Annual patterns of litterfall in a lowland and tableland rainforest in tropical Australia

Fine litterfall (primarily leaves, twigs up to 1 cm diameter, and reproductive parts) was collected weekly over a 5 year period from 30 traps randomly arranged in each of two 0.5 ha plots in tropical rainforests at two contrasting sites (lowland and tableland) in North Queensland and sorted by species and components. Annual fine litterfall (+/- 95% confidence limits) was 8.00 +/- 0.36 Mg ha(-1) at the lowland site and 11.03 +/- 0.47 Mg ha-L at the tableland site. The range over 5 years of annual fine litterfall was not great (7.04-8.74 Mg ha(-1) at the lowland site; 10.02-13.64 Mg ha(-1) on the tableland), but reproductive material varied substantially, both in absolute amount (0.85-1.86 and 1.41-4.74 Mg ha(-1)) and as a percentage of total litterfall for any year (12-21% and 14-35%) for lowland and tableland sites respectively. A seasonal maximum (October/November-hot dry season) was most evident for the old leaf component. Fruits and flowers were more irregularly spread through the year. The mean ratio of annual litterfall mass of reproductive material to leaves was 0.32. We attributed the high value of this ratio to our shorter sampling interval (7 days) compared to longer intervals used in most other tropical rainforest litterfall studies. Comparing our results with other Australian studies, we estimated that fruit and flower mass in litter traps in tropical rainforest declines 50 percent every 10 days relative to leaf litter mass.