Phenology and floral synchrony of Rhizophora mangle along a natural salinity gradient

Abstract

AbstractRhizophora mangle is the most common species of mangrove within its range and a major component of coastal ecosystems in the tropics and subtropics. Its phenology is affected by seasonal variations in temperature, salinity, and precipitation, all of which may be altered by impending climate change. In this work, the monthly leaf, flower, and fruit phenology of R. mangle was assessed at three sites, along a natural salinity gradient for 12 months. We assessed phenological states using litter traps installed in mangrove stands, and by direct observation of leaf production at two sites, and flower, and fruit production at a single site. Phenological events were compared with seasonal climatic variations (in wind, rain, and temperature) to explore potential abiotic controls on the phenology of this species. Leaf shedding was lowest at the low salinity site. Leaf and stipule production showed a seasonal trend, decreasing during the cool and dry winter months. Flowering was highly seasonal and synchronous and peaked during the rainy season. Flowering was correlated with average temperature (r = 0.82; p < 0.05) at all three study sites, but was not correlated with precipitation. At the high‐salinity site, flowering was restricted to the rainy season. Fruit abortion was associated with wind speed (r = 0.79; p < 0.05). Flowering of R. mangle is induced by increasing temperatures and the onset of rains. Rising temperatures, drier summers, and more frequent and intense storms, due to climate change, may influence mangrove productivity, population dynamics, and floral synchrony.