on the intraspecific competition of Artermisia ordosica population in different areas can provide a scientific basis for its conservation and restoration. The intraspecific competition of Artermisia ordosica population in arid regions was studied by using Hegyi＇s competition index model for individual tree, ehose three typical distribution area for Artermisia ordosica, which are Shapotou Region in Ningxia Province, Mingshazui in Gulang County and Zhazigou in Minqin County in Gansu Provinee. The results demonstrated that, 6 meters was the optimal competition distance for intraspecifie competition of Artermisia ordosiea population in arid regions. The intraspeeific competition in natural Artermisia ordosiea population gradually became weakened with the crown width of the objective trees increasing. The competition intensity was relatively great when erown area of objective trees was less than 0.08 m2, and the competition intensity decreased rapidly with the crown area of objective trees was greater than 0.08 m2. The intraspecific competitive intensity was different in the different area. The intraspecific competitive intensity in different regions ranked in order of fixed dune in Mingshazui, the plot in Shapotou, Zhazigou. A power function was developed to describe the crown width of Artermisia ordosica. semi-fixed dune in Mingshazui and the plot in relationship between competition intensity andcrown width of Artermisia ordosiea.