We have established a soil-age gradient spanning 1 to 3,000 ky in northern Arizona, USA. The climate along this chronosequence is semi-arid (MAAT = 10.8 ^oC and MAP = 280 mm), and piņon (Pinus edulis) and one-seed juniper (Juniperus monosperma) trees dominate the open woodland overstory. All soils are derived from basaltic cinders. Chronosequence studies in more humid ecosystems suggest that C and N storage increase during early stages of soil formation, but a shift from N- to P-limitation combined with increases in the crystallinity of clays lead to a decline in C and N storage late in ecosystem development. Changes in total C and N storage in the semi-arid chronosequence was consistent with this prediction. Experimental water, N, and P additions to the grass-dominated, intercanopy spaces demonstrated a combined water and N limitation to understory plant growth at the 55 ky site, no water, N, or P limitation at the 750 ky site, and a P limitation to plant growth at the 3,000 ky site. We expected that differences in C and N content between soils under tree canopies and in the intercanopy spaces would lessen with time because of changes in tree distribution on the landscape. However, we found that soil total C and N were higher under tree canopies than in the intercanopy spaces across the entire chronosequence, with the smallest differences among canopy types occurring at the 55 ky site. Both soil total δ¹⁵N and foliar δ¹⁵N of the two dominant tree species became more enriched across the chronosequence, indicating an increased rate of N loss with soil age. Our results suggest that the trajectories of C, N, and P cycling with soil development are fundamentally similar in semi-arid and humid environments despite large differences in organic matter decomposition and mineral weathering rates.