Functional traits and nutrient limitation in the rare mangrove Pelliciera rhizophorae

Abstract

Nutrient limitation is a major factor structuring mangrove forests, with nitrogen (N) and phosphorus (P) limitation causing stunted growth forms around the world. The rare mangrove Pelliciera rhizophorae exists in both fringe and dwarf forms on both coasts of Panama, but the reasons for the differences in growth form are unknown. Nutrient content, functional traits and herbivory were measured in fringe and dwarf trees from 14 populations on the Pacific and Caribbean coasts of Panama. Dwarf trees had a mean N of 1.51% on the Caribbean and 1.37% on the on the Pacific, lower than the 1.58% N fringe trees had on both coasts. Dwarf trees also had lower P concentrations (Caribbean: 0.10%, Pacific: 0.11%) in their green leaves than fringe trees (Caribbean: 0.12%, Pacific: 0.13%), indicating nutrient limitation may be responsible for the dwarf growth form of this species. Additionally, Caribbean trees had higher rates of P resorption (70.97-72.65%) compared to Pacific trees (58.87-60.8%) and lower P content in senescent leaves, suggesting Caribbean trees are P limited relative to Pacific trees. Dwarf trees allocate biomass differently than fringe trees, with smaller stem length to stem biomass, and leaf weight, shoot weight, and leaf area ratios. Dwarf trees experience less herbivory than fringe trees, which may be a result of lower leaf nutrient content. This is the first study to examine nutrients and growth traits in Pelliciera rhizophorae, and the only study to date comparing nutrients and growth traits in mangroves from both the Caribbean and Pacific coasts of Panama