Effects of N addition on ecological stoichiometric characteristics in six dominant plant species of alpine meadow on the Qinghai-Xizang Plateau,China

Aims Our purpose was to characterize the effects of nitrogen (N) addition on plant carbon (C), N, phosphorus (P), and C:N:P ecological stoichiometric characteristics in six dominant plant species, including Kobresia myosuroides, Elymus nutans, Anemone rivularis, Pedicularis kansuensis, Potentilla fragarioides and Oxytropis ochrocephala, of alpine meadow on the Qinghai-Xizang Plateau, China.
Methods N was added at four levels. Concentrations of C, N and P were measured, and C:N:P was estimated in the six plant species following the N addition treatments.
Important findings Significant differences in leaf N and P concentrations existed among the six species under natural conditions. The N and P concentrations were highest in O. ochrocephala, at 24.5 and 2.51 g·kg^-1, respectively. The leaf N concentration was significantly lower and leaf P concentration was significantly higher in O. ochrocephala than in legume plants of other grasslands in China. Leaf N and P concentrations in the other five species were in the ranges of 11.5-18.1 and 1.49-1.72 g·kg ^-1, respectively. Kokresia myosuroides had the lowest N concentrations and E. nutans had the lowest P concentrations; they were significantly lower than the non-legume plants in other grasslands in China (p < 0.001). P and C concentrations did not respond to N addition in all the six plant species, but N concentration significantly increased with N addition in five species other than O. ochrocephala, which did not respond to N addition. Values of the N:P varied in the range of 7.3-11.2 in treatment without N addition, indicating that the plant growth was limited by N in the alpine meadow. Values of the N:P increased and were greater than 16 with N addition in five species other than O. ochrocephala, indicating that N addition induced P deficiency in these five species. Our results point to very low leaf N concentration and limitation of N on plant growth in alpine meadow on the Qinghai-Xizang Plateau, China, but different species had different responses to N addition. The legume plant O. ochrocephala was not susceptible to N addition, but leaf N concentration in other five plant species was increased by N addition. Findings in this study highlight the importance for fertilization and management of alpine meadow.