Legacy Effects of Flooding Duration on Growth and Reproductive Traits of <i>Carex cinerascens</i> in the Poyang Lake Wetland

Alteration of flooding regimes due to global change may have cascading effects on plant community composition and associated ecosystem services. Here, we experimentally investigated the effects of six flooding regimes with contrasting combinations of flooding duration (5.5, 6 and 6.5 months) and submergence rate (from 3.3 to 17.5 cm/day) on the growth and reproductive traits of <i>Carex cinerascens</i>, a dominant plant species of the Poyang Lake wetland in southern China. The time span of this study included a summer flooding event and the following growing seasons (autumn of first year and spring of following year) before the return of the next flooding event. The six flooding treatments affected plant traits during the flooding and the following growing seasons, but the different submergence rates under the same flooding duration did generally not show significant influence on plant traits. The 6.5-month flooding treatments had many fewer old (0.4 on average) and new stems (1 on average) than the 5.5-month treatments (8.3 and 29 stems, respectively) at the end of the flooding. The treatments with 5.5 months of flooding had 23% more stems than the other treatments and 26% more community biomass than the 6-month flooding treatments during the autumn growing season. The effects of summer flooding persisted in spring of the following year, but with an opposite trend of <i>C. cinerascens</i> growth traits response to flooding treatments compared to autumn. In addition, the 6-month flooding treatments induced a higher number of inflorescences (39) than the 5.5-month (22) and 6.5-month floods (3). Altogether, our findings highlighted the important legacy effects of summer flooding with some trade-offs between growth recovery (autumn) and resilience (following spring) and between resource allocation to biomass production in autumn and resource allocation to sexual reproduction in the following spring, that were both mediated by flooding duration.