Processing of leaf litter in a northern jarrah forest stream,Western Australia: I. Seasonal differences

Seasonal differences in the processing of jarrah (Eucalyptus marginata) leaves were examined in a small forest stream of the Darling Range, Western Australia. Processing rates in both summer and winter were very low, placing this species in the slow category (k < 0.005) of Petersen & Cummins (1974).Macroinvertebrates did not contribute to the processing of jarrah leaves during summer and autumn, coincident with the period of peak litter fall. The low quality of detritus entering the streams, and possibly some adverse interactions with the physical and chemical environment, inhibits processing during the summer months. As a consequence, a significant proportion of the coarse-particle detritus entering these streams may be exported unprocessed at the onset of high winter flows.In contrast with previous studies, jarrah leaves were processed at a faster rate during winter than summer. This seasonal difference can, in part, be attributed to the increased density and proportion of shredders at this time. Despite this, the processing of jarrah leaves during winter was very slow and must reflect the poor quality of this detritus as food for invertebrate consumers.