Nutrient spiraling from hillslopes to rivers and oceans

            The Nutrient Spiraling Concept (NSC) provides a conceptual framework for analyzing the cycling of elements as they flow through ecosystems. Several examples show how the concept may be applied to ecosystems far beyond the stream channels for which the concept was developed.  (1) Hillslope nutrient spirals consist of the cycling of nutrients between plants/microbes and downslope soil-water seepage. Surprising conclusions about 100+ yr climatic legacies and terrestrial controls of inputs to streams arise from hillslope spiraling simulations. (2) In-stream nutrient spiraling studies have focused primarily on channels but the incorporation of transient storage and floodplain processes challenges our traditional concepts of retention. (3) DOC transport in arctic rivers is high during spring runoff but processing is slow at near freezing temperatures. This material is processed in the surface layers of the Arctic Ocean where it has a 10-year mean lifetime as illustrated by ocean circulation models.  The distances from DOC inputs to streams to mineralization at sea are thousands of kilometers. (4) Another large spiral with a 1000 yr time scale involves the global ocean conveyor current where particulate nutrients sink, are remineralized at depth and subsequently upwelled.  The enduring legacy of the NSC promises expanding applications in the future.    

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