Changing patterns of nitrogen and phosphorus contents in leaf-branch-root of natural Pinus tabuliformis with precipitation and temperature

Objective Studying the response of nitrogen and phosphorus contents in leaf-root of Pinus tabuliformis to hydrothermal changes can enhance our understanding of the strategies for forest community plants in warm temperate regions of China to confront the challenges posed by climatic shifts.

Method Seven representative sample locations were selected in the main distribution areas of natural P. tabuliformis forests in China, and the nitrogen (N) and phosphorus (P) contents in the leaves, branches, and roots of P. tabuliformis were meticulously assessed according to the theory of ecological stoichiometry.

Result (1) Differences in nitrogen (N) and phosphorus (P) contents among various plant organs of leaves, branches, and roots were evident. Notably, concentrations of N and P in leaves surpassed those in branches and roots. Additionally, both current leaves and branches exhibited higher N and P levels compared with their perennial counterparts, while absorbed roots displayed elevated N and P contents compared with secondary roots. The N∶P ratios in current leaves and branches were lower than those in perennial leaves and in perennial branches, whereas secondary roots demonstrated a higher N∶P ratio than absorbed roots. (2) Variability in nitrogen (N) and phosphorus (P) content differed among leaves, branches, and roots, as indicated by the overall coefficient of variation ranging from 12.3% to 44.4%. Notably, the highest variability was observed in absorbed roots, contrasting with the lowest variability observed in perennial leaves. (3) The adaptive responses of nitrogen (N) and phosphorus (P) stoichiometry within distinct organs of P. tabuliformis to environmental shifts exhibited notable variations. Specifically, the N content in perennial leaves, perennial branches, and current branches, along with the P content in perennial branches and both current branches and leaves, experienced significant decreases with escalating precipitation. Conversely, a significant uptrend in P content was observed in perennial leaves, perennial branches, current leaves, and current branches as the temperature increased. Simultaneously, the N∶P ratio in perennial leaves, perennial branches, and both current leaves and branches demonstrated substantial declines with rising temperatures. Notably, the P content in secondary roots displayed a marked increase with elevated temperature, whereas the N∶P ratio in secondary roots exhibited a notable decrease.

Conclusion Both precipitation and temperature exert significant impacts on the nitrogen (N) and phosphorus (P) stoichiometry in the leaves, branches, and roots of P. tabuliformis. The diverse response trends and adaptation mechanisms of distinct organs to these two environmental factors exhibite marked variations.