No evidence of resource limitation to aboveground growth of blue grama (<Emphasis Type="Italic">Bouteloua gracilis</Emphasis>) on 1 ky-old semi-arid substrate

Biogeochemical theory and a substantial body of empirical data show that nitrogen (N), an atmospherically derived nutrient, limits plant growth on young substrates, while phosphorus (P), a rock-derived nutrient, limits plant growth on old substrates. In arid regions, water is also often a limiting resource to plant growth. We applied resource amendments of N, P, N + P, and water to blue grama (Bouteloua gracilis) growing on a 1 ky-old basaltic cinder substrate to test the hypothesis that N and water limit aboveground net primary production (ANPP) in a semi-arid climate, early in soil development. Contrary to our hypothesis, ANPP did not differ among treatments, suggesting that none of the resource amendments were limiting to blue grama growth. Unamended aboveground tissue N and P concentrations were three to five times lower at the 1 ky-old site than on older (55–3000 ky-old) substrates, suggesting differences in nutrient use efficiency across the substrate age gradient.