Leaf litter in a Sonoran Desert stream ecosystem

Leaf litter is an important functional component of mesic stream ecosystems; however, the importance of leaf litter has not been established for streams of the southwestern North American deserts. These streams exhibit many functional and structural characteristics that are the result of the pattern and amount of precipitation and whim differ from their mesic counterparts. Our objective was to determine the influence of leaf litter on ecosystem processes of Sycamore Creek, Arizona, a typical Sonoran Desert stream, and to compare these results with knowledge gained from other regions. Patterns of nitrogen dynamics and respiration during leaf decomposition were similar for leaf packs in Sycamore Creek and previous studies of mesic streams. Macroinvertebrates in Sycamore Creek colonized natural and artificial leaf packs equally, and taxonomic composition did not differ significantly between leaf types, or between leaf pack communities and benthic communities. Shredder macroinvertebrates feeding on leaf material were absent. Leaf litter input to Sycamore Creek was low and litter residence time was reduced by flash floods. As a result, leaves played an insignificant role in terms of nutrient dynamics, energy flow, and macroinvertebrate assemblages in this ecosystem. Differences in the role of leaf litter between regions are attributed to channel and riparian form and to the frequency of severe disturbance, which are functions of meteorologic, hydrologic, and geomorphic features of the landscape.