Stoichiometric homeostasis reflects a plant’s ability to maintain a stable internal nutrient composition despite variations in environmental nutrient availability. The homeostatic coefficient ( H ), derived from the homeostatic equation y = c·x¹⁄ᴴ , serves as a key measure of this stability. Previous research has mainly focused on herbaceous plants, revealing substantial variation in H among different organs. However, whether H varies among tree species across developmental stages and geographical regions remains poorly understood. In this study, the homeostatic coefficients of leaf nitrogen (N), phosphorus (P), and the N: P ratio were quantified for the first time in Juniperus przewalskii across both temporal (5–10 months of growing seasons) and spatial (an 800 km southeast-to-northwest transect) gradients within the northeastern Tibetan Plateau. Two parameters, the homeostatic coefficient ( H ) and the allometric exponent, were employed to characterize nutrient homeostasis and the relative investment of trees in N and P acquisition, respectively. Across the growing season, leaf N, P, and N: P ratios all showed significant homeostasis ( p < 0.05), with the homeostatic coefficient for N ( H N ) being significantly higher than that for P ( H P ) ( p < 0.05). Although H N: P varied among regions, trees demonstrated selective uptake of elements in response to environmental changes. These findings indicate that J. przewalskii shows both temporal and spatial stoichiometric homeostasis, underscoring its role as a fundamental trait in plant adaptation to external environmental variability. However, the H values may fluctuate with changing environmental conditions. This study enhances our understanding of the ecological adaptation and evolutionary strategies of J. przewalskii in response to climate change in arid and semi-arid forest ecosystems, providing valuable insights for improving drought resilience and guiding forest management in J. przewalskii plantations across the Qilian Mountains.
Li et al. (Sun,) studied this question.