Patterns of Variation and Coordination in Shoot Traits Across Four Branching Orders of <i>Larix principis-rupprechtii</i>

Abstract

Intraspecific variation in functional traits can more accurately quantify plant responses to environmental changes and resource competition, while the plant economic spectrum provides a fundamental framework for understanding trait variation along environmental gradients. As the structural units of the aboveground branching system in woody plants, it remains unclear whether shoots exhibit a universal whole-plant economic spectrum and whether branch order significantly affects the patterns of trait variation and coordination. We collected 1551 shoots of Larix principis-rupprechtii to examine the patterns of trait variation and coordination from different branch orders to the whole-plant level. From the perspective of the plant economic spectrum, five functional traits were selected to represent the trade-off between structural and nutrient investment: the stem diameter (SD), stem length (SL), stem dry mass (SDM), specific stem length (SSL), and stem tissue density (STD). From different branch orders to the whole-plant level, allocation played a relatively more important role, and the patterns of pairwise trait correlations and trade-offs along the resource economic axis were consistent. Branch order did not strongly influence the correlations and degree of coordination within the shoot economic spectrum, as the whole-plant shoot economic spectrum was evident within each branch order. Our results support the hypothesis that the coordinated economic spectrum across branch orders forms an integrated whole-plant economic spectrum representing a “conservative–collaborative” resource management strategy. This strategy is robust to recent evolutionary changes (such as genotypic variation and even differences among shoots within the same species) as well as to variation across different branch orders.

Keywords

• intraspecific
• shoot
• branch orders
• allocation
• morphology
• functional traits