Abstract:

Objective: Based on the vertical distribution of soil organic carbon and total nitrogen in different soil layers, this study aims to examine the coordination and trade-offs among leaf, branch, and root functional traits of Quercus mongolica, and to clarify its resource-use strategy, thereby providing a theoretical basis for its scientific management. Method: The functional traits of leaves, branches, and roots of typical Q. mongolica in the Liaodong mountainous area, including total carbon content, total nitrogen content, leaf dry matter content, specific leaf area, specific root length, root average diameter, and root tissue density, were measured. Combined with soil organic carbon and total nitrogen contents measured at depths of 0?10, 10?20, and 20?30 cm, the relationships among functional traits of different organs of Q. mongolica and their associations with soil carbon and nitrogen stoichiometric characteristics were analyzed. Result: 1) There were significant differences in carbon and nitrogen contents, as well as their stoichiometric ratios among organs of Q. mongolica (P<0.01). Among them, carbon content followed a pattern of root > leaf > branch, nitrogen content followed a pattern of leaf > root > branch, and the carbon to nitrogen ratio followed a pattern of branch > root > leaf. The spectrum of continuous resource utilization strategies overall formed from “fast investment-return” in leaves to “slow investment–return” in branches and “persistent maintenance” in roots, corresponding to the resource-use strategy of “acquisitive–conservative–persistent” . 2) There were significant correlations among functional traits of different organs of Q. mongolica. Among them, branch carbon to nitrogen ratio was negatively correlated with specific leaf area (P<0.01) and positively correlated with leaf dry matter content (P<0.01), root nitrogen content was positively correlated with leaf nitrogen content (P<0.01), and specific leaf area was positively correlated with specific root length (P<0.01), indicating that functional traits of different organs of Q. mongolica did not vary independently, but rather coordinated resource allocation and use through internal linkages. In addition, average diameter of roots was negatively correlated with root tissue density (P<0.01), indicating a trade-off between structural construction and resource acquisition in roots of Q. mongolica, showing a “structure–function decoupling” pattern and reflecting the complexity of belowground resource acquisition. 3) Soil organic carbon and total nitrogen contents decreased with increasing soil depth, showing a clear surface enrichment pattern, while soil carbon to nitrogen ratio did not differ significantly among layers. The first principal component, representing the soil carbon and nitrogen content gradient, had a significant effect on the variation of functional traits of different organs of Q. mongolica (P<0.05), while the second principal component, representing soil carbon to nitrogen ratio, showed no significant effect. Additionally, functional traits of different organs of Q. mongolica showed consistent or opposite trends along the soil carbon and nitrogen content gradient, indicating that Q. mongolica responded to soil carbon and nitrogen content gradient through coordination and trade-offs among multiple organ functional traits. Conclusion: Functional traits of different organs of Q. mongolica do not significantly respond to soil carbon to nitrogen ratio, but respond to variations in soil carbon and nitrogen contents through coordination and trade-offs among organ functional traits, showing an “acquisitive–conservative–persistent” resource-use strategy.

Key words: Quercus mongolica, functional traits, soil carbon and nitrogen, ecological stoichiometry, adaptive strategy