Multiple global change factors alter the scaling of nitrogen to phosphorus in alpine plants

The stoichiometry and allometry of nitrogen (N) and phosphorus (P) reflect plant nutrient absorption and dynamic allocation. They can be regulated by global change factors (e.g., climate warming, nitrogen enrichment, and altered precipitation). Yet, how multiple global change factors act interactively to influence the stoichiometric characteristics of N and P and their scaling relationships in different plant organs remains poorly understood. In a field experiment with treatments of nitrogen addition (Nadd), warming (W), and reduced precipitation (Pr) in an alpine meadow, we examined how global change factors interact to alter N and P stoichiometric characteristics of leaves and seeds. An allometry model (i.e., N = βPα) was employed to detect changes in the scaling of plant N to P under different treatments. Our results showed that nitrogen addition significantly increased leaf N concentration (+44.0 %), seed N concentration (+16.9 %) and leaf N : P ratios (+27.8 %) under ambient temperatures and significantly increased leaf N concentration (+53.7 %) and leaf N : P ratios (+46.4 %) under ambient precipitation. Importantly, nitrogen addition and warming/reduced precipitation had synergistic effects on P concentration of leaves and seeds, and antagonistic effects on N : P ratios of leaves. Moreover, although none of the three global change factors individually altered the scaling of N to P, nitrogen addition interacted with warming or with reduced precipitation to decrease the scaling exponents in leaves and increased them in seeds. Our results suggest that multiple global change factors can alter the N and P allocation patterns and result in a decoupling of N and P in different plant organs. These findings highlight the importance of considering interactions of multiple factors when predicting dynamic changes in plant stoichiometric characteristics and nutrient utilization strategies under global change scenarios.