PJB-2016-115
RELATIVE RESPONSE TO MECHANICAL STRESS OF CO-EXISTING AQUATIC SPECIES, FLOATING-LEAVED NYMPHOIDES PELTATA AND SUBMERGED MYRIOPHYLLUM SPICATUM
QIAN-JIN CAO*, NA LIU AND LING WANG
Abstract
With the increasing impact of human activities on the environment, the effects of mechanical disturbance on aquatic plants are increasingly evident. Mechanical perturbations at the upper layer and surface of water frequently damage floating-leaved and caulescent submerged plants. Here, we co-cultivated floating-leaved Nymphoides peltata and submerged Myriophyllum spicatum in mesocosms and then subjected leaf laminas of N. peltata and stems of M. spicatum to different levels of mechanical damage. Similar experiments were conducted twice, the second with having an increased intensity and frequency of disturbance. Generally, mechanical disturbances impacted the growth of these species more significantly in the second experiment than in the first. In the second experiment, the total biomass of N. peltata was decreased and the biomass proportion to leaf laminas increased with increasing disturbance intensity; leaf area was maintained across treatments. For M. spicatum, all disturbance treatments decreased total biomass and the total length of stems, compared to non-damage controls. However, in M. spicatum the number of ramets were increased with increasing disturbance intensity. Our results indicate that N. peltata has a high capacity for foliage compensation, and vegetative reproduction of M. spicatum may be improved by intense mechanical disturbance, though severe damage will suppress growth. Mechanical disturbances in upper water layers may change the relative performance of co-existing submerged and floating-leaved species with a repressive effect on submerged species. Management of mechanical disturbance by human activities is urgently required to maintain the function of submerged plants when restoring contaminated wetlands.
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