Volcano fixes nitrogen into plant-available forms

Hawaiian montane ecosystems developing on recent tephra deposits contain mo re fixed nitrogen than conventional sources can explain. Heath and Huebert (1999) demonstrated that cloud water interception is the mechanism by which this extra nitrogen is deposited, but could not identify its source. We sh ow here that atmospheric dinitrogen is fixed at the surface of active lava flows, producing concentrations of NO which are higher than those found in most urban rush hour air pollution. Over a period of hours this NO is blown away from the island and oxidized to nitrate. Interruptions in the trade w ind flow can return this nitrate to the island to be deposited in cloud wat er. Thus, fixation on active lava flows is able to provide nitrogen to deve loping ecosystems on flows emplaced earlier.