A pioneering study has revealed that the coco de mer palm (Lodoicea maldivica) retains its dead leaves for up to three years before shedding them. This phenomenon, known as marcescence, occurs when dead plants parts, such as leaves, remain attached to the plant for an extended period instead of falling off immediately. Marcescence has significant implications on the forest’s ecology, nutrient cycles, and fire risk.
The research found that nearly half of the dead leaf material in the coco de mer palm forests of the Vallee de Mai remains suspended in the trees, unlike in other tropical forests where leaves falls to the ground as soon as they senesce. This retention of the dead leaves in the canopy is one of several unusual features of coco de mer that create the unique ecological environment of the Valle de Mai. Dead leaves of the coco de mer are poor in nutrients, having exceptionally low levels of phosphorus and nitrogen compared to other tropical forests, which significantly slows their decomposition. For example, during the period they remain attached to the tree, dead leaves only lose about one quarter of their dry weight. Additionally, the arrangement of the leaves around the trunk forms makes the coco de mer a gigantic funnel that directs water down the trunk while drying out the surrounding forest floor, which also delays decomposition.
Researchers of this study have suggested that the retention of these dead leaves on the trunks of the coco de mer palms may be one of the traits that enable the species to improve its nutrient supply and grow as a large, dominant plant in nutrient-poor soils. They note that the dead leaves are an important structural element of coco de mer forest, providing food and shelter for some of the unique animals of this ecosystem. From a management, however, large masses of dead material both in the trees and on the forest floor, pose a challenge, creating an environment with some of the highest levels of dry, flammable material found in any tropical forest. This buildup of dry material, in turn, significantly increases the fire risk in these forests.
The full paper is open access. Full reference: Edwards P, Fleischer-Dogley F. (2025) Leaf litter turnover in monodominant forest of the marcescent palm Lodoicea maldivica. Oecologia Res 207:35. https://doi.org/10.1007/s00442-025-05673-9
Source: Seychelles Nation, Monday April 7, 2025