Nitrogen (N) and phosphorus (P) fertilizers have recently been used to enhance the productivity of grasslands and forage quality for alpine meadows on the Tibetan Plateau. However, few have examined the impact of N and P fertilization on the stoichiometry of plant species in these cold, high-altitude environments. Characterization of plant nutrient stoichiometry responses to N and P inputs in these grasslands can not only fill a gap of global nutrient data sets, but also contribute to understanding of plant adaptation to a changing environment.
We conducted a multi-year field experiment to assess the impact of N or P inputs on plant nutrient stoichiometry in an alpine meadow on eastern Tibetan Plateau, through manipulating the inputs of N (0, 5 or 15 g N m-2 yr−1) and P (0, 2 or 8 g P m-2 yr−1). Two questions guided this research: How do N and P inputs affect the stoichiometry of common plant species? Whether do high N or P inputs shift nutrient limitation of common plant species and alter the scaling relationships between C, N and P？
Results/Conclusions
N additions increased aboveground plant N concentrations and N:P ratios at the high N level and reduced C:N ratios across all fourteen common species. Similarly, P addition increased aboveground plant P concentrations and reduced C:P ratios and N:P ratios. Consequently, the N:P ratio of the alpine meadow community increased with N fertilization and decreased with P fertilization. N additions resulted in P limitation, leading to the disappearance of the scaling relationship of C vs. N. P limitation led to a decoupling of C and P in aboveground plant biomass. When P limitation was eased by P addition, however, the scaling relationships of C vs. N and C vs. P in aboveground plant biomass re-emerged. Together, these results indicated that changes in soil N and P availability alter plant nutrient concentrations and stoichiometry over a short time and can alter the scaling relationships among plant C, N and P. These findings advance our understanding of the bio-geographic patterns of plant aboveground nutrient traits in response to N and P inputs in cold and dry environments and may help design fertilization practices for sustaining the productivity and quality of alpine meadow grasslands in the eastern Tibetan Plateau.