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ABSTRACT
The pattern of leaf pack decomposition and density and biomass of the associated invertebrate detritivore community of an intermittent and a perennially flowing headwater stream were compared in autumn and spring. Leaf packs of high (Alnus rugosa) and low (Fraxinus americana) nitrogen content were used.
Leaf litter was processed at similar rates in both streams during autumn (−k: 0.015 g d−1). In spring the decomposition rates more than doubled in the permanent stream (−k>0.03) and only slightly increased in the intermittent stream (e.g. Fraxinus: −k: 0.017). Differences in decomposition rates between leaf species were seen only in the fall in the intermittent stream where Fraxinus litter decomposed slower than Alnus. Shredder biomass was greater than other invertebrate guilds in both streams, was reduced in the intermittent stream, and varied with season (spring > fall), particularly in the permanent stream. Shredder biomass was greater in Alnus leaf packs. Shredder densities were significantly lower in the intermittent stream, during both seasons, compared with the permanent stream. Greater densities of shredders occurred on Alnus leaf packs. Collectors outnumbered other guilds.
The intermittent stream had a depauparate shredder fauna and was numerically dominated by collectors. Lack of shredding detritivores, combined with decreased duration of submersion, resulted in reduced potential for processing of particulate carbon relative to the permanently flowing stream.
