Mangrove community structure and regeneration potential on a rapidly expanding,river delta in Java

Key message

Mangroves in rapidly expanding Southeast Asian river deltas form floristically simple zones dominated by a few highly regenerative species adaptable or tolerant to rapid sedimentation and extensive river flooding.

Abstract

The size class distribution, community composition and spatial structure of five representative mangrove forests in the rapidly expanding Cimanuk river delta on Java were determined. These deltaic forests are species-poor (eight true mangrove species) and spatially segregated into three distinct floristic zones: (1) a fringing, low intertidal zone co-dominated by Avicennia marina and A. officinalis, with less abundant Bruguiera parviflora, Rhizophora apiculata, and R. mucronata; (2) a zone transitional between the low and mid intertidal in which Avicennia and Rhizophora spp. co-dominate; and (3) a mid intertidal zone dominated by R. mucronata and R. apiculata. Numerically dominated by seedlings (52,500–73,500 seedlings ha^?1) and saplings (5,268–5,660 saplings ha^?1), all five forests are relatively young and actively regenerating. Positive correlations of tree stem diameter and tree height with soil organic matter and P concentrations, salinity, the soil C/N ratio, pH, and silt/clay composition highlight the importance of soil factors in sustaining forest growth. The low diversity and relative structural simplicity of these rapidly growing and regenerating forests may be attributed to adaptation or tolerance to flooding and the rapid sedimentation and seaward expansion of the delta.