BASE-LINE STUDIES OF TEMPERATE MANGROVE GROWTH AND REPRODUCTION - DEMOGRAPHIC AND LITTERFALL MEASURES OF LEAFING AND FLOWERING

Growth and reproduction in two species of mangrove, Avicennia marina a nd Aegiceras corniculatum, were measured over three years in Jervis Ba y, New South Wales, by demographic censuses of leaf and floral compone nts supplemented by litterfall collections. Sampling was designed to a ssess spatial and temporal variability for purpose of a baseline again st which future variation can be compared. In terms of annual litterfa ll Avicennia produces about 310 g/m2 whereas Aegiceras produces 210 g/ m2 with 9.2 and 32.2 % of litterfall respectively devoted to reproduct ive parts. Both mangrove species showed much spatial and temporal vari ation in growth and reproduction and, in general, leafing and litterfa ll declined from 1989 through to 1990. This decline may be related to regional climatic phenomena but longer-term data are required to confi rm this relationship. Over the period of a year, Avicennia and Aegicer as each has a single peak of leafing and reproduction, although the ti ming of this differs between them. Phenologically, in both species, re productive 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 p ool may also be a factor that contributes to low productivity and stat ure at high latitudes.