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

Zhu, Guorong, Zhang, Meng, Cao, Te, Ni, Leyi
Environmental earth sciences 2015 v.74 no.5 pp. 3907-3916
Vallisneria, aquatic ecosystems, biomechanics, forces, geographical distribution, lakes, leaves, littoral zone, macrophytes, mechanical damage, mechanical properties, mechanical stress, photosynthesis, plant growth, wind, China
Submerged macrophytes mainly distribute in the wind-protected littoral zones, rather than continuously distribute around the lake due to mechanical damage by strong wave. However, it is unknown how the biomechanical properties, the key targets against mechanical stress, contribute to its survival and distribution in natural aquatic ecosystem. In this study, the distribution, plant growth, and leaf biomechanical and morphological traits of different segments of Vallisneria natans were examined at 25 sites with three wind strength [sites exposed to strong ES wind (HW), sites exposed to moderate ES wind (MW) and sites sheltered by lakeshore with weak wind disturbance], in Lake Erhai, of Yunnan Province, China. Results showed that V. natans mainly distributed in the wind-protected eastern and northern littoral zones within 5 m water depth. The smallest plant growth, strongest and least flexible leaves were at MW, indicating that V. natans is prone to dominate the littoral zones exposed to strong but short wave. Additionally, the high plant growth and relatively stronger and less flexible leaves at HW suggested that the maximization of photosynthesis was at the cost of reduced biomechanical properties and increased drag forces from similar waves, which were unfavourable to complete their life cycles and ultimately reduce the survival and distribution of V. natans under strong wave disturbance. The significant associations between the biomechanical and morphological traits may trigger trade-offs between the mechanical resistance and other plant functions, such as photosynthesis, ultimately determining survival and distribution of submerged macrophytes in natural aquatic ecosystems.