Abstract: Tetraena mongolica is a national second-class protected plant and epibiotic species. The research objective in this paper was to reveal the structure,intraspecific interactions,and adaptation strategies to the environment of different types of T. mongolica species in the Western Ordos National Nature Reserve.,Utilizing size structure,the T. mongolica individuals were divided into three classes of size(class 1，d≤40 cm；class 2，40 cm＜d≤80 cm；class 3,d＞80 cm. Letter D denotes the cube root of the product of plant height and crown length and crown width). The spatial pattern and correlation of plants at all levels were analyzed by point pattern analysis. The results showed that:the individuals of T. mongolica were mainly concentrated in the class 2. Moreover,the age structure was stable,which reflected the stability of the environment in the research plots;The class 1 plants of T. mongolica in the three sample plots were clustered at medium and small scales,while the others were mainly randomly distributed;Most of the class 1 and class 2 plants showed significant positive correlation. However,the class 3 plants had significant negative correlations with the other 2 classes at medium and small scales,which showed the inhibitory effect of senior individuals on other classes. The results provide a basis for the scientific protection of T. mongolica population.

Key words: Tetraena mongolica, Spatial distribution pattern, Spatial association, Size structure

摘要： 四合木(Tetraena mongolica)是国家二级保护植物，为古老残遗种。为了揭示不同四合木种群的结构、种内相互作用以及对环境的适应策略，本研究以西鄂尔多斯地区四合木为研究对象，采用大小结构法将四合木植株划分为3个大小级(1级，d≤40 cm；2级，40 cm＜d≤80 cm；3级，d＞80 cm。d为株高×冠幅长×冠幅宽的立方根)，运用点格局分析法对各级植株的空间格局及关联性进行分析。结果表明：3个样地中的四合木均以2级为主，年龄结构为稳定型，反映出样地环境的稳定性；3个样地四合木1级植株在中小尺度均呈集群分布，其他均以随机分布为主；1级和2级植株多呈现出显著正关联，3级植株在中小尺度均与其他2个级呈显著负关联关系，反映出高龄级对其他龄级的抑制作用。研究结果为科学地保护四合木种群提供依据。

关键词: 四合木, 空间分布格局, 空间关联, 大小结构