Litter inputs to a tropical Australian rainforest stream

Vertical litterfall and lateral litter movement were monitored in the riparian zone of Birthday Creek, a small upland rainforest stream in north Queensland, from June 1987 to May 1990. Total litterfall (mean = 484 g m−2 year-1) was low in comparison with other tropical sites both within Australia and elsewhere. Litterfall was distinctly seasonal, with maxima occurring in the spring (October-November) and minima in winter (June–July). Tropical storms caused short-term increases in litterfall, especially of the small wood fraction. Overall, laterally transported litter contributed 6.8% of the total litter input to the monitored section of the stream. Lateral movement varied according to bank slope and microtopographic features and was not related to wind. Nitrogen and phosphorus concentration of leaves were low (mean N= 1.26%, P = 0.029% by weight). Nitrogen concentration of laterally transported levels overall was about 19% higher than that of leaves falling directly into the stream.