Historically, ecologists thought that though ecosystems were resilient to (or even benefitted from) mild or moderate disturbances, extreme disturbances “reset” ecosystems to some uniform, baseline state. Habitat portfolios which are heterogeneously affected by extreme disturbances may promote resilience in meta-ecosystems, however the role of community traits and interactions in mediating such responses remains unclear. In 2022, rain-on-snow events triggered an extreme flood in Yellowstone National Park. Pre-flood, we investigated stream-riparian ecosystems in Yellowstone and observed that terrestrial wildlife dynamics had contributed to a mosaic of ecosystem states by altering riparian plant communities. Each ecosystem hosted unique organism, community, and foodweb traits. Here, we evaluated whether such spatial complexity in community structure shaped the resistance, resilience, and trajectories of change for stream-riparian ecosystem function (i.e., production dynamics and organic matter flows) post-flood.
Pre- and post-flood, we intensively sampled eight headwater streams to characterize their multi-trophic level productivity, organic matter flow food webs, and diversity. We also characterized the reciprocal fluxes of aquatic and terrestrial invertebrates and responses by birds, bats, spiders, and small mammals. Further, we evaluated how these characteristics changed for each site individually as well as the meta-community and ecosystem.
Rather than a homogenous “reset” of ecosystems following the extreme flood, both the sign (i.e., positive/negative) and magnitude of change in productivity, organic matter flow, and diversity varied across the mosaic of sites. Such heterogeneity was associated with varying community traits and interactions, including riparian plants (e.g., woody vs. herbaceous-dominated), benthic invertebrates (e.g., flood/predation vulnerability), fish (e.g., life history and foraging), and spiders (e.g., web-orientation). These findings suggest that the character of the meta-community and ecosystem was maintained due to trait-mediated responses to the extreme flood. Thus, we provide empirical evidence that managing for complex and biodiverse ecosystems in the present can support ecosystem resiliency to future extreme events.