Abstract
Investigating the effects of ontogenetic stage and leaf age on leaf traits is important for understanding the utilization and distribution of resources in the process of plant growth. However, few studies have been conducted to show how traits and trait-trait relationships change across a range of ontogenetic stage and leaf age for evergreen coniferous species. We divided 67 Pinus koraiensis Sieb. et Zucc. of various sizes (0.3–100 cm diameter at breast height, DBH) into four ontogenetic stages, i.e., young trees, middle-aged trees, mature trees and over-mature trees, and measured the leaf mass per area (LMA), leaf dry matter content (LDMC), and mass-based leaf nitrogen content (N) and phosphorus content (P) of each leaf age group for each sampled tree. One-way analysis of variance (ANOVA) was used to describe the variation in leaf traits by ontogenetic stage and leaf age. The standardized major axis method was used to explore the effects of ontogenetic stage and leaf age on trait-trait relationships. We found that LMA and LDMC increased significantly and N and P decreased significantly with increases in the ontogenetic stage and leaf age. Most trait-trait relationships were consistent with the leaf economic spectrum (LES) at a global scale. Among them, leaf N content and LDMC showed a significant negative correlation, leaf N and P contents showed a significant positive correlation, and the absolute value of the slopes of the trait-trait relationships showed a gradually increasing trend with an increasing ontogenetic stage. LMA and LDMC showed a significant positive correlation, and the slopes of the trait-trait relationships showed a gradually decreasing trend with leaf age. Additionally, there were no significant relationships between leaf N content and LMA in most groups, which is contrary to the expectation of the LES. Overall, in the early ontogenetic stages and leaf ages, the leaf traits tend to be related to a "low investment-quick returns" resource strategy. In contrast, in the late ontogenetic stages and leaf ages, they tend to be related to a "high investment-slow returns" resource strategy. Our results reflect the optimal allocation of resources in Pinus koraiensis according to its functional needs during tree and leaf ontogeny.
Highlights
Trees, as long-lived organisms, increase in size and structural complexity during ontogeny
The overall trend was that the leaf mass per area (LMA) and leaf dry matter content (LDMC) showed an upward trend with increasing ontogenetic stage
Our results demonstrate that ontogenetic stages and leaf age had significant effects on the LMA, LDMC, N and P of P. koraiensis (Fig. 1), which may be due to genetic variation in trees and the response of plants to environmental factors, such as light intensity and soil nutrient availability (Scheepens et al 2010; Wright et al 2004)
Summary
As long-lived organisms, increase in size and structural complexity during ontogeny. Increasing tree age may result in changes in leaf mechanical strength, hormonal regulation, vegetative/reproductive allocation, the ability to absorb nutrients, and adaptation to environmental conditions, all of which may induce associated changes in tree structure and function Tree age or ontogenetic stage may be an important cause of trait variation (Steppe et al 2011; Kuusk et al 2018). Previous studies on functional traits have generally focused on a certain ontogenetic stage (Azuma et al 2019) or comparisons based on young and mature individuals (i.e., young trees and canopy trees) (Greenwood et al 2008; Mediavilla and Escudero 2009; Palow and Kitajima 2012; Kuusk et al 2018), with fewer studies based on all ontogenetic stages. Revealing variations in traits throughout ontogenetic stages will advance our understanding of the causes of intraspecific trait variation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
