Alterations to ecosystem nitrogen ( N) cycling by introduced plant species may increase the invasibility of habitat providing a positive feedback for the introduced species to become invasive. Spatial patterns of foliar and soil δ15 N ratios reflect variation in rates and process of N-cycling across invaded landscapes and provide insight into N-source uptake and utilization strategies of invasive plant species. To evaluate invasion-associated changes in soil and foliar δ15 N at different scales: regional (among different sites), local (between north- and south-facing aspect at the same site), and microsite (within populations in the same community), we measured foliar and soil δ15 N, animal faeces cover (as a proxy for grazing intensity) and N2-fixing species cover from inside to outside T hymus vulgaris L. (thyme)-invaded lightly grazed pastoral communities in Central Otago, southern South Island, New Zealand. Mean thyme foliar δ15 N were near-zero across the invaded landscape, and did not change across the advancing edge of invasion or with aspect. There was no evidence that associations with N2-fixing species provide a potential N source. Soil δ15 N was lower inside of thyme compared to at the edge or outside of thyme and was varied between aspects at some sites. Animal faeces cover as a proxy for grazing intensity explained only 23% of this observed variation of soil δ15 N. Thyme invasion may result in lowered soil δ15 N reflecting alterations to N dynamics. Associated invasion-related impacts of animal grazing may also impact soil δ15 N. Further studies are required to distinguish the underlying mechanism responsible for the observed patterns of foliar and soil δ15 N values across thyme-invaded Central Otago landscapes. [ABSTRACT FROM AUTHOR]