Measuring ecosystem nitrogen status: a comparison of proxies

4� 6� 7� Abstract. There are many proxies used to measure nitrogen (N) availability in watersheds, but 8� the degree to which they do (or do not correlate) within a watershed has not been systematically 9� addressed. We surveyed the literature for intact forest or grassland watersheds in which several 10� metrics of nitrogen availability have been measured. Our metrics included: foliar δ 15 N, soil δ 15 N, 11� net nitrification, net N mineralization, and the ratio of dissolved inorganic to organic nitrogen 12� (DIN:DON) in soil solution and streams. Not surprisingly, the strongest correlation (Kendall's 13� tau) was between net nitrification and N mineralization (τ=0.61, p 0.05). To our surprise, the only significant 17� correlation we found between terrestrial- and water-based metrics was that of net N