Modern pollen rain on treeless subarctic islands: Evaluating vegetation–pollen signals on the Commander Islands

Treeless oceanic islands in the North Pacific preserve important postglacial records of vegetation, climate and biotic exchange, but modern pollen-rain reference data from these settings remain scarce. We analysed annual pollen rain from modified Behling traps and paired vegetation surveys on Bering and Toporkov islands, Commander Archipelago. Modern pollen spectra differentiated the main vegetation types but did not reproduce plot-scale plant cover in detail. Clustering and non-metric multidimensional scaling (NMDS), together with Mantel and Procrustes analyses, indicated a statistically detectable correspondence between vegetation and pollen structure. Regional arboreal pollen formed a persistent background signal despite the absence of trees from the islands. Highly productive wind-pollinated taxa, especially Poaceae and some meadow herbs, locally swamped finer floristic signals. A Quadrant Plot combining the coefficient of variation and Spearman's correlation identified several taxa with more interpretable local or extralocal behaviour, including Betula nana , Ericaceae, Cyperaceae, Apiaceae, Artemisia and Asteraceae. Pollen influx added information not captured by percentage data alone: percentage spectra from tundra plots with low influx were more strongly influenced by extralocal pollen, whereas high pollen influx marked productive meadow settings, including ornithogenic grasslands. These results suggest that fossil pollen spectra from the Commander Islands are best interpreted as integrative records of broad island-scale tundra-meadow mosaics, regional pollen transport and local productivity contrasts, rather than as direct reconstructions of small local plant communities.