Surface soil chemistry at an alpine procellariid breeding colony in New Zealand, and comparison with a lowland site

Abstract

Procellariid seabirds occupied colonies on the pre‐human New Zealand mainland from the lowlands to alpine areas, but the effect of geographic environment on soil nutrient cycling has not been investigated. To facilitate qualitative predictions of seabird breeding effects on terrestrial ecology and biogeochemistry, we compared surface soil (0–15 cm) results from a Hutton's shearwater colony at 1230 m with a Westland petrel colony in lowland forest. Soil acidity, total C, total N, total Cd, and Cdexcess (the soil Cd which cannot be accounted for by parent material weathering) concentrations were all lower at the Hutton's shearwater colony despite higher burrow occupancy and density. Lower δ15N values and higher pH imply that guano was less nitrified in the soil before being lost. At both colonies, parent material contributed a large portion of total P and total Cd. Correlations between total N, Pexcessand Cdexcess with total C suggested that guano nutrient retention is driven by soil organic matter. We conclude that seabird colony location affected the cycling of seabird‐derived nutrients in pre‐human New Zealand.