Stoichiometric characteristics of carbon, nitrogen, and phosphorus in Sophora moorcroftiana shrubs in the middle reaches of the Yarlung Zangbo River, Xizang, China

The stoichiometry of plant organs reveals their nutrient partitioning strategies and ecological adaptability. Sophora moorcroftiana plays an important role in soil and water conservation in the middle reaches of the Yarlung Zangbo River; however, few studies have analyzed its stoichiometric characteristics, which limits our understanding of its ecological adaptability and response mechanisms to climate change. In this study, we collected leaf, branch, and root samples from S. moorcroftiana at 18 sampling sites in the middle reaches of the Yarlung Zangbo River and analyzed carbon (C), nitrogen (N), and phosphorus (P) concentrations and their stoichiometric ratios. The results showed that C ꞉ N ꞉ P stoichiometry was significantly different among the different organs, and the distribution of C and N concentrations were as follows: branch > root > leaf, and leaf > root > branch, respectively; P concentration was the highest in the leaves and not significantly different in the branches and roots. A highly significant correlation was observed between the nutrient concentrations, especially N and P, in the leaves and branches; however, the root concentrations did not correlate strongly with either leaf or branch concentrations. The N vs. P scaling exponent was 0.67 in the branches and 0.65 in the leaves, but not significant in the roots. The C ꞉ N ꞉ P stoichiometry in different organs of S. moorcroftiana was consistent with the hypothesis of stability of leaf nutrient content and growth rate hypothesis to some extent; the nutrient content in the leaves was relatively stable, with high N and P contents. The results of this study enrich our understanding of the nutrient partitioning strategies and adaptation mechanisms of S. moorcroftiana to the environment and provide guidance for shrub restoration and management.