PLANT DELTA-N-15 VALUES ALONG A FOG GRADIENT IN THE ATACAMA DESERT, CHILE

The Atacama Desert is characterized by a fog zone occurring between 50 0 and 800 m elevation. We hypothesized that atmospheric deposition fro m marine sources was the primary source of nitrogen for plants in the fog zone, and so the delta N-15 of plants should differ between those above and below that zone. No significant differences in leaf delta N- 15 values were detected among the three locations. The delta N-15 valu es for non-nitrogen fixing species (6-12 parts per thousand) were subs tantially more positive than that of atmospheric deposition (-1 parts per thousand) suggesting immediate assimilation of nitrogen from fog w as not an important source of plant nitrogen.