A Comparison of Phosphorus Forms and Concentrations in Midden Samples and Forest Soils from Calvert Island, BC, Using Sequential Fractionation and Solution P-NMR Spectroscopy.

Long-term human habitation can alter nutrients and other soil characteristics, especially in buried sites such as middens. We compared soil samples from a large shell midden (waste disposal site) from Calvert Island, BC, in the traditional territory of the Heiltsuk and Wuikinuxv First Nations, to soils from the adjacent forest. The surface of the midden was > 300 years old, while deeper layers were > 5000 years old. Refuse in the midden reflects a coastal diet of clams, mussels, salmon, herring, sea lions and seals. Samples from the midden were collected at 1.75, 2.1, 3.0, and 4.3 m depths; samples in the two forest profiles included forest floor and mineral soil to 175 cm depth, sampled by horizon.  Total phosphorus (P) ranged from 15408-23745 mg kg^-1 in the midden samples and 10-162 mg kg^-1 in the forest soils.  Total organic P was 11-27% of total P in the midden samples, increasing with depth, but was 11-81% of the forest soils, decreasing with depth. Fractionation showed P to be associated with calcium in the midden samples, and with aluminum and iron in the forest soils. And preliminary ³¹P-nuclear magnetic resonance (NMR) spectroscopy showed a greater range of P forms in forest soil samples than in the midden samples. These results suggest that buried middens can significantly alter nutrient cycling in forest soils.