Effects of seagulls on ecosystem respiration, soil nitrogen and vegetation cover on a pristine volcanic island, Surtsey, Iceland

[摘要] When Surtsey rose from the North Atlantic Ocean south of Iceland in 1963, itbecame a unique natural laboratory on how organisms colonize volcanicislands and form ecosystems with contrasting structures and functions. InJuly, 2004, ecosystem respiration rate (R_e), soil properties and surfacecover of vascular plants were measured in 21 permanent research plotsdistributed among the juvenile communities of the island. The plots weredivided into two main groups, inside and outside a seagull (Larus spp.) colonyestablished on the island. Vegetation cover of the plots was stronglyrelated to the density of gull nests. Occurrence of nests and increasedvegetation cover also coincided with significant increases in R_e, soilcarbon, nitrogen and C:N ratio, and with significant reductions in soil pHand soil temperatures. Temperature sensitivity (Q10 value) of R_e wasdetermined as 5.3. When compared at constant temperature the R_e wasfound to be 59 times higher within the seagull colony, similar to thehighest fluxes measured in drained wetlands or agricultural fields inIceland. The amount of soil nitrogen, mainly brought onto the island by theseagulls, was the critical factor that most influenced ecosystem fluxes andvegetation development on Surtsey. The present study shows how ecosystemactivity can be enhanced by colonization of animals that transfer resourcesfrom a nearby ecosystem.

[学科分类] 地球化学与岩石