Adaptation of submerged macrophytes to both water depth and flood intensity as revealed by their mechanical resistance

Abstract

Little is known about the mechanical resistance response of submerged macrophytes to floods. An experiment was conducted to investigate the plant growth, root anchorage strength, and stem tensile properties of five submerged macrophytes under three initial water levels (1.0, 2.5, and 4.0 m) with four water level fluctuation speeds (0, 5, 15, and 25 cm d -1 ). Our results demonstrate that the biomass, relative growth rate, root anchorage strength, and stem tensile properties of the five species decreased with increasing initial water level, suggesting that deep water can inhibit plant growth and decrease their mechanical resistance. Floods weakened the stem tensile properties and strengthened the root performances of Myriophyllum spicatum, Hydrilla verticillata, and Potamogeton malaianus in shallow water. However, floods induced opposite mechanical resistance responses from plants in deep water, indicating a possible trade-off between stem breakage and uprooting under flooding conditions. M. spicatum, Ceratophyllum demersum, and P. malaianus were more tolerant of deep water and flood intensity than Potamogeton maackianus and H. verticillata, as indicated by their larger biomass, plant heights, stem tensile properties, and root anchorage strength. This is the first article that mechanically explains the competitive capability and survival potential of submerged macrophytes to water depth and flood intensity. Handling editor: Koen MartensElectronic supplementary material The online version of this article

Size-dependent C, N and P stoichiometry of three submersed macrophytes along water depth gradients

“…Generally, light intensity is sufficient for growth of submersed macrophytes in shallow water, where intensive competition may lead to insufficient resources for plant growth across space and time, while the contrasting situations would be expected in deep water. Submersed macrophytes have large phenotypic plasticity ingrowth rate, biomass allocation and stem elongation in response to different water depths (Strand and Weisner 2001;Fu et al 2012;Zhu et al 2012;Bai et al 2013). However, this phenotypic plasticity did not largely change the internal tissue element ratios of submersed macrophytes as also indicated by the evidence in our study Fig.…”

“…They occur ubiquitously in the littoral zone (0.5-5 m water depth) of Lake Erhai, and are easily sampled in the field. These three macrophytes differ in leaf morphology that P. maackianus has alternate, oblong or linear entire leaves, M. spicatum owns divided and featherlike leaves, and C. demersum is rootless with whorled palmate dissected leaves (Zhu et al 2012), giving opportunity for examining effects of different biomass allocations on C:N:P stoichiometry of the plants.…”

“…Submersed macrophytes occupy littoral zone in lakes, where water level fluctuation affects growth and distribution of the plants (Strand and Weisner 2001;Fu et al 2012;Zhu et al 2012). Water level fluctuation alters light availability in water column, waves and water-air gas exchange, sediment texture and element composition, which affect physiology, morphology, biomass allocation, growth rate and distribution of submersed macrophytes (Strand and Weisner 2001;Fu et al 2012;Yuan et al 2013;Christia et al 2014).…”

“…Water level fluctuation alters light availability in water column, waves and water-air gas exchange, sediment texture and element composition, which affect physiology, morphology, biomass allocation, growth rate and distribution of submersed macrophytes (Strand and Weisner 2001;Fu et al 2012;Yuan et al 2013;Christia et al 2014). Growth of submersed macrophyte is reduced in deep water due to low light availability (Fu et al 2012;Zhu et al 2012;Li et al 2013). Most submersed macrophytes tend to allocate more biomass to stem and increase shoot height in deep water so as to alleviate low light stress (Strand and Weisner 2001;Fu et al 2012).…”

Associations between the morphology and biomechanical properties of submerged macrophytes: implications for its survival and distribution in Lake Erhai

“…Wallsten and Forsgren 1989;Gacia and Ballesteros 1996;Cui et al 2000;Havens 2003;Yang et al 2004). Due to the light intensity, submerged macrophytes grow particularly well in littoral waters and organize themselves in patches of different sizes (Spence 1982;Zhu et al 2012a;Søndergaard et al 2013). However, shallow waters are often exposed to strong flow conditions due to waves and currents (Denny 1988;Henry and Myrhaug 2013), and most submerged macrophytes dominate in the wind-protected littoral or lake bends in natural lakes (Yu et al 1996;Istvánovics et al 2008).…”