Hydroperiod modulates early growth and biomass partitioning in Rhizophora mangle L.

Abstract

In mangrove forests, the hydroperiod is strongly related to tidal dynamics, where the periodic oceanic water movement regulates the level, duration, and frequency of the flooding events. In fringe mangrove forests, Rhizophora mangle propagules deal with variable hydroperiod conditions that sometimes compromise their survival. To disentangle the combined effects of duration and intensity of flooding on physiological and growth variables, we imposed a continuous experiment with three levels of flooding and four flooding durations on seedlings of R. mangle. We collected data at 3 and 6.5 months after exposure to the treatments. Propagule reserves allowed plants to evade the effects of the flood level after a 3-month treatment period. After a 6.5-month exposure, physiology and growth were modulated by the flooding time. Individual plants had higher stem length and lower root and total biomass at prolonged and high flooding levels compared to any other flooding combinations. In both ages, the highest total plant biomass was exhibited in the medium flooding levels and 6 h flooding duration. The plasticity index was higher for morphological and biomass variables than for physiological variables. The high morphological plasticity of R. mangle plants constitutes a competitive advantage to colonize flooded sites in fringed mangrove areas. Our results identify schemes to improve the success of mangrove restoration plans, a critical tool for carbon sequestration and ecosystem service provision.