Abstract: Aims Exploring the differences in the life strategies of the “twig system” (old twigs, new twigs, and leaves) of Corylus mandshurica in different seasons can provide a theoretical basis for the protection and management of wild C. mandshurica. At the same time, it can promote the understanding of the multi-organ coordinated re-sponse of plants to climate change. Methods In this study, taking C. mandshurica, the dominant species in the shrub layer of the broad-leaved Ko-rean pine forest, as an example, the old twigs, new twigs, and leaves of C. mandshurica were collected in spring, summer, and autumn respectively. Three types of traits were measured, including chemical traits (carbon, nitro-gen, and phosphorus), non-structural carbon (soluble sugar, starch, and total non-structural carbohydrates), and defense traits (total phenols, tannins, and flavonoids), to explore the growth and defense strategies of the plant’s “twig system”. Important findings The results showed that: except that the effect of organs on starch was not significant (p >0.05, partial Eta squared value = 0.016), season, organs and their interactions had significant effects on the functional traits of C. mandshurica (p <0.05). In spring, among the six overall characteristic parameters of the trait network of leaves, five and four parameters (such as the number of nodes, the number of edges, diameter, and edge density) were higher than those of new twigs and old twigs respectively. Among the six overall charac-teristic parameters of the trait network of leaves, four parameters (such as the number of nodes, average path length, and modularity) were lower than those of new twigs and old twigs. In spring, in the “twig system” (old twigs, new twigs, and leaves) of C. mandshurica, leaves and new twigs tended towards the “growth” strategy, while old twigs tended towards the “defense” strategy. In summer, leaves tended towards the “growth” strategy, while new twigs and old twigs tended towards the “defense” strategy. In autumn, leaves tended towards the “de-fense” strategy, and new twigs and old twigs tended towards the “resource recovery” strategy. The research results revealed differences in the growth and defense strategies of the “twig system” of C. mandshurica, which is con-ducive to promoting the theoretical research on how plants respond to environmental changes in a more system-atic and refined direction.

Key words: season, organ, stoichiometry, shrub, growth and defense strategies, trait network