A unified meta?ecosystem dynamics model: Integrating herbivore?plant subwebs with the intermittent upwelling hypothesis

Determining the relative influence of biotic and abiotic processes in structuring communities at local to large spatial scales is best understood using a biogeographic comparative-experimental approach. Using this approach, previous work suggests that intertidal community dynamics (top-down bottom-up effects) vary unimodally along an upwelling-based productivity gradient, termed Intermittent Upwelling Hypothesis (IUH). Evidence consistent with IUH comes from sessile invertebrate/predator (SIP) subweb certain rocky communities, but whether pattern extends macrophyte/herbivore (MH) subwebs unknown. Here we ask: Are MH also structured as predicted by IUH? What importance herbivory predation these communities? Under what conditions do ecological subsidies like nutrients or propagule production drive dynamics? And are omnivorous interactions important? We hypothesize driven new construct, Grazing-Weakening (GWH), which states weaken monotonically increasing nutrients, strong (weak) low (high) macrophyte nutrients. explored local-to-large scale both factorial field experiment testing joint separate effects herbivores predators between two continents. Experiments 10 sites ranging persistent upwelling downwelling regimes ran for 26–29 months Oregon California, New Zealand (NZ) South Island. For subweb, results were GWH: declined macrophytes increased As expected, SIP IUH: predator effect size was related upwelling. Overall, explained more variation structure than did predation, especially NZ. Omnivory weak, invertebrates outcompeted macrophytes, ocean-driven provided basic template driving ecosystem dynamics. propose unified meta-ecosystem model combining results: upwelling, underlying (as IUH), while decreases generally increase. While based on research temperate ecosystems varying regime, its wider applicability remains be tested.