# Altitude‐Related Variation in Carbon, Nitrogen, and Phosphorus Contents and Their Stoichiometry of Woody Organs in the Subtropical Mountain Forests, South China

## TL;DR

This study examines how carbon, nitrogen, and phosphorus levels in plant organs change with altitude in subtropical forests and how these changes affect plant growth and nutrient strategies.

## Contribution

The study reveals altitude-driven nutrient allocation patterns and identifies soil stoichiometry as a key factor influencing plant nutrient strategies in subtropical forests.

## Key findings

- Branches had higher C content and C:N and C:P ratios than roots and leaves.
- Leaves had higher N and P content than roots and branches, while roots had higher N:P ratios.
- Soil C:P ratio was a common factor influencing C, N, and P stoichiometry across plant organs.

## Abstract

Altitude‐induced variations in hydrothermal conditions and vegetation affect plant nutrients and induce tradeoffs in survival strategies. However, nutrient allocation to different plant organs along altitudinal gradients remains unclear. Here, 24 plots were established across eight altitudinal gradients (300, 500, 700, 900, 1100, 1200, 1300, and 1400 m) in subtropical forests on Daming Mountain, South China. We analyzed the altitudinal patterns and factors influencing carbon (C), nitrogen (N), and phosphorus (P) content and their ratios in the leaves, branches, and roots of woody plants. We found that branches had higher mean C content and C:N and C:P ratios than roots and leaves, leaves had higher N and P content than roots and branches, and roots exhibited a higher mean N:P ratio than the other organs. With increasing altitude, the leaf and branch C, C:N, and leaf C:P increased, whereas the leaf N and P, branch N and N:P, and root N:P decreased. Plant N:P ratios above 16 indicate that plant growth in the study area was mainly restricted by P. The positive correlation between N and P content across plant organs suggests synergistic absorption of these nutrients by plants. These results demonstrate that soil nutrients and stoichiometry directly influenced C, N, and P stoichiometry among different organs and that the soil C:P ratio was a common impact factor for these organs. These findings may elucidate the nutrient allocation patterns and adaptive strategies of plants in subtropical mountains and provide a foundation for forest management and restoration.

In this study, we explore the altitudinal variations in stoichiometric traits of carbon (C), nitrogen (N), and phosphorus (P) across plant organs and identify the critical environmental factors affecting these traits in a subtropical evergreen broad‐leaved forest. These findings shed light on nutrient cycling, ecological strategies, and environmental adaptation mechanisms of subtropical forest plants, providing a foundation for forest management and restoration.