Base-Line Studies of Temperate Mangrove Growth and Reproduction; Demographic and Litterfall Measures of Leafing and Flowering

Abstract

Growth and reproduction in two species of mangrove, Avicennia marina and Aegiceras corniculatum, were measured over three years in Jervis Bay, New South Wales, by demographic censuses of leaf and floral components supplemented by litterfall collections. Sampling was designed to assess spatial and temporal variability for purpose of a baseline against which future variation can be compared. In terms of annual litterfall Avicennia produces about 310 g/m2 whereas Aegiceras produces 210 g/m2 with 9.2 and 32.2 % of litterfall respectively devoted to reproductive parts. Both mangrove species showed much spatial and temporal variation in growth and reproduction and, in general, leafing and litterfall declined from 1989 through to 1990. This decline may be related to regional climatic phenomena but longer-term data are required to confirm this relationship. Over the period of a year, Avicennia and Aegiceras each has a single peak of leafing and reproduction, although the timing of this differs between them. Phenologically, in both species, reproductive events and leaf demography were correlated. It is suggested that demands of precocious embryos for assimilates affects the timing of leafing. The relatively high resource demand of the reproductive pool may also be a factor that contributes to low productivity and stature at high latitudes.