Testing urban drivers of riparian woody vegetation composition in a precipitation-limited system

In precipitation-limited regions, where water availability is a key driver of vegetation patterns, altered hydrology in urban areas may have a particularly strong effect on riparian plant communities. Urban water inputs can create perennial flows in formerly intermittent streams, potentially providing a water subsidy to riparian plants during dry seasons. However, during rainy seasons, increased storm flow magnitudes in urban areas can cause stream channel incision and associated lowered water tables. Channel incision may reduce riparian soil moisture throughout the year and limit the effect of dry-season stream flow.
We asked whether channel incision and dry-season stream flow were related to the composition of riparian vegetation communities along small streams in Sacramento, California, United States, and whether these two factors interacted. Sacramento has a Mediterranean climate with a long summer dry season. We sampled the riparian woody plant community along 66 stream reache...