Data collection
In early August each year, percent cover of all vascular plants, bare mineral soil, bryophytes and litter were estimated in the central 0.7 m x 0.7 m area of each plot by the same observer (JC). 106 plant taxa were recorded across all plots and years. We measured light availability and volumetric soil moisture content (surface and subsurface) four times throughout each growing season. We collected and mixed four soil cores (10 cm deep) from each plot in June and July each year, extracted the samples with 0.01 M KCl and measured extractable soil nitrate, the key limiting resource at Cedar Creek (Tilman 1990). Appendix S1 includes further details.