中文摘要：

水生植物之间的竞争作用在水体生态系统恢复过程中具有重要作用。本研究采用取代系列实验方法,对穗状狐尾藻（Myriophyllum spicatum L.）与不同生长期（幼苗期和成株期）苦草（Vallisneria natans（Lour.）Hara）的种间竞争进行了研究。结果显示,对于不同生长期的苦草,穗状狐尾藻均具有较强的竞争优势,成株期苦草的竞争能力强于其幼苗期;苦草成株组中的穗状狐尾藻平均株高比苦草幼苗组中的穗状狐尾藻平均株高增加了128.6%（P〈0.05）,但苦草成株组中的穗状狐尾藻植株平均干重比苦草幼苗组中的穗状狐尾藻植株平均干重降低了62.8%（P〈0.05）;苦草幼苗组中的穗状狐尾藻分枝较多、株丛大,对苦草幼苗形成了较大的遮光作用;苦草成株组中的穗状狐尾藻分枝少、植株较长,顶端漂浮于水面生长,表明受苦草的种间竞争压力增大,但仍小于穗状狐尾藻的种内竞争;另外,苦草幼苗组中的苦草根长比苦草成株组中的苦草根长平均长28.6%（P〈0.05）,表明在与穗状狐尾藻竞争过程中,苦草幼苗更趋于竞争地下资源。本研究结果说明穗状狐尾藻竞争能力强于苦草,苦草幼苗受穗状狐尾藻的竞争影响较大。

英文摘要：

Competition between aquatic plants plays a crucial role in ecosystem recovery in water bodies.Replacement series experiments were performed to explore the interspecific competition between Myriophyllum spicatum L.and Vallisneria natans（Lour.）Hara at different growth stages.Results showed that competitive capacity of M.spicatum L.was superior to that of V.natans（Lour.）Hara whether it was in the seedling or adult stage.Comparatively speaking,adult stage V.natans（Lour.）Hara had an advantage over its seedling stage.The average height of M.spicatum L.grown with V.natans（Lour.）Hara in the adult stage was 128.6%（P〈 0.05）higher than that grown with V.natans（Lour.）Hara in the seedling stage,whereas the average dry weight ofM.spicatum L.was 62.8%（P〈 0.05）lower.The M.spicatum L.grown with V.natans（Lour.）Hara in the seedling stage had more branches and larger plant plexus,thus forming a larger canopy and restraining light use by V.natans（Lour.）Hara seedlings.In contrast,M.spicatum L.grown with adult V.natans（Lour.）Hara had fewer branches,longer plants,and its top floated on the water,which was obviously inhibited due to increased competition from V.natans（Lour.）Hara,though this was less than the intraspecific competition of M.spicatum L.In addition,the average root length of seedling stage V.natans（Lour.）Hara was 28.6%（P〈 0.05）longer than that of adult stage V.natans（Lour.）Hara in competition with M.spicatum L.,which tended to compete for resources underground.This study showed that the competitive capacity of M.spicatum L.was superior to that of V.natans（Lour.）Hara,and seedling stage V.natans（Lour.）Hara was significantly impacted by competition with M.spicatum L.