Comparison of adaptive strategies to phosphorus-deficient soil between dominant species Artemisia frigida and Stipa krylovii in typical steppe of Nei Mongol

Aims Artemisia frigida and Stipa krylovii are two dominant species in the typical steppe of northern China, and highly adapted to the local edaphic conditions. However, little is known about their ecophysiological traits in terms of adaptation to soil nutrient regimes in general and low available phosphorus (P) in particular. To understand the ecophysiological mechanisms by which the two species adapt to low P availability in soil, root morphological traits, acid phosphatase (APase) activity secreted by roots, exudation of organic acid, P uptake rate and P utilization efficiency in the two species were measured under varying concentrations of P supply in pot experiments.
Methods Pot experiments were conducted to investigate the responses of the two species to varying concentrations of P supply by determining biomass, shoot and root morphology, average P uptake rate, P utilization efficiency, exudation of organic acid and acid phosphatase in A. frigida and S. krylovii.
Important findings Phosphorus deficiency induced root-secreted APase activity and acidification of rhizosphere in A. frigida, while S. krylovii exhibited an enhanced exudation of malate from roots under phosphorus-deficient conditions. Stipa krylovii displayed similar P uptake rate to that of A. frigida, but its P utilization efficiency was markedly higher than in A. frigida under phosphorus-deficient conditions. The two species showed similar growth patterns in response to P deficiency, but A. frigida seedlings required higher external P level for their maximal growth than those of S. krylovii, suggesting that the two species have different physiological requirement for P. The different adaptive strategies between A. frigida and S. krylovii to the low soil P availability may provide an ecophysiological explanation for their co-existence in the infertile grassland in northern China.