Life‐History Plasticity of Riparian Annual Plants Adapted to Extreme Variations in Water Level: Mesocosm Experiments

Abstract

The riparian zones of reservoirs associated with regulated rivers in China experience annual fluctuations in water level of up to 30 m that may vary in timing from year to year. Few plant species can tolerate such hydrological perturbation but short-lived riparian annuals might be evolutionarily pre-adapted to such conditions. This study investigated plasticity of life history in four annual species: one typically associated with free-flowing rivers (Panicum bisulcatum) and three that colonize reservoir margins (Cyperus michelianus, Fimbristylis miliacea and Eclipta prostrata). We found that all four species produced non-dormant seeds that survived prolonged submergence; germination percentage was independent of the time of exposure by receding waters. Although growth was reduced as a result of shorter growing seasons, all four species completed their life cycles and produced seeds before winter. In addition, P. bisulcatum and C. michelianus allocated biomass to seed production, at the expense of roots and stems, in response to later establishment. All species responded to later establishment with a reduced vegetative growth period before seed production. C. michelianus, F. miliacea and E. prostrata could also delay the onset of flowering time by up to 2 months. P. bisulcatum, a plant that can flower only after exposure to short days, consequently had a fixed flowering time and could accommodate delayed establishment only with a progressively shorter period of vegetative growth. This lower flexibility might explain its absence from reservoir margins. The conceptual framework presented here offers a tool to predict the establishment of vegetation under hydrological disturbance in riparian environments and thereby provides insights into improved restoration practice.

Fitness and growth of the ephemeral mudflat species Cyperus fuscus in river and anthropogenic habitats in response to fluctuating water-levels

“…Such additional possible responses described for various perennial wetland plants (e.g., rice; Voesenek and Bailey-Serres, 2015) were not in the focus of our study. Nevertheless, our results confirm that C. fuscus as an annual wetland plant is able to modify its morphology to cope with flooding like perennials, at least in nutrient-rich environments such as in our experiment (see also Voesenek et al, 2004; Song et al, 2015).…”

Seasonal and spatial variations of water use among riparian vegetation in tropical monsoon region of SW China

“…These ecosystems are very susceptible to natural and anthropogenic disturbances and considered as one of the most vulnerable ecosystems in the world (Bothwell et al, 2017). For instance, riparian vegetation along the bank of free-flowing tropical rivers is exposed to a dynamic water environment because of variation in rainfall and level of river water (Chimner & Resh, 2014;Song, Ke, Liu, Davy, & Liu, 2015). Given that once the habitat of riparian vegetation gets disturbed, many exotic plants can easily occupy the area because of seed input during the flood events ; Tabacchi, Planty- Tabacchi, Roques, & Nadal, 2005).…”

Spatiotemporal photosynthetic physiology responses of remnant Myricaria laxiflora populations to regulated water level fluctuations

“…Riparian plants have developed mechanisms to adapt river water fluctuations ( Glenz et al ., 2006 ; Song et al ., 2016 ). Although floods and droughts caused by normal water level fluctuations affect the fluctuations and changes in photosynthetic physiological activities in plants to some extent, plants can adapt to these environmental stresses through morphological and physiological changes, so that photosynthetic physiological activities are slightly altered and then subsequently restored to normalcy ( Kozlowski 1997 ).…”