Precipitation and topsoil samples from a climate transect over the Scandinavian Mountains, Norway, were analyzed for bulk and compound-specific δ¹⁸O values. The natural abundance of ¹⁸O in the plant-derived hemicellulose biomarkers arabinose and xylose correlates positively with δ¹⁸O of bulk soil, but not with δ¹⁸O of precipitation. This suggests that other factors than δ¹⁸O_prec, such as evaporative ¹⁸O enrichment of leaf water, exert a strong influence on the natural abundance of ¹⁸O in soils.