Soil solution chemistry at a Westland-petrel breeding colony, New Zealand - Paleoecological implications

Abstract

Surface soil samples from two sites in a breeding colony of Westland Petrels were compared with those from a control with no seabird breeding. Soil solution (-0.025 µm) analyses established significant differences in Al, P and natural organic matter (NOM) chemistry. At the breeding colony sites, low concentrations of total Al in soil solution, combined with high extractable phosphate, indicated formation of insoluble humic-Al-(Fe)-P complexes. NOM in soil solution was estimated from absorbances at 250 nn. NOM was at lower concentrations at the breeding colony and had a lower percentage of Al bound in non-labile complexes (38-86% compared with >97%). Gel filtration experiments showed that soil solution from the breeding area had an NOM size distribution weighted toward smaller size fractions. This is consistent with NOM having different properties at the two sites and could contribute to different processes in pedogenesis. The results reported in this paper support a hypothesis that localized extinction of breeding seabirds following Polynesian settlement has affected soil chemistry in the well leached soils on the West Coast of New Zealand's South Island.