Model systems, element inputs, and nutrient limitation

Abstract

A good model system for understanding biogeochemistry and ecosystem function is one in which all or most of the processes found in the world’s ecosystems occur in a relatively simple way that makes them readily understandable. As I discuss in this paper, the Hawaiian Islands provide a useful model system for the study of biogeochemical processes and ecosystem function. In that system, estimation of element input pathways across the age sequence, using isotopic, elemental and mineral tracers, leads to the simple conclusion that older, highly-weathered substrates in the Hawaiian Islands support ecosystems in which primary production is limited by phosphorus supply, rather than by more mobile cations, because adequate cations (and not phosphorus) are received from marine aerosol deposition. The oldest site receives a majority of its phosphorus in dust inputs from central Asia. Insights from the Hawaiian model system are used to consider possible nutrient limitations to primary production in the Amazon Basin, where experimental and analytical studies are more challenging and less complete.