Laguncularia racemosa phenology and resilience near its northern limit along the eastern coast of the USA

Abstract

The phenology of Laguncularia racemosa (L.) Gaertn. (Combretaceae) was investigated from a population located near the species’ northeastern range limit in Florida. Height, leaf dimensions, and the number of flower buds, flowers, and propagules were recorded, on average, every 2–3 months from May 2021 to October 2023. Irradiance, temperature, and inundation depth were measured hourly with data loggers and compared among seasons and years. Although plant heights were negatively impacted by freeze events in 2022 due to defoliation, vertical growth rates were significantly greater following the freeze. Flower bud and flower production were observed during the summer months and differed among years with greater abundances in 2021. Propagules were recorded in summer and autumn with greater abundances in 2021 and 2022 than in 2023. Light intensity was unlikely to limit growth without a canopy of L. racemosa. Maximum inundation depths > 1.2 m were recorded in autumn and winter when propagule dispersal was likely to occur. The greatest depth of 2.2 m was more than the tallest individual in the study and occurred when hurricanes coincided with extreme high tides. The L. racemosa population was resilient to freeze and flooding events suggesting that population densities may continue to increase in northeastern Florida marshes.