Potential impacts of fire on riparian plant communities and stream food webs in a wilderness setting

Despite the increasing recognition of riparian zones as important ecotonal areas linking terrestrial and aquatic ecosystems and of fire as a critical natural disturbance, much remains unknown regarding the influence of fire on riparian and aquatic ecosystems.  Our research focuses on characterizing and quantifying the effects of mixed severity wildfire on riparian plant communities and allochthonous inputs into headwater streams in the Frank Church River of No Return Wilderness, ID.  Five years after a large stand-replacing fire in the Lower Big Creek Basin, we conducted riparian vegetation surveys and collected allochthonous materials in 16 tributaries across a range of burn types.  Many riparian plant species are highly adapted to disturbance, and we expected these adaptations might lead to a quick recovery following wildfire.  We found that although total plant cover decreased at severely-burned reaches, many shrubs, herbs, and grasses recovered quickly, leading to an overall change in community composition and structure. While we expected total leaf input into the stream to be reduced at severely-burned reaches, deciduous inputs were greater than at unburned or low-severity burned reaches. Our results may indicate an increase in riparian-aquatic food web connectivity following severe wildfire that may affect many aquatic and semi-aquatic organisms including macroinvertebrates, amphibians, and fish.