Carbon‐13 and nitrogen‐15 enrichment in coastal forest foliage from nutrient‐poor and seabird‐enriched sites in southern New Zealand

Abstract

To assess the effect of nutrient inputs from breeding seabirds on forest foliage δ¹³C and δ¹⁵N, we collected foliage samples from two contrasting locations. Olearia lyallii forest on North East Island at The Snares hosts large numbers of (in particular) breeding sooty shearwaters (Puffinus griseus). At Mason Bay (Rakiura/Stewart Island), samples of Brachyglottis rotundifolia, Griselinia littoralis, and Dracophyllum longifolium were collected from two strata within diverse dune forest and one stratum from the open dunes. The δ¹³C results were typical of C₃ plants and did not differ significantly between Mason Bay and North East Island. In contrast, the δ¹⁵N results from Mason Bay (mean ± standard deviation, ‐6.1 ± 1.7‰) were significantly lower than expected for temperate forest (95% confidence interval of difference, 2.7–3.9‰), and dramatically lower (19.1–21.5‰) than North East Island where enrichments (+14.2 ±3.1 ‰) were among the highest ever reported for vegetation.

Keywords:

• Brachyglottis
• Dracophyllum
• Griselinia
• Olearia
• Snares
• sooty shearwater
• Stewart Island