浑善达克沙地黄柳种群性比及空间分布

Sex ratio and spatial distribution of Salix gordejevii in Hunshandake Sandy Land

雌雄异株植物的性比和空间分布格局对其繁殖策略、种群进化及发展起着至关重要的作用。黄柳是浑善达克沙地重要的固沙先锋植物,但针对其种群性比方面的研究却鲜有报道。采用点格局分析的方法,对黄柳4个天然种群的性比、空间分布格局以及空间关系进行了调查分析。结果表明:黄柳雌雄群体间在形态上的差异与种群所处环境条件密切相关;在调查样地内(50 m×50 m)种群性比(雌/雄)均极显著偏雌性(P<0.01)。决定性比的主要组成部分为第I径级和第II径级雌雄个体的数量;随着年龄的增长,性比由原本的偏雌性转变为接近于1∶1。4个种群的雌雄群体在全部尺度范围内主要以聚集分布为主,偶尔在小尺度内呈随机分布。扎格斯台、饮马井、巴格来3个种群雌雄群体的空间关系均表现为相互独立,说明性别之间对资源的竞争不激烈;而宝绍岱种群两性的空间关系为相互排斥,即存在性别空间分离现象。研究结果揭示了天然黄柳雌雄群体的组成、结构及分布特征,为提高人工黄柳林群落稳定性奠定了理论基础。

Sex ratio and spatial distribution of dioecious plants play an important role in reproductive strategy, population evolution, and development. Salix gordejevii, a typical dioecious plant, is an important sand-fixing pioneer plant in Hunshandake Sandy Land and is widely distributed in flowing and semi-flowing sandy land. But the current understanding of the structure and distribution of male and female populations is still limited. In our study, we chose natural populations in Zhagesitai, Yinmajing, Bagelai, and Baoshaodai, and investigated the sex ratio, spatial distribution pattern, and spatial relationship using statistics and point pattern analysis. Our objectives were to examine （ 1 ） whether the sex ratio deviated from 1：1 in the S. gordejevii population, and if so, （2） whether the sexual spatial segregation （SSS） phenomenon existed. The results showed that the morphological differences between male and female populations are closely related to the environmental conditions of the population. The sex ratio （female/male） was female-biased （P〈0.01） in different sampling plots （50 m × 50 m） and was determined by the number of male and female individuals in diameter classes Ⅰand Ⅱ. The sex ratio gradually approached 1：1 as age increased. Male and female populations of each population were mainly distributed in a clumped pattern on a 0-25 m scale, and were occasionally randomly distributed on a small scale. This phenomenon may be because the seed regeneration ability of S. gordejevii is weak, and clonal reproduction ability is strong. The spatial relationships between male and female populations were independent of each other in Zhagesitai, Yinmajing, and Bagelai, which indicated that competition between sexes was not intense. However, the spatial relationship of gender was mutually exclusive in Baoshaodai and SSS existed in the population. This phenomenon is mainly because of the relative lack of resources （e.g., lower soil moisture, organic matter, and total nitrogen） and the close proximity between male and female individuals in Baoshaodai. In conclusion, the sex ratio （female/male） was female-biased in the S. gordejevii population. Male and female populations were mainly distributed in a clumped pattern on all scales, and there was SSS in relatively resource-limited area. In addition, dioecious-plant-population regeneration was influenced by sex ratio and distribution pattern; thus, these should be considered when determining the proportion and spatial location of male and female individuals during afforestation. This study revealed the composition, structure, and distribution of male and female populations of S. gordejevii, and laid a theoretical foundation for improving the stability of the artificial forest community.