Leaf pack processing in a pastureland stream

Processing of Platanus occidentalis L. leaf packs in a pastureland stream was examined by placing leaf pack analogues in the stream and sampling over a 161-day period. Using an exponential decay model in which percent weight remaining was regressed on time, a processing coefficient of -0.0057 was obtained. The influence of macroinvertebrates on the processing of leaf packs was found to differ somewhat from the situation reported for woodland streams. In woodland streams, macroinvertebrate 'shredders' have been shown to be very important in the fragmentation of whole leaves which is the initial step in the processing of detrital material by stream consumers. Shredders were not important in this pastureland stream and fragmentation of whole leaves was mainly a function of microbial decomposition and mechanical breakage. It is speculated that the absence of shredders in the stream is linked to the absence of a functional leaf processing continuum in the stream due to the dominance of sycamore leaf input.