HR: 14:15h
AN: B43B-04    [Abstracts]
TI: Channel Pattern and the Intermediate Disturbance Hypothesis Predict Biodiversity in River-floodplain Ecosystems
AU: * Beechie, T
EM: tim.beechie@noaa.gov
AF: NOAA Fisheries, NW Fisheries Science Center 2725 Montlake Blvd E, Seattle, WA 98112 United States
AU: Pollock, M
EM: michael.pollock@noaa.gov
AF: NOAA Fisheries, NW Fisheries Science Center 2725 Montlake Blvd E, Seattle, WA 98112 United States
AU: Baker, S
EM: sarah.baker@noaa.gov
AF: NOAA Fisheries, NW Fisheries Science Center 2725 Montlake Blvd E, Seattle, WA 98112 United States
AU: Morley, S
EM: sarah.morley@noaa.gov
AF: NOAA Fisheries, NW Fisheries Science Center 2725 Montlake Blvd E, Seattle, WA 98112 United States
AB: River-floodplain ecosystems are among the most diverse and dynamic environments in the world, yet mechanisms that regulate biodiversity in river corridors are poorly understood. In part, this stems from a lack of integration of geomorphological and biological concepts that link fluvial processes to biological diversity. Here we illustrate how channel pattern predicts biodiversity via the intermediate disturbance hypothesis (IDH). We show that (1) channel pattern predicts disturbance frequency and age diversity of patches, (2) there are distinct life history tradeoffs among colonizing and climax species, and (3) diversity should be highest in channel patterns with intermediate levels of disturbance. We first classify river-floodplains in northwestern USA using geomorphological channel patterns, and show how these patterns predict patch dynamics in river-floodplain systems. We then use space-for-time substitution to illustrate successional patterns of trees and aquatic invertebrates. Finally, we link reach-level patch dynamics to reach-level biodiversity of trees and aquatic invertebrates using the IDH. Patch age diversity is low in straight channels with low movement rates and mostly old surfaces, and low in braided channels with high movement rates and mostly young surfaces. Patch age diversity is highest in channels with intermediate movement rates (meandering and island-braided channels). Vegetation succession drives temporal patterns of biological diversity within individual terrestrial and aquatic patches (alpha diversity). Trees exhibit clear successional trade-offs as patches age, succeeding from hardwood-dominated at the colonizing stage to conifer-dominated at the climax stage. Highest within-patch species richness occurs at an intermediate age. Alpha diversity of aquatic invertebrates follows a similar pattern, probably in response to riparian forest succession and the shifting composition of detrital resources entering river and floodplain channels. We predict that aggregate diversity of trees and aquatic invertebrates in river-floodplain reaches (gamma diversity) follows the pattern of age diversity, with low biodiversity in straight and braided channels. Straight channels should be dominated by climax species, whereas braided channels should be dominated by colonizing species. Meandering and island-braided channels have mixed patch ages, maintaining the coexistence of climax and colonizing species and supporting high species diversity.
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1851 Plant ecology
SC: Biogeosciences [B]
MN: 2005 Joint Assembly