两种沉水植物黑藻和伊乐藻的种间竞争

INTER-SPECIFIC COMPETITION BETWEEN TWO SUBMERGED MACROPHYTES, ELODEA NUTTALLII AND HYDRILLA VERTICILLATA

采用取代系列实验方法,主要从竞争期的长短出发,研究了黑藻(Hydrillaverticillata)和伊乐藻(Elodeanut-tallii)的种间竞争关系,并考查了在不同底质(土壤)肥力下两者种间竞争能力的变化情况。实验发现,伊乐藻由于具有较强的耐寒能力,在冬春时空竞争方面占有明显的优势,从而在周年实验中表现出较强的竞争优势,取代黑藻生长。而在短期实验中,黑藻由于可在水面生长形成较上位的冠层的特性,与伊乐藻相比在水体上层空间占领和阳光获取方面具有一定的优势,因此造成两种间竞争的不平衡,竞争偏利于黑藻,且这种优势随底质(土壤)肥力的增加而有所增强,但并没有明显取代现象的发生,两物种可以在混合种群中共存。

Aims Elodea nuttallii and HydriUa verticillata have similar morphology. E. nuttallii is an alien aquatic plant introduced into China in 1980s. Both species occupy similar habitat; therefore, they are potential competitors. We investigated： 1） weather inter-specific competition occurred, 2） which species had superior competitive abilities, and 3） what factors influenced competitive results. Methods Two replacement series experiments were carried out to analyze interspecific competition between E. nuttallii and H. verticillata. In replacement series experiments, the planting densities of the two species were varied but the total density was held constant. The first experiment assessed competitive ability at two levels of soil fertility, and the second investigated the long-term competitive growth of E. nuttallii and H. verticillata. Important findings E. nuttallii had superior cold resistance and advantages in competing for space-time during winter and spring, so it grew well in the long-term experiment and eventually replaced H. verticillata. In the short-term experiment, H. verticillata formed an upper canopy, giving it advantages in competing for light and occupying the water surface, causing imbalanced competition between H. verticllata and E. nuttallii. H. verticillata was the stronger competitor at both levels of soil fertility, and increased soil fertility could strengthen its competitive abilities; however, it could not replace E. nuttallii and they could coexist in the mixed population. This study suggests competitive abilities are integrated abilities of plants and those morphological traits, life history traits and environmental factors could affect the results of competition. Therefore, investigations of plant interactions should encompass a wide array of factors.