DOI: 10.32912/papahou.60.179125

Authors: Wendy Nelson, Kate Neill, Roberta D'Archino

Abstract: No abstract

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DOI: 10.32912/papahou.60.176367

Authors: Kendall Morman, Jacqueline Beggs, Peter Bellingham, Gavin Lear

Abstract: This report characterises the soil chemistry beneath kahika trees (Metrosideros kermadecensis) on two remote, subtropical oceanic islands in the South Pacific, Rangitāhua, which currently has a lower abundance of seabirds but supported dense populations until the 20th century, and North Meyer Island, which supports a dense seabird population. Soil was collected from five locations on both islands in November 2023. Soil Chemistry testing was conducted by Maanaki Whenua Environmental Laboratory, and, for Rangitāhua samples, further testing was carried out by Hills Laboratory. Key results: ∙ Soil pH was 6.16 ± 0.22 (mean ± SE) on Rangitāhua and 4.12 ± 0.25 on North Meyer Island. ∙ Soil organic carbon was 10.36% ± 1.09 on Rangitāhua and 11.39% ± 3.51 on North Meyer Island. ∙ Total soil nitrogen was 0.58% ± 0.039 on Rangitāhua and 0.77% ± 0.226 on North Meyer Island. ∙ Soil C:N ratios were 17.74 ± 0.93 on Rangitāhua and 14.16 ± 0.72 on North Meyer Island. ∙ Total phosphorus was 856.8 mg/kg ± 81.53 on Rangitāhua and 3462.8 mg/kg ± 908.74 on North Meyer Is. Soil nutrient concentrations offer critical insights into soil fertility, forest health and the functioning of soil microbial communities. The differences observed between the two islands may reflect variations in seabird abundance and disturbance history (including invasive mammals) and can inform future ecosystem management and conservation strategies. These results suggest that seabird presence is linked with lower pH and elevated phosphorus on North Meyer. Meanwhile, carbon and nitrogen values remain within a comparable range across both islands.

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