SPATIAL AND TEMPORAL VARIATION IN LITTER FALL OF AVICENNIA-MARINA (FORSSK) VIERH IN THE BRISBANE-RIVER, QUEENSLAND, AUSTRALIA

Leaf, woody and reproductive litter fall in a sub-tropical stand of Av icennia marina (Forssk.) Vierh. was measured monthly, along four trans ects (two in mature forest, two in regrowth) at three tidal inundation levels, for 2 years to investigate the spatial patterns of litter fal l in relation to position on the shore and vegetation maturity. Litter fall in 1992/1993 was 831.3 g dry weight (DW) m(-2) year(-1) and in 1 993/1994, 921.7 g DW m(-2) year(-1). Over the 2 year period, leaf litt er fall accounted for 47% of total litter fall, reproductive litter 30 % and woody litter 23%. Leaf fall was seasonal with a maximum in the w et summer season; wood fall was aseasonal but positively correlated wi th periods of high wind. Reproduction was biennial with fruit fall in the dry winter season. Litter fall was consistently higher at the mid tidal level and decreased up- and down-shore from this point. Rates of litter fall were independent of the maturity of the stand and tree de nsity but organic cycling was much slower in the mature forest. Larger trees produced more fruit, but fruit production per unit of tree biom ass was greater in smaller trees.