Terrestrial litter inputs as determinants of food quality of organic matter in a forest stream

Inputs of leaf litter and other organic matter from the catchment exceed autochthonous production and provide an important food ,resource in most streams (WEBSTER & MEYER 1997, ANDERSON & SEDElL 1979). An experimental long-term exclusion of terrestrial litter inputs to a forested headwater stream (WALLACE et al. 1997) provided an opportunity to determine if the food quality of organic matter would be altered by, the dimination of inputs of fresh litter. Secondary production of benthic invertebrates in mixed substrate habitats (cobble, pebble, and silt-sand) declined after litter was excluded from this stream (WALLACE et aI. 1997), but it is not clear whether the reduction in secondary production was a consequence of reduction in organic matter quantity, quality, or both. We have reported on a decline in quantity of some organic matter fractions after litter excluSion (W ALLACB 'et aI. 1997, MEYER et al. 1998); here we use chironomid growth assays to investigate whether quality of organic matter also changed.