Herbaria century record of increasing eutrophication in Spanish terrestrial ecosystems

Additional biological evidence is presented for the alteration of biogeoche mical cycles by human activities. The leaf delta N-15 and the concentration s of nutrients in herbarium specimens of 24 species of vascular plants and 3 species of bryophytes collected in northern and eastern regions of Spain have substantially changed throughout the XX century. In the second half of the century, when anthropogenic nitrogen fixation and mobilization started to increase rapidly, leaf delta N-15 values started to decrease strongly, indicating that additional anthropogenic nitrogen is being retained in Span ish terrestrial ecosystems. The concentration of nutrients in vascular plan ts did not present any clear pattern, but there were increasing concentrati ons of N and other nutrients (P, K, and S) in the last decades in bryophyte s, which are usually better biomonitors of airborne chemicals than vascular plants. Important consequences for ecosystem structure and functioning suc h as enhancement of the carbon sink or changes in community biodiversity an d species distribution may be expected from this increase in eutrophication .