Response of functional traits in Machilus pauhoi to nitrogen addition is influenced by differences of provenances

Abstract

Comprehensive studies on the response of whole plant functional traits to nitrogen deposition can provide insight into the resource acquisition strategies of plants. However, current studies on nitrogen deposition have mainly focused on leaves or roots.We conducted nitrogen deposition simulation experiments with Machilus pauhoi (Lauraceae) from five provenances in a common garden experiment in the southeast of China. We measured 29 traits (biomass, phenology traits, and nutrient concentrations) of leaves, stems, and roots in response to nitrogen addition and selected 26 distinct important functional traits related to resource acquisition strategies of the whole M. pauhoi seedlings.We found that N (Nitrogen) addition significantly increased the biomass of M. pauhoi seedlings and altered biomass allocation among organs. The response of the leaf, stem and root traits to nitrogen addition was not always consistent among the different provenances of M. pauhoi seedlings. A uniform variation pattern of the three organs was found in the C (Carbon) and P (Phosphorus) concentrations, as well as N:P ratio. In contrast, N concentration, the C:N ratio and the phenotypic trait specific leaf area (SLA) and specific root area (SRL) did not respond in the same direction at the organ level.We concluded that nitrogen addition alters the biomass allocation pattern of M. pauhoi and the resource acquisition capacity of above- and below-ground organs. N concentrations and C:N ratio may play a key role in this regulatory process. Overall, N addition increased leaf mass fraction (LMF) and SRL, and instead decreased SLA and root mass fraction (RMF) of M. pauhoi. There are also differences in biomass allocation and resource acquisition patterns between the different provenances. AF and SC seedlings can be preferred provenances for M. pauhoi due to their balanced resource acquisition strategy and high phenotypic plasticity, respectively.Our study may contribute to a more comprehensive understanding of how N deposition affects the plant as a whole and provide a theoretical basis for precise nutrient management of M. pauhoi seedlings and their plantations in the context of nitrogen deposition.