PARENT SESSION
Oral Session #68: Nutrient Cycling. Presiding: D. Johnson.
Thursday, August 9, 2001. 1:00 PM to 5:00 PM. Hall of Ideas G.
Element inputs and outputs across a substrate age gradient in the Hawaiian Islands.
Vitousek, Peter1, Chadwick, Oliver2, Crews, Tim 3, Heath, Jackie4, Hedin, Lars5, Kurtz, Andy6, Matson, Pamela1, 1 2 3 4 5 6
ABSTRACT- We determined inputs and outputs of major elements in Hawaiian forest ecosystems on a 4 million year substrate age gradient. The pathways of input measured were rock and soil weathering, atmospheric deposition (including cloudwater), Asian dust, and N fixation; pathways of output were leaching and trace gas emissions. In young sites the dominant inputs were rock weathering for Ca, Mg, and P, and volcanic sources for S and N. In older sites, overall inputs were less and cloudwater became the dominant source of most elements - except for P, for which the most important source was long distance transport of Asian dust. Losses of most elements were high in young sites, and then declined. An exception to this pattern was N, for which losses were low (<2 kg/ha/yr) in young sites where plant and soil pools of N were accumulating, and greater (4-10 kg/ha/yr) in older sites. For most biologically essential elements, fluxes are greatest at the time in ecosystem development when a plant-soil system is becoming established.
KEY WORDS: element budgets, hawaiian islands, nitrogen, phosphorus