|
|
|
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.
Key words: Nymphoides peltata, Myriophyllum spicatum, Mechanical damage,
Biomass, Morphological traits.
School of Life Sciences, Central China Normal University, Wuhan 430079,
Hubei, P. R. China
*Corresponding author’s e-mail: caoqj1009@163.com;
caoqj1009@mail.ccnu.edu.cn; Tel: +86 27 67867221
|
|
|