Effects of increased precipitation on C, N and P stoichiometry at different growth stages of a cold desert annual

Plant C, N and P can reflect plant strategies of nutrient utilization and allocation. Precipitation is a key factor affecting plant nutrient uptake and utilization strategies especially in arid and semiarid regions, and it is predicted to increase in the cold deserts of Northwest China due to climate change. However, the balance of C, N and P stoichiometry in annual plants at different growth stages in response to increased precipitation is not known. Thus, we performed an experiment on the annual grass Eremopyrum distans in the Gurbantunggut Desert to determine the effect of increased precipitation on C, N and P utilization and allocation at different growth stages. In the control, organ C concentration was relatively stable during the life cycle, but leaf and root N and P concentration increased during the vegetative stage; culm N concentration decreased and P concentration increased and then decreased with plant growth. Increased precipitation significantly increased the leaf N and P concentration and decreased the C:N and C:P ratios at the vegetative growth stage, but leaf N:P was lower than 14 during the whole growth stage. Increased precipitation could improve the leaf N and P resorption efficiency to cope with the reproduction allocation, and the root nutrients are more sensitive to increased precipitation. These results indicate that increased precipitation could improve the nutrient absorption and utilization for vegetative and reproductive growth of E. distans, and the root system plays crucially important role to influence the stoichiometry under varied environment.