We propose to identify the physical and biological mechanisms responsible for restoration of damaged streams. Specifially, we will determine whether an increase in the diversity of physical habitat types on a streambed promotes restoration of a stream ecosystem following a perturbation. Further, we will assess how flooding interacts with habitat diversity to impede or promote ecosystem recovery following damage. We will physically partition multiple sections of a stream into paired halves (one control and one restoration treatment), disturb treatment halves, and then alter the size and complexity of the streambed substrate in the treatments halves. We will measure physical and biological responses to the disturbance and to the restoration treatments, and determine when and how the disturbed sections "recover." Recovery will be estimated as the similarity between biological diversity and ecosystem function in control and treatment sections of the stream. This experiment mimics restoration methods currently used by state and national environmental management groups. These methods have never been evaluated scientifically to determine if (and why) they enhance restoration of damaged stream ecosystems. Our experiment will also test a central ecological question of broad relevance to environmental science: does increasing physical habitat diversity enhance species diversity and ecosystem function? ??
