不同基质中水鳖对共存的穗花狐尾藻和金鱼藻的影响

研究设置了营养水平不同的3种基质，在有或无浮水植物水鳖共存的情况下，混合种植营养吸收方式不同的两种沉水植物（仅从水中吸收营养的金鱼藻和从水和基质都能吸收营养的穗花狐尾藻），探讨在不同的基质中浮水植物对沉水植物的影响。结果显示:实验中水鳖的存在均未对共存的两种沉水植物的生长产生抑制作用。当水鳖覆盖水面时，与无根的金鱼藻竞争光照和水体营养，促使其增加分枝数和茎长，并增加叶生物量的分配，最终导致水鳖的共存促进了金鱼藻的生物量积累。但与金鱼藻不同，有根的穗花狐尾藻可通过基质吸收营养，与共存的水鳖之间只存在光照竞争，使穗花狐尾藻仅以改变植株形态来适应浮水植物的表层覆盖，生物量积累并未发生显著变化。与沙处理相比，水鳖在营养水平较高的泥处理和泥沙混合处理中生长更旺盛，基质没有显著影响沉水植物的生物量和分株数。因此，在退化湿地生态系统中恢复水生植物时，为了提高群落的物种多样性，可以将沉水植物与少量的浮水植物组合配置，少量的浮水植物不会对沉水植物的生长带来负面影响。

EFFECTS OF FLOATING HYDROCHARIS DUBIA ON CO-CULTURED SUBMERGED MYRIOPHYLLUM SPICATUM AND CERATOPHYLLUM DEMERSUM IN DIFFERENT SEDIMENTS

Cultivating combination of different life forms is an efficient way to restore aquatic vegetation. A common combination is the floating and submerged plants. In this study, we cultivated two submerged plants with different types of nutrient uptake (rootless Ceratophyllum demersum, absorbing nutrients only from water column; and rooted Myrio-phyllum spicatum, taking up nutrients from both water and sediment) in three kinds of sediment with different levels of nutrients. The floating Hydrocharis dubia was added to explore the effects of floating plants on submerged plants in different sediments. The results showed that H. dubia grew more vigorously in silt and the mixed sediment of sand and silt that contained higher level of nutrients than sand sediment. However, the total mass and ramet number of C. demer-sum and M. spicatum were not affected significantly by sediment. The floating H. dubia did not suppress the growth of the two submerged plants. To compete with H. dubia for light and nutrients in water, rootless C. demersum tended to increase leaf mass ratio, branch number and stem length. As a result, C. demersum accumulated higher total mass in presence of H. dubia. Rooted M. spicatum adapted to shading of H. dubia by regulating plant morphology without sup-pressing growth of M. spicatum. These results revealed an efficient way to increase the species diversity of aquatic community by cultivating submerged plants with a small amount of floating plants.