Seedling survivorship, growth, and response to disturbance in Belizean mangal

Background

Species zonation patterns across tidal gradients in mangrove forests are formed by successful seedling establishment and maintained by replacement of adults by conspecific seedlings. These two processes have rarely been examined experimentally in neotropical mangrove. This study examines survivorship and growth of seedlings of Rhizopora mangle and Avicennia germinans across a tidal gradient in Belize.

Research goals & methods

Propagules of each species were planted in nurseries at tidal elevations corresponding to lowest low water, mean water, and highest high water and monitored for survival over one year. 69% of Rhizopora seedlings planted at midwater and 56% of those planted at low water survived one year. 47% of midwater Avicennia seedlings also survived one year. No individuals of either species survived at high water, nor did any Avicennia seedlings at low water. Rhizopora seedlings grew more rapidly at low water than midwater; insect herbivory was greater on midwater seedlings than low water.

Conclusions & takeaways

The authors also examined the response of Rhizopora seedlings to experimental removal of the adult Rhizopora canopy after six months of growth. Seedlings in canopy removal areas had higher survivorship and growth rates and lower herbivory compared to seedlings below an intact canopy. These results provide insights into the underlying causes and maintenance of species zonation in Caribbean mangrove forests and may inform restoration design.