Provenance differences in functional traits and N: P stoichiometry of the leaves and roots of Pinus tabulaeformis seedlings under N addition

Abstract

To study the response of Pinus tabulaeformis Carrière, an endemic species in China, to N deposition and the adaptive mechanisms involved, the leaves and fine roots functional traits and N:P stoichiometry of Beijing provenances seeding (BY), Shanxi provenances seeding (SY), and Inner Mongolia provenances seeding (NY) were investigated in the this study. Five levels of artificial N addition were applied to seedlings of different provenance for 3 years. Our results showed that, at high-N levels, the specific leaf area of SY plants decreased significantly, while leaf weight ratio increased, which indicated that SY plants have higher light and nutrient absorption capacity under high-N deposition. Leaf total N, leaf N:P ratio, root total N, and root N:P ratio of BY plants increased at medium-N levels, indicating that properly N addition promoted the accumulation of N in BY plants, while N absorption in SY and NY plants was inhibited. Furthermore, N addition promoted the accumulation of P in SY leaves and fine roots. From the adaptation mechanism of P. tabulaeformis, N addition promoted the utilization of nutrients in BY fine roots, which was conducive to the growth of underground parts and the accumulation of biomass. These results also showed that BY plants had adapted to low-N environments. At the same time, P investment in SY leaves and fine roots increased in high-N environments to meet the demands of growth, which also demonstrated adaptation to high-N environments. Owing to the differences in the adaptation mechanism of plants to the environment, the adaptation strategies of P. tabulaeformis of different provenances was significantly different under different nitrogen depositions. This study further provides theoretical foundation for plantation management and vegetation restoration.