Effects of travertine on leaf retention in Fossil Creek, Arizona, before and after stream restoration

Leaf retention is important in transferring energy from riparian trees to stream food webs. Retention increases with geomorphic complexity such as substrate coarseness, sinuosity and the presence of debris dams. High discharge can reduce retention, particularly when streams lack physical retention features. Although travertine formations can alter stream morphology, we know of no study testing the effect of travertine on leaf retention. This study capitalized on a river restoration project in Fossil Creek, Arizona, where water was returned to the river after a century of diversion. We compared leaf retention at travertine and riffle-pool sites before and after flow restoration to determine the roles of travertine and flow on leaf retention. Our results show leaf retention was higher in sites where travertine forms barriers across the river, relative to sites with riffle-pool morphology. Leaves retained in travertine reaches were largely concentrated in the bottom of pools formed between travertine dams. Though flow restoration did not alter retention rates across sites, it diminished retention in travertine sites. We conclude that in-stream complexity is enhanced by travertine deposition, that this complexity is extremely important in leaf retention, and that flow can undermine the influence of this complexity on leaf retention.