1. Changes in Phosphorus Fractions During Primary Succession in Lake Michigan Sand Dunes, USA Scott Bridgham 1 and E. Ryan Murray, Univ. of Notre Dame, IN USA R. G. (Jerry) Qualls and Julia Lilienfen Univ. of Nevada, Reno, NV USA 1 As of Jan. 1, Univ. of Oregon

2. P i apatite P i occluded P i non-occluded PoPo P total Time g P / unit area profile From Walker and Syers 1976

3. Modified Hedley Sequential P Fractions 0.5 g sample Anion-Exchange Membrane (P i ) 0.5 M NaHCO 3 (P i + P o ) Chloroform + 0.5 M NaHCO 3 (P t ) 0.1 M NaOH (P i + P o ) 1 M HCl (P i ) Conc. HCl (P i + P o ) Digest in conc. H 2 SO 4 and 30% H 2 O 2 (P t ) 0.5 g sample Anion-Exchange Membrane (P i ) Set ASet BFraction P i = Readily available P o = labile organic Microbial P P i = Non-occluded + occluded Fe-Al phosphates and sesquioxides P o = stable organic Sonicate + 0.1 M NaOH (P i + P o ) Stable Ca-bound P i Highly recalcitrant P i + P o Residual P

6. ~ 50-year old site

7. ~50- year old site. No A-horizon, little soil development.

8. 400-year old site. ~10-cm A horizon, Stained ‘B’ horizon

9. 900-year old site. ~10-cm A horizon, Stained ‘B’ horizon

10. 8,000-year old site. ~10-cm A horizon, Stained ‘B’ horizon

11. 12,000-year old site. ~10-cm A horizon, Stained ‘B’ horizon

19. Conclusions As opposed to classic ecosystem successional theory, total P increases over time in Lake Michigan sand dunes due to very low initial concentrations. Changes in individual P fractions as a percentage of the total P more closely follow classical theory.

20. % total P i decreases with age and increases with depth. The opposite trends occur for % total P o. % readily available P i increases with age. % Fe and Al-associated P i increase with age. Ca-associated P i decreases with age.

21. Both recalcitrant and available P o fractions increase with time, with the majority of P o in recalcitrant fractions. While this study and others have demonstrated the general applicability of classical successional theory for soil P retention, differences in initial soil substrata can lead to important differences in the trajectories of both total P and the individual P fractions.