Objective The ecophysiological characteristics and ecological homeostasis of plants are key indicators of their abaptability to environmental changes. Given sex-specific differences in reproductive costs in dioecious plants, resource allocation strategies may exhibit dynamic sexual dimorphism across phenological stages and between years. Uncovering this sexual dimorphism is of crucial for understanding the adaptability of dioecious plants to environmental fluctuations. This study investigated sexual dimorphism in the leaf carbon (C), nitrogen (N), and phosphorus (P) stoichiometry and ecological homeostasis of the dioecious plant Rhamnus schneideri var. manshurica across different growth stages. Based on reproductive cost theory, we analyzed these sexual differences and examined the impact of habitat changes on the sexual dimorphism of Rhamnus schneideri var. manshurica by assessing interannual variations in environmental factors.

Method Leaf samples from male and female Rhamnus schneideri var. manshurica plants, along with corresponding samples, were collected during the flowering and fruiting periods in 2021 and 2025 from a long-term permanent plot in a needle-broadleaved mixed forest in Jiaohe, Jilin Province. Leaf C, N and P contents were determined using a laser hyperspectral elemental analyzer. Combined with soil total nutrient data, the Wilcoxon rank-sum test and permutation test were employed to analyze sexual differences in ecological stoichiometric characteristics, and a linear regression model was used to calculate the homeostatic index to evaluate ecological homeostasis.

Result (1) During 2021 flowering period, female plants exhibited significantly higher leaf C content and C∶N ratio (p < 0.05), extremely significantly higher C∶P and N∶P ratios (p < 0.001), but extremely significantly lower P content (p < 0.001) than male plants. In the fruiting period of 2021, female plants had extremely significantly lower leaf C content and C∶N, C∶P, N∶P ratios (p < 0.001), but extremely significantly higher N and P contents (p < 0.001) than male plants. In 2025, sexual differences were substantially weakened: only C and N contents of females were significantly higher than those of males during flowering (p < 0.05), and no significant sexual differences were detected for other stoichiometric traits (p ≥ 0.05). (2) Ecological homeostasis analysis showed that in 2021, male plants exhibited weak homeostasis for leaf C content during flowering and for the C∶N ratio during both flowering and fruiting periods, indicating some environmental sensitivity. Male plants also showed a steady state for C content and a weak steady state for P content in the fruiting period, while all other indices remained in absolute homeostasis. Female plants maintained a steady state only for the C∶N ratio in the fruiting period and absolute homeostasis for all other indices. In 2025, with improved water and heat conditions, all ecological homeostasis indices for both sexes returned to absolute homeostasis.

Conclusion Sexual dimorphism in the stoichiometric characteristics and ecological homeostasis of male and female plants of Rhamnus schneideri var. manshurica is fundamentally attributable to differences in reproductive costs. As female plants bear the energy-intensive task of fruit and seed development, they actively accumulate nitrogen and phosphorus during the fruiting stage to enhance leaf photosynthetic efficiency, thereby compensating for reproductive expenditure and maintaining a high level of ecological homeostasis. In contrast, the reproductive investment of male plants is primarily concentrated during the flowering stage, rendering their homeostasis relatively susceptible to environmental influences. This difference in resource allocation strategies, driven by reproductive costs, constitutes a key mechanism underlying sexual dimorphism in dioecious plants.