环境和扩散对草地群落构建的影响

Effect of species dispersal and environmental factors on species assemblages in grassland communities

植物群落构建机制是生态学研究的热点之一。长久以来这个难题并没有得到很好的解释,且争议较多。生态位理论或中性理论,或是二者的共同作用,这样的结论在不同的研究中都有印证。以黄土高原子午岭地区的草地群落为例,对3种不同的草地群落(5a的弃耕地、阴坡和阳坡的草地)进行了野外群落学调查,采用Mantel test和主轴邻距法(PCNM)分析方法,研究了空间地理距离和环境资源差异对于草本植物群落分布的影响,结果表明:地理距离和环境差异共同解释了群落组成相似性的79.3%,剔除环境因子的影响,地理距离解释了群落组成相似性的33.8%;而剔除地理距离的影响,环境因子解释了群落组成相似性的14.2%。无论是生态位理论还是中性理论,其在黄土高原草本群落构建过程中都有作用,但中性理论扮演了更为重要的角色。

The construction mechanisms of plant communities are a hot topic in the field of ecology. However, the question of how communities are constructed has not yet been adequately explained. Whether these mechanisms are driven by niche theory, neutral theory, or a combination of the two has been confirmed in a variety of research studies; most of them concentrated on the study of tropical rain forests. So we looket at grassland communities on China＇s Loess Plateau as example, hoping to provide some grounds for answering this question in this paper. Three different grass habitats were selected： land which had been abandoned for five years, north-facing slopes and south-facing slopes. The Mantel test analysis was applied to test the correlation between similarity in community composition, geographic distance and environment distance. The result of our research suggested that geographic distance has a significant effect on the community composition （P〈0.01） ; there is a correlation between environment distance and community composition （P〈0.01）, hut the function of environment distance is not as good as geographic distance. In order to further explore the influence, PCNM analysis was used to test for fitness： the percentage of community assembly can be explained in terms of the geographic distance and environmental distance. The results indicate the distribution of plants are highly variable and more strongly related to geographical distance rather than to environmental differences. Together, geographical distance and environmental distance explained 79.3 % of the variation in floristic similarity. Pure geographic distance or pure environmental distance alone explained 33.8% and 14.2% of the variation in floristic similarity, respectively. The neutral theory plays a strong role in the species assemblages within ecological communities, but the function of the niche can＇t be ignored.